Translate this page into:
Treatment of lead contaminated water using synthesized nano-iron supported with bentonite/graphene oxide
⁎Corresponding author. xnyu@wzu.edu.cn (XiaoNiu Yu)
-
Received: ,
Accepted: ,
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.
Peer review under responsibility of King Saud University.
Abstract
Conventional nano-iron is widely used in heavy metal contaminated groundwater remediation. However, it is easily oxidized when exposed to the air or re-aggregated under water soaking conditions. In this study, a nano-sized iron supported by graphene oxide/bentonite is proposed which is synthesized by liquid-phase reduction method. The TEM test results showed that the support effect of graphene oxide/bentonite well solved shortcomings of conventional nano-iron, since the flaky structure of graphene oxide and layered bentonite could effectively disperse nano-iron particles. The TEM images indicated that nano-iron supported by graphene oxide/bentonite at a weight ratio of 4:1:7.3 (nanoiron:graphene oxide:bentonite) yielded the smallest particle size, and most particle size was less than 30 nm. The test results show that addition of graphene oxide could improve the removal of lead ions, especially in acidic environment as compared to bentonite alone supported nano-iron. The optimum dosage of graphene oxide was found to be 6.98% based on the removal rate of lead. It was found that the removal rate of lead by graphene oxide/bentonite supported nano-iron increased with the increase of pH of simulated contaminated groundwater. The temperature was found to affect the removal rate of lead ions as well. The adsorption of lead ions by graphene oxide/bentonite supported nano-iron conformed to quasi-second order reaction kinetic model, and the adsorption isotherm well fit the Langmuir model.
Keywords
Graphene oxide
Bentonite
Nano-iron
Lead ions
Removal rate
1 Introduction
Water is of great significance to mankind, it is the basic material for building up the human body, and is also an indispensable medium for our production activities. Among the functional areas divided by the Earth's water environment, closely related to human beings are the functional areas for surface water and groundwater environment. Due to the influence of human activities, the pollutants entering the surface water and groundwater environment have been increasing year by year. These toxic and harmful substances have brought many problems to the global environment and human health, seriously hindering the development of human civilization. Heavy metal pollution is an important part of environmental pollution, of which lead ions pollution is increasingly valued by all countries (Du et al., 2012, 2014, 2014; Fan et al., 2017; Yang et al., 2017). Lead is a chemical element whose chemical symbol is Pb, which has an atomic number of 82 and is the largest non-radioactive element. Lead is a soft and toxic, belongs to heavy metals. Through the water, food, breathing, skin contact, etc., heavy metal lead ions into the body and produce injuries. Lead ions can damage adult nervous system, digestive system, can lead to children's growth retardation, loss of appetite, walking inconvenience, lack of concentration and mental retardation and other issues (Li et al., 2005; Gump et al., 2017). The treatment methods of lead ions have ion exchange (Berber-Mendoza et al., 2006), chemical precipitation (Leupin et al., 2005); biosorption (Mahmut et al., 2008), infiltration, electrolysis, membrane separation (Sang et al., 2008), and so on. At present, nano-iron has been used in heavy metal pollution of groundwater, soil and other governance. Compared with the traditional methods of heavy metal treatment, the removal efficiency of nano-iron is high and the time required is short (Zhao et al., 2016; Theron et al., 2008). These advantages make nano-iron more and more important in removing heavy metal pollution. The nano-iron has the advantages of small particle size (<100 nm), large specific surface area and high reactivity (Dong et al., 2017; Qian et al., 2017; Tiberg et al., 2016), which is easily oxidized or spontaneous in the air (Su et al., 2016; Ezzatahmadi et al., 2017). In addition, the nano-iron has magnetism and is easily aggregated in water (Sun et al., 2017). In order to solve this problem, nano-iron has been studied in silica, activated carbon, starch, polymers and other substances.
In this study, bentonite and graphene oxide were used to support nano-iron. Bentonite (montmorillonite unit layers) has enough space to support zero-valent iron particles, and can swell and uniform dispersion in water, is a nice carrier (Du et al., 2015). In addition, bentonite is cheap, easy to get and without pollution on the environment. Graphene oxide has excellent hydrophilicity and uniformly dispersed in water under the action of ultrasound, and has strong adsorption properties and flake structure, can be utilized for the removal of heavy metal ions and support other substances (Li et al., 2008; Terrones et al., 2010; Dreyer et al., 2010; Jabeen et al., 2013; Lu et al., 2018a, 2018b; Zhang et al., 2015; Quan et al., 2017). Therefore, bentonite and graphene oxide can be used as carrier for support nano-iron.
