Sandwich-like nano-system for simultaneous ... - ACS Publications

Subscriber access provided by University of Sussex Library

Applications of Polymer, Composite, and Coating Materials

Sandwich-like nano-system for simultaneous removal of Cr(VI) and Cd(II) from water and soil Dongfang Wang, Guilong Zhang, Zhangyu Dai, Linglin Zhou, Po Bian, Kang Zheng, Zhengyan Wu, and Dongqing Cai ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b03379 • Publication Date (Web): 07 May 2018 Downloaded from http://pubs.acs.org on May 7, 2018

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 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 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.

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 40 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

Sandwich-like nano-system for simultaneous removal of Cr(VI) and Cd(II) from water and soil Dongfang Wang,†,§ Guilong Zhang,†,‡ Zhangyu Dai,†,§ Linglin Zhou,†,§ Po Bian,†,‡ Kang Zheng,┴,* Zhengyan Wu,†,‡,* Dongqing Cai,†,‡,* †

Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei

Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui 230031, People’s Republic of China §

University of Science and Technology of China, Hefei, Anhui 230026, People’s

Republic of China ┴

Institute of Applied Technology, Hefei Institutes of Physical Science, Chinese

Academy of Sciences, Hefei, Anhui 230031, People’s Republic of China ‡

Key Laboratory of Environmental Toxicology and Pollution Control Technology of

Anhui Province, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui 230031, People’s Republic of China

KEYWORDS: FeS, Carboxyl-functionalized ferroferric oxide, Cr(VI), Cd(II), Remove

1

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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

ABSTRACT: In this work, a novel nano-system with sandwich-like structure was synthesized via face-to-face combination of two pieces of waste cotton fabrics (CFs) carrying ferrous sulfide (FeS) and carboxyl-functionalized ferroferric oxide (CFFM) respectively, and the obtained nano system was named as FeS/CFFM/CF. Therein, FeS has high reduction and adsorption capabilities for hexavalent chromium (Cr(VI)), CFFM possesses a high adsorption ability on cadmium ion (Cd(II)) through electrostatics attraction and chelation, and CF displays high immobilization ability for FeS and CFFM and adsorption performance on Cd(II). FeS/CFFM/CF could simultaneously remove Cr(VI) and Cd(II) from water, inhibit the uptake of Cr and Cd by fish and water spinach, ensuring the food safety. Besides, this technology could efficiently control migration of Cr(VI) and Cd(II) in sand-soil mixture, which was favorable to prevent their wide diffusion. Importantly, FeS/CFFM/CF possessed a high flexibility and could be conveniently produced with needed scale and shape, and easily separated from water and soil, displaying a promising approach to remediate Cr(VI)/Cd(II)-contaminated water and soil and a huge application potential.

2


Page 2 of 40

Page 3 of 40 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


INTRODUCTION With the rapid development of industries including refining, steel and alloys production, electroplating, battery, smelting and so on, a large number of heavy metal ions such as chromium and cadmium discharged into environment and then tended to be uptaken by human body through food chain, resulting in severe harms for ecosystem and health of human beings.1-7 Therein, chromium generally possessed two stable states including hexavalent chromium (Cr(VI)) and trivalent chromium (Cr(III)), wherein Cr(VI) as one kind of typical heavy metal ion displayed significantly higher toxicity and carcinogenicity compared with Cr(III).8,9 As for bivalent cadmium (Cd(II)) which was another kind of typical heavy metal ion, it tended to be accumulated in human body and caused kidney, bone, and lung diseases.10-13 In addition, both Cr(VI) and Cd(II) possessed good dissolubility in water, high migration through waterflow and atmospheric dry/wet deposition, and thus tended to coexist in water and soil, causing synergically higher toxicity compared with each alone.14,15 Therefore, it is rather important to develop promising approaches to remove Cr(VI) and Cd(II) simultaneously from water and soil to lower their harmful effects on environment and human beings. Until now, a variety of nanomaterials based on carbon, clay, polymer, and metallic oxide have been fabricated to remove Cr(VI) and Cd(II) through reduction and adsorption, which has become one of the hottest methods because of the high efficiency and simple procedure.16-26 However, these nanomaterials were commonly used to remove Cr(VI) or Cd(II) separately rather than simultaneously because of the opposite zeta potentials of Cr(VI) and Cd(II), which became the dominant limitation factor for their application to remediate Cr(VI)/Cd(II)-contaminated water and soil.27-30 Although some neutral nanomaterials could adsorb both of them, they 3



displayed rather low reduction ability on Cr(VI).31,32 Importantly, owing to the lack of ideal carrier, it was difficult to efficiently and conveniently collect the nanomaterials together with Cr(VI)/Cr(III) and Cd(II) from water especially soil, which was another bottleneck to restrict their engineering application.33-36 Therefore, it is urgent to fabricate novel nanomaterials carried by an ideal carrier to remove Cr(VI) and Cd(II) simultaneously and be separated from wastewater and soil after treatment conveniently. According to survey, there was about 24 million tons of cotton fabrics (CFs) produced and used throughout the world, resulting in a large amount of waste CFs.37 However, only a small amount of waste CFs were reused for production of mop, plush toys, low-grade cotton textile and so on.37 A lot of waste CFs are disposed via landfill or incineration, resulting in not only a great waste of cotton resource but also severe environmental contamination.37 Therefore, development of promising approaches to reuse waste CF, improve commercial value, and lower pollution is attracting more and more attention in textile and environment fields.38 In this work, ferrous sulfide (FeS) nanoparticles and carboxyl-functionalized Fe3O4 microspheres (CFFM) were loaded in a piece of waste CF respectively to obtain FeS/CF and CFFM/CF which were then combined together to construct a sandwich-like flexible nanosystem named FeS/CFFM/CF. Ethylenediamine is used for FeS synthesis because of its water solubility and easy handling compared with other surfactants or polymers such as hydrazine and oleic acid, ethanolamine, polylactic acid, PA66, polycarbonate, poly(vinyl alcohol), and so on.39-45 The removal performance of FeS/CFFM/CF on Cr(VI) and Cd(II) in water and soil was investigated under different conditions. To reveal the mechanism on Cr(VI) and Cd(II) removal, the interactions among FeS/CFFM/CF, Cr(VI), and Cd(II) were analyzed. 4


Page 4 of 40

Page 5 of 40 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


Importantly, fish tank and pot experiments were performed to prove the effectiveness of this technology. This work provides not only an efficient and environmentally friendly approach to remove Cr(VI) and Cd(II) from wastewater and soil simultaneously, but also a promising method for high-value recycling of waste CF.

