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Cite This: ACS Sustainable Chem. Eng. 2017, 5, 10826-10839

Selective, Photoenhanced Trapping/Detrapping of Arsenate Anions Using Mesoporous Blobfish Head TiO2 Monoliths H. Gomaa,† H. Khalifa,† M. M. Selim,‡ M. A. Shenashen,† S. Kawada,† A. S. Alamoudi,§ A. M. Azzam,† A. A. Alhamid,∥,⊥ and S. A. El-Safty*,†

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National Institute for Materials Science (NIMS), Research Center for Functional Materials, 1-2-1 Sengen, Tsukuba-shi, Ibaraki-ken 305-0047, Japan ‡ Department of Mathematics, Al-Aflaj College of Science and Human Studies, Prince Sattam Bin Abdulaziz University, Al-Aflaj 710-11912, Saudi Arabia § Desalination Technologies Research Institute (DTRI), P.O. Box 8328, Al-Jubail 31951, Saudi Arabia ∥ Prince Sattam Bin Abdulaziz University, P.O. Box 173, Al-Kharj 11942, Saudi Arabia ⊥ Civil Engineering Department, College of Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia S Supporting Information *

ABSTRACT: The efficient and low-cost adsorption of arsenic toxins from drinking water is a global concern because of its adverse health effects. The simple extraction and eco-friendly environmental waste management of arsenic(V) species using hierarchy rutile TiO2 were reported. Mesoporous microscale TiO2 sphere 3D monoliths were successfully fabricated with uniform mesopores morphology-like blobfish head containing open nanoscale eyes through hydrothermal one-pot synthesis. The blobfish head TiO2 (BHT) was mainly oriented along the predominant {110} facet and with dense top-surface atomic Ti4+ and O2− sites along the crystal edge surface and central crystals. These characteristics lead to efficient adsorption and selective binding to As(V) species in acidic medium. The photoinduced irradiation of the BHT adsorbent promoted significant trapping and high adsorptivity, with a maximum capacity reaching 125 mg/g from drinking water. The BHT adsorbent selectively binds As(V) species among competitive anions, such as chlorides, bicarbonates, and sulfates, as well as cations, such as Ca2+, Mg2+, Co2+, Al3+, Ni2+, Cd2+, Mn2+, and Fe3+cations, in real samples. Results indicated that the BHT hierarchy can be cycled several times without deteriorating in its significant performances despite the severe treatment under irradiation or chemical treatment agents. The BHT monoliths might be an effective photoadsorbent for final disposals, particularly at low levels of As(V) species in real water sources. KEYWORDS: Blobfish head, Mesoporous, Rutile TiO2 monolith, BHT, As(V) species, Selectivity, Real applicability and recyclability

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INTRODUCTION Water is essential to our lives. Hence, water contamination caused by organic and inorganic pollutants has currently become a serious global environmental issue and received significant attention.1 As an inorganic pollutant, arsenic is considered as a highly hazardous pollutant because of its high toxicity and serious health effects. The arsenic oxyanion forms included arsenite (AsIII) species (H3AsO3, H2AsO3−, HAsO32−, and AsO33−) and arsenate (AsV) species (H3AsO4, H2AsO4−, HAsO42−, and AsO43−) are existed in solution, depending on the media pH.1−3Arsenic species may be released to the environment through natural sources, such as weathering reactions, biological activities, geochemical reactions, and volcanic emissions. Arsenic may also be released through anthropogenic sources, such as industrial activities and the use of pesticides, herbicides, and fertilizers.4,5 The World Health © 2017 American Chemical Society

Organization determined the permissible level of arsenic in drinking water; arsenic levels must not exceed 10 ppb (10 μg/ L).6 Millions of people in many countries such as Bangladesh, Vietnam, Nepal, India, Ghana, Argentina, Mexico, and China suffer from arsenic contamination problem in water.6 The ingestion of large amounts of arsenic leads to some health problems, including growth imbalance, lung ailments, and nerve damage. This environmental problem aggravates over a relatively short period and may cause injury of cancer, and sometimes death.7−10 Ultratraces of arsenic content can be determined using different analytical techniques, including electrothermal atomic Received: August 11, 2017 Revised: September 9, 2017 Published: September 28, 2017 10826

DOI: 10.1021/acssuschemeng.7b02766 ACS Sustainable Chem. Eng. 2017, 5, 10826−10839

Research Article

ACS Sustainable Chemistry & Engineering

electrons to prevent the reversible reaction for a long time and involve the recombination of e− with h+, which are considered wholesome to photoadsorption/desorption processes under UV irradiation.50 The charge transfer along the inner and exterior surfaces of adsorbents may facilitate the photoadsorption/releasing of the captured targets under a longtime of exposure to UV irradiation, leading to create a surfacefree adsorbent. In this study, a simple fabrication of monolithic hierarchal mesoporous rutile TiO2 blobfish-like head morphology was investigated and featured actively interior/exterior surface along {110} crystal facets for the adsorption and photoadsorption of As(V) species. In addition, results showed that BHT with a 3D smooth surface, nanoscale open-hole-eye grooves, uniformly sized mesopore-like windows of TiO2 framework structures are key components in effectively capturing/trapping As(V) species among other competitive ions at pH 3.The study results indicated that the trapping process is pH dependent, and the adsorption capacity was enhanced under the irradiated conditions compared with the nonirradiated process, where the adsorption capacity increased from 105 to 125 mg/g. Moreover, the BHT photoadsorbent exhibited a high adsorption capacitance toward As(V) species removal from real environmental samples. In addition, the result indicates the possibility of adsorbent regeneration for more than 20 times without a clear change in the trapping efficiency from the water.

absorption spectrometry, graphite furnace atomic absorption, atomic absorption spectroscopy, atomic fluorescence, induced coupled plasma-mass spectroscopy (ICP-MS), and highperformance liquid chromatography.11−17 Recently, intensive efforts have been exerted to remove, detect, and extract As(V) species from contaminated water through various techniques. The strategies applied include coagulation and flocculation, reverse osmosis, chemical precipitation, ion exchange, membrane filtration, and adsorption.18−24Although these techniques presented somewhat high efficiency, some limitations exist in terms of high cost, practically complex, and low efficiency. The challenge to overcome the deficiencies of the As species removal persists. Meanwhile, the adsorption technique has attracted considerable attention as an effective technique in water treatment and waste management fields because of its practicality, simplicity, low cost, life applicability, and ecofriendliness.25,26 In this context, a wide range of adsorbents have been used to remove the As species, including zerovalent iron, activated alumina, sand, silica ceramics, carbon and its modified materials, and metal oxides.27−31 For removing anionic As species pollutants from contaminated water, metal oxides received special attention because of their distinctive characteristics, such as high removal capacity and nontoxicity, long-term stability, and low cost.32,33 Metal oxides also can be used as photoadsorbent materials because of their high optical activity and electronic properties.34 One of the most important features of adsorbent materials is the materials recyclability, in which the adsorbent can be effectively worked against subsequent reuse/cycles. The geometrical structure stability, matrix composition domains and retention of the morphological shape without agglomeration are key components for the function of materials recyclability. In such reversibility process, a simple regeneration treatment of reused adsorbents may lead to (i) control hazardous waste management, and (ii) reduce the waste volume of used solid adsorbent.35−37 The multiple reuse/cycles of the adsorbents lead to decrease the overall cost of water purification system. Aside of this functionality, the recyclability process of adsorbents is beneficial in the extraction/recovery of precious and rare elements in ore samples. However, the ability to effectively release of the target elements from the modified adsorbent surfaces enabled selective collection/recovery of metals from sources.38−40 Several methodologies can be applied to regenerate of adsorbent functionality or to recover of adsorbed species such as chemical releasing, ultrasonic desorption, ion-exchange desorption, and photoreleasing. With all of these methods, decomplexation agents were applied to release the target ions from solid surfaces into the contacteffluent solution and to produce target-free solid adsorbents.41,42 Among the metal oxides, titanium dioxide (TiO2) greatly considers the field of photoadsorbent applications because of the massive band gap energy and high generation rate of electron−hole pairs.43−45 The efficiency of photoadsorbent TiO2 in water treatment depends on morphological structures of adsorbent, active surface sites that exposed to UV irradiation, and pH solution.46−49 The mesoporosity and high surface coverages of TiO2 may enhance the surface ability to captured/ separated ultratrace amounts of As pollutants.46 Furthermore, the existing band position and the transport mobility of charge carriers, including photoexcited holes (h+) and electrons (e−), increase the photoreactions and photoadsorption. This charge transfer step would accelerate the consumption of photo-

