Nanopyroxene Grafting with Î²-Cyclodextrin Monomer for Wastewater

Subscriber access provided by READING UNIV

Article

Nanopyroxene grafting with #-Cyclodextrin monomer for wastewater applications Ghada Nafie, Gerardo Vitale, Lante Antonio Carbognani Ortega, and Nashaat N. Nassar ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b13677 • Publication Date (Web): 07 Nov 2017 Downloaded from http://pubs.acs.org on November 10, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Nanopyroxene grafting with β-Cyclodextrin monomer for wastewater applications Ghada Nafie, Gerardo Vitale, Lante Carbognani Ortega and Nashaat N. Nassar* Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, Alberta, Canada Email: [email protected]; Tel: 403-210-9772 Abstract

Emerging nanoparticle technology provides opportunities for environmentally-friendly wastewater treatment applications, including those in the large liquid tailings containments in the Alberta oil sands. In this study, we synthesize β-Cyclodextrins grafted nanopyroxenes to offer an eco-friendly platform for the selective removal of organic compounds typically present in these types of applications. We carry out computational modeling at a micro level through molecular mechanics and molecular dynamics (MD) simulations and laboratory experiments at the macro level to understand the interactions between the synthesized nanomaterials and two-model naphthenic acids molecules (cyclopentanecarboxylic and trans-4-Pentylcyclohexanecarboxylic acids), typically existing in tailing ponds. This proof-of-concept computational modeling and experiments demonstrate that monomer grafted nano-AE are found to be promising candidates for the removal of polar organic compounds from wastewater among other applications. These nano-AE offer new possibilities for treating tailing ponds generated by Oil Sands industry.

Keywords: β-Cyclodextrins, nanopyroxenes, wastewater, polymer grafting, computational modeling

ACS Paragon Plus Environment

1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 45

1. Introduction Nanoparticles have a wide variety of applications in energy and environment related processes, including wastewater treatment,1-5 heavy oil upgrading,6-9 drug delivery,10-13 and polymer composites14-16 among other applications.17-21 However, the effects of human exposure to nanoparticles are either unknown or present potentially negative health impacts.22-24 This mandated the need for environmentally-friendly nanoparticles to ensure safe application. While pyroxenes are naturally occurring in the earth’s crust, they have recently been synthesized using a hydrothermal method, which requires low temperature and pressure, forming a pure nanopyroxene or nano-AE of the sodium iron-silicate Aegirine.25 Due to their low affinity towards the removal of organic contaminants, surface modification and functionalization is required. Currently, one of the most commonly used functionalizing agent for nanoparticles targeted towards the removal of organic contaminants are organic polymers (e.g., polyethylenimine, PEI), due to their wide range of buffering capacity in a broad range of pH levels.26 However, in addition to PEIs high cost, it is toxic to aquatic life when released, at relatively low concentrations.27 An important measure for the preparation of the proposed material is its environmentallyfriendly framework. β-Cyclodextrins (β-CD) natural polymers are cyclic oligosaccharides consisting of (α1,4)-linked-α-D-glucopyranose units and their numerous derivatives.28 The β-CD polymer contains large numbers of primary and secondary hydroxyls sitting on hydrophilic shells contained in lipophilic cavities. These polymers are known for their low toxicity that do not provoke an immune response in humans.29 Therefore, they are widely used as carriers for drug delivery.30-31 The β-CD polymer is very soluble in water28 and cannot be anchored onto the


2

Page 3 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


surface of the nano-AE without the use of a hybrid binder approach. Therefore, β-CD monomers were chemically grafted to the pyroxene nanoparticles using a hybrid organic-inorganic material. In this study, a new synthesis route is introduced for the grafting of β-CD to nano-AEs, producing new hybrid inorganic-organic nanoparticles: inorganic nanoparticles with organic branches to capture and trap polar organic compounds from wastewater by forming inclusion complexes with the anchored β-CD. We carried out both computational modeling and laboratory experiments to understand the removal mechanisms of β-CD grafted nano iron silicate for twomodel

naphthenic

acids

molecules

(cyclopentanecarboxylic

and

trans-4-

Pentylcyclohexanecarboxylic acids). This study introduces a designed β-CD grafted nano iron silicate or “GNIS” for its application in wastewater treatment. 2. Experimental Section The synthesis of grafted nanoparticles involves three steps: first, a hydrothermal preparation of the nano-AE (surface-enriched in hydroxyls groups); second, a chemical bonding of the bridge compound to the surface of the nano-AE; and finally, a nucleophilic attack from the ionized βCD to the bridge anchoring it to the nanoparticle. Wastewater treatment experiments are then conducted to test the effectiveness of the synthesized material for removing contaminants from wastewater.

2.1. Materials

The materials used to prepare the nano-AE are anhydrous iron (III) chloride hexahydrate (FeCl3, 6H2O, 99 wt%, Merck), sulfuric acid (18.067 g H2SO4, Fisher Scientific, dissolved in 90 g of deionized water), sodium silicate (27 wt% SiO2, 10.85 wt% Na2O, Sigma-Aldrich) and sodium hydroxide (NaOH, 99 wt%, VWR). The materials used for grafting are β-CD monomer


3


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 45

(C42H70O35, ≥ 98%, MW 1135 g/mol, average diameter of the cavity is 8.0 Å, Sigma-Aldrich, please refer to the Supporting Information section for the chemical structure), 3Glycidyloxypropyl trimethoxysilane or 3GT (C9H20O5Si, ≥ 98%, Sigma-Aldrich), toluene (C6H5CH3, anhydrous, 99.8%, Sigma-Aldrich), N, N-DiMethylFormamide (HCON(CH3)2, ≥ 99.8%, Sigma-Aldrich) or DMF and Sodium hydride (NaH, dry, 95%, Sigma-Aldrich). Finally, the materials used to prepare the synthetic wastewater solution are the model molecules cyclopentanecarboxylic acid or CP (C5H9CO2H, 99% purity, MW 114.14 g/mol, Sigma-Aldrich) and trans-4-Pentylcyclohexanecarboxylic acid or T4P (CH3(CH2)4C6H10CO2H, 97% purity, MW 198.30 g/mol, Sigma-Aldrich).

2.2. Synthesis of β-CD grafted nanoparticles

To prepare the nano-AE, first, an acidic solution was prepared by dissolving 9.2 g anhydrous iron (III) chloride hexahydrate in diluted sulfuric acid solution under magnetic stirring at 300 rpm. This was followed by the preparation of a basic solution by adding 60.129 g sodium silicate to a previously dissolved 22.495 g of sodium hydroxide in 60 g of water solution under magnetic stirring at 300 rpm. The basic solution was left under agitation until it became homogenous. The acid solution was then added to the basic solution very slowly under agitation forming a fluid gel. The mixture was left to homogenize before it was ready for the hydrothermal treatment. Crystallization begins by pouring the mixture into a stirred stainless-steel PARR reactor; and then, filtering to recover the produced solid nanoparticles, washed with deionized water until the pH of the washed water was close to 7 and, then the material was dried at room temperature. The nano-AE particles were then ready as an insoluble solid substrate for grafting or surface modification.


4

Page 5 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Grafting the nano-AE with β-CD monomer must take place in a dry environment since methoxysilyl and epoxy groups used for the synthesis react with water.32-33 As such, the experiment was performed in an atmosbag filled with dried nitrogen (99.99%) and connected to a vacuum outlet. The nano-AE, β-CD monomer along with 4A molecular sieves were dried in vacuum at 333 K. Grafting the nano-AE with β-CD monomer was accomplished via an inorganic-organic hybrid–3-Glycidyloxypropyl trimethoxysilane (3GT) by a two-step reaction, between the inorganic nanoparticles and the hybrid bridge and between the hybrid bridge and the organic polymer.33 1 ml was the calculated amount of 3GT which was added to 100 ml toluene percolated through 4A molecular sieves desiccants and added dropwise. During this time, covalent bonding of methoxy oxygen occurred, thus, anchoring the 3GT to the nano-AE.33 After 3 h, the suspension was filtered and washed with toluene at least three times. The next step was grafting the β-CD monomer to the bridge, which involved anchoring to the epoxy ring. 0.5 g of dried β-CD monomer was dissolved in 10 ml dried DMF dried by percolation through 4A molecular sieves. DMF was used as the solvent as β-CD monomer is only soluble in a few solvents, including DMF. This is an important consideration for an aprotic reagent.34 To activate the hydroxyls on the surface of the monomer, 0.15 g of sodium hydride, as the basic catalyst, was added to the mixture and was left for 15 min while swirling to allow it to react with the β-CD monomer in DMF under dry conditions. The solution was filtered to remove excess NaH. An additional reflux system was undertaken using 100 ml dried DMF in a three-neck flask including the 10 ml DMF containing the β-CD slurry after filtration. The solid particles of the nano-AE with the previously anchored bridge were added to this mixture and heated to 423 K for


5


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 45

2 h under agitation (300 rpm) to react. At this point, activated O- from the β-CD hydroxyls conducted a nucleophilic attack opening the epoxy ring and bonding to it. The monomer was then anchored through oxygen to the bridge, thereafter filtered, washed with DMF, toluene, and methanol and placed under vacuum at 333 K.32