MATERIALS AND METHODS Materials: L-cysteine (98.5%) and Fe(acac)3 (98%) were provided by Aladdin Chemical Co. Ltd. (Shanghai, China). FeCl3·6H2O (99%), ethylenediamine (99%), ethylene glycol (99%) and other chemicals of analytical grade were purchased from Sinopharm Chemical Reagent Company (Shanghai, China). Sodium acrylate (98%) was provided by Nanjing Chemlin Chemical Industry Co. Ltd. (Nanjing, China). CF (thickness of approximately 1 mm) made of cotton with components of 92% cellulose, 7% hemicellulose, and 1% wax was purchased from Xi Mo Textile Co. Ltd. (Shaoxing, China). Fish (grass goldfish) were purchased from Tianjin Chenhui Feed Co. Ltd. (Tianjin, China). Water spinach was purchased from a supermarket in Dongpu Island (Hefei, China). Deionized water was used in all the experiments except fish tank and pot experiments. Soil and sand (20-50 mesh) were taken from Dongpu Island (Hefei, China). Pretreatment of CF: A piece of square CF (40 cm×40 cm) was immersed in 1.5 L of water at 100oC for 2 h, and then soaked in ethanol for 2 h to remove the wax in CF. After that, the resulting CF was dried at 60oC for 12 h and cut into small circular pieces with diameter of 3.8 cm. Preparation of FeS/CF and CFFM/CF: FeS was synthesized using solvothermal method.46 Ferric chloride (FeCl3·6H2O) (2 g) and 0.97 g of L-cysteine (C3H7NO2S) were added to 70 mL of ethylenediamine/deionized water (v/v=1:1) solution and then the resulting solution was stirred (550 rpm) for 30 min. After that, 5



the solution was transferred into a Teflon-lined stainless autoclave (150 mL) and maintained at 200oC for 24 h. Then, the product was collected through centrifugation (4000 rpm), washed with deionized water and then ethanol for three times respectively, dried at 60oC in a vacuum oven for 12 h, and ground to FeS powder (200-300 mesh). After that, FeS aqueous suspension with given concentration and volume was deposited on the surface of a piece of CF with given size, and the resulting system was dried at 60oC in a vacuum oven for 12 h to form FeS/CF. CFFM was also synthesized using solvothermal method. Ferric acetylacetonate (Fe(acac)3) (0.8 g) was added to 80 mL of ethylene glycol, and the solution was stirred (550 rpm) for 1 h. Subsequently, 1.6 g of sodium acrylate was added to the solution wherein 2.0 g of sodium acetate was added after 30 min, and then the resulting solution was stirred (550 rpm) for 30 min respectively. After that, the solution was transferred into a Teflon-lined stainless autoclave (150 mL) and maintained at 180oC for 20 h. Then, the product was collected through centrifugation (4000 rpm), washed with deionized water and then ethanol for three times respectively, dried at 60oC in a vacuum oven for 12 h, and ground to CFFM powder (200-300 mesh). After that, CFFM aqueous suspension with given concentration and volume was deposited on the surface of a piece of CF with given size, and the resulting system was dried at 60oC in a vacuum oven for 12 h to form CFFM/CF. Removal of Cr(VI) and Cd(II) from aqueous solution: FeS/CF was added to 30 mL of Cr(VI) (20 mg/L) aqueous solution. After being shaken for a given time, the residual concentration of Cr(VI) was measured by DPC spectrophotometric method.47 CFFM/CF was added to 30 mL of Cd(II) (25 mg/L) aqueous solution. After being shaken for a given time, the residual concentration of Cd(II) was measured by spectrophotometry at a wavelength of 573.2 nm.48 The influence of FeS (or CFFM) 6


Page 6 of 40

Page 7 of 40 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


amount in CF, pH, and temperature on the removal efficiency of FeS/CF (or CFFM/CF) for Cr(VI) (or Cd(II)) was investigated. After that, the removal efficiency of Cr(VI) or Cd(II) was calculated according to equation (1): Removal efficiency (%) =(C0-Ct)/C0×100%

(1)

where C0 and Ct are the initial and residual concentrations (mg/L) of Cr(VI) or Cd(II). All experiments were performed in triplicate. Removal of FeS/CFFM/CF for Cr(VI) and Cd(II) and fish viability in fish tank: FeS/CF (240 mg of FeS on rectangular CF (length of 10.8 cm, width of 7.5 cm)) and CFFM/CF (32 mg of CFFM on rectangular CF (length of 10.8 cm, width of 7.5 cm)) were combined together with clips to form FeS/CFFM/CF, wherein FeS and CFFM were between two CFs. After that, FeS/CFFM/CF was added to 600 mL of Cr(VI) (10 mg/L) and Cd(II) (2 mg/L) mixed aqueous solution (pH 6.7) and moved slowly back and forth. After 24 h, the FeS/CFFM/CF was taken out and the residual concentrations of Cr(VI) and Cd(II) were measured, and then 18 fish were placed in the resulting solution to investigate the viability with time. After 59 h, the total amount of Cr and Cd in the fish were measured according to method in previous work.47 All experiments were performed in triplicate. Effect of FeS/CFFM/CF on the migration of Cr(VI) and Cd(II) in sand-soil column: FeS/CF (20.8 mg of FeS on a circular CF with diameter of 5 cm) and CFFM/CF (34.7 mg of CFFM on a circular CF with diameter of 5 cm) were combined together with clips to form FeS/CFFM/CF, wherein FeS and CFFM were between the CFs. The dry sand (20-50 mesh) was mixed with soil (50-100 mesh) at a weight ratio (Wsand/Wsoil=7:3), and then the resulting sand-soil mixture (420 g) was put in a cylindrical polyvinyl chloride tube (diameter of 5 cm, length of 30 cm). After that, FeS/CFFM/CF was placed on the top of the sand-soil mixture, and then 40 g of 7



sand-soil mixture was placed on the top of FeS/CFFM/CF. 200 mL of Cr(VI) (5 mg/L) and Cd(II) (10 mg/L) mixed solution (pH 5.1) was added to the top of the system. After 24 h, 5 g of sand-soil mixture in different distances (every 3 cm) from FeS/CFFM/CF was transferred to 25 mL of deionized water, respectively, and the resulting system was shaken for 24 h. After centrifugation (12000 rpm) for 5 min, the concentrations of Cr(VI) and Cd(II) in the supernatant were measured to obtain the effect of FeS/CFFM/CF on the distributions of Cr(VI) and Cd(II) in the sand-soil column. All experiments were performed in triplicate. Pot experiment: FeS/CFFM/CF with 160 mg of FeS, 21 mg of CFFM, and 480 cm2 of rectangular CF (length of 24 cm, width of 20 cm) was prepared. After that, 400 mL of Cr(VI) (10 mg/L) and Cd(II) (2 mg/L) mixed aqueous solution (pH 6.7) was put in a pot (trapezoidal shape, height of 6.5 cm, width of 7.8 cm (bottom) and 11.3 cm (top), and length of 13.4 cm (bottom) and 17.2 cm (top)). Then, 12 water spinaches (length of 5-10 cm, diameter of approximately 1 cm) evenly carried by a rectangular foam board (10×20 cm) were placed on the surface of the resulting solution. After that, the pot was kept in a greenhouse at 25oC with humidity of 60%. After 72 h, the chlorophyll content in the water spinach leaves and the amounts of Cr and Cd in water spinach were measured. All experiments were performed in triplicate. Characterizations: The morphology and elemental mapping were observed using a scanning electron microscope (SEM) (Sirion 200, FEI Co., USA) and an H-800 transmission electron microscope (TEM, Hitachi Co., Japan). The composition and structure analyses were performed on a Fourier transform infrared (FTIR) spectrometer (iS10, Nicolet Co., USA), an X-ray photoelectron spectroscope (XPS, ESCALAB 250, Thermo-VG Scientific Co., USA), and a TTRIII X-ray diffractometer (XRD, Rigaku Co., Japan). Brunauer Emmett-Teller (BET) specific surface areas of 8


Page 8 of 40

Page 9 of 40 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


FeS and CFFM were determined by physisorption of N2 using an automatic surface area and pore analyzer (Tristar II 3020M, Micromeritics, USA). The pore volume and pore size distribution were measured through the Barrett-Joyner-Halenda (BJH) method. The concentration of Cr(VI) and Cd(II) were detected on a UV-vis spectrophotometer (UV Lambda 365, PerkinElmer Co., USA) at 540 and 573.2 nm respectively. The amounts of Cr and Cd in water spinach were determined using an inductively coupled plasma-optical emission spectrometer ((ICP-OES) (ICAP7200, Thermo Fisher Scientific, USA)).