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EXPERIMENTAL SECTION

Fabrication Procedures of Mesoporous BHT Adsorbent. BHT was successfully fabricated by adding of titanium isopropoxide (TIP) dropwise to a solution of 40 mL of HCl (1 mol/L) under gentle stirring for 6 h. Stirring was continued until the TIP was completely dissolved and a homogeneous solution was obtained. Then, 3 mL of hydrogen peroxide (H2O2, 30%) was added dropwise to the homogeneous solution with continuous stirring for 2 h. The mixture was transferred to a Teflon-lined stainless steel autoclave and heated at 170 °C for 12 h with ramping 5 °C/min. After cooling to room temperature, the resultant white precipitate collected centrifugally at 4000 rpm then washed through Milli-Q water several times to remove soluble impurities. Then, the white precipitate was dried at 60 °C in an oven overnight. The as-synthesized TiO2 powder was calcined at 470 °C (ramping, 2 °C/min) in an air atmosphere for 6 h in order to obtain the crystalline BHT monoliths. Nonirradiated and Irradiated Adsorption of As(V) Species Procedure. Before conducting each experiment, the glassware was cleaned with 1% HNO3 then Milli-Q water. This step is important for disposing of chemical and microbial impurities. In addition, each experiment was repeated many times to reduce the error percentage. In 50 mL Erlenmeyer flasks, different concentrations of standard As(V) solution were prepared immediately before use and stored at room temperature (25 ± 2 °C). In experimental studies, the standard feed solution of As(V) ion was prepared using Na3AsO4·7H2O salt. In a typical adsorption experiment, 20 mg of freshly papered BHT was brought in contact with 40 mL of As(V) species solution. The adsorption capacity qe (mg/g) of As(V) species was calculated using qe = (Co − Ce)V/m equation, where Co and Ce are the initial concentrations of the feed As(V) solution and As(V) concentration at equilibrium (mg/L), respectively; V is the volume of the As(V) solution (L), and m is the amount of BHT adsorbent (g). The efficiency of As(V) uptake was investigated as a function of pH, stirring time, adsorbent dose, and temperature in accordance with the equation of uptake % = {(Co − Ce)/Co} × 100. In a closed/dark system, a UV lamp (SLUV-6) reactor at wavelength λmax = 365 nm was positioned at 15.5 cm above the top of the reaction vessel. ICP-MS was used to measure the total amount of As(V) species in the solution before and after contact. In the same method and optimum conditions, the effect of coexisting anions and cations with As(V) species were 10827


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Scheme 1. (A−D) Mechanism Formation of BHT, which Indicate Formation of Oxy-Bridge-like TiOO• and Ti−OOH• Species and then to −Ti−O−Ti−O− as Stable Form after Calcination

crystalline form of −Ti−O−Ti−O− (Scheme 1B,C, Scheme S1).51,52 The surface functionality, mobility, and active surface charge formation of the OH• radical play key roles in (i) the fast kinetic condensation of {Ti(OH)4} complexes and (ii) in the stable growth of homogeneously aggregated particles with spherical-like blobfish heads. The monodispersed blobfish head spheres may form due to the stable electrostatic interaction between the positively charged Ti4+ species and the negatively charged OH− anion surface species. This formation leads to the possible control of the production of hierarchical micrometric blobfish sphere-head monoliths. The formation of microspherical blobfish head monoliths with 3D smooth surfaces, nanoscale open-hole-eye grooves, and uniformly sized mesopore-like windows of the BHT framework structures leads to the key broadening of the photoinduced functionality of BHT adsorbents for the selective capture/trapping of As(V) species (Scheme 1D). To investigate the architectural features and morphology of BHT, we studied the calcined TiO2 by FESEM. The representative micrographs are displayed in Figure 1A,B. The FESEM graphs clearly demonstrated and depicted uniform 3D spherical architectures of TiO2. These architectures included the blobfish head morphology with a uniform average particle size of approximately 2.0 μm in diameter, as well as some holes, which indicated hollowness (Figure 1A). The top view of the FESEM image (Figure 1B) reveals that these hierarchal microspheres were composed of two open nanoscale eyes with clear blobfish heads. The size of these nanoeyes was approximately several tens of nanometers, and numerous small pores were observed. The formation of nanoscale open-eye-like pores may be attributed to the generation of protrusions along the octahedral TiO2 clusters that formed throughout the entire length of the cross-linkage microsphere surface components

tested in varying concentrations. To use the BHT adsorbent in removing As(V) species as many times as possible, we recovered the captured As(V) species by UV light for photorelease or by NaOH eluent agent for chemical release. Characterization Instruments of Mesoporous BHT Monoliths. Shape and surface topology of BHT were studied using field emission scanning electron microscopy (FESEM, JEOL Model 6500) at 20 kV. The morphologies and particle diameters of BHT were determined by high-resolution transmission electron microscopy (HRTEM, JEOL 2100F Japan) at 200 kV. Scanning TEM-energy dispersive X-ray spectroscopy (STEM-EDS) characterization was carried out using a JEOL JEM model 2100F microscope. Wide-angle powder X-ray diffraction (WA-XRD) was applied using an 18 kW diffractometer (Bruker D8 Advance) to investigate the phase and crystal structure of rutile TiO2. The porous structure and specific surface area of the samples were measured by N2 adsorption− desorption isotherms at 77 K using a BELSORP36 analyzer (JP. BEL Co., Ltd.). The As(V) concentration was determined by using inductively coupled plasma mass spectrometry ICP-MS (PerkinElmer, Elan-6000). The surface charge of BHT adsorbent was detected using dynamic light scattering (Photal, ELSZ-1000, Otsuka electronics, Japan).

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RESULT AND DISCUSSION Control Structural Formation and Characterization of BHT. BHT was fabricated by a simple, one-pot hydrothermal process and surfactant-free method, in which the hydrolysis of the TIP to Ti(OH)4 occurred using acidic catalysts (i.e., HCl) under hydrothermal treatments at 170 °C for 12 h. The synthetic design of the 3D BHT provides an adequate and stable fabrication process with structural features as shown in Scheme 1. Adding an H2O2 agent generates a reactive surface dressing with OH• and HO2• species that may react with Ti4+ ions to form titanium(IV) oxy-bridge-like TiOO• and Ti− OOH species. Then, the sample is calcined to produce a stable 10828


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Figure 1. (A and B) Representative FE-SEM and (C) STEM micrographs of microsphere TiO2 adsorbent with clearly blobfish head containing open nanoscale eyes as shown in the real image of blobfish image (middle). (D and E) STEM-EDS mapping shows the elemental composition of oxygen and titanium with the corresponding percentage of each element. F and G HR-TEM and corresponding EDS images of BHT adsorbent indicated the formation of crystalline structures.

transitions as set out in the Figure 2A−D. Results show the dense arrangement and homogeneous distribution of central Ti4+ (green balls) and O2− (red balls) atomic sites along the binding active plane {110} facet. These properties lead to the stability of the charge or electron transfer process during the AsV-to-TiO2 surface interaction. This phenomenon indicates the specific activity of the BHT microsphere in adsorption/ capturing/trapping the target As(V) species. The phase and crystal structure of the final products of BHT were investigated by WA-XRD technique. The BHT was prepared by the hydrothermal process at 170 °C for 12 h and calcined at 470 °C for 6 h. The XRD profiles clearly revealed intense diffraction peaks at approximately 27.2° and 36.11° of 2θ (Figure 3A), which can be assigned as the (110) and (101) planes, respectively. These diffraction peaks could be well indexed to the rutile phase of TiO2 as indicated by the Joint Committee on Powder Diffraction Standards reference {JCPDS: 21-1276}. Three slightly strong peaks around 41.31°, 54.21°, and 63.01° of 2θ correspond to the (111), (211), and (002) reflections, respectively. The broad peaks around 68.99° and 69.73° indicated the (301) and (112) reflections. Moreover, four weak peaks at 39.11°, 43.61°, 56.31°, and 76.71° of 2θ were observed, which mostly resulted from the (200), (210), (220), and (202) reflections, respectively. All diffraction peaks of the as-prepared product were assigned to pure rutile TiO2 phase. This result indicates

during the polycondensation process (Scheme 1). The synthesis protocol offers reproducible and versatile access to microscale rutile particles with good control of the resultant physical properties (structure and morphology) of the BHT adsorbent. The morphology and structure of the 3D BHT microspheres with considerable dispersion and without agglomerations were further confirmed in detail by HR-TEM analyses. HR-TEM analysis was conducted to display the constructed individual mesoporous BHT microspheres. As shown in Figure 1C, the edge image of the blobfish head TiO2 samples clearly reveals that BHT was a microsphere anchored by nanoeyes. This result closely agrees with the FESEM analyses. In Figure 1D,E, the STEM-EDS mapping of the TiO2 photoadsorbent exhibited the presence of oxygen and titanium, which indicate uniform distributions of 42.17% O and 57.27% Ti atoms. The uniform pore sizes of BHT are clearly visible in Figure 1F, and the selected area of distinctive electron diffraction (SAED) patterns (110), (101), (211), and (002) can be readily matched with all planes of the single-crystalline BHT type (Figure 1G). In brief, the HR-TEM image and the SAED pattern indeed confirm the highly crystalline nature of the BHT and are consistent with the X-ray diffraction (XRD) results. Density functional theory (DFT) calculations were used to understand the electronic structure of BHT through theoretical modeling, surface electron distribution, and the nature of the electronic 10829