2.3.Characterization of the synthesized polymer grafted nanoparticles

Fourier transform infrared spectroscopy (FTIR) was used to provide information about the local molecular environment of the inorganic-organic hybrid and the monomer grafted on the surface of the nanoparticles. The FTIR was operated in the diffuse reflectance mode in the range of 4000-400 cm-1 with a 4 cm-1 resolution and being the spectrum the average of 50 scans. Potassium bromide (KBr) was used for dispersing the powder sample (2 mg per 200 mg, 1% wt/wt). Thermogravimetric analysis (TGA) was conducted to confirm the grafting of the monomer on the nano-AE surface. The TGA analyses were performed by heating the sample from 293 to 973 K using a thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) analyzer (SDT Q600, TA Instruments, Inc., New Castle, DE) using ~4 mg of the nanoparticles sample, to avoid mass transfer limitations. Air was used at a rate of 100 cm3/min and a heating rate of 10 ᵒK/min. Nano-AE dry powders were characterized by X-ray diﬀraction (XRD) as well as the grafted nano-AE to confirm that the nanoparticles were not destroyed during the grafting process. The scan was performed in the 2θ range of 3-90 ͦ using a 0.05 ͦ step and a counting time of 1 ͦ/min. The crystalline domain sizes of the original material were measured using the Scherrer equation as implemented in the commercial software JADE (provided with the diffractometer), achieved by


6

Page 7 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


calculating the full width at half maximum (FWHM) of the peaks fitting the experimental profile to a pseudo-Voigt profile function. The Brunauer–Emmett–Teller (BET) method was employed to study the textural properties of the nanoparticles by measuring the nitrogen physisorption of the samples at 77 K on a Micromeritics Tristar 3000 analyser. The BET equation was utilized to calculate the surface area for 300 mg of each sample. The samples were pre-treated overnight on a stream of nitrogen at 423 K before carrying out the measurements under nitrogen at atmospheric pressure inside the sample holder cells. The high-resolution transmission electron microscopy (HRTEM) analysis was carried out using a FEI Tecnai F20 FEG TEM with an accelerating voltage of 200 kV. 3 mg of the nano-AE sample was dispersed in ethanol and sonicated for 5 min. 1 µL drop of the dispersed solid in the ethanol solution was then deposited onto a standard 300 mesh carbon copper grid treated with plasma cleaning. The drop was then air dried at room temperature, thus, depositing a solid nanoAE sample on the grid. Another sample was stained with 2% diluted phosphotungstic acid for 24 h before the images were taken in an attempt to observe the grafted β-CD monomer.35 Atomic resolution definition of GNIS was carried out to identify the surface topology by using a JPK instruments atomic force microscope (AFM). The sample was prepared by dispersing a few milligrams of the GNIS nanoparticles in ethanol. The sample was then placed on a freshly cleaved sheet of mica and the ethanol was left to evaporate. The sample was imaged using a conical AFM Tips (nanoscience instruments) in air tapping mode. The images were processed in the JPK software accompanying the instrument.


7


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 45

2.4.The removal of organic pollutants from wastewater using GNIS

To investigate the removal mechanism of the organic contaminants experimentally, the two carboxylic model molecules used to conduct the computational modeling were used, CP (C5H9CO2H, 99% purity, MW 114.14 g/mol, Sigma-Aldrich) and T4P (CH3(CH2)4C6H10CO2H, 97% purity, MW 198.30 g/mol, Sigma-Aldrich). To prepare the wastewater solution using the model molecules with 80 ppm initial contaminant concentration mimicking the real wastewater contaminant content, the pH was adjusted to 8.5 using 50% wt/wt sodium hydroxide (NaOH, 99 wt%, VWR) then titrated with the acids under magnetic stirring (at 300 rpm) reducing the pH to about 7.5 (original pH of the water). In the case of the T4P, heat was applied to solubilize the contaminant in the water at 353 K for about 15 min. 100 mg of monomer grafted nanopyroxenes were added to 20 ml of the synthetic wastewater solution then shaking took place for about 10 min. The samples were then centrifuged and the supernatant was analyzed using GC-MS. Gas chromatography-mass spectrometry (GC-MS, QP5000, Shimadzu, equipped with AOC20i auto sampler) has been employed for the study of naphthenic acids removal. 2 µL of samples were injected for each run with 3 water blanks in between samples. The GC temperature remained at 313 K for 2 min hold time then ramp at 12 ᵒC/min to finally get to 573 K which was then held for 10 min. Helium was used as the carrier gas (57.5 KPA 3 ml/min to maintain a linear velocity of 63.5 cm/s and a split ratio of 2:1). The mass spectrometer was operated in EI ionization mode, with a scan range of 35-300 m/z and 0.56 second scan interval. The interface heated at 553 K coupled with a GC-17A equipped with an Agilent Hp-5 column (30 m × 0.32 mm ID and 0.25 µm stationary phase thickness or DF). NIST 2005 MS spectra library, accompanying the instrument, was used to identify the compounds observed in the liquid samples. The samples were run neat with no dilution for obtaining stronger signals.


8

Page 9 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3. Computational Modeling Computational modeling was carried out to provide a deeper insight on the conformational structure of the hydroxylated nanoparticle surface, the β-CD monomer and the 3GT molecule before and after its reaction, and to stipulate understanding about the bonding of the β-CD to the epoxy bridge in 3GT as well as to the bonding of the 3GT to the hydroxyls on the surface of the nanoparticles. Two-model naphthenic acids molecules were chosen to gain an understanding of their interaction with, first the β-CD molecule alone, followed by the β-CD molecule attached to the hydroxylated silica surface through the 3GT molecule. The commercially available model molecules

are

cyclopentanecarboxylic

acid

referred

to

as

CP

and

trans-4-

Pentylcyclohexanecarboxylic acid or T4P. Molecular dynamics simulations modeling were carried out to recognise the mechanism of adsorption of naphthenic acids model molecules occurring on the developed adsorbents in the presence of water molecules. The following subsections describe each type of the performed calculation. The β-CD, 3GT, CP, T4P, and H2O molecules were generated with the BIOVIA Builder module and geometrically optimized with BIOVIA Forcite. The quality of the geometry optimization in BIOVIA Forcite was set to Fine and the force field to BIOVIA COMPASSII since this force field is compatible with inorganic oxides.36 This was used to study the interactions of these molecules with the silica surface. 4. Results and Discussions

4.1.Characterization Studies

FTIR spectroscopic tentative assignments to the infrared signals were previously assigned on the framework region for several pyroxene minerals.37 A very strong signal between 1065 and


9


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 45

1075 cm-1 assigned to the vibration (O–Si–O); a strong signal between 965 and 974 cm-1 was assigned to the vibration (Si–O–Si); a weak signal between 910 and 920 cm-1 was assigned to the vibration (Si–O–Si); a very strong signal between 870 and 865 cm-1 was assigned to the vibration (Si–O–Si); a very strong signal between 465 and 475 cm-1 was assigned to the vibration (Y–O), where Y represents Mg, Fe or Mn; and a medium to weak signal between 390 and 395 cm-1 was assigned to the vibration (X–O), however, not showing in the spectrum, where X represents Na or Ca. These reported signals were present in the nano-AE material produced in this work corroborating its formation by this technique.37 The signals were still present after the different treatments to anchor the β-CD molecules, indicating the stability of the pyroxene structure after each treatment.25, 38 The bands observed at about 1650 cm-1 are associated with the O–H bending. These peaks were found to shift to higher frequencies by up to 35 cm-1 increments with the reaction steps, possibly changing their original position as a function of the synthesis. This could be an indication correlated to the changes introduced in the chemical environment of –OH moieties by the attached 3GT molecules. The epoxide functional groups in the 3GT have characteristic IR absorbance bands: the ring breathing between 1260 and 1240 cm-1, asymmetrical ring stretching between 950 and 810 cm-1 and the ring C–H stretch between 3050 and 2995 cm-1.39-41 In the GNIS spectra, the β-CD monomer was exposed to sodium hydride (NaH) where the hydride reacted with the hydrogen from the hydroxyl present in the monomer forming in this way H2 gas and leaving an alkoxide like ion as per the following reaction. − + → − +

The presence of the ethoxide functional group triggered the nucleophilic attack over the epoxy ring from the bridge, as shown in Fig. 1. When the nucleophilic attack takes place, it opens the epoxy ring. Hence, a significant change occurs in the epoxide bands absorption observed in the


10

Page 11 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


GNIS spectrum, which provides additional confidence that β-CD monomer was indeed bonded to the 3GT, where ring breathing and C–H stretch are absent from the band and the ring stretching is drastically reduced.41

Fig. 1 Schematic of the nucleophilic substitution between the β-CD monomer and the epoxy group at the end tail of the 3GT.