2 Experimental methods and materials
2.1 Materials
Bentonite was purchased from Heishan Chunyuan Bentonite Factory, China. Graphene oxide (99%, thickness: 0.55–1.2 nm, diameter: 0.5–3 μm, layers: <3) was provided by J&K Scientific Ltd. FeCl2·4H2O (analytical pure), NaBH4 (analytical pure), anhydrous C2H5OH (analytical pure), NaOH (chemical pure) and Pb(NO3)2 (analytical pure) were obtained from Xilong Scientific Ltd.
2.2 Preparation of bentonite/graphene oxide -supported nanoiron (GO-B-nZVI)
The first step, 0.15 g of graphene oxide and 150 ml of high purity water were added into a beaker for ultrasonic vibration 1 h. The second step, 0.7 g of bentonite was added to above solution and stirred for 12 h. The third step, 1.069 g of FeCl2·4H2O was added into the mixture solution of graphene oxide and bentonite for ultrasonic vibration 1 h after stirring 2 h. The fourth step, 150 ml of anhydrous C2H5OH was added into the mixture solution of graphene oxide, bentonite and FeCl2·4H2O for ultrasonic vibration 1 h after stirring 2 h. The pH of the mixture solution was adjusted to 11 with NaOH solution. The fifth step, 0.815 g of NaBH4 was slowly added to the mixture solution of graphene oxide, bentonite and FeCl2·4H2O (500 ml, pH = 11). The dropping process was about 15 min and stirring 20 min. The sixth step, the supernatant was decanted by centrifugation and the remaining solid was washed three times with high purity water and anhydrous C2H5OH, respectively. The material was then lyophilized in a lyophilizer. Finally, the specimen was kept in the refrigerator (−85 °C) with ziplock bag, recorded as 0.15GO-B-nZVI. Under the same conditions, different GO-B-nZVI were synthesized when the amount of graphene oxide was 0, 0.05 and 0.4g, recorded as: B-nZVI, 0.05GO-B-nZVI, 0.4GO-B- nZVI, respectively. The graphene oxide could be reduced with sodium borohydride, recorded as: rGO.
2.3 Removal of lead ions
Lead ions solution could well be prepared by Pb(NO3)2 dissolving in high purity water. The pH of mixture solution was adjusted by 1 mol/L of HNO3 solution or 1 mol/L of NaOH solution. The 1 g of adsorbent was put into the lead ions solution (1L) and placed in a constant temperature and humidity chamber after ultrasonic vibration for 10 min (Zhu et al., 2018a, 2018b; Zheng et al., 2018; Chen et al., 2018; Zhao et al., 2018). Adsorption experiments were performed at room temperature. The precipitated materials were untreated and put in an oven at 60 °C for 24 h. The concentration of lead ions was measured by atomic absorption spectrometer (Shimadzu Technology Trading Company). Removal rate of lead ions was calculated by the formula: where R is the removal rate of lead ions, Ce is the equilibrium concentration of lead ions (mg/L), Co is the initial concentration of lead ions (mg/L).
2.4 Characterization of bentonite, B-nZVI, GO-B-nZVI, and rGO
Fourier-transform infrared spectroscopy (FTIR) analysis of all specimens was performed on a TENSOR27 FTIR (4000–400 cm−1, Zhengzhou Great Wall Science and Industry Co., Ltd.). X-ray diffraction (XRD, Bruker Company, Germany) analysis of all samples was carried out on D8-Advance X diffractometer (40 kV, 40 mA) with Cu radiation (λ = 1.5406 Å) at a rate of 0.15 s/step in a range of 5–90°. Lorentz-Transmission Electron Microscopy (TEM) images of the specimens were observed on a JEM, 2100F equipment. All samples were dispersed in anhydrous acetone before test.
3 Results and discussion
3.1 XRD patterns of B-nZVI, bentonite, GO-B-nZVI, and rGO
The XRD patterns of B-nZVI, bentonite, GO-B-nZVI, and rGO are shown in Fig. 1. The diffraction peaks of B-nZVI, 0.05GO-B-nZVI, 0.15GO-B-nZVI and 0.4GO-B-nZVI synthesized by liquid-phase reduction method corresponding to 2θ = 44.8°, which is the characteristic peak of elemental iron, indicating that the material contains elemental iron, as shown in Fig. 1a. The diffraction peaks of GO are similar with rGO (2θ = 10.7°) (Fig. 1b).