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Figure 2. DFT calculations of BHT structures. (A) Tetragonal prismshaped structures oriented in a long-range polyhedral surface as chainlike structures of edge sharing TiO62− octahedral shapes. (B) The cell unit of BHT showed two octahedrally distorted TiO62− sharing edges that running parallel to c-direction, as shown in atomic building modeling. (C) The simple crystal units with 5- or 6-fold coordinated Ti-atom arrangement of rutile blobfish that mainly oriented along predominant {110} facet. (D) top-surface atomic Ti4+ and O2− sites with high densely electronic clouds along the crystal edge surface and central crystal of BHT.

that the as-resulted samples possessed a highly pure rutile phase. The calculated cell parameters were as follows. a = 4.594 Å and c = 2.959 Å, which are in good agreement with the JCPDS 21-1276 values (a = 4.5937 Å; c = 2.9587 Å). The average grain size of the nanocrystals was calculated on the basis of the widths of the major diffraction peak (2θ= 27.2°) (along the (110) plane) using the Scherrer formula t = 0.91λ/ (B cos θ), where t is the crystallite size, λ is the incident radiation wavelength, θ is the Bragg angle, and B is the fullwidth at half-maximum of the diffraction peak. Calculations showed that large crystallite TiO2 particles were fabricated at a size of approximately 13 nm. This finding indicates the successful fabrication of TiO2 in rutile structures. Overall, the control design of BHT structures shows (i) the anisotropic formation of the microsphere BHT hierarchy, (ii) a high degree of spherical surface uniformity of blobfish heads, (iii) defect “protrusion” during the condensation process that led to the formation of open-eye holes, and (iv) the homogeneous dispersion of nanoscale voids across the surfaces of the BHT hierarchy. The characteristics of the hierarchical BHT uniformity might create a potential accessibility of As(V) species into the interior/exterior active sites. Multifunctional holes along surfaces significantly enable light-induced windows for fast electron surface movements during the UV irradiation of the BHT hierarchy. The N2 adsorption/desorption isotherms show evidence of the fabrication of meso-cage structures of BHT monoliths. The N2 isotherm shows explicit hysteresis loop and sharp inflection of adsorption/desorption curves at relative partial pressure 0.48 ≤ P/Po≤ 0.8 (where P and Po are measured and initial pressure at a given pore size), which corresponded to type IV of

Figure 3. (A) WAXRD patterns of BHT adsorbent. All the diffraction peaks can be indexed to TiO2 rutile phase with high-intense (110) diffraction plane before (a) and after reuse cycles of adsorption of arsenic As(V) anions (b). The calculated cell parameters: a = 4.594 Å and c = 2.959 Å are in good agreement with the reference values (JCPDS 21-1276, a tetragonal crystal system with a = 4.593 Å and c = 2.959 Å of the space group of P42/mnm). (B) N2 adsorption− desorption isotherms of BHT adsorbent indicated the formation of BHT in meso-cage structures. (C) NLDFT pore size distribution profile of BHT adsorbent before (a) and after reuse cycles of adsorption of arsenic As(V) anions (b).

mesopore sorption behavior (Figure 3B). The steepness of the isotherms is well-defined, indicating the formation of large and uniform meso-cage structures, as reported previously.53−55 Figure 3B offers that the 3D cage architecture involves a high surface area with SBET 52.239 m2/g, and pore volume (Vp) 0.37 cm3/g according to Brunauer−Emmett−Teller (BET) theory. Figure 3C shows the nonlocal density functional theory (NLDFT) of pore size distribution, the strong peak at 18.6 nm refers to the high uniformity of BHT pore size. The N2 isotherms show evidence of the stability of the blobfish structure after the arsenate species capture reuse cycling. The decrease in the surface features (Figures 3B,C) with the maintained TiO2 structural crystallinity and morphology (Figure 3A) after the reuse cycles of the adsorption/desorption of the As(V) species indicates the following findings: (i) Adsorption of a large amounts of arsenate species into the interior the meso-caves of BHT adsorbent. 10830


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ACS Sustainable Chemistry & Engineering Scheme 2. Photoadsorption Reaction of Adsorbed As(V) Species onto BHT Surfacesa

a

(A, B, and C) electrostatic potential mapping and electron density surfaces that indicate the As(V) anion-to-TiO2 surface binding and the preferable anion configurations around top-surface atomic Ti4+ and O2− sites in dense-electron top-layer crystal surfaces. (B) photoinduced releasing of As(V) species. (C) Mechanism formation of actively-positive TiOOH in aqueous solution under UV irradiation. In addition, the interaction between the TiOOH and As(V) anion species at pH 3 during the adsorption process.

solution (Figure 4A). Meanwhile, the efficiency of As(V) species removal tended to decrease with increasing pH because of the formation of As(V) oxyanion species in solution and the partially negative charge of BHT surfaces. In this pH range, oxyanions are more plentiful on the adsorbent surface. This high oxyanion content results in the electrostatic repulsion between a negative sorbent surface TiO− and anionic assist, as evidenced by ζ-potential analysis (Figure 4B).62−66 Figure 4B exhibits that top-peak of positive charge takes place at pH 3 and then decreases to negative values with rising of pH value as a result of formation of TiO− active sites. Meanwhile, conducting similar experimental conditions under UV irradiation (λmax = 365 nm) may enhance the removal and uptake amount of As(V) species by BHT adsorbent ≫99.8%. The reinforcement of adsorption efficiency was due to the formation of an electron e−CB (conduction band) and hole h+VB (valence band) pair caused by the generated photons from UV light. These photons may have energy that may be equal or higher than that of band gap energy of BHT adsorbent. The formation of h+VB holes leads to increase the positively charged active sites along the BHT adsorbent surfaces, indicating the enhancement of BHTto-AsV binding. The effect of BHT adsorbent dose on the adsorption efficiency of As(V) species was investigated under optimum pH conditions by using different doses of BHT adsorbent (2.5 to 50 mg). The illustrated data in Figure 4C refer to the increasing adsorption of As(V) species as the adsorbent doses increase until 20 mg at 96.5%. After that, the arsenic adsorption efficiencies were increased slightly with growing adsorbent amounts. This increase explains that the adsorption capacity of BHT adsorbent depends on the amount of coverage surface active sites. Under UV light, the efficiency of As(V) species removal was enhanced to more than 99.9% because of the formation of additional positively active sites. A series of batchcontact-time experiments were performed to study the effect of

(ii) The mobility, mass transport and diffusion of As(V) species into the hole windows associated with the surface matrices of BHT monoliths. (iii) The retention of the structural integrity in terms of rutile TiO2 crystals, monolithic frameworks, and cage with double open-pore eyes without blocking after multiple reuse/cycles of the As(V) capture/trapping. Nonirradiated and Irradiated Trapping of As(V) Species from Water. Several key factors, such as pH, adsorbent dosage, contact time, and temperature, were investigated in a batch-contact-time system. These factors can affect As(V) species removal. pH is considered as a highly important key parameter controlling the arsenic sorption process and can affect (i) the surface active site charge and (ii) type of arsenic As(V) species (H3AsO4, H2AsO4−, HAsO42−, and AsO43−) in the solution.56,57 Therefore, the adsorption process of As(V) species using mesoporous BHT monolith adsorbent is pH dependent. The As(V) species can form mono and bidentate complexes through the binding with As−OH groups in the pH range 1−11. This formation is based on the chemistry of the As(V) species, which has two main forms, namely, H2AsO4− and HAsO42−, in this region of pH (Scheme 2A−C).58−61A series of benchtop-batch tests were conducted at a wide pH range to evaluate the optimum pH conditions for As(V) species capturing/trapping. The pH of solution was adjusted manually via the addition of sulfuric acid (H2SO4) and sodium hydroxide (NaOH). However, the other parameters were kept constant (20 mg BHT, 40 mL volume, 1 ppm As(V) solution, and contact time 120 min at 25 ± 2 °C). The 96% maximum adsorption efficiency was obtained at pH 3 because of the chemical attraction between the negative As(V) species and positive active sites at the BHT surface as shown in Figure 4A. The formation of such inverse U-shape curvature of the As(V) adsorption of species indicated that the As(V) removal using BHT is dependent on the pH value of contact10831


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Figure 5. (A, B) effect of the initial concentrations (0.25, 0.5, and 1 ppm) of As(V) species and different temperature (25, 30, 35, and 40 ± 2 °C) on the adsorption amount of As(V) species as a function of contact time/min (qt, mg/g), under exposure to UV irradiation at λmax = 365 nm. Where, 20 mg of BHT adsorbent contacted/stirred with 40 mL of the arsenic solution at pH 3.