Hydroxyl content in the nano-AE results from the hydrothermal treatment during their preparation that would not otherwise be present in natural AE samples.42 Thus, observing additional hydroxyl stretching and bending bands centred at 3440 and 1635 cm-1 can be understood. The spectra observed in the region between 3700 and 3200 cm-1 corresponds to O–H with H-bonding stretching since the wide band extends down to about 2600 cm-1 (Fig. 2a presents this observation in greater detail).43 In comparison, the OH content in the nano-AE and the 3GT together show a narrower band with OH absorbance reduction, which is in agreement with the anchoring of the hydroxyls on the surface of the nano-AE to 3GT, thus decreasing the existing number of OH groups as would be expected if the bonding occurred. This reflects the first reaction during reflux where the methoxy group on the 3GT reacts with the surface of the nano-AE as shown schematically in Fig. 3.44


11


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 45

Fig. 2 Infrared Spectroscopy of a) hydroxyl region, b) structural framework region and c) the βCD monomer grafted nanopyroxene GNIS.


12

Page 13 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 3 Direct exchange chemical reaction with the substrate. (a) shows electronegativity differences of the nano-AE and methoxy on the 3GT, (b) reaction between the Ö and Si with methanol as the leaving group and (c) bonding of the 3GT to the nano-AE.

A different OH bonding band is observed in GNIS, where some of the free stretching hydroxyls are not present compared to nano-AE between 3700 and 3400 cm-1. The increase in the hydroxyls present for GNIS compared to the solid with grafted bridge arises from the –OH groups present in the β-CD. This indicates the presence of the β-CD in the sample. Furthermore, the peaks observed at 2936 and 2860 cm-1 are the absorbance vibrations of νC–H, initially appearing in the bridge spectrum representing the alky groups. It is clear how the intensity of the GNIS spectrum increases when the β-CD monomer is added because of its CH2 groups stretching.45-46 Infrared Spectroscopy of the β-CD monomer grafted nano-AE shows a strong broad adsorption peak at 3421 cm-1 attributed to the many OH groups present over the β-CD. The peak observed at 2983 cm-1 results from the CH2 stretching and the band in the region between 1500 and 1425 cm1

is the CH2 bending.47 The broad bands visible at 1158, 1028 and 946 cm-1 (Fig. 3b) are

associated with the C–O and the C–O–C absorption of glucose units and glucose rings.40,

46

These glucose units contributed to the sharp band at 875 cm-1. The peak observed at approximately 1630 cm-1 is the O–H bending absorption vibration of the hydroxyl groups.44 The GNIS spectra displays the final synthesized material with the monomer grafted on the surface of the nano-AE. Therefore, it is apparent that the CH2 region between 1500 and 1425 cm-1 is visible on the GNIS spectrum versus the nano-AE spectrum because of the presence of CH2 in the β-CD monomer.


13


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 45

The FTIR spectroscopy provides a strong indication of the linkage between the nano-AE, 3GT and the β-CD monomer. This is especially evident in the following active IR modes: 2900 cm-1, 1500 cm-1, 1250 cm-1, 1158 cm-1 and 900 cm-1 (Fig. 3c). The significant changes in the hydroxyl area provides additional confidence that the monomer linkage to the 3GT was formed and that the CH2 present in the β-CD monomer is now present in the GNIS spectrum. The TGA thermograms of the nano-AE are not expected to show much weight loss for the inorganic powder in agreement to the typical TGA of AE previously reported.25, 47 Weight loss detected up to a temperature of 423 K is attributed to physisorbed water molecules on the nanoAE (loss of bound water from surface sites and interparticle micropore domains), the moisture loss is associated with a reduced area for the endotherm, followed by about 2% weight loss. The surface hydroxyl groups density for the nano-AE was calculated from TGA weight loss between 673 and 973 K using the expression previously reported47 and found to be 4.1 OH/nm2. This indicates that the probability is much higher to anchor one or two of the methoxy groups on the 3GT than all 3 groups present. The TGA thermograms shown in Fig. 4 corresponds to the synthesized material GNIS. A clear peak is observed for the heat flow curve reflecting the oxidation of organic matter in air. This exothermic peak appears between 473 and 673 K, centred around 573 K. Temperature below 473 K reflects the decomposition of the glucopyranose units followed by thermal cracking of the organic moieties. It is worth noting that the TGA thermogram for the β-CD monomer exhibits the same exothermic curve observed in the GNIS TGA.48 However, the curve corresponding to GNIS is shifted to the left, which indicates that the oxidation occurs at a lower temperature than for the virgin monomer. That offset in the temperature (∆T = 20 oC) suggesting that the nano-AE was acting as a catalyst, thus, speeding up the oxidation reaction at a lower temperature.49


14

Page 15 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 4 TGA thermograms of GNIS including weight loss (%) in black, weight derivative (%W/C) in red and heat flow (mW) in blue. Fig. 5 compares the decomposition behaviours of both nano-AE and GNIS. It is observed that the weight loss undertaken for GNIS is drastically less than nano-AE in the water loss stage. This is a result of the dry nature of the material where there is no physiosorbed trapped water. There is an 8 wt% loss occurring for the GNIS sample in which all the organics of the β-CD and the bridge were oxidized and some of the residual OH on the surface of the nano-AE were dehydroxylated.


15


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 45

Fig. 5 TGA thermograms weight loss in % of both nano-AE and GNIS.


16

Page 17 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


X-ray diffraction patterns of nano-AE and GNIS are illustrated in Fig. 6. The pattern indicates characteristic peaks at 2θ = 14ᵒ, 20ᵒ, 30ᵒ, 35ᵒ and 36ᵒ revealing the same structure of AE when compared with the reported signals in the pdf card #01-076-2564 of the 2005 International Centre for Diffraction Data (ICSS) database included in the program JADE V.7.5.1.50-51 After synthesis, it is observed that the GNIS pattern looks almost identical to the AE. This is expected since the amount of monomer and bridge are low compared to the AE. Additionally, both are disorganized on the surface of the nanoparticles, and cannot be detected by XRD. However, it is essential to use XRD to confirm that the nano-AE was not destroyed during the grafting process and that it is still visible in the sample. The diffraction patterns are identical and match precisely the AE in the aforementioned pdf card, thus, confirming the existence of AE before and after grafting.

Fig. 6 XRD pattern of β-CD grafted nano-AE and GNIS. The vertical lines shown in green represent the reference data for nanopyroxene AE from the Materials Data XRD Pattern Process Identification and Quantification. Fig. 7 shows the typical physisorption isotherm obtained from the BET for nano-AE displaying the presence of mesoporosity and microporosity. Clearly, the most descriptive


17


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 45

isotherm for the nano-AE is Type IV(a) as classified by the IUPAC.52 Nano-AE is a nonmicroporous material therefore the hysteresis loop observed is caused by interparticle porosity due to particle aggregation.25 Evidently, the presence of the monomer on the surface of the nanoAE increased the mesoporosity. For both cases, Type H3 loop is the best description for the hysteresis loop observed in the isotherms where the loops are an indication of non-rigid aggregates of disk-like particles.52

Fig. 7 BET nitrogen physisorption isotherms for (a) nano-AE and (b) GNIS. This is also confirmed by the HRTEM images shown below. In addition, the BET-specific surface area, pore volume, and pore size distributions are displayed in Table 1. The pore size distribution and the pore volume are calculated using the Barrett-Joynes-Halenda (BJH) method. The surface area of GNIS is less than the measured surface area of nano-AE as shown in Table 1. This is attributed to the monomer capping sites on the surface of the nano-AE by blocking the interparticle microporosity (as seen in Table 1 the microporosity has disappeared for the GNIS material) thus, the nitrogen-sensing molecule is limited in accessing and estimating the surface area that should be formed under aqueous solutions. However, it would be expected that under


18

Page 19 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


aqueous conditions, the monomers would not embed the AE nanoparticles, hence, increasing the surface area exposed. The nanoparticle size is estimated at 11 nm, whose value could also be estimated from the XRD and HRTEM characterizations. of disk-like particles.

Table 1 BET surface areas of nano-AE and GNIS. BET measurements

Nano-AE

GNIS

BET Surface Area (m2/g)

189 ± 3

120 ± 4

Micropore Area (m2/g)

39 ± 2

0

External Surface Area (m2/g)

150 ± 5

120 ± 4

Pore volume × 102 (cm3/g)

21

33

Average Pore width (nm)

58

103

The high-resolution transmission electron microscopy (HRTEM) analysis was carried out using a FEI Tecnai F20 FEG TEM with an accelerating voltage of 200 kV. 3 mg of the nano-AE sample was dispersed in ethanol and sonicated for 5 min. 1 µL drop of the dispersed solid in the ethanol solution was then deposited onto a standard 300 mesh carbon copper grid treated with plasma cleaning. The drop was then air dried at room temperature, thus, depositing a solid nanoAE sample on the grid. Another sample was stained with 2% diluted phosphotungstic acid for 24 h before the images were taken in an attempt to observe the grafted β-CD monomer.35 HRTEM images of the nanoparticles, original and grafted, are displayed in Fig. 8 where (a) shows the low magnification bright field image of the nano-AE. The agglomeration behaviour could be observed where the image contrast refers to the thickness changes across the sample.