RESULTS AND DISCUSSION Removal of Cr(VI) and Cd(II) from aqueous solution: FeS possesses reduction and adsorption capabilities for Cr(VI) in aqueous solution, however it tends to aggregate in water and is difficult to be separated, which greatly restrict the removal performance and application.8,49,50 To solve this problem, FeS nanoparticles were fabricated using porous fibrous-structured CF as the substrate to obtain FeS/CF, displaying a high dispersion and collectability, which could greatly facilitate the removal performance on Cr(VI). The influence of FeS amount in FeS/CF on the removal efficiency of Cr(VI) in aqueous solution was investigated to obtain the optimal FeS amount (Figure 1A). With the increase of FeS amount, the removal efficiency of Cr(VI) increased gradually and reached the value of 100% at 24 mg. This result indicated that FeS/CF displayed an outstanding removal capacity for Cr(VI), and the optimal FeS amount in FeS/CF was 24 mg and the resulting FeS/CF was designated as FeS/CF-24. In addition, the stability of FeS/CF-24 in Cr(VI) aqueous solution was investigated. The result (Figure S1A) showed that the loss amount of FeS from FeS/CF-24 was nearly zero after 7 d, indicating that FeS/CF-24 had a high stability. 9



Page 10 of 40

Subsequently, the influence of initial pH of Cr(VI) solution on the removal efficiency of FeS/CF-24 was investigated. It was found in Figure 1B that the removal efficiency of FeS/CF-24 decreased with the increase of initial pH. Noteworthily, the differences of removal efficiency under three initial pHs were significant during the initial 10 h while narrowed thereafter, which was because of the decreasing H+ amount according to reactions (1) and (2): FeS + H+ =Fe2++HS-

(1)

3Fe2++Cr(VI) =3Fe3++Cr(III)

(2)

This result indicated that FeS/CF-24 displayed a high removal performance for Cr(VI) under different pH from 4 to 8. Besides, the influence of temperature on the removal efficiency of FeS/CF-24 for Cr(VI) was also investigated (Figure 1C), and the result indicated that the removal efficiency increased significantly with temperature during the initial 10 h, which was due to the enhanced Brownian movement of FeS particles and Cr(VI) ions and thus higher contact probability between them at higher temperatures. In other words, the removal of FeS/CF-24 for Cr(VI) is an endothermic process, which could be illustrated by thermodynamic parameters (Table S1).51,52 Noteworthily, the difference of removal efficiency under different temperature decreased after 10 h, suggesting that this technology displayed a high removal performance for Cr(VI) from 30 to 50oC. Similarly, CFFM with a large number of -COO- was also loaded in CF to fabricate CFFM/CF whose removal efficiency for Cd(II) was investigated. As shown in Figure 1D, CF alone displayed a removal efficiency (approximately 50%) to some extent for Cd(II) because CF consisted of micro fibrous cellulose with high porosity and negative zeta potential.37 Additionally, the influence of CFFM amount in CFFM/CF 10


Page 11 of 40 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


on the removal efficiency of Cd(II) was investigated to obtain the optimal CFFM amount. With the increase of CFFM amount, the removal efficiency of Cd(II) increased gradually and reached the value of 100% at 20 mg, demonstrating that CFFM could effectively remove Cd(II). Considering the negative zeta potential of CFFM (inset in Figure 1E), electrostatic attraction and chelation effect of -COO- in CFFM probably played a key role for the removal of Cd(II). As such, the optimal CFFM amount in CFFM/CF was 20 mg and the resulting CFFM/CF was designated as OCFFM/CF. Besides, the stability of OCFFM/CF in Cd(II) aqueous solution was investigated. Figure S1B indicated that CFFM displayed a tiny loss amount from OCFFM/CF after 7 d, suggesting that OCFFM/CF possessed a high stability. Subsequently, the influence of the initial pH of Cd(II) solution on the removal efficiency of OCFFM/CF was investigated. It was found in Figure 1E that the removal efficiency of OCFFM/CF increased obviously with increase of pH during the initial 14 h, which was because of the increasing zeta potential (absolute value) originated from abundant -COO- in OCFFM/CF. Notably, the difference of removal efficiency under three initial pHs decreased after 14 h, suggesting the high property of OCFFM/CF under different pH. Besides, the influence of temperature on the removal efficiency of OCFFM/CF for Cd(II) was also investigated (Figure 1F), and the result indicated that the removal efficiency increased significantly with temperature during the initial 14 h, which was attributed to the enhanced Brownian movement of CFFM particles and Cd(II) ions and thus the higher contact probability between them at higher temperatures, which means the removal of OCFFM/CF for Cd(II) is also an endothermic process, which could be illustrated by thermodynamic parameters (Table S2). While the difference of removal efficiency under different temperature decreased after 14 h, proving that this technology displayed a high removal performance for 11



Cd(II) from 30 to 50oC. Finally, the removal efficiencies of FeS/CF-24 and OCFFM/CF for Cr(VI) and Cd(II) respectively in Cr(VI) and Cd(II) mixed solution with time were investigated. As shown in Figure S2A and B, the removal efficiency of Cr(VI) or Cd(II) in Cr(VI) and Cd(II) mixed solution was almost the same with that in Cr(VI) or Cd(II) aqueous solution. This results indicated that FeS/CF-24 (or OCFFM/CF) displayed similar removal performance in Cr(VI) and Cd(II) mixed solution compared with individual Cr(VI) (or Cd(II)) aqueous solution. Additionally, the selectivity of FeS/CF-24 and OCFFM/CF on Cr(VI) and Cd(II) was investigated. As shown in Figure S3, the removal efficiency of FeS/CF-24 for Cd(II) is about 62.4% and Cr(VI) is about 98.1%. The removal efficiency of OCFFM/CF for Cd(II) is about 99.7% and Cr(VI) is about 4.8%. Thus, FeS/CF-24 has a relatively high selectivity for Cr(VI) and OCFFM/CF has a high selectivity for Cd(II). Removal of Cr(VI) and Cd(II) in fish tank: Based on the preceding analyses, FeS/CF and CFFM/CF displayed high removal performance for Cr(VI) and Cd(II) respectively. Actually, Cr(VI) and Cd(II) tended to coexist in aqueous solution because of their high solubility and migration.31,32 As such, in order to remove Cr(VI) and Cd(II) simultaneously from water, FeS/CF and CFFM/CF were combined together to obtain FeS/CFFM/CF with sandwich-like structure and a good flexibility. Subsequently, fish tank experiment was performed to investigate the removal performance of FeS/CFFM/CF on Cr(VI) and Cd(II) and the viability of fish. As shown in Figure 2A-D, the yellow color of the Cr(VI) and Cd(II) mixed solution (600 mL) disappeared after the treatment of FeS/CFFM/CF, indicating that most of the Cr(VI) was removed. It could be clearly seen in Figure 2E that FeS/CFFM/CF could remove approximately 95% of Cd(II) and 80% of Cr(VI) after 24 h, proving the high 12