3.2 FTIR spectra of B-nZVI, bentonite, B-nZVI, GO-B-nZVI and rGO
FTIR spectra of the specimens are shown in Fig. 2. Fig. 2(a) shows the absorption peak at 3620 cm−1 is the vibrational absorption peak of hydroxyl. The bending vibration peak of HOH at 1630 cm−1 is water. The strong absorption peak at 1030, 525 and 479 cm−1 is Si-O, Al-Si-O and Si-O-Si bending vibration peak, respectively (Tabak et al., 2007). Bentonite composition contains silicon dioxide, aluminium oxide and water. Their components can be found in FTIR spectra of the corresponding peak. The FTIR spectra of B-nZVI, 0.05GO-B-nZVI, 0.15GO-B-nZVI and 0.4GO-B-nZVI synthesized by liquid-phase reduction method show the characteristic peaks is same with bentonite. Therefore, the synthetic material process did not destroy the bentonite structure and chemical composition, which plays a role in the dispersion of nano-iron.
0.15GO-B-nZVI and 0.4GO-B-nZVI have C⚌C stretching vibration absorption peak at 1593 cm−1, which is due to the addition of graphene oxide (Zhang et al., 2010). The addition of graphene oxide also plays a role of coating nano-iron. A suitable amount of graphene oxide can be more uniform dispersion and the formation of smaller size for nano-iron particles, of which 0.15 g is the best. 0.05 GO-B-nZVI at 1593 cm−1 did not find the corresponding absorption peak, which probably due to the amount of graphene oxide is too small. Fig. 2(b) shows 1630 and 1730 cm−1 corresponding to C⚌C and C⚌O stretching vibration in graphene oxide (Shang et al., 2016). The rGO did not absorption peak at 1730 cm−1, which was caused by the reduction of sodium borohydride. 1400 and 1055 cm−1 are the stretching vibration of C—OH and C—O, respectively (Bai et al., 2016; Loryuenyong et al., 2013). GO or rGO are used to enlarge disperse nZVI and the specific surface area of B-nZVI. Therefore, the adsorption capacity of bentonite for lead ions can be improved by GO or rGO bentonite.
3.3 Micro/nano-structure of B-nZVI, bentonite, GO-B-nZVI, and rGO
TEM images show bentonite is uniform sheet-like structure and provide a load platform for the iron particles, as shown Fig. 3. The shape of GO is uniform sheet structure. However, the morphology of rGO is flocculent, which can support nano-iron and also avoid agglomeration phenomenon. The black particles are the zero-valent nano-iron. It is easy to find that the addition of the graphene oxide makes the nano-sized iron smaller in size by comparison. The average size of iron particles is the smallest with size range below 30 nm. Therefore, the nano-iron particles can be evenly dispersed in the graphene oxide and bentonite.
3.4 The effect of pH, temperature, concentration of lead ions, and time on removal rate
The BET area of GO-B-nZVI is 47.33 m2/g measured according to literature reported (Du et al., 2014). Fig. 4(a) shows that the removal rate of lead ions by the 0.15GO-B-nZVI is better than that of bentonite, graphene oxide, reduced graphene oxide and bentonite-supported graphene oxide when pH is 5 ± 0.3, adsorbent is 1 g/L, concentration of lead ions is 200 mg/L, temperature is 18 °C. After 16 h, the removal rate of 0.15GO-B-nZVI reaches 99%. Removal rate of lead ions by B-nZVI, GO, rGO and bentonite are 90%, 38%, 73% and 63%, respectively. Fig. 4(b) indicates that 0.15 g of graphene oxide is the best with time increases. When the content of graphene oxide reaches 0.4 g, the removal rate of lead ions obviously decreases, which may be caused by the excessive amount of graphene oxide wrapping nano-iron to make it difficult to remove lead ions (Jabeen et al., 2013).