19


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 45

Fig. 8b is the high magnification of the same sample where individual nano-AE particles can be observed. The nano-AE particles showed a mean diameter of 4±1 nm. The average crystalline domain size obtained by XRD was consistent with the estimated particle size from the BET which was estimated as 10 ± 2 nm. It is common to have smaller sizes detected by the HRTEM located on the edges and outer surface of the material as the outer particles are the last to form, and thus, tend to grow smaller for the lack of the limiting reactant (in this case, iron). Fig. 8c is a low magnification HRTEM of the synthesized GNIS material. The agglomeration behaviour is still observed though, the higher magnification in Fig. 8d and 8e show the individual nanoparticles. The high-magnified HRTEM image could not resolve the sub nanometer β-CD monomer.


20

Page 21 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 8 HRTEM images for (a) low magnification nano-AE, (b) high magnification nano-AE, (c) low magnification GNIS, (d) & (e) high magnification GNIS and (f) stained GNIS. This is likely due to fading of the nanoparticles in the carbon copper grid background used for the sample. Therefore, the GNIS sample was stained to overcome the constraint of the background. The rationale was if one binds the acid to the hydrocarbons in GNIS with the heavy metal it possesses, the image contrast should be enhanced. Fig. 8f presents the HRTEM of the stained GNIS sample showing no signs of enhancement notwithstanding the staining. This is an indication that the acid did not react with the sample as expected. Thus, the monomer could not be observed. The HRTEM images confirm the nanoparticle diameter, the agglomeration behavior, and the need for a monolayer graphene sample holder coupled with a different staining agent that would alleviate the constraints with the


21


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 45

background fading occurring with the carbon copper grids. This would enhance the images and resolve the sub nanometre β-CD monomer. AFM was used to provide further structural details enabling direct imaging of the local configurations at small distances. It is a technique aimed at performing topographic measurements on material surfaces to obtain surface roughness and high-resolution topography images.53 The AFM cantilever probe applies very small-scale forces on the material while it is moving the work piece to scribe the material.54-55 Fig. 9 presents AFM images of GNIS as scanned by microscope probe in tapping mode, chosen to reduce nanocutting,56 under ambient conditions where Fig. 9a provides a crosssectional topographic image of the sample in 2D. Unlike other characterization techniques, AFM can produce 3D images with the particular stacking and height of the nanoparticles as shown in Fig. 9b displaying the topology of the GNIS nanoparticles with the nanoscale. Using the JPK image processing software accompanying the instrument,57 the height profile for the single layer selected in Fig. 9a, denoted with a cross line, was obtained providing the height profile of the nanoparticles (Fig. 9c). The AFM estimated an average particle size of 12 ± 3nm. This is interestingly consistent with the estimates obtained by BET and XRD as shown in Table 2 presenting a comparison of the approximated nanoparticles size per different characterization techniques. The nanoparticles aggregation is evident in the AFM images with a bulk of about 70 nm at an offset of 100 nm where a reasonable conclusion could be drawn that about 6 to 7 particles are stacked on top of each other (Fig. 9c). The concentration of the nanoparticles seems to start decreasing at an offset of about 250 nm indicating the absence of nanoparticles in this region. The β-CD monomer was not observed by the AFM which was attributed to the hindrance of the instrument in detecting this structure.


22

Page 23 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(a)

(b)

(c)

Fig. 9 AFM topographical image of GNIS (a) topographic image of the sample in 2D, (b) 3-D cross-sectional topographic image and (c) the height profile of the nanoparticles for the specified cross section. Table 2 Nanoparticle size comparison for BET, XRD and AFM characterization techniques. Parameters

Size

BET particle size (nm)

11

XRD crystalline domain size (nm)

10 ± 2

AFM particle size (nm)

12 ± 3

HRTEM

4±1


23


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 45

4.2.Computational modeling

The geometrically optimized β-CD, 3GT, CP and T4P molecules are presented in Fig. 10, where the obtained lower energy configuration of each molecule can be observed. The experimental structural data for AE previously reported58 was transferred to the BIOVA Builder module and a 10 nm nanoparticle of the material was generated with the building nanostructure module in MS2017. The surface of the nanoparticle was capped with hydroxyl groups. Based on this representation, it is expected to see a huge hydroxyl band in the infrared spectrum for the nanopyroxene material as was experimentally observed. The surface of the generated nanoparticle indicated that the hydroxyl groups were bonded to the silicon atoms forming the well-known silanol groups that will eventually serve as the anchoring sites for the 3GT molecules. To facilitate the calculations, a silica surface was used for the modeling. The amorphous silica model within the BIOVIA structural database was optimized with Forcite using the COMPASSII force field.

Fig. 10 Geometry optimization of the selected molecules carried out with the module Forcite and the COMPASSII force field within BIOVIA Materials Studio 2017. (a) Top and side views


24

Page 25 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


of the optimized β-CD molecule; (b) optimized 3GT molecule before (top) and after (bottom) reaction of the methoxy groups and (c) optimized CD (top) and T4P (bottom) molecules. Red atoms represent oxygen, grey atoms represent carbon, white atoms represent hydrogen and yellow atoms represent silicon.

The optimized unit cell was then used within BIOVIA Builder module to create the surface (100) for the amorphous silica. The surface was created with an area of approximately 8 nm2 (2.85 nm × 2.85 nm) capping the broken bonds with hydroxyl groups. The depth of this surface was set to approximately 2.8 nm to ensure that it was greater than the non-bond cutoff used in the calculation. The vacuum thickness was set to 20 nm so the organic and water molecules do not interact with the periodic image of the bottom layer of atoms in the surface. The internal coordinate atoms in these surfaces were fixed to their bulk values. The top layers of atoms (∼ 0.5 nm) however, which will interact with the water and organic molecules, were allowed to relax under the geometric optimization carried out with BIOVIA Forcite with the BIOVIA COMPASSII force field. The COMPASSII force field has been parametrized for inorganic oxides and organic molecules, thus, it is suitable for studying the interactions between organics and inorganics.36 It has been documented that the β-CD molecule can form inclusion complexes with organic molecules trapped inside its cavity;59-65 thus, as a first approximation, the interaction of the model naphthenic acids molecules CP and T4P was carried out to get a glimpse on the possible geometry configurations of these two naphthenic acids model molecules within the β-CD molecule. BIOVIA Forcite module, with the quality set to Fine and the BIOVIA COMPASSII force field, was used to geometrically optimize the inclusion complexes gaining insights into the interactions of the selected molecules with the β-CD molecule. An understanding on how this molecule can trap the naphthenic acids needs to be investigated. As shown in Fig. 10a, β-CD is


25


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 45

formed when seven glucose units producing a circular cone structure with a hydrophobic cavity and a hydrophilic surface. There are seven alcohol groups (–CH2–OH) in the narrow part of the cavity in the molecule. A great variety of guest molecules can be trapped into the annular structure of β-CD forming nano-sized host-guest inclusion complexes.

59-65

Experimentally, it

was found that a benzoic acid molecule can be trapped inside each β-CD molecule protruding its –COOH group outside the part of the cone having the –CH2–OH groups.65 In the present work, the two-selected model naphthenic acids molecules differ in molecular sizes and shapes (Fig. 10c), and therefore, a different arrangement for the CP and T4P molecules should occur within the β-CD molecule. Fig. 11 shows the top and side views of the inclusion complex of the CP molecule with the β-CD molecule. The conformations that the CP molecule can obtain within the β-CD molecule are clearly illustrated by the figure. Fig. 11a shows the configuration in which the –COOH group of CP interacts with the seven –CH2–OH groups inside the cavity of β-CD and Fig. 11b shows the configuration in which the –COOH group of CP interacts with the fourteen external -OH groups of β-CD. As shown, the CP molecule is small enough to fit completely inside the β-CD cavity; however, the conformation of CP in which the – COOH group interacts with the seven –CH2–OH groups of β-CD molecule was 1.76 kcal/mol more stable than the other configuration, which is consistent with the aforementioned experimental findings for the benzoic acid inclusion complex.65


26

Page 27 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 11 Top and side views of the β-CD-CP inclusion complex: (a) Conformation with the carboxylic group interacting with the 7 –CH2OH groups and (b) Conformation with the carboxylic group interacting with the 14 –OH groups. Conformation (a) is 1.76 kcal/mol more stable than conformation (b). Red atoms represent oxygen, grey atoms represent carbon and white atoms represent hydrogen.

Fig. 12 illustrates the top and side views of the inclusion complex of the T4P molecule with the β-CD molecule. Fig. 12a shows the configuration in which the –COOH group of T4P interacts with the seven – CH2–OH groups inside the cavity of β-CD and Fig 12b shows the configuration in which the – COOH group of CPs interacts with the fourteen external -OH groups of β-CD. For this case, the molecule is larger than the cavity of the β-CD and the alkyl chain protrudes outside of the β-CD molecule; however, as seen with the CP molecule, the conformation of T4P in which the – COOH group interacts with the seven –CH2–OH groups of β-CD molecule was found to be 1.98


27


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 45

kcal/mol more stable than the other configuration, which seems to agree with what was found for CP conformation and for the benzoic acid inclusion complex aforementioned.65 These results indicate that the sizes and shapes of the naphthenic acids molecules do indeed play an important role in the formation of the inclusion complex; and thus, the way the β-CD molecule is anchored onto the surface of the nanoparticle should affect the way the molecules can interact with it.