charge transport along the BHT surface sites can react with OH− and O2 to form actively hydroxyl radicals OH• and superoxide anion radical O2−• or H2O•, or H2O2 species into aqueous solutions, as reported elsewhere (see Scheme 2).67 In this regard, the h+VB charge and actively radical species can lead to (i) enhanced removal/adsorption of As(V) species into the BHT surfaces, and (ii) photoinduced oxidation of any traces of As(III) to As(V) species that may exist in aqueous solution.68 The source of As(V) species (i.e., Na3AsO4, or AsO43− anion) at pH 3 may lead to the formation of stable HAsO42−, H2AsO4− target species. In addition, the exposure of TiO2 (BHT) surfaces to UV irradiation at λmax = 365 nm may form reactive Ti-superoxide (TiOOH) and actively charged surfaces, which enhanced the AsV-to-surface binding under our photoheterogeneous adsorption process conditions, as shown in Scheme 2A− C. Figure 4B shows the ζ-potential analysis of the BHT adsorbent in the range of pH 1−10 under normal and irradiation conditions. The enhancement of As(V) adsorption at pH 3 and under exposure to UV irradiation at λmax = 365 nm may indicate the formation of (i) the actively positive surface species and (ii) reactive Ti-superoxide (TiOOH) site, respectively. The formation of such actively charged positive surfaces onto solid BHT adsorbent might boost the removal of HAsO42−/ H2AsO4− species throughout the fast and strong AsV-to-BHT binding (see Scheme 2). Isotherm Studies of As(V) Species Adsorption. In this study, the Langmuir and Freundlich isotherms were applied to evaluate the adsorption behavior of As(V) species onto BHT adsorbent. These isotherms were also used to determine the amount of adsorbate that can be adsorbed as a function of As(V) initial concentration at room temperature.69,70 The parameters that indicate the type of adsorption, whether physically or chemically, can be determined experimentally and theoretically using the both models. A wide range of aqueous As(V) concentration was used to study the adsorption isotherm with and without UV irradiation. Batch-contact experiments

Figure 4. (A) Effect of pH on uptake/adsorption efficiency % of As(V) species. The adsorption assay was carried out with (b) and without (a) exposure to UV irradiation at λmax = 365 nm to the reaction vessel containing 20 mg of BHT adsorbent, volume solution of 40 mL of As(V) standard solution 1 ppm, at 25 ± 2 °C, and pH 3 for 60 min. (B) ζ-Potential profile of BHT adsorbent based on the change of pH values (pH 1−10). (C) Effect the amount of BHT adsorbent on uptake/adsorption efficiency % of As(V) species with (b) and without (a) exposure to UV irradiation at λmax = 365 nm.

time in capturing/trapping As(V) species as a function of As(V) concentration (0.25, 0.5, and 1 ppm) and reaction temperature (25 ± 2 °C to 40 ± 2 °C). The results provided in Figure 5A,B indicates that the adsorption of the As(V) species is time-dependent. Figure 5A shows that the adsorption amount qt of As(V) species increased from 0.75 to 1.9 mg/g with increasing the As(V) concentrations (i.e., from 0.25 to 1.0 ppm) at contact time 45 min, and 25 ± 2 °C. Meanwhile, Figure 5B reveals that the adsorption amounts (qt) of the As(V) species increased from 1.9 to 3.2 mg/g with increasing temperatures from 25 to 40 ± 2 °C and contact time of 45 min, when 20 mg of BHT adsorbent was brought in contact with 40 mL of 1 ppm As(V) solution. These results demonstrated that the removal of the As(V) species is an endothermic process. However, high temperature hastens the reaction rate and helps accelerate the diffusion of As(V) between the bulk solution and adsorbent surface. Adsorption Mechanism of As(V) Species Using BHT Adsorbent. Figure 4 shows the significant role of (i) longterm exposure to UV irradiation at λmax = 365 nm, (ii) pH solution, and (iii) BHT doses in boosting the adsorption efficiency of As(V) species. For instance, the irradiation of the micrometric-sized TiO2 monolith particles (BHT) under UV light leads to generate e−CB and h+VB pair. The e−CB and h+VB 10832


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capacity (qm) of the As(V) calculated from the overturn of slope value as 125 and 105.26 mg/g of irradiated and nonirradiated adsorbent, respectively. These values are compatible with experimental values (see Figure 6A). Then, the loaded As(V) species amounts have remained a constant indication of BHT adsorbent reached the maximum capacity (saturation capacity). To investigate the reversibility of As(V) adsorption process at our adsorption conditions, we study the dimensionless parameter RL based on the Langmuir isotherm characteristics of RL = 1/(1 + KLCo), which is referred to as the separation factor or equilibrium parameter. RL values indicate whether the adsorption process is irreversible, favorable, linear, or unfavorable.78 At the first cycle of reusability, the RL values (RL < 1) of irradiated and nonirradiated adsorption of As(V) species using BHT adsorbent indicate that the adsorption process is favorable and fully reversible. This result suggests that the adsorbed As(V) species can be eluted from BHT adsorbent surface during the regeneration treatment. Furthermore, the large KL indicates the strong AsV-to-BHT binding events (Table S1). Kinetic Studies of As(V) Species Adsorption. The reaction kinetics of As(V) species adsorption using BHT adsorbent was investigated as a function of contact time ranging from 5 to 360 min. By contrast, other factors were kept constant at 20 mg of BHT adsorbent contact with 40 mL of 1 ppm As(V) aqueous solution at 25 ± 2 °C and pH 3. As shown in Figure S2, results indicate that the adsorption process involves two stages, wherein the first stage of the adsorption rate is fast and the time required for the As(V) species loading efficiency at 97.8% is achieved within 60−90 min. In the second stage, the adsorption capacity remained slow and reached an equilibrium state after 90 min. However, the maximum loading efficiency of 99.9% can be achieved 30 min after using UV radiation for photoinduced adsorption, which can enhance the adsorption process and reduce the adsorption process time. In order to elucidate the mechanism of adsorption processes and kinetic characteristic of As(V) adsorption/trapping, kinetic models like pseudo-first-order and pseudo-second-order were used to investigate the best fitting of the experimental data of As(V) adsorption. The obtained data were analyzed by plotting the log(qe − qt) and t/qt versus t of pseudo-first-order and pseudo-second-order models, respectively.79−83All constant values of K1, K2, and qe of pseudo-first-order and pseudosecond-order equations are obtained from the slope and intercept of the obtained linear relations (see Figure S2, Table S2). The values of the correlation coefficient (R2) suggest a strong relationship between the parameters and also explain that the processes of As(V) species sorption follow the pseudosecond-order kinetic model. The rate constant of the As(V) species also appears to be controlled by a chemisorption process. Selective Adsorption of As(V) Species. The selective adsorption/capture/trapping of As(V) species from water sources is important in avoiding the possible adverse health effects of arsenic in many areas, without removal of the essential mineral content of water. The influences of the anions and cations that normally interfere with As(V) species selectivity were investigated. This investigation was achieved by initially adding a feed solution of competitive anions and cations to a wide range of tolerance concentrations ranging from 1 to 50 times greater than the As(V) concentration (Figure 7). The different competing anions, such as PO43−, HCO3−, CO32−,

were performed by bringing into contact the BHT adsorbent (20 mg) with 40 mL of 0.001−300 ppm As(V) solution at pH 3 and 25 ± 2 °C. The Freundlich model was studied to estimate the physical multilayer adsorption of the As(V) adsorbate at the actively heterogeneous BHT adsorbent surface (Figure S1).71,72 The values of Kf and n constants can be calculated from the slope and intercept of ln qe versus ln Ce linear relationship (see Figure S1 and Table S1). The low values of 1/n (less than unity) refer to the chemical interaction between As(V) species and surface active sites of BHT adsorbent. Furthermore, the Langmuir isotherm is related to adsorption uptake quantity (qe, mg/g) at equilibrium (Ce, mg/L) in accordance with the linear relationship of the Langmuir equation Ce/qe = 1/KL·qm + Ce/qm.73,74 From the obtained data in Figure 6A, the activity of arsenic uptake is highly

Figure 6. (A) Langmuir adsorption isotherms and (B) its linear form of As(V) species adsorption using BHT adsorbents. The adsorption assay was carried out without (a) and with (b) exposure to UV irradiation λmax = 365 nm to the reaction vessel, where 20 mg of BHT adsorbent contacted/stirred with 40 mL of As(V) standard solution 1 ppm, at 25 ± 2 °C and pH 3 for 60 min.

dependent on the initial concentrations of the As(V) species. Results reveal an increased adsorption amount qe (mg/g) until the maximum uptake values of the As(V) species were reached at 124.1 and 104.09 mg/g of the irradiated and nonirradiated BHT, respectively. After saturation point, the qe (mg/g) remained constant, indicating that BHT adsorbents have reached to its maximum adsorption capacity. These results refer to the applicability of removing a wide range of As(V) species concentrations from the water. A plot of Ce/qe versus Ce (with and without using of UV irradiation) resulted in upright lines with a slope [1/qm] and an intercept [1/qm·KL], where qm and KL constants were calculated from the slope and intercept outcomes, as shown in Table S1. According to the values of correlation coefficient (R2), the Langmuir adsorption model is fitted and confirms the formation of the monolayer As(V) species coverage at the interior/exterior framework of mesocage BHT adsorbent (i.e., chemical adsorption),75−77 as illustrated in Figure 6B and Table S1. The maximum loading 10833


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Figure 7. (A) Photoselective adsorption/uptake of As(V) species with interfering anions at different concentration 0.1 and 0.5 mM. (B) the uptake % of BHT adsorbent toward As(V) species and other metal species in the single-contact system and (C) the efficiency of As(V) adsorption/uptake in the presence of other interfering cations in a binary and mixture-contact systems using BHT adsorbent at pH 3, as summarized in Table S3. (D) Photoselective uptake efficiency % of As(V) species from groundwater, real samples, and tap water using BHT adsorbent.