Page 12 of 40

Page 13 of 40 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


effectiveness of this technology. The removal mechanism was proposed that, when FeS/CFFM/CF was moved slowly in the fish tank, Cr(VI) and Cd(II) ions were adsorbed onto FeS/CFFM/CF, wherein the Cr(VI) tended to be adsorbed onto the FeS/CF side and then reduced to Cr(III) by FeS while Cd(II) tended to be adsorbed onto the CFFM/CF side (Figure 2F and 2G). The removal efficiency of individual FeS/CF (or CFFM/CF) on Cr(VI) (or Cd(II)) in fish tank was investigated compared with FeS/CFFM/CF. As shown in Figure 2E and Figure S2C and D, the removal efficiency of individual FeS/CF (or CFFM/CF) on Cr(VI) (or Cd(II)) was lower compared with FeS/CFFM/CF, which was because of the synergistic effect of FeS/CF and CFFM/CF. Besides, the influence of FeS/CFFM/CF on fish viability was also investigated to further prove the effectiveness of this technology. As illustrated in Figure 2H-L, the fish viability in the fish tank without FeS/CFFM/CF decreased gradually with time and all the fishes were dead after 59 h, while all the fishes in the fish tank treated with FeS/CFFM/CF were still alive after 83 h. Moreover, FeS/CFFM/CF treatment could effectively reduce the Cr and especially Cd contents in the fishes after 59 h compared with those without treatment (Figure 2M and 2N). This result indicated that FeS/CFFM/CF could efficiently remove Cr(VI) and Cd(II) simultaneously from water, inhibiting the uptake of Cr and Cd by fishes, which could greatly favor the growth of fishes. Importantly, the movement of FeS/CFFM/CF in water could be conveniently controlled and it could be easily separated from water, displaying a simple operation performance. Removal of Cr(VI) and Cd(II) in sand-soil mixture: Owing to the excellent solubility, Cr(VI) and Cd(II) tended to migrate in soil, resulting in wider contamination. Therefore, it was urgent to control the migration of Cr(VI) and Cd(II). 13



The influence of FeS/CFFM/CF on the distribution of Cr and Cd in sand-soil column was investigated (Figure 3A). As shown in Figure 3B and C, the concentrations of both Cr and Cd with or without FeS/CFFM/CF decreased gradually with the increasing distance from the top of column. Therein, in a certain distance, the concentrations of both Cr and Cd with FeS/CFFM/CF treatment were significantly lower than those without FeS/CFFM/CF treatment, indicating that FeS/CFFM/CF had high immobilization efficiencies for Cr and Cd. Notably, FeS/CFFM/CF displayed a significantly higher immobilization performance for Cd compared with Cr, which was in accordance with the result of fish tank experiment. The influence of individual FeS/CF or CFFM/CF on the distribution of Cr or Cd in sand-soil column was investigated. As shown in Figure 3 and Figure S2E and F, Cr concentration in FeS/CF-treated sand-soil at a certain distance was higher than that of FeS/CFFM/CF, proving that FeS/CFFM/CF displayed a higher removal ability for Cr than FeS/CF. Additionally, after treatment of CFFM/CF and FeS/CFFM/CF, little Cd existed in sand-soil, suggesting that they both possessed excellent removal ability on Cd(II). Mechanism Study: To elucidate the mechanism of FeS/CF and CFFM/CF on the removal of Cr(VI) and Cd(II), the morphologies of FeS/CF and CFFM/CF were observed. As shown in Figure 4A and B, CF consisted of a large number of microfibers with main components of cellulose and hemicelluloses which cross-linked with each other to form a porous micro-networks structure, which was beneficial for the loading of FeS and CFFM. FeS possessed a micro-flower-like structure composed of abundant porous nanoflakes (Figure 4C). As shown in Figure 4D, after the loading of FeS in CF, plenty of FeS particles distributed evenly on the surface of the microfibers and in the pores among the microfibers, indicating that CF could 14


Page 14 of 40

Page 15 of 40 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


effectively prevent the aggregation of FeS particles through steric hindrance, which was favorable for the adsorption and reduction ability of FeS/CF. After the treatment of FeS/CF on Cr(VI) in water under shaking for 24 h, some particles still existed on the surface of the microfibers, suggesting the high adhesion of the Cr-containing product on the surface of the CF (Figure 4E), which could greatly favor the separation of Cr from water. As shown in Figure 4F and f, CFFM consisted of abundant porous spherical nanoclusters formed by a large number of nanoparticles and displayed a good dispersion. Additionally, CFFM possessed a negative zeta potential and abundant -COO- and thus tended to be adsorbed on the surface of the microfibers in CF through electrostatics attraction and hydrogen bonds (Figure 4G). After the treatment of CFFM/CF on Cd(II) in water under shaking for 24 h, a large quantity of particles still existed on the surface of the CF, suggesting the high adhesion of Cd-containing product on the surface of the CF (Figure 4H), which could facilitate the separation of Cd from water. Besides, element mapping was performed to investigate the distributions of FeS-Cr or CFFM-Cd in CF. As shown in Figure 5a-f, C, O, Fe, and S evenly distributed in the elemental map of FeS/CF, suggesting that FeS distributed on the surface of CF. After Cr(VI) treatment, Cr was obviously observed in the elemental map of FeS/CF (Figure 5g-m), indicating that Cr was adsorbed in FeS/CF. As shown in Figure 5n-r, C, O, and Fe evenly distributed in the elemental map of CFFM/CF, presenting that CFFM distributed on the surface of CF. After Cd(II) treatment, Cd was obviously observed in the elemental map of CFFM/CF (Figure 5s-x), suggesting that Cd(II) was adsorbed on CFFM/CF. To elucidate the interactions between CFFM and Cd(II), FTIR measurement was carried out. As shown in Figure 6A, CFFM possessed characteristic peaks (587 cm-1 15



Page 16 of 40

for the Fe-O stretching vibration, 1408 cm-1 for the C-OH stretching vibration, 1711 cm-1 for the C=O stretching vibration, and 3405 cm-1 for the O-H stretching vibration), displaying the existence of -COOH in CFFM.3,53 After Cd(II) treatment, the peaks (1410 cm-1 for the C-OH stretching vibration, 1716 cm-1 for the C=O stretching vibration, and 3421 cm-1 for the O-H stretching vibration) in the spectrum of CFFM/Cd slightly blue-shifted and no new peak was found compared with CFFM (Figure 6B), which was probably attributed to the electrostatic attraction and chelation between Cd(II) and CFFM. XRD measurements were also carried out to analyze the crystal structures of FeS and CFFM. As shown in Figure 6Ca, the main diffraction peak of FeS was found at 17.1o, which agreed with the XRD spectrum of typical FeS crystal, indicating that the synthesized FeS nanoparticles had a high crystallinity.50,54 As shown in Figure 6Cb, several distinct new diffraction peaks appeared in the spectrum of FeS/Cr, proving the formation of S (PDF# 08-0247) through reaction 3.55 This result demonstrated that S2also played a key role in the reduction of Cr(VI). 3S2-+2Cr(VI)=3S+2Cr(III)

(3)

Additionally, as shown in Figure 6Da and b, the diffraction peaks of Fe3O4 at 30.2°, 35.5°, 43.2°, 53.7°, 57.4° and 62.5° which corresponded to the (220), (311), (400), (422), (511), and (440) were recognized in the XRD pattern of CFFM, indicating that the crystalline structure of Fe3O4 nanoparticle did not change after the surface modification with -COOH.1,56 After Cd(II) treatment, no obvious change occurred to the XRD pattern of CFFM, suggesting that no obvious intercalation or reaction occurred during the adsorption process of Cd(II) by CFFM. Besides, pore size distribution and nitrogen adsorption-desorption isotherms of FeS and CFFM analyses were carried out to investigate their microstructures. As 16