Fig. 12 Top and side views of the β-CD-T4P inclusion complex: (a) Conformation with the carboxylic group interacting with the 7–CH2OH groups and (b) Conformation with the carboxylic group interacting with the 14 –OH groups. Conformation a) is 1.98 kcal/mol more stable than conformation b). Red atoms represent oxygen, grey atoms represent carbon and white atoms represent hydrogen.


28

Page 29 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Several models of the reacted 3GT molecule anchoring the hydroxyls groups on the previously generated silica surface were produced as well as their bonding to the –CH2-OH groups of a βCD molecule; and thus, geometrically optimized using BIOVIA Forcite module with the quality set to Fine and the COMPASSII force field. The 3GT molecule must be reacted to anchor it to the silanol groups present on the surface of the nanoparticles, as shown in Fig. 3. Several possibilities exist for the anchoring of the 3GT molecule on the surface (i.e., the formation of one, two or three bonds with the surface through one, two or three methoxy groups). Fig. 13 presents the feasible three possibilities for the anchoring of the reacted 3GT molecule. The distribution of hydroxyl groups as well as the topography of the surface will influence the number of bonds that can actually be formed by the reacted 3GT molecule. The structural geometric optimization indicated that anchoring by forming three bonds with the surface (Fig. 13c) requires three –OH groups very close to each other; however, this arrangement implies some physical constraints because of the three formed bonds, which will impede the stabilization of the 3GT molecule anchored in this way on the surface. On the other hand, if only a few silanol groups are present on the surface, the only possibility for anchoring the reacted 3GT molecule is by forming only one bond (Fig. 13a). However, the experimental TGA and FTIR analysis of the used nanopyroxene indicated a critical number of hydroxyl groups on its surface suggesting that there are enough hydroxyl groups to bond two of them to each methoxylated 3GT molecule; thus, based on this reasoning, the following calculations were based on the premise that each 3GT molecule bonds to two hydroxyl groups on the surface of the silica as show in Fig. 13b.


29


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 45

Fig. 13 45° perspective view showing different anchoring of a reacted 3GT molecule (ball and stick representation) over an amorphous hydroxylated silica surface (CPK representation): (a) One hydroxyl anchoring, (b) two hydroxyls anchoring and (c) three hydroxyls anchoring. Red atoms represent oxygen, grey atoms represent carbon, white atoms represent hydrogen and yellow atoms represent silicon.

As previously reported,31-33 the β-CD molecule will bond to the 3GT molecule through its – CH2-OH groups. This is particularly true since these groups are easily activated to form alkoxy groups performing the nucleophilic attack to the epoxy ring present in the 3GT molecule already anchored onto the surface of the nanopyroxene. Therefore, the calculations were carried out anchoring the β-CD molecule through the –CH2–OH groups. There are seven of these groups present in each β-CD molecule; however, it is not desirable to anchor all of them to the surface as this will impose physical and chemical constrains to the possibility of the β-CD molecule for trapping and forming inclusion complexes with small or large naphthenic acids molecules, recalling that the –COOH groups of the naphthenic acids have a better interaction with the –CH2OH groups of the β-CD molecule. Thus, the calculations were carried out anchoring the β-CD molecule through two –CH2–OH groups located in opposite sides of the β-CD molecule as shown in Fig. 14. Fig. 14a shows the top and side views of the geometrically optimized


30

Page 31 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


composite material, and Fig. 14b, illustrates the optimized composite material expanded to show how the surface will look with several anchored β-CD molecules.

Fig. 14 (a) Top and side views of the optimized composite material formed by the β-CD molecule (CPK representation) bonded to two hydrolyzed 3GT molecules (ball and stick representation) which are anchored to two hydroxyls groups onto the silica surface (CPK representation). (b) Top and side views of the expanded view of a showing several anchored βCD molecules. Red atoms represent oxygen, grey atoms represent carbon, white atoms represent hydrogen and yellow atoms represent silicon. To gain additional insights into the adsorption behaviour of naphthenic acids inside the β-CD molecule in the presence of water, molecular dynamics (MD) simulations were performed using the Forcite module within BIOVIA MS2017 software on the two model molecules. The interatomic interactions were described by using the COMPASSII force field. The MD simulations were conducted in NVT ensemble at 298 K. The Nosé method66 was employed in the thermostat to control the thermodynamic temperature with a Q ratio of 0.01. The time step in the MD simulation was set to 1.0 fs, and the data were collected every 2 ps. The simulation time was set to 2 ns to detect several cycles of thermal vibrations where the full-precision trajectory was recorded. Energies and other statistical data (coordinates, velocities, etc.) were stored every 5000


31


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 45

steps during the simulations. For the simulation, the system was defined as a periodic slab with the (100) surface. The dimensions of the surface were similar to those used in the previous Forcite calculations (i.e. 2.85 nm × 2.85 nm). The thickness of the slab was set to 2.8 nm and the three upper layers of atoms were allowed to freely evolve without any geometrical constraints during the calculations. The rest of the atoms were fixed to the geometrically optimized values in the bulk. A vacuum of 20 nm was imposed on top of the silica surface and a slab of about 6 nm containing 1500 water molecules, generated by the BIOVIA Amorphous Cell module and the COMPASII force field, was added close to the silica surface within the periodic cell and surrounding the anchored β-CD, the CP and/or T4P molecules. Three molecular dynamics simulations were carried out with the composite material SiO23GT-β-CD. The first with one CP molecule together with 1500 water molecules; the second with one T4P molecule and 1500 water molecules and the third with one CP, one T4P and 1500 water molecules. These simulations allow for a more realistic insight into the behaviour of the composite material in the presence of water and its capacity to form a complex with each molecule and to get a glimpse on what happens when there are two molecules of different sizes competing for the same site. Fig. 15 shows the total energy of the system SiO2–3GT–β–CD–CP– H2O as a function of simulation time with insets of the close-up evolution of the system with selected simulation time frames. An important drop of the total energy for the system from -29.6 Mcal/mol to about -32.3 Mcal/mol was obtained when the water molecules got distributed and some of them got adsorbed on the silica surface (approximately between 0 and 84 ps of simulation time). A second small drop of the total energy was observed when the CP molecule got closer to the β-CD (approximately between


32

Page 33 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


100 and 140 ps of simulation time). Around 160 ps of simulation time, the CP molecule entered inside the cavity of the β-CD molecule inducing some change on the conformation of the anchored β-CD molecule. It began to move closer to the silica surface while the CP molecule moved inside the cavity decreasing slowly the total energy until around 900 ps of simulation time. Finally, the system with the CP molecule inside the β-CD molecule, being closer to the silica surface, reached equilibrium maintaining the total energy around -32.8 Mcal/mol until the end of the simulation time (2000 ps). An interesting finding with the performed molecular simulation was that the –COOH groups of the CP molecule tended to be stabilized towards the side of the β-CD molecule having the 14 –OH groups indicating the importance of the presence of the water molecules to stabilize this configuration.

Fig. 15 Total energy as a function of simulation time for the system comprising the SiO2 (100) surface, 2 anchored 3GT molecules, 1 β-CD molecule, 1 CP molecule and 1500 water molecules. In the insets, the 3GT, β-CD and silica surface are represented as ball and stick, the CP is represented as CPK spheres and the water molecules are represented as sticks: grey atoms represent carbon, white atoms represent hydrogen, red atoms represent oxygen and yellow atoms represent silicon.


33


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 45

Fig. 16 shows the total energy of the system SiO2–3GT–β–CD–T4P–H2O as a function of simulation time with insets of the close-up evolution of the system with selected simulation time frames. The same occurrence with the previous case, an important drop of the total energy for the system from -29.5 Mcal/mol to about -32.1 Mcal/mol was obtained when the water molecules got distributed and some of them got adsorbed on the silica surface; however, in this case the T4P molecule also got closer to the β-CD molecule (approximately between 0 and 40 ps of simulation time). Thus, for this case, a smooth decrease in total energy was observed after this period of time until around 1000 ps of simulation time where the system entered in equilibrium maintaining the total energy around -32.7 Mcal/mol until the end of the simulation time (2000 ps). Two interesting findings were obtained in this case, and both are related to the behaviour of the T4P around the β-CD molecule. First finding has to do with the fact that the T4P molecule was attracted by the β-CD molecule, nevertheless it did not enter the cavity of the β-CD molecule. The second finding is that the interaction of the T4P molecule with the β-CD molecule was through the –COOH group but only with the hydrophilic surface of the β-CD molecule containing the 14 external –OH groups. During the entire simulation time, the T4P molecule got attracted by the β-CD molecule, which then moved around on the upper part of the cup keeping the –COOH group close to the mouth of the β-CD molecule upper part but never entered inside the cup. Water molecules inside the cup seemed to help this behaviour. Thus, the sizes and shapes of the naphthenic acids molecules do indeed impact their interaction with the anchored βCD molecule revealing the importance of the fundamental understanding of the design of the nano-trap adsorbents.