SiO44−, SO42−, Cl−, C2O42−, ClO4−, and NO3− are mostly existent with the arsenate species in water. The 0, 0.1, and 5.0 mM concentrations of these anions mixed with 1 ppm of As(V) standard solution and then contacted with 20 mg of BHT adsorbent for 45 min at the optimum pH of 3 under UV light (λmax = 365 nm). From the obtained data (Figure 7A), most coexisting anions did not exert an effect on the removal of arsenic, except that the existence of PO43−, HCO3−, SO42−, and SiO44− exerted a negative and deteriorating influence. These anions present increasingly significant effects when their concentrations are also increased. In particular, the inhibitory effects of the PO43−, HCO3−, SO42−, and SiO44− anions at 0.5 mM reduce the adsorption efficiency from 99.9% to 39%, 73%, 43%, and 81%, respectively, as shown in Figure 7A. Phosphate, bicarbonate, sulfate, and silicate anions contain multihydroxyl groups and similar chemical properties in the aqueous system, which may severe compete with the arsenate species and react with active sites on the BHT surface.66,84 Moreover, the lack of adsorption efficiency in the presence of these actively competitive species was due to the small crystallographic size, ionic radii, and the coagulant dose of the high-concentration competitive ions.85,86 Practically implementing this ion-selective strategy, as well as adding a group of interfering cationic species to the As(V) species feed solution, revealed that the BHT adsorbent is ideal for the selective adsorption of the As(V) species. A set of batchcontact experiments were performed by adding of cationic interfering species to 1 ppm As(V) solution at pH 3. The maximum limit of the cations interfering with As(V) species in solution, such as 50 ppm of Ca2+, Mg2+, and Na+; 20 ppm of Co2+, Pb2+, Cu2+, and Al3+; 15 ppm of Ni2+, Cd2+, Mn2+, Hg2+, and Fe3+, as well as the interfering ion groups in binary and

mixture systems (G1−G9), are presented in Table S3. Figure 7B,C shows that the coexisting cations did not influence the recovery of the As(V) species at the optimal pH 3. Thus, the photoadsorbent BHT possesses a strong anti-ion interference ability and traps As(V) species with selective discrimination. Removal of As(V) Species from Real Water Samples. To validate the practicality and assess the efficiency of the BHT adsorbent in selectively removing the As(V) species from actual contaminated samples, we conducted batch-contact experiments by using four pretreated real sample effluents. Ground water, tap water, and three different samples obtained from different sites in the Doho Park lake of Tsukuba City, Ibaraki Prefecture, Japan, were used to test the practical implementation of BHT adsorbent. The As(V) concentrations of all the samples were below 0.0007 ppm; all samples were analyzed by ICP-MS at each stage as shown in Table S4. The real application process was performed by feeding 1 ppm of As(V) species to natural samples and stirring with a constant adsorbent dosage of 1 g/L. Interestingly, the results indicate the feasibility of using the BHT adsorbent as As(V) species captor at high and low concentrations of As(V) species (Figure 7D). The natural existence of the multiple components in the real water sample leads to decrease the efficiency of BHT adsorbent from 99.9% to of 91.5%, as shown in Figure 7D. Despite this decrease in the As(V) adsorption efficiency, the BHT is still effective to remove the ultratrace levels of As(V) concentrations in the presence of multicompetitive components in real samples, leading to reduce the problem of drinking water contamination by arsenic. These analytical data indicate that the proposed method that utilizes BHT adsorbent can be a potential candidate for actual environmental remediation and pollution control of water sources. 10834


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ACS Sustainable Chemistry & Engineering Photoinduced and Chemical Releasing of As(V) Species. The reusability and durability of the BHT adsorbent/captor under repeated use comprise an essential perspective in applied green chemistry.87,88 The adsorption process is also the most economical method because of the regeneration ability of adsorbent materials. The process allows the use of the adsorbent several times to reduce the overall treatment cost.89−91 This study aims to assess how to efficiently reuse the BHT adsorbent/captor for long-term use. The strong binding events of the target As(V) species at the interior/ exterior active sites of mesoporous BHT adsorbent (AsV-toBHT) may lead to the following consequences: (i) decreasing of surface area and pore volume and size of BHT adsorbent while the architectures staying rigid and (ii) decreased number of interior/exterior active sites that reduce the adsorption capacity of the BHT adsorbent with reuse/cycles. The recovery/releasing efficiency % of adsorbed As(V) species from AsV-to-BHT solid was calculated as follows: Recovery % = (CR/CA) × 100, where CR and CA are the concentration of released and adsorbed As(V) species in mg/L (ppm), respectively. A set of batch-contact experiments were conducted in a closed system to study the light-induced releasing/desorption/ recovery of the adsorbed As(V) species. The irradiation of BHT adsorbent impregnated by As(V) species using UV light at λmax = 365 nm leads to produce of HO2•, HO•, and O• radicals.42 One of these active HO2•, HO•, or O• radicals render the facile deactivation (i.e., dissociation) of the binding BHT-to-AsV events in this heterogeneous system. For example, the O• radicals may interact the BHT surfaces as follows: AsV− O−Ti + O• → Ti−O− + AsV−O−, enabling regeneration of BHT adsorbent for next cycle. The electrostatic repulsion forces between these negatively active sites generated on the BHT surface and As(V) anions lead to release of As(V) ions into solution vessel under continuous UV irradiation for longtime exposure. In the first cycle, the analytical data showed that more than 99.8% of adsorbed As(V) were released/recovered from the solid BHT-to-AsV during 15 h under UV light, as evident from ICP-MS analysis (Figures 8A and S3). The high recovery percentage of As(V) anions indicates the effectiveness photoregeneration process of BHT under UV irradiation. After each fifth cycle, the slight decrease of adsorption efficiency of As(V) species up to 3% from its original feed concentration may be due to the decrease of interior/exterior cavity to adsorb As(V) within cycling. The BHT photoregeneration process was repeated for 20th cycles. The finding shows the stability of the BHT photoadsorbent during the multiprocess adsorption of As(V) species that contributes effectively to environmental waste management and water purification. Moreover, the chemical release of As(V) species was examined in this study using aqueous sodium hydroxide NaOH as the hardest Lewis base eluent in the recovery of adsorbed As(V) species. The effects of eluent concentration and elution time were investigated by bringing 20 mg of BHT loaded by As(V) ions into contact with 20 mL of NaOH solution at 25 ± 2 °C. Figure S4 shows that the recovery efficiency of the As(V) species was 100% at 0.1 M of NaOH with stirring time of 45 min. The increasing media pH value (i.e., increased hydroxide groups) increases the electrostatic repulsion between negatively charged arsenate species and negative active sites on the BHT surface. This repulsion force may drive the breakdown and cleavage bonding (i.e., covalent and hydrogen bonds) of Ti−O−AsV and Ti−O···H−O−AsV.37

Figure 8. (A) Photoinduced uptake % from water and photoinduced recovery % of As(V) species under UV radiation at λmax = 365 nm as a function of recyclability at 25 ± 2 °C. (B) Chemical releasing treatment has carried out using 0.1 M NaOH as a function of adsorption−desorption 20 cycles at 25 ± 2 °C.

As shown in Figure 8B, the regenerated BHT adsorbent remains highly efficient and can be used for multiple reuse/ cycles, as evidenced from high removal efficiency of about 98%. After every five cycles, the efficiency slightly decreased and the As(V) residual concentration can be slightly increased. After the 20th cycle, the uptake efficiency of the As(V) species was 89%, and 99.5% of the adsorbed amount can be recovered. Thus, the resulting data reveal the possibility of using BHT adsorbent several times in arsenic removal without apparent reduction. As shown in Figure 9, the low- and high magnification of FE-SEM profiles provide evidence about the high stability of BHT morphology (shape and size) containing nanoscale eyes after several reuse/cycles. Pointing that BHT considered as a promising adsorbent material with ideally applied in purifying of nonpotable water from poisonous arsenic. That is, the current adsorption protocol provides real evidence about the following three major aspects for environmental protection from hazards: (i) the toxicity control and selective collection of As(V) species through the BHT adsorbent, which helps reduce the adverse health risks of As(V) toxicant release; (ii) the feasibility of using the solid BHT adsorbent/captor, in which the BHT adsorbent can be repeatedly recycled for 20th reuse/cycles with no negative change in the unique blobfish head architectures, leading to reduce the cost of water purification process; and (iii) the simple releasing process of the target As(V) species from the BHT adsorbent. Outdoor Arsenate Adsorption Treatment under Direct Sunlight. A real arsenate adsorption treatment process under UV light and direct sunlight (i.e., indoor and outdoor) was carried out at pH 3, volume 40 mL, and 25 ± 2 °C. To show the efficient, out-door arsenate adsorption treatment under direct sunlight, a number of batch-contact adsorption experiments of As(V) anion [1 ppm] using 20 mg BHT 10835



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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.7b02766. Materials and reagents, material characterization, isotherms and kinetics equations of irradiated and nonirradiated As(V) species adsorption, selectivity study, DFT calculations, chemical releasing treatment for recovery of As(V) species, outdoor arsenate adsorption treatment, and comparison between our material and wide variety of arsenic adsorbent materials according to its saturation capacity (PDF)

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AUTHOR INFORMATION

Corresponding Author

*Sherif A. El-Safty. TEL: +81-29-859-2135; FAX: +81-29-8592501; E-mail: [email protected].