The effect of pH on removal rate of lead ions is shown in Fig. 5. Under a certain range of pH, the removal rate of lead ions by 0.15GO-B-nZVI, B-nZVI, GO, rGO and bentonite increases with the increase of pH when adsorbent is 1 g/L, concentration of lead ions is 200 mg/L, the temperature is 18 °C, time is 8 h. In an acidic environment (pH = 3), the removal rate of lead ions by bentonite is only 12%. When the pH value is too small, H+ ions can affect the surface structure of bentonite, and H+ competes with metal ions, it is not conducive to the removal of heavy metals (Zhu et al., 2011; Li et al., 2009; Zhang et al., 2010). At pH = 3, the removal rate of lead ions by 0.15GO-B-nZVI has reached 78%, much higher than 0.05GO-B-nZVI, 0.15GO-B-nZVI and 0.4GO-B-nZVI. Therefore, the addition of graphene oxide can improve the removal rate of lead ions in an acidic environment.
The effect of temperature on the removal rate of lead ions is shown in Fig. 6. At lower concentration (200 mg/L) of lead ions, the increase of temperature led to the obvious increase of the removal rate of lead ions by bentonite. For 0.15GO-B-nZVI, the influence of temperature on the removal rate of lead ions is not obvious.
The effect of concentration of lead ions on the removal rate of lead ions is shown in Fig. 7. The concentration of lead ions is 100, 200, 300, 400 and 500 mg/L. 0.1 g of 0.15GO-B-nZVI is added to different concentration of lead ions (100 ml). The removal time, pH and temperature are 24 h, 5 ± 0.3 and 18 °C respectively. The removal rate of lead ions decreases with concentration of lead ions increases. The removal rate of lead ions by 0.15GO-B-nZVI has the best effect than B-nZVI, GO, rGO and bentonite. When the concentration of lead ions is 500 mg/L, the removal rate of lead ions by 0.15GO-B-nZVI is 66%, while that of other materials is less than 50%.
The removal rates of lead ions by 0.15GO-B-nZVI at different concentrations and temperatures are shown in Fig. 8. The concentration of lead ions is 250, 300, 350, 400, 450 and 500 mg/L. 0.1 g of 0.15GO-B-nZVI is added to different concentration of lead ions (100 ml). The removal time and pH are 4 h and 5 ± 0.3, respectively. With the increase of concentration of lead ions, the removal rate of lead ions by 0.15GO-B-nZVI is decreased due to the limited active site of the adsorbent (Ritter et al., 2002; Hao et al., 2012). When concentration of lead ions is 200 mg/L, temperature has little effect on the removal rate of lead ions. When the concentration of lead ions increases to 500 mg/L, the removal rate of lead ions by 0.15GO-B-nZVI firstly increases and then decreased slightly with the increase of temperature. When temperature is 20, 30, 40 and 50 °C, the removal rate of lead ions by 0.15GO-B-nZVI is 56, 60, 65 and 64%, respectively. The results show that the proper temperature increase can improve the diffusion and mobility of lead ions at the higher concentration of lead ions (500 mg/L), which is beneficial for the removal of lead ions. The best temperature is 40 °C. When the temperature rises to 50 °C, the effect of temperature on the removal rate of lead ions is reduced because excessive temperature may cause desorption of nano-iron.
3.5 Adsorption mechanism, thermodynamics, kinetics and adsorption isotherms of lead ions
Lead ions can be reduced by nano-iron and adsorbed through Fe(OH)2 and Fe(OH)3 after corrosion of nano-iron in aqueous solution (Zhao et al., 2017; Chen et al., 2017; Li et al., 2016, 2018). Therefore, the nano-iron has adsorption and reduction on lead ions. The thermodynamics parameters (〈DELTA〉G, 〈DELTA〉H, and 〈DELTA〉S) of nano-iron can be calculated at 298 K by Eqs. (1)–(4) and Table 1. Therefore, 〈DELTA〉G, 〈DELTA〉H, and 〈DELTA〉S are 1424.81 KJ/mol, 1759.27 KJ/mol, and 663.64 J/ (mol·K), respectively (Bezerra da Silva et al., 2018; Mahdi et al., 2017).