34

Page 35 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 16 Total energy as a function of simulation time for the system comprising the SiO2 (100) surface, 2 anchored 3GT molecules, 1 β-CD molecule, 1 T4P molecule and 1500 water molecules. In the insets, the 3GT, β-CD and silica surface are represented as ball and stick, the T4P is represented as CPK spheres and the water molecules are represented as sticks: grey atoms represent carbon, white atoms represent hydrogen, red atoms represent oxygen and yellow atoms represent silicon. Finally, Fig. 17 shows the total energy of the system SiO2–3GT–β–CD–CP–T4P–H2O as a function of simulation time with insets of the close-up evolution of the system with selected simulation time frames. The behaviour of the system, when the two molecules are present, was quite similar to the case of T4P alone. Specifically, with the crucial drop of the total energy for the system from -29.6 Mcal/mol to about -32.0 Mcal/mol, which was obtained when the water molecules got distributed or when some of them got adsorbed on the silica surface. However, in this case, the CP and T4P molecules also got closer to the β-CD molecule and began to interact with each other (approximately between 0 and 40 ps of simulation time). Followed by a subtle increase in the total energy, which occurred beyond 200 ps of simulation time to finally decrease at around 500 ps of simulation time. During this period of time, both molecules were departing


35


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 36 of 45

from one another where the T4P molecule tended to be closest to the β-CD upper part (the zone with the –OH groups). After this time, the CP molecule got closer to the T4P molecule that was interacting with the –OH groups of the β-CD molecule and began to form a cluster that then vibrated and moved around the β-CD upper part and the energy finally reached the equilibrium value of around -32.6 Mcal/mol. Interestingly, it seems that the bigger molecule (T4P) was more attracted to the β-CD than the smaller CP molecule, even though the CP can enter the cavity of the β-CD and the T4P cannot. The water molecules seemed to be playing a role in not allowing the CP to enter as the interaction of the T4P with the β-CD seemed to be stronger and dominated the direct interaction. The CP molecule was attracted to the complex formed by the T4P–β–CD, and then, formed part of the cluster; thus, indicating that more than one naphthenic acids molecule could be trapped by each β-CD anchored on the surface by forming a cluster around the naphthenic acids that was already forming the initial complex. To obtain finer details of the process, a video of the evolution of the system can be found in the accompanying Supporting Information.


36

Page 37 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 17 Total energy as a function of simulation time for the system comprising the SiO2 (100) surface, 2 anchored 3GT molecules, 1 β-CD molecule, 1 CP molecule, 1 T4P molecule and 1500 water molecules. In the insets, the 3GT, β-CD and silica surface are represented as ball and stick, the CP and T4P are represented as CPK spheres and the water molecules are represented as sticks: grey atoms represent carbon, white atoms represent hydrogen, red atoms represent oxygen and yellow atoms represent silicon. 4.3.The removal of organic pollutants from wastewater using GNIS

Grafted nano-AEs are a unique class of hybrid inorganic-polymeric materials that have several key characteristics, including high affinity towards polar organic compounds, high external active surface area, largely dispersible, and environmentally friendly. These characteristics form a powerful material platform with several feasible possibilities for environmental applications; specifically, wastewater treatment applications. Among the many challenges facing the oil and gas industry today is the high toxicity of wastewater that is mainly caused by the presence of naphthenic acids.67-69 The removal of naphthenic acids has been challenging due to their high solubility in the wastewater.70 The material synthesized in this study provides an ideal


37


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 38 of 45

nanoadsorbent for those toxic compounds as indicated by the molecular dynamics calculations presented previously. GC-MS was used to evaluate GNIS removal of model molecules CP and T4P previously used for the computational modeling. This was performed by calculating the total areas under the observed integrated peaks and calculating the adsorbed amount using a unitary response factor. The components present in the samples were identified using the library accompanying the instrument. Fig. 18 shows the chromatogram of the organic contaminants in the original CP and T4P model molecules synthetic wastewater solution in comparison to their amount after removal using the previously prepared GNIS nanoparticles. Fig. 18a shows a major peak of interest at retention time 4.35 min corresponding to cyclopentylcarboxylic acid (C6H10O2, MW of 114). This matches identically the model molecule used in the preparation of this sample. The removal efficiency was estimated at 98.8 % where essentially all the model molecule was removed. This was also found to be true for the second model molecule, T4P, where the peak of interest was observed at a retention time of 11.415 min (Fig 14b). The peak was identified by the structure matching tool in the software as Trans-4-pentylcyclohexanecarboxylic acid (C12H22O2, MW of198). The removal efficiency was estimated at 99.7%, where essentially all the contaminant was removed. A secondary peak was detected in Fig. 18b at retention time 10.51 min. This peak was identified by the structure match tool as Phenol,3,5-bis(1,1-dimethylethyl). As indicated in the figure, it was not fully adsorbed by the GNIS but was certainly reduced. This could be a result of the methyl and ethyl groups attached to the phenol which would indeed impact its adsorption. This phenol is possibly present in the sample as an impurity in the T4P used from Sigma (97% purity). The driving force for the formation of the β-CD complex for the two model molecules, CP and T4P, are the hydrophobic and van der Waals interactions between the inner


38

Page 39 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


cavity in the β-CD and the hydrophilic carboxylic acids sites on the guest or model molecules in this case. The hydrophobic interior of the cavity of the β-CD is 8.0 Å in diameter which allows encapsulation of up to two organic molecules (size permitting), such as CP. This formation of the inclusion complex is promoted by the hydrophobic interaction. In the case when the size of the molecule is too large to fit inside the cavity, the hydrophilic hydroxyl groups on the edge of the cup like β-CD monomer will attract the molecule forming hydrogen bonding with the carboxylic groups by clustering around the edge. An alternative scenario would be for carboxylic molecules with long alkane chains that promote their inclusion inside the cavity while the carboxyl group interacts with the OH groups on the edge. This form strong bonding in the water medium that remains stable.

Fig. 18 GC-MS of model molecules before and after adsorption with GNIS for (a) CP and (b) T4P.


39


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 40 of 45

5. Conclusions Monomer grafted nano-AE are found to be promising candidates for the removal of polar organic compounds from wastewater among other applications. This study provided synthesis experiments that yielded the grafted β-CD monomer nanoparticles and their characterization. It also provided a deep insight on the interaction between those β-CD monomers grafted nanoparticles and carboxylic standard compounds present in the water. Additionally, resulting from the computational modelling, it was found that the sizes and shapes of the model contaminants were found to be key in the formation of the inclusion complex impacting their interaction with the grafted β-CD monomer. Modifying the surface of the inorganic nanopyroxene by grafting was effective for the selective removal of organic contaminants solubilized in wastewater.

Acknowledgments We are grateful to the Natural Sciences and Engineering Research Council of Canada (NSERC). We thank Dr. Ali Darbandi for assistance with HRTEM, Fay Munro for her assistance with AFM and Brian Baillie for his assistance with calibrating the GC-MS. Supporting Information Physical and chemical properties and chemical structure of the β-CD monomer. Chemical Structure of the (3-Glycidyloxypropyl) trimethoxysilane organic-inorganic hybrid. References (1) Kaegi, R.; Voegelin, A.; Sinnet, B.; Zuleeg, S.; Hagendorfer, H.; Burkhardt, M.; Siegrist, H. Behavior of Metallic Silver Nanoparticles in a Pilot Wastewater Treatment Plant. Environmental Science & Technology 2011, 45 (9), 3902-3908, DOI: 10.1021/es1041892.