Figure 9. (A−D) Low- and high magnification FE-SEM images of BHT adsorbent after using it for several uptake/recovery recycles. The micrographs showed the structured stability of BHT adsorbent containing nanoscale eyes after adsorption and desorption of As(V) species.

ORCID

S. A. El-Safty: 0000-0001-5992-9744 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work is supported by deanship of Scientific Research of Prince Sattam Bin Abdulaziz University under the Research Project No. 6602/2016.

adsorbent was performed under exposure the heterogeneous adsorption vessel directly to both sunlight and UV irradiation at λmax = 365 nm. Figure S5 shows that the photoadsorption of As(V) under UV irradiation at λmax = 365 nm effectively leads to fast response removal and efficient adsorption compared with the treatment the heterogeneous reaction vessel under sunlight radiation. Despite the long-term radiation under sunlight, the out-door removal of As(V) species is achieved using the BHT adsorbent. This finding indicates the potential use of BHT adsorbent in the out-door arsenate adsorption treatment under sunlight exposure.

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ABBREVIATIONS BHT blobfish head TiO2; ICP-MS induced coupled plasmamass spectroscopy; 3D three-dimensional; TIP titanium isopropoxide; FESEM field-emission scanning electron microscope; TEM transmission electron microscopy; STEM-EDS scanning TEM-energy dispersive spectroscopy; SAED selected area of distinctive electron diffraction; DFT density functional theory; WA-XRD wide angle powder X-ray diffraction; JCPDS Joint Committee on Powder Diffraction Standards reference; NLDFT nonlocal density functional theory; BET Brunauer− Emmett−Teller theory

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CONCLUSION In summary, highly efficient mesoporous BHT was simply fabricated with uniform microsphere-like blobfish head morphology for use in purifying drinking water from poisonous pollutants of arsenate species with and without shedding UV light. The outcome of the work refers to the high selectivity and high adsorption capacity (125 mg/g) of BHT toward ultratrace amounts of As(V) species among other coexisting ions at pH 3, under UV irradiation. A similar adsorption process complied with the Langmuir isotherm model and pseudo-second-order kinetic model because of the rapid capture of the arsenate species onto the homogeneous surface of the adsorbent. The BHT adsorbent can be regenerated easily, and arsenate anions were quantitatively eluted under irradiation or feeding with 0.1 M NaOH for 20 reuse/cycles. The reusability and real applicability of this adsorbent are key to the future development of water purification. The practical feasibility of using BHT in selectively removing/trapping As(V) species from actual contaminated samples collected from the tap and underground water sources in Tsukuba-shi, Ibaraki-ken, Japan was remarkable. The real analytical data of the proposed method indicate that the BHT adsorbent can serve as a candidate captor for disposal of toxic arsenic pollutants.

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REFERENCES

(1) Xu, T.; Kamat, P. V.; O’Shea, K. E. Mechanistic evaluation of arsenite oxidation in TiO2 assisted photocatalysis. J. Phys. Chem. A 2005, 109, 9070−9075. (2) Ray, P. Z.; Shipley, H. J. Inorganic nano-adsorbents for the removal of heavy metals and arsenic: a review. RSC Adv. 2015, 5, 29885−29907. (3) Wu, P. Y.; Jiang, Y. P.; Zhang, Q. Y.; Jia, Y.; Peng, D. Y.; Xu, W. Comparative study on arsenate removal mechanism of MgO and MgO/TiO2composites: FTIR and XPS analysis. New J. Chem. 2016, 40, 2878−2887. (4) Guo, S.; Sun, W.; Yang, W.; Li, Q.; Shang, J. K. Superior As(III) removal performance of hydrous MnOOH nanorods from water. RSC Adv. 2015, 5, 53280−53288. (5) Mohan, D.; Pittman, C. J. Arsenic removal from water/ wastewater using adsorbents-A critical review. J. Hazard. Mater. 2007, 142, 1−53. (6) Smith, A. H.; Lopipero, P. A.; Bates, M. N.; Steinmaus, C. M. Arsenic epidemiology and drinking water standards. Science 2002, 296, 2145−2146. (7) Reyna, N. R.; Reyes, L. H.; Mar, J. L. G.; Cai, Y.; O’Shea, K.; Ramírez, A. H. Photocatalytical removal of inorganic and organic 10836


Research Article

ACS Sustainable Chemistry & Engineering arsenic species from aqueous solution using zinc oxide semiconductor. Photochem. Photobiol. Sci. 2013, 12, 653−659. (8) US EPA. Water: DrinkingWaterContaminants, http://water.epa. gov/drink/contaminants/index.cfm#Inorganic, 01/07/2015. (9) Dutta, P. K.; Ray, A. K.; Sharma, V. K.; Millero, F. J. Adsorption of arsenate and arsenite on titanium dioxide suspensions. J. Colloid Interface Sci. 2004, 278, 270−275. (10) Guan, X.; Du, J.; Meng, X.; Sun, Y.; Sun, B.; Hu, Q. Application of titanium dioxide in arsenic removal from water: A review. J. Hazard. Mater. 2012, 215−216, 1−16. (11) Khatamian, M.; Khodakarampoor, N.; Saket Oskouia, M.; Kazemian, N. Synthesis and characterization of RGO/zeolite composites for the removal of arsenic from contaminated water. RSC Adv. 2015, 5, 35352−35360. (12) Behari, J. R.; Prakash, R. Determination of total arsenic content in water by atomic absorption spectroscopy (AAS) using vapour generation assembly (VGA). Chemosphere 2006, 63, 17−21. (13) Kubota, T.; Yamaguchi, T.; Okutani, T. Determination of arsenic content in natural water by graphite furnace atomic absorption spectrometry after collection as molybdoarsenate on activated carbon. Talanta 1998, 46, 1311−1319. (14) Niedzielski, P.; Siepak, M. Analytical methods for determining arsenic, antimony and selenium in environmental samples. Polym. J. Environ. Stud. 2003, 12, 653−667. (15) Morita, K.; Kaneko, E. Spectrophotometric determination of arsenic in water samples based on micro particle formation of ethyl violet− molybdoarsenate. Anal. Sci. 2006, 22, 1085−1089. (16) Pal, S. K.; Akhtar, N.; Ghosh, S. K. Determination of arsenic in water using fluorescent ZnO quantum dots, Anal. Anal. Methods 2016, 8, 445−453. (17) Featherstone, A. M.; Butler, E. C. V.; O’Grady, B. V.; Michel, P. Determination of arsenic species in sea-water by hydride generation atomic fluorescence spectroscopy. J. Anal. At. Spectrom. 1998, 13, 1355−1360. (18) Choong, T. S.; Chuah, T.; Robiah, Y.; Koay, F. G.; Azni, I. Arsenic toxicity, health hazards and removal techniques from water: an overview. Desalination 2007, 217, 139−166. (19) Johnson, P. D.; Girinathannair, P.; Ohlinger, K. N.; Ritchie, S.; Teuber, L.; Kirby, J. Enhanced removal of heavy metals in primary treatment using coagulation and flocculation. Water Environ. Res. 2008, 80, 472−479. (20) Bakalár, T.; Búgel, M.; Gajdošová, L. Heavy metal removal using reverse osmosis. Acta Montanistica Slovaca. 2009, 14, 250−253. (21) Moussawi, R. N.; Patra, D. Modification of nanostructured ZnO surfaces with curcumin: fluorescence-based sensing for arsenic and improving arsenic removal by ZnO. RSC Adv. 2016, 6, 17256−17268. (22) Verbych, S.; Hilal, N.; Sorokin, G.; Leaper, M. Ion exchange extraction of heavy metal ions from wastewater. Sep. Sci. Technol. 2005, 39, 2031−2040. (23) Barakat, M. A. New trends in removing heavy metals from industrial wastewater. Arabian J. Chem. 2011, 4, 361−377. (24) Fu, F.; Wang, Q. Removal of heavy metal ions from wastewaters: A review. J. Environ. Manage. 2011, 92, 407−418. (25) Yu, L.; Ma, Y.; Ong, C. N.; Xie, Ji.; Liu, Y. Rapid adsorption removal of arsenate by hydrous cerium oxide−graphene composite. RSC Adv. 2015, 5, 64983−64990. (26) Benjwal, P.; Kumar, M.; Chamoli, P.; Kar, K. K. Enhanced photocatalytic degradation of methylene blue and adsorption of arsenic(III) by reduced graphene oxide (rGO)−metal oxide (TiO2/ Fe3O4) based nanocomposites. RSC Adv. 2015, 5, 73249−73260. (27) Guan, X.; Dong, H.; Ma, J.; Jiang, L. Removal of arsenic from water: Effects of competing anions on As(III) removal in KMnO4− Fe(II) process. Water Res. 2009, 43, 3891−3899. (28) Lee, M.; Paik, I. S.; Kim, I.; Kang, H.; Lee, S. Remediation of heavy metal contaminated groundwater originated from abandoned mine using lime and calcium carbonate. J. Hazard. Mater. 2007, 144, 208−214.