Page 17 of 40 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


illustrated in Figure 6E, FeS possessed plenty of pores with a size of 10-100 nm with the most pores at 25 nm (inset of Figure 5E) and a BET specific surface area of 7.72 m2/g. Noteworthily, FeS displayed a low specific surface area but a high removal efficiency for Cr(VI), illustrating that physical adsorption was not the dominant mechanism for the removal of Cr(VI), while the reactions (1-3) played key roles. As shown in Figure 6F, CFFM possessed plenty of micro pores (inset of Figure 6F) and a high BET specific surface area of 137.4 m2/g, indicating that adsorption was the dominant mechanism of removal Cd(II) by CFFM. In order to further explore the interaction between Cr(VI) and FeS, XPS was employed to investigate the forms of Fe, S and Cr before and after Cr(VI) removal. As shown in Figure 7A-C, the peaks at 710.93 and 168.31 eV of FeS corresponded to Fe2+ and S2- respectively.57,58 As shown in Figure 7D, after Cr(VI) treatment, the appearance of Fe(III)-O peak at 711.1 eV in the spectra of FeS/Cr confirmed that Fe(II) was oxidized to Fe(III).3 Additionally, the S2p peak at 163.92 eV in the spectra of FeS/Cr (Figure 7E) displayed that S2- was reduced to S. Meanwhile, two bands at 577.07 and 586.75 eV corresponding to Cr2p3/2 and Cr2p1/2 of Cr(III) were found in the spectra of FeS/Cr (Figure 7F), indicating that Cr(VI) was reduced to Cr(III).3,59 This result suggested that both Fe2+ and S2- played key roles in the reduction of Cr(VI), which was the dominant mechanism of Cr(VI) removal by FeS.

Effects of FeS/CFFM/CF on water spinach: Cr(VI) and Cd(II) in water could greatly influence the growth of crops because they tended to be uptaken and accumulated in crops, inducing generation of toxic substances harmful to metabolism.4,60 Herein, pot experiments were performed to obtain the remediation effect of FeS/CFFM/CF on Cr(VI)/Cd(II)-contaminated water using water spinach as the model crop. As shown in Figure 8A-E, it was clear that the addition of 17



FeS/CFFM/CF displayed significantly positive effects on the growth of water spinach and chlorophyll content in the leaves. In addition, after FeS/CFFM/CF treatment, water spinach contained significantly lower amounts of Cr and Cd compared those without treatment (Figure 8F), indicating that FeS/CFFM/CF could efficiently inhibit the uptake of Cr and Cd by water spinach, which was probably attributed to the high removal efficiency of FeS/CFFM/CF on Cr(VI) and Cd(II) in water. Notably, FeS/CFFM/CF treatment decreased Cd amount in water spinach more significantly than Cr, which was consistent with the results of fish tank and leaching experiments. Therefore, FeS/CFFM/CF could be used as a promising agent to efficiently remediate Cr(VI)/Cd(II)-contaminated water and ensure the food safety of corps growing in the water. As for the practical application of this technology in water, a large scale of FeS/CFFM/CF could be produced and act as a flexible net-like filter driven by a boat to simultaneously remove Cr(VI) and Cd(II) from Cr(VI)/Cd(II)-contaminated river or lake (Figure 9A). As for the practical application in a field, FeS/CFFM/CF could also be used as a filter system which was placed in a pipe to remove Cr(VI) and Cd(II) from Cr(VI)/Cd(II)-contaminated water (Figure 9B). As such, the effluent clean water could be used to irrigate crops and thus ensure the food safety. Hence, this technology has a promising industrial scale application prospect in agriculture and environment fields. In summary, a novel sandwich-like nano-system (FeS/CFFM/CF) was fabricated. Therein, FeS has high reduction and adsorption capabilities for Cr(VI), and CFFM possesses a high adsorption efficiency on Cd(II) through electrostatics attraction and chelation. As such, FeS/CFFM/CF could efficiently and simultaneously remove Cr(VI) and Cd(II) from water, decrease the uptake of Cr and Cd by fish and water spinach, 18


Page 18 of 40

Page 19 of 40 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


and thus favor the food safety. Additionally, this technology could also control migration of Cr(VI) and Cd(II) in sand-soil mixture, which was beneficial to inhibit their diffusion. Importantly, FeS/CFFM/CF, with a good flexibility, could be conveniently produced with needed scale and shape, and easily collected from water and soil, displaying a high industrialization prospect. This work provides a promising approach to remediate Cr(VI)/Cd(II)-contaminated water and soil, which has a huge application value.

ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website. Figure S1 (A) Loss amount of FeS from FeS/CF-24 in Cr(VI) aqueous solution within 7 d; (B) Loss amount of CFFM from OCFFM/CF in Cd(II) aqueous solution within 7 d. Figure S2 (A and B) Removal efficiencies of FeS/CF-24 for Cr(VI) and OCFFM/CF for Cd(II) respectively in Cr(VI) and Cd(II) mixed aqueous solution with time; (C) Removal efficiency of FeS/CF for Cr(VI) in a fish tank with time; (D) Removal efficiency of CFFM/CF for Cd(II) in a fish tank with time; (E) Effect of FeS/CF on Cr distribution in sand-soil column; (F) Effect of CFFM/CF on Cd distribution in sand-soil column. Figure S3 Removal efficiencies of (A) FeS/CF-24 and (B) OCFFM/CF for Cr(VI) and Cd(II) in Cr(VI) and Cd(II) mixed aqueous solution after 24 h. Table S1 Thermodynamic parameters for removal of Cr(VI) by FeS/CF-24. Table S2 Thermodynamic parameters for removal of Cd(II) by OCFFM/CF. AUTHOR INFORMATION Corresponding Authors. *E-mail: [email protected] (K.Z.). 19



*E-mail: [email protected] (Z.W.). *E-mail: [email protected] (D.C.). Notes The authors declare no competing financial interest. ACKNOWLEDGMENTS The authors acknowledge financial support from the National Natural Science Foundation of China (No. 21407151), the Youth Innovation Promotion Association of Chinese Academy of Sciences (No. 2015385), the Key Program of Chinese Academy of Sciences (No. KSZD-EW-Z-022-05), the Science and Technology Service Programs of Chinese Academy of Sciences (Nos. KFJ-STS-ZDTP-002 and KFJ-SW-STS-143), the Science and Technology Major Project of Anhui Province (No. 17030701051), and the Environmental Protection Department of Anhui Province (No. 2017-04).