40

Page 41 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(2) Limbach, L. K.; Bereiter, R.; Müller, E.; Krebs, R.; Gälli, R.; Stark, W. J. Removal of Oxide Nanoparticles in a Model Wastewater Treatment Plant: Influence of Agglomeration and Surfactants on Clearing Efficiency. Environmental Science & Technology 2008, 42 (15), 58285833, DOI: 10.1021/es800091f. (3) Yang, Y.; Zhang, C.; Hu, Z. Impact of metallic and metal oxide nanoparticles on wastewater treatment and anaerobic digestion. Environmental Science: Processes & Impacts 2013, 15 (1), 39-48, DOI: 10.1039/C2EM30655G. (4) Brar, S. K.; Verma, M.; Tyagi, R. D.; Surampalli, R. Y. Engineered nanoparticles in wastewater and wastewater sludge – Evidence and impacts. Waste Management 2010, 30 (3), 504-520, DOI: http://dx.doi.org/10.1016/j.wasman.2009.10.012. (5) Gao, L.; Zhuang, J.; Nie, L.; Zhang, J.; Zhang, Y.; Gu, N.; Wang, T.; Feng, J.; Yang, D.; Perrett, S.; Yan, X. Intrinsic peroxidase-like activity of ferromagnetic nanoparticles. Nat Nano 2007, 2 (9), 577-583, DOI: http://www.nature.com/nnano/journal/v2/n9/suppinfo/nnano.2007.260_S1.html. (6) Pereira-Almao, P. In situ upgrading of bitumen and heavy oils via nanocatalysis. The Canadian Journal of Chemical Engineering 2012, 90 (2), 320-329, DOI: 10.1002/cjce.21646. (7) Stoyanov, S. R.; Gusarov, S.; Kuznicki, S. M.; Kovalenko, A. Theoretical Modeling of Zeolite Nanoparticle Surface Acidity for Heavy Oil Upgrading. The Journal of Physical Chemistry C 2008, 112 (17), 6794-6810, DOI: 10.1021/jp075688h. (8) Nassar, N. N.; Hassan, A.; Pereira-Almao, P. Application of Nanotechnology for Heavy Oil Upgrading: Catalytic Steam Gasification/Cracking of Asphaltenes. Energy & Fuels 2011, 25 (4), 1566-1570, DOI: 10.1021/ef2001772. (9) Hashemi, R.; Nassar, N. N.; Pereira Almao, P. Nanoparticle technology for heavy oil in-situ upgrading and recovery enhancement: Opportunities and challenges. Applied Energy 2014, 133, 374-387, DOI: http://dx.doi.org/10.1016/j.apenergy.2014.07.069. (10) Kumari, A.; Yadav, S. K.; Yadav, S. C. Biodegradable polymeric nanoparticles based drug delivery systems. Colloids and Surfaces B: Biointerfaces 2010, 75 (1), 1-18, DOI: http://dx.doi.org/10.1016/j.colsurfb.2009.09.001. (11) Hans, M. L.; Lowman, A. M. Biodegradable nanoparticles for drug delivery and targeting. Current Opinion in Solid State and Materials Science 2002, 6 (4), 319-327, DOI: http://dx.doi.org/10.1016/S1359-0286(02)00117-1. (12) LaVan, D. A.; McGuire, T.; Langer, R. Small-scale systems for in vivo drug delivery. Nat Biotech 2003, 21 (10), 1184-1191. (13) Horcajada, P.; Chalati, T.; Serre, C.; Gillet, B.; Sebrie, C.; Baati, T.; Eubank, J. F.; Heurtaux, D.; Clayette, P.; Kreuz, C.; Chang, J.-S.; Hwang, Y. K.; Marsaud, V.; Bories, P.-N.; Cynober, L.; Gil, S.; Ferey, G.; Couvreur, P.; Gref, R. Porous metal-organic-framework nanoscale carriers as a potential platform for drug delivery and imaging. Nat Mater 2010, 9 (2), 172-178, DOI: http://www.nature.com/nmat/journal/v9/n2/abs/nmat2608.html - supplementaryinformation. (14) RamanathanT; Abdala, A. A.; StankovichS; Dikin, D. A.; Herrera Alonso, M.; Piner, R. D.; Adamson, D. H.; Schniepp, H. C.; ChenX; Ruoff, R. S.; Nguyen, S. T.; Aksay, I. A.; Prud'Homme, R. K.; Brinson, L. C. Functionalized graphene sheets for polymer nanocomposites. Nat Nano 2008, 3 (6), 327-331, DOI: http://www.nature.com/nnano/journal/v3/n6/suppinfo/nnano.2008.96_S1.html. (15) Balazs, A. C.; Emrick, T.; Russell, T. P. Nanoparticle Polymer Composites: Where Two Small Worlds Meet. Science 2006, 314 (5802), 1107-1110, DOI: 10.1126/science.1130557.


41


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 42 of 45

(16) Wool, R.; Sun, X. S. Bio-Based Polymers and Composites, Elsevier Science: 2011. (17) Kamat, P. V. Meeting the Clean Energy Demand: Nanostructure Architectures for Solar Energy Conversion. The Journal of Physical Chemistry C 2007, 111 (7), 2834-2860, DOI: 10.1021/jp066952u. (18) Snow, D. G.; Brumlik, C. J. Nanoparticles for hydrogen storage, transportation, and distribution. 2003. (19) Cingarapu, S.; Singh, D.; Timofeeva, E. V.; Moravek, M. R. Nanofluids with encapsulated tin nanoparticles for advanced heat transfer and thermal energy storage. International Journal of Energy Research 2014, 38 (1), 51-59, DOI: 10.1002/er.3041. (20) Wu, S. F.; Li, Q. H.; Kim, J. N.; Yi, K. B. Properties of a Nano CaO/Al2O3 CO2 Sorbent. Industrial & Engineering Chemistry Research 2008, 47 (1), 180-184, DOI: 10.1021/ie0704748. (21) McFarland, A. D.; Van Duyne, R. P. Single Silver Nanoparticles as Real-Time Optical Sensors with Zeptomole Sensitivity. Nano Letters 2003, 3 (8), 1057-1062, DOI: 10.1021/nl034372s. (22) Hoet, P. H.; Brüske-Hohlfeld, I.; Salata, O. V. Nanoparticles–known and unknown health risks. Journal of nanobiotechnology 2004, 2 (1), 12. (23) Singh, N.; Jenkins, G. J. S.; Asadi, R.; Doak, S. H. Potential toxicity of superparamagnetic iron oxide nanoparticles (SPION). Nano Reviews 2010, 1, 10.3402/nano.v1i0.5358, DOI: 10.3402/nano.v1i0.5358. (24) Voinov, M. A.; Pagán, J. O. S.; Morrison, E.; Smirnova, T. I.; Smirnov, A. I. SurfaceMediated Production of Hydroxyl Radicals as a Mechanism of Iron Oxide Nanoparticle Biotoxicity. Journal of the American Chemical Society 2011, 133 (1), 35-41, DOI: 10.1021/ja104683w. (25) Vitale, G. Iron Silicate Nano-Crystals as Potential Catalysts or Adsorbents for Heavy Hydrocarbons Upgrading. University of Calgary, 2013. (26) Lakshmanan, R.; Sanchez-Dominguez, M.; Matutes-Aquino, J. A.; Wennmalm, S.; Kuttuva Rajarao, G. Removal of Total Organic Carbon from Sewage Wastewater Using Poly(ethylenimine)-Functionalized Magnetic Nanoparticles. Langmuir 2014, 30 (4), 1036-1044, DOI: 10.1021/la404076n. (27) Hong, S.; Leroueil, P. R.; Janus, E. K.; Peters, J. L.; Kober, M.-M.; Islam, M. T.; Orr, B. G.; Baker, J. R.; Banaszak Holl, M. M. Interaction of Polycationic Polymers with Supported Lipid Bilayers and Cells: Nanoscale Hole Formation and Enhanced Membrane Permeability. Bioconjugate Chemistry 2006, 17 (3), 728-734, DOI: 10.1021/bc060077y. (28) Cheng, J.; Khin, K. T.; Jensen, G. S.; Liu, A.; Davis, M. E. Synthesis of linear, betacyclodextrin-based polymers and their camptothecin conjugates. Bioconjug Chem 2003, 14 (5), 1007-1024, DOI: 10.1021/bc0340924. (29) Uekama, K.; Hirayama, F.; Irie, T. Cyclodextrin Drug Carrier Systems. Chemical Reviews 1998, 98 (5), 2045-2076, DOI: 10.1021/cr970025p. (30) Jacobsen, P. A.; Nielsen, J. L.; Juhl, M. V.; Theilgaard, N.; Larsen, K. L. Grafting cyclodextrins to calcium phosphate ceramics for biomedical applications. Journal of Inclusion Phenomena and Macrocyclic Chemistry 2012, 72 (1-2), 173-181. (31) Lv, Y.; Mei, D.; Pan, X.; Tan, T. Preparation of novel β-cyclodextrin functionalized monolith and its application in chiral separation. Journal of Chromatography B 2010, 878 (26), 2461-2464, DOI: http://dx.doi.org/10.1016/j.jchromb.2010.07.020. (32) Armstrong, D. W. Bonded phase material for chromatographic separations. 1985.