(29) Cvetkovic, V. S.; Purenovic, J. M.; Purenovic, M. M.; Jovicevic, J. N. Interaction of Mg-enriched kaolinite-bentonite ceramics with arsenic aqueous solutions. Desalination 2009, 249, 582−590. (30) Lee, Y. C.; Park, W. K.; Yang, J. W. Removal of anionic metals by amino-organoclay for water treatment. J. Hazard. Mater. 2011, 190, 652−658. (31) Seddique, A. A.; Masuda, H.; Mitamura, M.; Shinoda, K.; Yamanaka, T.; Nakaya, S.; Ahmed, K. M. Mineralogy and geochemistry of shallow sediments of Sonargaon, Bangladesh and implications for arsenic dynamics: Focusing on the role of organic matter. Appl. Geochem. 2011, 26, 587−599. (32) Sasaki, K.; Nakano, H.; Wilopo, W.; Miura, Y.; Hirajima, T. Sorption and speciation of arsenic by zero-valent iron. Colloids Surf., A 2009, 347, 8−17. (33) Horzum, N.; Demir, M. M.; Nairat, M.; Shahwan, T. Chitosan fiber-supported zero-valent iron nanoparticles as a novel sorbent for sequestration of inorganic arsenic. RSC Adv. 2013, 3, 7828−7837. (34) Asadullah, M.; Jahan, I.; Ahmed, M. B.; Adawiyah, P.; Malek, N. H.; Rahman, M. S. Preparation of microporous activated carbon and its modification for arsenic removal from water. J. Ind. Eng. Chem. 2014, 20, 887−896. (35) Kołodynska, D.; Krukowska, J.; Thomas, P. Comparison of sorption and desorption studies of heavy metal ions from biochar and commercial active carbon. Chem. Eng. J. 2017, 307, 353−363. (36) Azzam, A. M.; Shenashen, M. A.; Selim, M. M.; Yamaguchi, H.; ElSewify, I. M.; Kawada, S.; Alhamid, A. A.; El-Safty, S. A. Nanospherical inorganic α-Fe core-organic shell necklaces for the removal of arsenic(V) and chromium(VI) from aqueous solution. J. Phys. Chem. Solids 2017, 109, 78−88. (37) El-Safty, S. A.; Shenashen, M. A.; Sakai, M.; Elshehy, E.; Halada, K. Detection and recovery of palladium, gold and cobalt metals from the urban mine using novel sensors/adsorbents designated with nanoscale wagon-wheel-shaped pores. J. Visualized Exp. 2015, 6, 53044−53059. (38) El-Safty, S. A.; Sakai, M.; Selim, M.; Hendi, A. A. Mesosponge optical sinks for multifunctional mercury ion assessment and recovery from water sources. ACS Appl. Mater. Interfaces 2015, 7, 13217− 13231. (39) El-Safty, S. A.; Awual, M. R.; Shenashen, M. A.; Shahat, A. Simultaneous optical detection and extraction of cobalt(II) from lithium ion batteries using nanocollector monoliths. Sens. Actuators, B 2013, 176, 1015−1025. (40) El-Safty, S. A.; Khairy, M.; Shenashen, M. A.; Elshehy, E.; Warkocki, W.; Sakai, M. Optical mesoscopic membrane sensor layouts for water-free and blood-free toxicants. Nano Res. 2015, 8, 3150−3163. (41) Emran, M. Y.; Khalifa, H.; Gomaa, H.; Shenashen, M. A.; Akhtar, N.; Mekawy, M.; Faheem, A.; El-Safty, S. A. Hierarchical C-N doped NiO with dual-head echinop flowers for ultrasensitive monitoring of epinephrine in human blood serum. Microchim. Acta 2017, DOI: 10.1007/s00604-017-2498-3. (42) Bhatt, R. R.; Shah, B. A. Sorption studies of heavy metal ions by salicylic acid−formaldehyde−catechol terpolymeric resin: Isotherm, kinetic and thermodynamics. Arabian J. Chem. 2015, 8, 414−426. (43) Song, G.; Chu, Z.; Jin, W.; Sun, H. Enhanced performance of gC3N4/TiO2 photocatalysts for degradation of organic pollutants under visible light. Chin. J. Chem. Eng. 2015, 23, 1326−1334. (44) Yan, H.; Yang, H. TiO2−g-C3N4 composite materials for photocatalytic H2 evolution under visible light irradiation. J. Alloys Compd. 2011, 509, 26−29. (45) Chen, D.; Jiang, Z.; Geng, J.; Wang, Q.; Yang, D. Carbon and nitrogen Co-doped TiO2 with enhanced visible-light photocatalytic activity. Ind. Eng. Chem. Res. 2007, 46, 2741−2746. (46) Qian, S.; Huang, Z.; Fu, J.; Kuang, J.; Hu, C. Preconcentration of ultra-trace arsenic with nanometre-sized TiO2 colloid and determination by AFS with slurry sampling. Anal. Methods 2010, 2, 1140−1143. (47) Wan, Y.; Zhao, D. Y. On the controllable soft-templating approach to mesoporous silicates. Chem. Rev. 2007, 107, 2821−2860. 10837


Research Article

ACS Sustainable Chemistry & Engineering (48) Shenashen, M. A.; Akhtar, N.; Selim, M. M.; Morsy, W. M.; Yamaguchi, H.; Kawada, S.; Alhamid, A. A.; Ohashi, N.; Ichinose, I.; Alamoudi, A. S.; El-Safty, S. A. Effective, low-cost recovery of toxic arsenate anions from water by using hollow-sphere geode traps. 2017, DOI: 10.1002/asia.201700666. (49) Guan, X.; Du, J.; Meng, X.; Sun, Y.; Sun, B.; Hu, Q. Application of titanium dioxide in arsenic removal from water: A review. J. Hazard. Mater. 2012, 215−216, 1−16. (50) Yan, L.; Du, J.; Jing, C. How TiO2 facets determine arsenic adsorption and photooxidation: spectroscopic and DFT studies. Catal. Sci. Technol. 2016, 6, 2419−2427. (51) Antcliff, K. L.; Murphy, D. M.; Griffiths, E.; Giamello, E. The interaction of H2O2 with exchanged titanium oxide systems (TS-1, TiO2, [Ti]-APO-5, Ti-ZSM-5). Phys. Chem. Chem. Phys. 2003, 5, 4306−4316. (52) Seok, S. I.; Ahn, B. Y.; Pramanik, N. C.; Kim, H.; Hong, S. I. Preparation of nanosized rutile TiO2 from an aqueous peroxotitanate solution. J. Am. Ceram. Soc. 2006, 89, 1147−1149. (53) Shenashen, M.; Derbalah, A.; Hamza, A.; Mohamed, A.; ElSafty, S. Antifungal activity of fabricated mesoporous alumina nanoparticles against root rot disease of tomato caused by Fusarium oxysporium. Pest Manage. Sci. 2017, 73, 1121−1126. (54) El-Safty, S. A.; Shahat, A.; Awual, M. R.; Mekawy, M. Large three-dimensional mesocage pores tailoring silica nanotubes as membrane filters: Nanofiltration and Permeation Flux of Proteins. J. Mater. Chem. 2011, 21, 5593−5603. (55) Shenashen, M. A.; Hassen, D.; El-Safty, S. A.; Isago, H.; Elmarakbi, A.; Yamaguchi, H. Axially oriented tubercle vein and Xcrossed sheet of N-Co3O4@C hierarchical mesoarchitectures as potential heterogeneous catalysts for methanol oxidation reaction. Chem. Eng. J. 2017, 313, 83−98. (56) Amin, M. N.; Kaneco, S.; Kitagawa, T.; Begum, A.; Katsumata, H.; Suzuki, T.; Ohta, K. Removal of arsenic in aqueous solutions by adsorption onto waste rice husk. Ind. Eng. Chem. Res. 2006, 45, 8105− 8110. (57) El-Safty, S. A.; Shenashen, M. A.; Khairy, M. Optical detection/ collection of toxic Cd(II) ions using cubic Ia3d aluminosilica mesocage sensors. Talanta 2012, 98, 69−78. (58) Xu, T.; Kamat, P. V.; O’Shea, K. E. Mechanistic evaluation of arsenite oxidation in TiO2 assisted photocatalysis. J. Phys. Chem. A 2005, 109, 9070−9075. (59) El-Safty, S. A.; Shenashen, M. A.; Ismail, A. A. A multi-pHdependent, single optical mesosensor/captor design for toxic metals. Chem. Commun. 2012, 48, 9652−9654. (60) Li, Z.; Deng, S.; Yu, G.; Huang, J.; Lim, V. C. As(V) and As(III) removal from water by a Ce−Ti oxide adsorbent: Behavior and mechanism. Chem. Eng. J. 2010, 161, 106−113. (61) El-Safty, S. A.; Shenashen, M. A.; Ismael, M.; Khairy, M. Mesocylindrical aluminosilica monolith biocaptors for size-selective macromolecule cargos. Adv. Funct. Mater. 2012, 22, 3013−3021. (62) Zhu, J.; Lou, Z.; Liu, Y.; Fu, R.; Baig, S. A.; Xu, X. Adsorption behavior and removal mechanism of arsenic on graphene modified by iron−manganese binary oxide (FeMnOx/RGO) from aqueous solutions. RSC Adv. 2015, 5, 67951−67961. (63) El-Safty, S. A.; Khairy, M.; Ismael, M. Visual detection and revisable supermicrostructure sensor systems of Cu(II) analytes. Sens. Actuators, B 2012, 166−167, 253−263. (64) Alkan, M.; Demirbas, O.; Celikcapa, S.; Dogan, M. Sorption of acid red 57 from aqueous solution onto sepiolite. J. Hazard. Mater. 2004, 116, 135−145. (65) Chaudhary, B. K.; Farrell, J. Understanding regeneration of arsenate-loaded ferric hydroxide-based adsorbents. Environ. Eng. Sci. 2015, 32, 353−360. (66) El-Safty, S. A. Instant synthesis of mesoporous monolithic materials with controllable geometry, dimension and stability: a review. J. Porous Mater. 2011, 18, 259−287. (67) Cheng, W.; Zhang, W.; Hu, L.; Ding, W.; Wu, F.; Li, J. Etching synthesis of iron oxide nanoparticles for adsorption of arsenic from water. RSC Adv. 2016, 6, 15900−15910.