20


Page 20 of 40

Page 21 of 40 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


References (1) Ghasemi, E.; Heydari, A.; Sillanpää, M. Superparamagnetic Fe3O4@EDTA nanoparticles as an efficient adsorbent for simultaneous removal of Ag(I), Hg(II), Mn(II), Zn(II), Pb(II) and Cd(II) from water and soil environmental samples. Microchem J. 2017, 131, 51-56. (2) Shen, W. J.; Mu, Y.; Xiao, T.; Ai, Z. H. Magnetic Fe3O4-FeB nanocomposites with promoted Cr(VI) removal performance. Chem. Eng. J. 2016, 285, 57-68. (3) Wang, D. F.; Zhang, G. L.; Zhou, L. L.; Wang, M.; Cai, D. Q.; Wu, Z. Y. Synthesis of a multifunctional graphene oxide-based magnetic nanocomposite for efficient removal of Cr(VI). Langmuir 2017, 33, 7007-7014. (4) Rajeev Kumar, J. C. Removal of cadmium ion from water/wastewater by nano-metal oxides: a review. Water Qual. Expo. Health 2014, 5, 215-226. (5) Ma, Y. L.; Lv, L.; Guo, Y. R.; Fu, Y. J.; Shao, Q.; Wu, T. T.; Guo, S. J.; Sun, K.; Guo, X. K.; Wujcik, E. K.; Guo, Z. H. Porous lignin based poly (acrylic acid)/organo-montmorillonite nanocomposites: Swelling behaviors and rapid removal of Pb(II) ions. Polymer 2017, 128, 12-23. (6) Xiang, B.; Ling, D.; Lou, H.; Gu, H. B. 3D hierarchical flower-like nickel ferrite/manganese dioxide toward lead(II) removal from aqueous water. J. Hazard. Mater. 2017, 325, 178-188. (7) Wang, Y. P.; Zhou, P.; Luo, S. Z.; Guo, S. J.; Lin, J.; Shao, Q.; Guo, X. K.; Liu, Z. Q.; Shen, J.; Wang, B.; Guo, Z. H. In situ polymerized poly(acrylic acid)/alumina nanocomposites for Pb2+ adsorption. Adv. Polym. Technol. 2018, 00, 1-16. (8) Zhang, J.; Zhang, G. L.; Wang, M.; Zheng, K.; Cai, D. Q.; Wu, Z. Y. Reduction of aqueous CrVI using nanoscale zero-valent iron dispersed by high energy electron beam irradiation. Nanoscale 2013, 5, 9917-9923. 21



(9) Zhang, J.; Zhang, G. L.; Cai, D. Q.; Wu, Z. Y. Immediate remediation of heavy metal (Cr(VI)) contaminated soil by high energy electron beam irradiation. J. Hazard. Mater. 2015, 284, 208-211. (10) Álvarez-Ayuso, E.; García-Sánchez, A. Removal of cadmium from aqueous solutions by palygorskite. J. Hazard. Mater. 2007, 147, 594-600. (11) Chen, K.; He, J. Y.; Li, Y. L.; Cai, X. G.; Zhang, K. S.; Liu, T.; Hu, Y.; Lin, D. Y.; Kong, L. T.; Liu, J. H. Removal of cadmium and lead ions from water by sulfonated magnetic nanoparticle adsorbents. J. Colloid Interface Sci. 2017, 494, 307-316. (12) Liu, C. K.; Liang, X. Y.; Liu, J. A.; Lei, X. B.; Zhao, X. Z. Preparation of the porphyrin-functionalized cotton fiber for the chromogenic detection and efficient adsorption of Cd2+ ions. J. Colloid Interface Sci. 2017, 488, 294-302. (13) Mallakpour, S.; Motirasoul, F. Bio-functionalizing of α-MnO2 nanorods with natural L-amino acids: a favorable adsorbent for the removal of Cd(II) ions. Mater. Chem. Phys. 2017, 191, 188-196. (14) Clemente, J. S.; Beauchemin, S.; MacKinnon, T.; Martin, J.; Johnston, C. T.; Joern, B. Initial biochar properties related to the removal of As, Se, Pb, Cd, Cu, Ni, and Zn from an acidic suspension. Chemosphere 2017, 170, 216-224. (15) Gao, A. Q.; Xie, K. L.; Song, X. Y.; Zhang, K.; Hou, A. Q. Removal of the heavy metal ions from aqueous solution using modified natural biomaterial membrane based on silk fibroin. Ecol. Eng. 2017, 99, 343-348. (16) He, L. L.; Wang, M.; Zhang, G. L.; Qiu, G. N.; Cai, D. Q.; Wu, Z. Y.; Zhang, X. Remediation of Cr(VI) contaminated soil using long-duration sodium thiosulfate supported by micro-nano networks. J. Hazard. Mater. 2015, 294, 64-69. (17) Cui, H. J.; Fu, M. L.; Yu, S.; Wang, M. K. Reduction and removal of Cr(VI) from aqueous solutions using modified by products of beer production. J. Hazard. Mater. 22


Page 22 of 40

Page 23 of 40 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


2011, 186, 1625-1631. (18) Liu, Q. X.; Zeng, C. M.; Ai, L. H.; Hao, Z.; Jiang, J. Boosting visible light photoreactivity of photoactive metal-organic framework: Designed plasmonic Z-scheme Ag/AgCl@MIL-53-Fe. Appl. Catal. B-Environ. 2018, 224, 38-45. (19) Huang, J. N.; Cao, Y. H.; Shao, Q.; Peng, X. F.; Guo, Z. H. Magnetic nanocarbon adsorbents with enhanced hexavalent chromium removal: Morphology dependence of fibrillar vs particulate structures. Ind. Eng. Chem. Res. 2017, 56, 10689-10701. (20) Gu, H. B.; Xu, X. J.; Zhang, H. Y.; Liang, C. B.; Lou, H.; Ma, C.; Li, Y. J.; Guo, Z. H.; Gu, J. W. Chitosan-coated-magnetite with covalently grafted polystyrene based carbon nanocomposites for hexavalent chromium adsorption. Eng. Sci. 2018, doi: 10.30919/espub.es.180308. (21) Ai, L. H.; Li, L. L. Efficient removal of organic dyes from aqueous solution with ecofriendly biomass-derived carbon@montmorillonite nanocomposites by one-step hydrothermal process. Chem. Eng. J. 2013, 223, 688-695. (22) Li, X. Y.; Zeng, C. M.; Jiang, J.; Ai, L. H. Magnetic cobalt nanoparticles embedded in hierarchically porous nitrogen-doped carbon frameworks for highly efficient and well-recyclable catalysis. J. Mater. Chem. A 2016, 4, 7476-7482. (23) Yang, X. T.; Liang, C. B.; Ma, T. B.; Guo, Y. Q.; Kong, J.; Gu, J. W.; Chen, M. J.; Zhu, J. H. A review on thermally conductive polymeric composites: classification, measurement, model & equations, mechanism and fabrication methods. Adv. Compos. Hybrid Mater. 2018, 1, 56-78. (24) Li, B.; Yang, L.; Wang, C. Q.; Zhang, Q. P.; Liu, Q. C.; Li, Y. D.; Xiao, R. Adsorption of Cd(II) from aqueous solutions by rape straw biochar derived from different modification processes. Chemosphere 2017, 175, 332-340. (25) Ghasemi, E.; Heydari, A.; Sillanpää, M. Superparamagnetic Fe3O4@EDTA 23



Page 24 of 40

nanoparticles as an efficient adsorbent for simultaneous removal of Ag(I), Hg(II), Mn(II), Zn(II), Pb(II) and Cd(II) from water and soil environmental samples. Microchem J. 2017, 131, 51-56. (26)

Chowdhury,

P.;

Athapaththu,

S.;

Elkamel,

A.;

Ray,

A.

K.