| Fe2+(aq) | BH4−(aq) | H2O(l) | Fe(s) | B(OH)3(aq) | H2(g) | |
|---|---|---|---|---|---|---|
| 〈DELTA〉G | −78.9 | 27.31 | −237.13 | 0 | −11.12 | 0 |
| 〈DELTA〉H | −89.1 | 11.51 | −285.83 | 0 | 11.30 | 0 |
| 〈DELTA〉S | −137.7 | 26.4 | 69.91 | 27.3 | 23.00 | 130.7 |
The quasi-first-order kinetic model and second-order kinetic model were applied to study the adsorption kinetics of the graphene oxide/bentonite-supported nano-iron:
Eqs. (5) and (6) are quasi-first-order and second-order kinetic equations, respectively. Where, t is the adsorption time. qt is the adsorption amount of lead ions on the adsorbent at time t, mg g−1. qe is the adsorption amount of lead ion on the adsorbent mg g−1. k1 and k2 are constants of quasi-first-order and quasi-second-order adsorption rate (Lagaly, 1981; Saruchi, 2019). The quasi-first-order and quasi-second-order kinetic model of the relevant parameters can be obtained according to the above equation fitting, as shown in Table 2. Therefore, k1 and k2 are likewise obtained by fitting curve (Fig. 9a and b). By comparing the fitting results of the two models, it is found that quasi-second-order kinetics fit better and the correlation coefficient is 0.998. According to quasi-second-order kinetic model, qe,cal (203.67 mg g−1) is closer to the experimental value qe, exp(199.21 mg g−1). Therefore, the graphene oxide/bentonite supported nano-iron adsorbs lead ions more in line with quasi-second-order kinetic model.
| Absorbents | qe,exp/(mg*g−1) | Pseudo-first-order kinetic model | Pseudo-second-order kinetic model | ||||
|---|---|---|---|---|---|---|---|
| K1 | qe,cal/(mg*g−1) | R2 | K2/h−1 | qe,cal/(mg*g−1) | R2 | ||
| GO-B-nZVI | 199.21 | 0.231 | 89.29 | 0.989 | 0.008 | 203.67 | 0.998 |
Graphene oxide/bentonite supported nano-iron adsorption of lead ions is a dynamic equilibrium process, in order to explore the law of the composite material adsorption of lead ions, the most commonly used to describe the chemical adsorption behavior of Langmuir and Freundlich isothermal model, as shown in Eqs. (7) and (8).
| Temperature (°C) | Langmuir | Freundlich | ||||
|---|---|---|---|---|---|---|
| qm/(mg·g−1) | kL/(L·mg−1) | R2 | kF | n | R2 | |
| 20 | 321.54 | 0.0259 | 0.995 | 66.52 | 3.746 | 0.986 |
| 30 | 364.96 | 0.0210 | 0.993 | 57.13 | 3.190 | 0.976 |
| 40 | 431.03 | 0.0158 | 0.994 | 41.68 | 2.527 | 0.989 |
| 50 | 404.89 | 0.0171 | 0.989 | 45.22 | 2.693 | 0.983 |
4 Conclusions
The graphene oxide/bentonite supported nano-iron can be easily prepared by the liquid-phase reduction method, which can solve the problems of oxidization and agglomeration of nano-iron.
The addition of graphene oxide can improve the dispersion of nano-zero-valent iron, and make the smaller particle size of zero-valent nano-iron particles. 0.15 g of graphene oxide is the best content.
The 0.15GO-B-nZVI has the strongest removal efficiency for lead ions. Under a specified pH, the removal rate of lead ions increases with the increase of pH.
The removal rate of lead ions by 0.15GO-B-nZVI changes little with the increase of temperature at low concentrations of lead ions solution. When lead ions concentration is high, the removal rate of lead ions by 0.15GO-B-nZVI firstly increases slightly and then decreases with the increase of temperature.
The adsorption of lead ions by 0.15GO-B-nZVI follows the pseudo-second-order kinetic equation and can be described by the Langmuir model.
Acknowledgements
This work was supported by the National Nature Science Foundation of China (Grant No. 51578427, 51572197, 41372264, and 51702238), the Plan Project of Science and Technology of Zhejiang Province (No. 2014C33015 and 2015C33220), the Opening Funds of Jiangsu Key Laboratory of Construction Materials, China (CM2018-02), and the Plan Project of Science and Technology of Wenzhou (No. ZS2017002).
References
- Brunauer-Emmet t-Teller (B.E.T.), Langmuir and Freundlich isotherm studies for the adsorption of nickel ions onto coal fly ash. Asian J. Water, Environ. Pollut.. 2016;13:49-53.
- [Google Scholar]
- Preparation and characterization of reduced graphene oxide/fluorhydroxyapatite composites for medical implants. J. Alloy. Compound.. 2016;688:657-667.
- [Google Scholar]
- Comparison of isotherms for the ion exchange of Pb(II) from aqueous solution onto homoionic clinoptilolite. J. Colloid Interface Sci.. 2006;301:40-45.