(68) Shenashen, M. A.; Kawada, S.; Selim, M. M.; Morsy, W. M.; Yamaguchi, H.; Alhamid, A. A.; Ohashi, N.; Ichinose, I.; El-Safty, S. A. Bushy sphere dendrites with husk-shaped branches axially spreading out from the core for photo-catalytic oxidation/remediation of toxins. Nanoscale 2017, 9, 7947−7959. (69) El-Safty, S. A.; Ismael, M.; Shahat, A.; Shenashen, M. A. Mesoporous hexagonal and cubic aluminosilica adsorbents for toxic nitroanilines from water. Environ. Sci. Pollut. Res. 2013, 20, 3863−3876. (70) El-Safty, S. A.; Abdellatef, S.; Ismael, M.; Shahat, A. Optical Nanosphere Sensor Based on Shell-By-Shell Fabrication for Removal of Toxic Metals from Human Blood. Adv. Healthcare Mater. 2013, 2, 854. (71) Shenashen, M. A.; Shahat, A.; El-Safty, S. A. Ultra-trace recognition and removal of toxic chromium (VI) ions from water using visual mesocaptor. J. Hazard. Mater. 2013, 244−245, 726−735. (72) Gomaa, H.; Farid, M.; Abd-Elraheem, M. A.; Seaf El-Naser, T. A.; Zidan, I. H. Removal of Uranium from Acidic Solution Using Activated Carbon Impregnated with Tri Butyl Phosphate. J. Bio. Chem. Res. 2016, 3, 313−340. (73) El-Safty, S. A.; Shenashen, M. A.; Ismael, M.; Khairy, M.; Awual, Md. R. Optical mesosensors for monitoring and removal of ultra-trace concentration of Zn(II) and Cu(II) ions from water. Analyst 2012, 137, 5278−5290. (74) El-Safty, S. A.; Shenashen, M. A.; Ismael, M.; Khairy, M.; Awual, M. R. Mesoporous aluminosilica sensors for the visual removal and detection of Pd(II) and Cu(II) ions. Microporous Mesoporous Mater. 2013, 166, 195−205. (75) Caccin, M.; Giacobbo, F.; Da Ros, M.; Besozzi, L.; Mariani, M. Adsorption of uranium, cesium and strontium onto coconut shellactivated carbon. J. Radioanal. Nucl. Chem. 2013, 297, 9−18. (76) Ma, L.; Tu, S. X. Removal of arsenic from aqueous solution by two types of nano TiO2 crystals. Environ. Chem. Lett. 2011, 9, 465− 472. (77) El-Safty, S. A.; Shenashen, M. A. Mercury-ion optical sensors. TrAC, Trends Anal. Chem. 2012, 38, 98−115. (78) Li, L.; Hu, N.; Ding, D.; Xin, X.; Wang, Y.; Xue, J.; Zhang, H.; Tan, Y. Adsorption and recovery of U(VI) from low concentration uranium solution by amidoxime modified Aspergillus niger. RSC Adv. 2015, 5, 65827−65839. (79) Liu, Q.; Li, W.; Zhao, W.; Tan, L.; Jing, X.; Liu, J.; Song, D.; Zhang, H.; Li, R.; Liu, L.; Wang, J. Synthesis of ketoximefunctionalized Fe3O4@C core−shell magnetic microspheres for enhanced uranium(VI) removal. RSC Adv. 2016, 6, 22179−22186. (80) Shenashen, M. A.; El-Safty, S. A.; Khairy, M. Trapping of biological macromolecules in the three-dimensional mesocage pore cavities of monolith adsorbents. J. Porous Mater. 2013, 20, 679−692. (81) Khairy, M.; El-Safty, S. A. Water treatment through chemical transformation andelimination of organic toxin based on mesoporous nickel oxide nanocrystals. Adv. Mater. Res. 2013, 685, 139−144. (82) Awual, M. R.; El-Safty, S. A.; Jyo, A. Removal of trace arsenic(V) and phosphate from water by a highly selective ligand exchange adsorbent. J. Environ. Sci. 2011, 23, 1947−1954. (83) El-Safty, S. A.; Shenashen, M. A. Optical mesosensor for capturing of Fe(III) and Hg(II) ions from water and physiological fluids. Sens. Actuators, B 2013, 183, 58−70. (84) Lee, S. H.; Kim, K. W.; Lee, B. T.; Bang, S.; Kim, H.; Kang, H.; Jang, A. Enhanced arsenate removal performance in aqueous solution by yttrium-based adsorbents. Int. J. Environ. Res. Public Health 2015, 12, 13523−13541. (85) Qian, S.; Huang, Z.; Fu, J.; Kuang, J.; Hu, C. Preconcentration of ultra-trace arsenic with nanometre-sized TiO2 colloid and determination by AFS with slurry sampling. Anal. Methods 2010, 2, 1140−1143. (86) Nazeeruddin, M. K.; Kay, A.; Rodicio, I.; Baker, R. H.; Mueller, E.; Liska, P.; Vlachopoulos, N.; Gr̈atzel, M. Conversion of light to electricity by cis-X2bis(2,2′-bipyridyl-4,4′-dicarboxylate)ruthenium(II) charge-transfer sensitizers (X = Cl−, Br−, I−, CN−, and SCN−) on nano crystalline titanium dioxide electrodes. J. Am. Chem. Soc. 1993, 115, 6382−6390. 10838


Research Article

ACS Sustainable Chemistry & Engineering (87) Sdiri, A.; Khairy, M.; Bouaziz, S.; El-Safty, S. A natural clayey adsorbent for selective removal of lead from aqueous solutions. Appl. Clay Sci. 2016, 126, 89−97. (88) Shenashen, M. A.; Elshehy, E. A.; El-Safty, S. A.; Khairy, M. Visual monitoring and removal of divalent copper, cadmium, and mercury ions from water by using mesoporous cubic Ia3d aluminosilica sensors. Sep. Purif. Technol. 2013, 116, 73−86. (89) Derbalah, A.; El-Safty, S. A.; Shenashen, M. A.; Abdel Ghany, N. A. Mesocage collector cavities as nanopockets for remediation and real assessment of carbamate pesticides in aquatic water. Nano-Struct. Nano-Objec. 2015, 3, 17−27. (90) Derbalah, A.; El-Safty, S. A.; Shenashen, M. A.; Khairy, M. Hierarchical nanohexagon ceramic sheet layers as platform adsorbents for hydrophilic and hydrophobic insecticides from agricultural wastewater. ChemPlusChem 2015, 80, 1769−1778. (91) Abdien, H. G.; Cheira, M. F.; Abd-Elraheem, M. A.; Saef ElNaser, T. A.; Zidan, I. H. Extraction and Pre-concentration of Uranium Using Activated Carbon Impregnated Trioctyl Phosphine Oxide. Elixir Appl. Chem. 2016, 100, 43462−43469.

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