42

Page 43 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(33) Ponchel, A.; Abramson, S.; Quartararo, J.; Bormann, D.; Barbaux, Y.; Monflier, E. Cyclodextrin silica-based materials: advanced characterizations and study of their complexing behavior by diffuse reflectance UV–Vis spectroscopy. Microporous and Mesoporous Materials 2004, 75 (3), 261-272, DOI: http://dx.doi.org/10.1016/j.micromeso.2004.07.005. (34) Yu, J.-G.; Huang, K.-L.; Liu, S.-Q.; Tang, J.-C. Preparation and characterization of soluble methyl-β-cyclodextrin functionalized single-walled carbon nanotubes. Physica E: Lowdimensional Systems and Nanostructures 2008, 40 (3), 689-692, DOI: http://dx.doi.org/10.1016/j.physe.2007.09.082. (35) Microsystems, L. EM Sample Preparation Contrasting. https://www.leicamicrosystems.com/fileadmin/academy/2013/Contrasting_final.pdf. (36) Zhao, L.; Liu, L.; Sun, H. Semi-ionic Model for Metal Oxides and Their Interfaces with Organic Molecules. The Journal of Physical Chemistry C 2007, 111 (28), 10610-10617, DOI: 10.1021/jp071775y. (37) Makreski, P.; Jovanovski, G.; Gajović, A.; Biljan, T.; Angelovski, D.; Jaćimović, R. Minerals from Macedonia. XVI. Vibrational spectra of some common appearing pyroxenes and pyroxenoids. Journal of Molecular Structure 2006, 788 (1), 102-114. (38) Almeida, R. M. Comment on "Infrared-reflectance spectra of heat-treated, sol-gel-derived silica". Physical Review B 1996, 53 (21), 14656-14658. (39) Comins, D. L.; O’Connor, S.; Al-awar, R. S. 7.02 - Pyridines and their Benzo Derivatives: Reactivity at the Ring A2 - Katritzky, Alan R. In Comprehensive Heterocyclic Chemistry III; Ramsden, C. A.; Scriven, E. F. V.; Taylor, R. J. K., Eds.; Elsevier: Oxford, 2008; p 99. (40) Grasselli, J. G.; Ritchey, W. M. Atlas of spectral data and physical constants for organic compounds, CRC Press: 1975. (41) Innocenzi, P.; Brusatin, G.; Guglielmi, M.; Bertani, R. New Synthetic Route to (3Glycidoxypropyl)trimethoxysilane-Based Hybrid Organic−Inorganic Materials. Chemistry of Materials 1999, 11 (7), 1672-1679, DOI: 10.1021/cm980734z. (42) Murad, E. Mineralogy of aegirine from Laven Island, Langesundfjorden, southern Norway. NORSK GEOLOGISK TIDSSKRIFT 2006, 86 (4), 435. (43) Marei, N. N.; Nassar, N. N.; Vitale, G. The effect of the nanosize on surface properties of NiO nanoparticles for the adsorption of Quinolin-65. Physical Chemistry Chemical Physics 2016, 18 (9), 6839-6849, DOI: 10.1039/C6CP00001K. (44) Ishida, H. Controlled interphases in glass fiber and particulate reinforced polymers: Structure of silane coupling agents in solutions and on substrates. In The interfacial interactions in polymeric composites; Springer: 1993; pp 169-199. (45) Lees, I. N.; Lin, H.; Canaria, C. A.; Gurtner, C.; Sailor, M. J.; Miskelly, G. M. Chemical Stability of Porous Silicon Surfaces Electrochemically Modified with Functional Alkyl Species. Langmuir 2003, 19 (23), 9812-9817, DOI: 10.1021/la035197y. (46) Guo, C.; Liu, H.; Wang, J.; Chen, J. Conformational Structure of Triblock Copolymers by FT-Raman and FTIR Spectroscopy. Journal of Colloid and Interface Science 1999, 209 (2), 368373, DOI: http://dx.doi.org/10.1006/jcis.1998.5897. (47) Hmoudah, M.; Nassar, N. N.; Vitale, G.; El-Qanni, A. Effect of nanosized and surfacestructural-modified nano-pyroxene on adsorption of violanthrone-79. RSC Advances 2016, 6 (69), 64482-64493, DOI: 10.1039/C6RA05838H. (48) Winters, C. S.; York, P.; Timmins, P. Solid state examination of a gliclazide:betacyclodextrin complex. European Journal of Pharmaceutical Sciences 1997, 5 (4), 209-214, DOI: http://dx.doi.org/10.1016/S0928-0987(97)00275-3.


43


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 44 of 45

(49) Nassar, N. N.; Hassan, A.; Vitale, G. Comparing kinetics and mechanism of adsorption and thermo-oxidative decomposition of Athabasca asphaltenes onto TiO2, ZrO2, and CeO2 nanoparticles. Applied Catalysis A: General 2014, 484, 161-171, DOI: http://dx.doi.org/10.1016/j.apcata.2014.07.017. (50) Decarreau, A.; Petit, S.; Vieillard, P.; Dabert, N. Hydrothermal synthesis of aegirine at 200 C. European Journal of Mineralogy 2004, 16 (1), 85-90. (51) Saedy, S.; Haghighi, M.; Amirkhosrow, M. Hydrothermal synthesis and physicochemical characterization of CuO/ZnO/Al2O3 nanopowder. Part I: Effect of crystallization time. Particuology 2012, 10 (6), 729-736, DOI: http://dx.doi.org/10.1016/j.partic.2012.05.001. (52) Thommes, M.; Kaneko, K.; Neimark, A. V.; Olivier, J. P.; Rodriguez-Reinoso, F.; Rouquerol, J.; Sing, K. S. W. Physisorption of gases, with special reference to the evaluation of surface area and pore size distribution (IUPAC Technical Report). Pure Appl Chem 2015, 87 (910), 1051-1069, DOI: 10.1515/pac-2014-1117. (53) Magonov, S. N.; Elings, V.; Whangbo, M. H. Phase imaging and stiffness in tapping-mode atomic force microscopy. Surface Science 1997, 375 (2), L385-L391, DOI: http://dx.doi.org/10.1016/S0039-6028(96)01591-9. (54) Binnig, G.; Frank, K. H.; Fuchs, H.; Garcia, N.; Reihl, B.; Rohrer, H.; Salvan, F.; Williams, A. R. Tunneling Spectroscopy and Inverse Photoemission: Image and Field States. Physical Review Letters 1985, 55 (9), 991-994. (55) Malekian, M.; Park, S. S.; Strathearn, D.; Md, G. M.; Jun, M. B. G. Atomic force microscope probe-based nanometric scribing. Journal of Micromechanics and Microengineering 2010, 20 (11), 115016. (56) Muñoz-Botella, S.; Martin, M. A.; del Castillo, B.; Vázquez, L. Differentiating inclusion complexes from host molecules by tapping-mode atomic force microscopy. Biophysical Journal 1996, 71 (1), 86-90. (57) JPK Data Processing Version SPM-5.0.96, J. I. A., Home page: http://jpk.com/, Berlin, Germany. Accessed 22 March, 2017. JPK Data Processing Version SPM-5.0.96, JPK Instruments AG, Home page: http://jpk.com/, Berlin, Germany. Accessed 22 March, 2017., 2015. (58) Cameron, M.; Sueno, S.; Prewitt, C. T.; Papike, J. J. High-Temperature Grystal Ghemistry of Acmite, Diopside, Hedenbergite, Jadeite, Spodumene, and Ureyite. American Mineralogist 1973, 58, 594-618. (59) Li, D.-X.; Chen, C.-L.; Liu, B.-L.; Liu, Y.-S. Molecular simulation of β-cyclodextrin inclusion complex with 2-phenylethyl alcohol. Molecular Simulation 2009, 35 (3), 199-204, DOI: 10.1080/08927020802419334. (60) Gerloczy, A.; Fonagy, A.; Szejtli, J. Reduction of Residual Toluene Content in beta‐ Cyclodextrin through Preparing Inclusion Complexes. Starch‐Stärke 1983, 35 (9), 320-322. (61) Roik, N.; Belyakova, L. IR spectroscopy, X-ray diffraction and thermal analysis studies of solid “β-cyclodextrin—para-aminobenzoic acid” inclusion complex. Phys. Chem. Solid State 2011, 12, 168-173. (62) Salvatierra, D.; Jaime, C.; Virgili, A.; Sánchez-Ferrando, F. Determination of the inclusion geometry for the β-cyclodextrin/benzoic acid complex by NMR and molecular modeling. The Journal of Organic Chemistry 1996, 61 (26), 9578-9581. (63) Pop, M. M.; Goubitz, K.; Borodi, G.; Bogdan, M.; De Ridder, D. J.; Peschar, R.; Schenk, H. Crystal structure of the inclusion complex of β-cyclodextrin with mefenamic acid from highresolution synchrotron powder-diffraction data in combination with molecular-mechanics calculations. Acta Crystallographica Section B: Structural Science 2002, 58 (6), 1036-1043.


44

Page 45 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(64) Hamilton, J. A.; Chen, L. Crystal structure of an inclusion complex of. beta.-cyclodextrin with racemic fenoprofen: direct evidence for chiral recognition. Journal of the American Chemical Society 1988, 110 (17), 5833-5841. (65) Aree, T.; Chaichit, N.; Engkakul, C. Polymorphism in β-cyclodextrin–benzoic acid inclusion complex: a kinetically controlled crystal growth according to the Ostwald’s rule. Carbohydrate research 2008, 343 (14), 2451-2458. (66) Nosé, S. A unified formulation of the constant temperature molecular dynamics methods. The Journal of chemical physics 1984, 81 (1), 511-519. (67) Mohseni, P.; Hahn, N. A.; Frank, R. A.; Hewitt, L. M.; Hajibabaei, M.; Van Der Kraak, G. Naphthenic Acid Mixtures from Oil Sands Process-Affected Water Enhance Differentiation of Mouse Embryonic Stem Cells and Affect Development of the Heart. Environmental Science & Technology 2015, 49 (16), 10165-10172, DOI: 10.1021/acs.est.5b02267. (68) Leung, S. S.; MacKinnon, M. D.; Smith, R. E. The ecological effects of naphthenic acids and salts on phytoplankton from the Athabasca oil sands region. Aquatic toxicology (Amsterdam, Netherlands) 2003, 62 (1), 11-26. (69) Headley, J. V.; Peru, K. M.; Barrow, M. P. Advances in mass spectrometric characterization of naphthenic acids fraction compounds in oil sands environmental samples and crude oil—A review. Mass Spectrometry Reviews 2016, 35 (2), 311-328, DOI: 10.1002/mas.21472. (70) Quagraine, E. K.; Peterson, H. G.; Headley, J. V. In situ bioremediation of naphthenic acids contaminated tailing pond waters in the athabasca oil sands region--demonstrated field studies and plausible options: a review. Journal of environmental science and health. Part A, Toxic/hazardous substances & environmental engineering 2005, 40 (3), 685-722. TOC:


45

Nanopyroxene Grafting with Î²-Cyclodextrin Monomer for Wastewater

Recommend Documents