Visible-solar-light-driven photo-reduction and removal of cadmium ion with Eosin Y-sensitized TiO2 in aqueous solution of triethanolamine. Sep. Purif. Technol. 2017, 174, 109-115. (27) Jabeen, H.; Chandra, V.; Jung, S.; Lee, J. W.; Kim, K. S.; Kim, S. B. Enhanced Cr(VI) removal using iron nanoparticle decorated grapheme. Nanoscale 2011, 3, 3583-3585. (28) Ludwig, R. D.; Su, C. M.; Lee, T. R.; Wilkin, R. T.; Acre, S. D.; Ross, R. R.; Keeley, A. In situ chemical reduction of Cr(VI) in groundwater using a combination of ferrous sulfate and sodium dithionite: a field investigation. Environ. Sci. Technol. 2007, 41, 5299-5305. (29) Shekhawat, A.; Kahu, S.; Saravanan, D.; Jugade, R. Removal of Cd(II) and Hg(II) from effluents by ionic solid impregnated chitosan. Int. J. Biol. Macromol. 2017, 104, 1556-1568. (30) Ge, H. C.; Wang, J. C. Ear-like poly (acrylic acid)-activated carbon nanocomposite: a highly efficient adsorbent for removal of Cd(II) from aqueous solutions. Chemosphere 2017, 169, 443-449. (31) Komárek, M.; Koretsky, C. M.; Stephen, K. J.; Alessi, D. S.; Chrastný, V. Competitive adsorption of Cd(II), Cr(VI), and Pb(II) onto nanomaghemite: a spectroscopic and modeling approach. Environ. Sci. Technol. 2015, 49, 12851-12859. (32) Guo, X. Y.; Du, B.; Wei, Q.; Yang, J.; Hu, L. H.; Yan, L. G.; Xu, W. Y. Synthesis of amino functionalized magnetic graphenes composite material and its application to 24


Page 25 of 40 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


remove Cr(VI), Pb(II), Hg(II), Cd(II) and Ni(II) from contaminated water. J. Hazard. Mater. 2014, 278, 211-220. (33) Zouboulis, A. I.; Kydros, K. A.; Matis, K. A. Removal of hexavalent chromium anions from solutions by pyrite fines. Wat. Res. 1995, 29, 1755-1760. (34) Wang, H.; Wang, X. J.; Ma, J. X.; Xia, P.; Zhao, J. F. Removal of cadmium(II) from aqueous solution: a comparative study of raw attapulgite clay and a reusable waste-struvite/attapulgite obtained from nutrient-rich wastewater. J. Hazard. Mater. 2017, 329, 66-76. (35) Wang, X. H.; Wang, A. Q. Removal of Cd(II) from aqueous solution by a composite hydrogel based on attapulgite. Environ. Technol. 2010, 31, 745-753. (36) Li, Y. H.; Wang, S. G.; Luan, Z. K.; Ding, J.; Xu, C. L.; Wu, D. H. Adsorption of cadmium(II) from aqueous solution by surface oxidized carbon nanotubes. Carbon 2003, 41, 1057-1062. (37) Wang, Z. H.; Yao, Z. J.; Zhou, J. T.; Zhang, Y. Reuse of waste cotton cloth for the extraction of cellulose nanocrystals. Carbohydr. Polym. 2017, 157, 945-952. (38) Lin, J.; Chen, X. Y.; Chen, C. Y.; Hu, J. T.; Zhou, C. L.; Cai, X. F.; Wang, W.; Zheng, C.; Zhang, P. P.; Cheng, J.; Guo, Z. H.; Liu, Hu. Durably antibacterial and bacterially antiadhesive cotton fabrics coated by cationic fluorinated polymers. ACS Appl. Mater. Interfaces 2018, 10, 6124-6136. (39) Sun, Z. Y.; Zhang, L.; Dang, F.; Liu, Y.; Fei, Z. Y.; Shao, Q.; Lin, H.; Guo, J.; Xiang, L. C.; Yerra, N.; Guo, Z. H. Experimental and simulation-based understanding of morphology controlled barium titanate nanoparticles under co-adsorption of surfactants. Crystengcomm 2017, 19, 3288-3298. (40) Song, B.; Wang, T. T.; Sun, H. G.; Shao, Q.; Zhao, J. K.; Song, K. K.; Hao, L. H.; Wang, L.; Guo, Z. H. Two-step hydrothermally synthesized carbon nanodots/WO3 25



photocatalysts with enhanced photocatalytic performance. Dalton Trans. 2017, 46, 15769-15777. (41) Hu, C.; Li, Z. Y.; Wang, Y. L.; Gao, J. C.; Dai, K.; Zheng, G. Q.; Liu, C. T.; Shen, C. Y.; Song, H. X.; Guo, Z. H. Comparative assessment of the strain-sensing behaviors of polylactic acid nanocomposites: reduced graphene oxide or carbon nanotubes. J. Mater. Chem. C 2017, 5, 2318-2328. (42) Guan, X. Y.; Zheng, G. Q.; Dai, K.; Liu, C. T.; Yan, X. R.; Shen, C. Y.; Guo, Z. H. Carbon nanotubes-adsorbed electrospun PA66 nanofiber bundles with improved conductivity and robust flexibility. ACS Appl. Mater. Interfaces 2016, 8, 14150-14159. (43) Luo, F.; Liu, X. H.; Shao, C. G.; Zhang, J. X.; Shen, C. Y.; Guo, Z. H. Micromechanical analysis of molecular orientation in high-temperature creep of polycarbonate. Mater. Design 2018, 144, 25-31. (44) Wang, X. D.; Liu, X. H.; Yuan, H. Y.; Liu, H.; Liu, C. T.; Li, T. X.; Yan, C.; Yan, X. R.; Shen, C. Y.; Guo, Z. H. Non-covalently functionalized graphene strengthened poly(vinyl alcohol). Mater. Design 2018, 139, 372-379. (45) Kang, H. j.; Cheng, Z. J.; Lai, H.; Ma, H. X.; Liu, Y. Y.; Mai, X. M.; Wang, Y. S.; Shao, Q.; Xiang, L. C.; Guo, X. K.; Guo, Z. H. Superlyophobic anti-corrosive and self-cleaning titania robust mesh membrane with enhanced oil/water separation. Sep. Purif. Technol. 2018, 201, 193-204. (46) Min, Y. L.; Chen, Y. C.; Zhao, Y. G. A small biomolecule-assisted synthesis of iron sulfide nanostructures and magnetic properties. Solid State Sci. 2009, 11, 451-455. (47) Wang, D. F.; Guo, W.; Zhang, G. L.; Zhou, L. L.; Wang, M.; Lu, Y. J.; Cai, D. Q.; Wu, Z. Y. Remediation of Cr(VI)-contaminated acid soil using a nanocomposite. ACS 26