- [Google Scholar]
- Vibrational properties of bulk boric Acid 2A and 3T polymorphs and their two-dimensional layers: measurements and density functional theory calculations. J. Phys. Chem. A. 2018;122:1312-1325.
- [Google Scholar]
- Efficient sorption and reduction of U(VI) on zero-valent iron-polyaniline-graphene aerogel ternary composite. J. Colloid. Interf. Sci.. 2017;490:197-206.
- [Google Scholar]
- Synthesis of Ag nanoparticles decoration on magnetic carbonized polydopamine nanospheres for effective catalytic reduction of Cr(VI) J. Colloid. Interf. Sci.. 2018;536:1-8.
- [Google Scholar]
- Stabilization of nanoscale zero-valent iron (nZVI) with modified biochar for Cr(VI) removal from aqueous solution. J. Hazard. Mater.. 2017;332:79-86.
- [Google Scholar]
- Experimental investigation of influence of acid rain on leaching and hydraulic characteristics of cement-based solidified/stabilized lead contaminated clay. J. Hazard. Mater.. 2012;225–226:195-201.
- [Google Scholar]
- Engineering properties and microstructural characteristics of cement solidified zinc-contaminated kaolin clay. Can. Geotech. J.. 2014;51:289-302.
- [Google Scholar]
- Effect of acid rain pH on leaching behavior of cement stabilized lead-contaminated soil. J. Hazard. Mater.. 2014;271:131-140.
- [Google Scholar]
- Impacts of presence of lead contamination in clayey soil–calcium bentonite cutoff wall backfills. Appl. Clay Sci.. 2015;108:111-122.
- [Google Scholar]
- Clay-supported nanoscale zero-valent iron composite materials for the remediation of contaminated aqueous solutions: A review. Chem. Eng. J.. 2017;312:336-350.
- [Google Scholar]
- Impacts of presence of lead contamination on settling behavior and microstructure of clayey soil - calcium bentonite blends. Appl. Clay Sci.. 2017;142:109-119.
- [Google Scholar]
- Background lead and mercury exposures: Psychological and behavioral problems in children. Environ. Res.. 2017;158:576.
- [Google Scholar]
- SiO2/graphene composite for highly selective adsorption of Pb(II) ion. J. Colloid Interf. Sci.. 2012;369:381-387.
- [Google Scholar]
- Synthesis of nano zerovalent iron nanoparticles–Graphene composite for the treatment of lead contaminated water. J. Environ. Manage.. 2013;130:429-435.
- [Google Scholar]
- Adsorption behavior of copper ions from aqueous solution onto graphene oxide-CdS composite. Chem. Eng. J.. 2015;259:603-610.
- [Google Scholar]
- Arsenic removal from Bangladesh tube well water with filter columns containing zerovalent iron filings and sand. Environ. Sci. Technol.. 2005;39:8032-8037.
- [Google Scholar]
- Adsorption thermodynamic, kinetic and desorption studies of Pb2+ on carbon nanotubes. Water Res.. 2005;39:605-609.
- [Google Scholar]
- Removal of nitrate by zero-valent iron and pillared bentonite. J. Hazard. Mater.. 2009;174:188.
- [Google Scholar]
- Reductive immobilization of Re(VII) by graphene modified nanoscale zero-valent iron particles using a plasma technique. Sci. China Chem.. 2016;59:150-158.
- [Google Scholar]
- Processable aqueous dispersions of graphene nanosheets. Nat. Nanotechnol.. 2008;3:101.
- [Google Scholar]
- Metal-organic framework-based materials: superior adsorbents for the capture of toxic and radioactive metal ions. Chem. Soc. Rev.. 2018;47:2322-2356.
- [Google Scholar]
- Preparation and characterization of reduced graphene oxide sheets via water-based exfoliation and reduction methods. Adv. Mater. Sci. Engi.. 2013;2013
- [Google Scholar]
- Hybridization of graphene oxide with commercial graphene for constructing 3D metal-free aerogel with enhanced photocatalysis. Appl. Catal. B: Environ.. 2018;226:16-22.
- [Google Scholar]
- Photoredox catalysis over graphene aerogel-supported composites. J. Mater. Chem. A. 2018;6:4590-4604.
- [Google Scholar]
- Behzad S, Boric acid production from a low-grade boron ore with kinetic considerations. Mod. Chem. Appl.. 2017;5:1000218.