Page 26 of 40

Page 27 of 40 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


Sustainable Chem. Eng. 2017, 5, 2246-2254. (48) Xu, H.; Zhu, B. S.; Ren, X. M.; Shao, D. D.; Tan, X. L.; Chen, C. L. Controlled synthesized natroalunite microtubes applied for cadmium(II) and phosphate co-removal. J. Hazard. Mater. 2016, 314, 249-259. (49) Du, J. K.; Bao, J. G.; Lu, C. H.; Werner, D. Reductive sequestration of chromate by hierarchical FeS@Fe0 particles. Wat. Res. 2016, 102, 73-81. (50) Liu, Y. Y.; Xiao, W. Y.; Wang, J. J.; Mirza, Z. A.; Wang, T. Optimized synthesis of FeS nanoparticles with a high Cr(VI) removal capability. J. Nanomater. 2016, 2016, 1-9. (51) Guo, H.; Zhang, S. F.; Kou, Z. N.; Zhai, S. R.; Ma, W.; Yang, Y. Removal of cadmium(II) from aqueous solutions by chemically modified maize straw. Carbohydr. Polym. 2015, 115, 177-185. (52) Zhang, J.; Cai, D. Q.; Zhang, G. L.; Cai, C. J.; Zhang, C. L.; Qiu, G. N.; Zheng, K.; Wu, Z. Y. Adsorption of methylene blue from aqueous solution onto multiparous palygorskite modified by ion beam bombardment: Effect of contact time, temperature, pH and ionic strength. Appl. Clay Sci. 2013, 83-84, 137-143. (53) Barick, K. C.; Singh, S.; Bahadur, D.; Lawande, M. A.; Patkar, D. P.; Hassan, P. A. Carboxyl decorated Fe3O4 nanoparticles for MRI diagnosis and localized hyperthermia. J. Colloid Interface Sci. 2014, 418, 120-125. (54) Li, Y. J.; Wang, W. Y.; Zhou, L. Q.; Liu, Y. Y.; Mirza, Z. A.; Lin, X. Remediation of hexavalent chromium spiked soil by using synthesized iron sulfide particles. Chemosphere 2017, 169, 131-138. (55) Mullet, M.; Boursiquot, S.; Ehrhardt, J. J. Removal of hexavalent chromium from solutions by mackinawite, tetragonal FeS. Colloids and Surfaces A: Physicochem. Eng. Aspects 2004, 244, 77-85. 27



(56) Du, Z. J.; Zhang, Y.; Li, Z. J.; Chen, H.; Wang, Y.; Wang, G. T.; Zou, P.; Chen, H. P.; Zhang, Y. S. Facile one-pot fabrication of nano-Fe3O4/carboxyl-functionalized baker’s yeast composites and their application in methylene blue dye adsorption. Appl. Surf. Sci. 2017, 392, 312-320. (57) Carver, J. C.; Schweitzer, G. K. Use of X-Ray photoelectron spectroscopy to study bonding in Cr, Mn, Fe, and Co compounds. J. Chem. Phys. 1972, 57, 973-982. (58) Gong, Y. Y.; Gai, L. S.; Tang, J. C.; Fu, J.; Wang, Q. L.; Zeng, E. Y. Reduction of Cr(VI) in simulated groundwater by FeS-coated iron magnetic nanoparticles. Sci. Total Environ. 2017, 595, 743-751. (59) Zhao, D. L.; Gao, X.; Wu, C. N.; Xie, R.; Feng, S. J.; Chen, C. L. Facile preparation of amino functionalized graphene oxide decorated with Fe3O4 nanoparticles for the adsorption of Cr(VI). Appl. Surf. Sci. 2016, 384, 1-9. (60) Rai, V.; Vajpayee, P.; Singh, S. N.; Mehrotra, S. Effect of chromium accumulation on photosynthetic pigments, oxidative stress defense system, nitrate reduction, proline level and eugenol content of Ocimum tenuiflorum L. Plant Sci. 2004, 167, 1159-1169.

28


Page 28 of 40

Page 29 of 40 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


Figure captions: Figure 1 (A) Influence of FeS amount in FeS/CF (area of 22.7 cm2) on removal efficiency of Cr(VI) (C0=20 mg/L, pH=4.6) at 30oC. (B) Influence of initial pH of Cr(VI) aqueous solution (C0=20 mg/L) on the removal efficiency of FeS/CF-24 at 30°C. (C) Influence of temperature on removal efficiency of FeS/CF-24 on Cr(VI) (C0=20 mg/L, pH=4.6). (D) Influence of CFFM amount in CFFM/CF (area of 11.3 cm2) on the removal efficiency of Cd(II) (C0=25 mg/L, pH=5.3) at 30oC. (E) Influence of initial pH of Cd(II) aqueous solution (C0=25 mg/L) on the removal efficiency of OCFFM/CF at 30°C, wherein the insert was the zeta potentials of CFFM under different pH. (F) Influence of temperature on removal efficiency of OCFFM/CF on Cd(II) (C0=25 mg/L, pH=5.3). Figure 2 (A-D) Digital photographs of the removal process of FeS/CFFM/CF for Cr(VI) and Cd(II) in a fish tank (A and B) before and (C and D) after treatment. (E) Removal efficiency of FeS/CFFM/CF for Cr(VI) and Cd(II) in a fish tank with time. (F) Schematic diagram of structure of FeS/CFFM/CF. (G) Schematic diagram of the removal mechanism. (H and I) Digital photographs of fish in fish tanks without and with FeS/CFFM/CF treatment at 0 h. (J and K) Digital photographs of fish in fish tanks without and with FeS/CFFM/CF treatment at 59 h. (L) Fish viability with time. (M and N) Total amounts of Cr and Cd in fish (a) without and (b) with FeS/CFFM/CF. Figure 3 (A) Schematic diagrams of leaching systems. (B and C) Effect of FeS/CFFM/CF on Cr and Cd distributions in sand-soil column. Figure 4 SEM images of (A and B) CF, (C) FeS, (D) FeS/CF, (E) FeS/CF/Cr, (F) CFFM, (G) CFFM/CF, and (H) CFFM/CF/Cd. (f) TEM image of CFFM. Figure 5 (a) SEM image of FeS/CF, (b) merged image of the distribution maps of (c) C, (d) O, (e) Fe, and (f) S in FeS/CF. (g) SEM image of FeS/CF/Cr, (h) merged image 29



of the distribution maps of (i) C, (j) O, (k) Fe, (l) S, and (m) Cr in FeS/CF/Cr. (n) SEM image of CFFM/CF, (o) merged image of the distribution maps of (p) C, (q) O, and (r) Fe in CFFM/CF. (s) SEM image of CFFM/CF/Cd, (t) merged image of the distribution maps of (u) C, (v) O, (w) Fe, and (x) Cd in CFFM/CF/Cd. Figure 6 (A and B) FTIR spectra of CFFM and CFFM/Cd. (C and D) XRD patterns of (a) FeS, (b) FeS/Cr, (c) CFFM, and (d) CFFM/Cd. (E and F) N2 adsorption-desorption isotherms of FeS and CFFM with insets of their pore size distributions respectively. Figure 7 (A) Full-range XPS spectra of FeS and FeS/Cr. (B and C) XPS spectra of Fe2p and S2p of FeS. (D-F) XPS spectra of Fe2p, S2p, and Cr2p of FeS/Cr. Figure 8 (A-D) Digital photographs of water spinach after seeding for 72 h in Cr(VI) (10 mg/L)-Cd(II) (2 mg/L) aqueous solutions (A and C) without or (B and D) with FeS/CFFM/CF. (E) Chlorophyll content in leaves and (F) amounts of Cr and Cd elements in water spinach after seeding for 72 h (a) without and (b) with FeS/CFFM/CF. Figure 9 (A and B) Schematic diagrams of practical application of FeS/CFFM/CF in river and field.

30


Page 30 of 40

Page 31 of 40 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


Figures:

Figure 1

31



Figure 2

32


Page 32 of 40

Page 33 of 40 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


Figure 3

33



Figure 4

34


Page 34 of 40

Page 35 of 40 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


Figure 5

35



Figure 6

36


Page 36 of 40

Page 37 of 40 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


Figure 7

37



Figure 8

38


Page 38 of 40

Page 39 of 40 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


Figure 9

39



TOC Graphic A novel nano-system with sandwich-like structure was synthesized to remove Cr(VI) and Cd(II) simultaneously from water and soil.

40


Page 40 of 40

Sandwich-like nano-system for simultaneous ... - ACS Publications

Recommend Documents