- [Google Scholar]
- Equilibrium and kinetic data, and adsorptionmechanism for adsorption of lead onto valonia tannin resin. Chem. Eng. J.. 2008;143:32-42.
- [Google Scholar]
- Nanoscale zero-valent iron supported by biochars produced at different temperatures: Synthesis mechanism and effect on Cr(VI) removal. Environ. Pollut.. 2017;223:153-160.
- [Google Scholar]
- Graphene and its derivatives as versatile templates for materials synthesis and functional applications. Nanoscale. 2017;9:2398-2416.
- [Google Scholar]
- An in situ study of the role of surface films on granular iron in the permeable iron wall technology. Contam. Hydrol.. 2002;55:87-111.
- [Google Scholar]
- Heavy metal-contaminated ground water treatment by a novel nanofiber membrane. Desalination. 2008;223:349-360.
- [Google Scholar]
- Adsorption kinetics and isotherms for the removal of rhodamine B dye and Pb2+ ions from aqueous solutions by a hybrid ion-exchanger. Arab. J. Chem.. 2019;12(3):316-329.
- [Google Scholar]
- Effect of the graphene derived from thermal reduction within matrix on the performance of graphene/poly (methyl methacrylate) composites. J. Anal. Appl. Pyrol.. 2016;120:215-221.
- [Google Scholar]
- Stabilisation of nanoscale zero-valent iron with biochar for enhanced transport and in-situ remediation of hexavalent chromium in soil. Environ. Pollut.. 2016;214:94-100.
- [Google Scholar]
- Nanoscale zero-valent iron for metal/metalloid removal from model hydraulic fracturing wastewater. Chemosphere. 2017;176:315.
- [Google Scholar]
- Characterization and pillaring of a Turkish bentonite (Resadiye) J. Colloid Interf. Sci.. 2007;313:5-11.
- [Google Scholar]
- Graphene and graphite nanoribbons: Morphology, properties, synthesis, defects and applications. Nano Today. 2010;5:351-372.
- [Google Scholar]
- Nanotechnology and water treatment: applications and emerging opportunities. Critic. Rev. Microbiol.. 2008;34:43-69.
- [Google Scholar]
- Immobilization of Cu and As in two contaminated soils with zero-valent iron–Long-term performance and mechanisms. Appl. Geochem.. 2016;67:144-152.
- [Google Scholar]
- Hydraulic conductivity and consolidation properties of soil-bentonite backfills exposed to CCR-impacted groundwater. J. Geotech. Geoenviron.. 2017;144
- [Google Scholar]
- Degradation of 2,4,6-trinitrotoluene (TNT) from explosive wastewater using nanoscale zero-valent iron. Chem. Eng. J.. 2010;158:566-570.
- [Google Scholar]
- P25-graphene composite as a high performance photocatalyst. ACS Nano. 2010;4:380-386.
- [Google Scholar]
- Waltzing with the versatile platform of graphene to synthesize composite photocatalysts. Chem. Rev.. 2015;115:10307-10377.
- [Google Scholar]
- An overview of preparation and applications of stabilized zero-valent iron nanoparticles for soil and groundwater remediation. Water Res.. 2016;100:245-266.
- [Google Scholar]
- EDTA functionalized Fe3O4/graphene oxide for efficient removal of U(VI) from aqueous solutions. J. Colloid. Interf. Sci.. 2017;504:300-307.
- [Google Scholar]
- Interaction between U(VI) with sulfhydryl groups functionalized graphene oxides investigated by batch and spectroscopic techniques. J. Colloid. Interf. Sci.. 2018;524:129-138.
- [Google Scholar]
- Investigation of the adsorption mechanisms of Pb(II) and 1-naphthol by beta-cyclodextrin modified graphene oxide nanosheets from aqueous solution. J. Colloid. Interf. Sci.. 2018;530:154-162.
- [Google Scholar]
- In situ carbothermal reduction synthesis of Fe nanocrystals embedded into N-doped carbon nanospheres for highly efficient U(VI) adsorption and reduction. Chem. Eng. J.. 2018;331:395-405.
- [Google Scholar]
- Gamma-ferric oxide nanoparticles decoration onto porous layered double oxide belts for efficient removal of uranyl. J. Colloid. Interf. Sci.. 2018;535:265-275.
- [Google Scholar]
- Sorption of Cu, Pb and Cr on Na-montmorillonite: Competition and effect of major elements. Chemosphere. 2011;84:484-489.
- [Google Scholar]