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200A Study on Adsorption Properties of Magnetic Citrate Bentonite for Hexavalent Chromium

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This research by the researcher of the College of Chemistry and Chemical Engineering of Guangxi University, discussed the paper on the adsorption performance of magnetic citric acid bentonite on hexavalent chromium, published in the important journal .


In order to improve the adsorption performance of bentonite on Cr(VI) and improve its solid-liquid separation and recovery capacity, a chitosan-modified composite magnetic adsorption material —— magnetic citrate bentonite (Magnetic Citric Acid Bentonite, MCAB) was constructed. SEM, XRD, VSM, FT-IR were used to characterize and compare the materials before and after modification. The results showed that functional groups such as ‒NH2, ‒OH and magnetic Fe3O4 particles in chitosan were loaded onto citric acid bentonite ( Citric Acid Bentonite, CAB). The adsorption performance of MCAB on Cr(VI) shows that compared with CAB, the adsorption performance of MCAB after compounding is obviously improved, and it has good magnetic separation ability; the pH value has a great influence on the adsorption of Cr(VI), the optimum pH. The value is in the range of 2.0 to 3.0; when the adsorbent dosage is 1.6 g · L‒1, pH value is 3.0, and the initial concentration of Cr(VI) is 10 mg · L‒1, the removal rate of Cr(VI) by MCAB Up to 99%; the fitting results of the adsorption isotherm equation and the kinetic equation are in accordance with the Langmuir adsorption isotherm model and the quasi-secondary kinetic model, respectively. Since the modified ‒NH2 on MCAB is protonated under acidic conditions, it will enhance the electrostatic attraction of Cr(VI). Therefore, the adsorption removal rate of Cr(VI) by MCAB is obviously improved. At the same time, the magnetic field is given to CAB. Fast solid-liquid separation ability. Studies have shown that MCAB has a good effect on the removal of Cr(VI) in simulated wastewater and is expected to be applied to the removal of Cr(VI) in actual wastewater.






(1) SEM, XRD, VSM, FT-IR and other characterization results show that magnetic Fe3O4 particles and chitosan have been loaded onto citric acid bentonite, which has the ability to quickly solid-liquid separation under external magnetic field conditions. (2) Compared with CAB, the composite modified MCAB has a significant improvement on the adsorption capacity of Cr(VI). With the increase of the amount of adsorbent, the removal rate increases obviously and tends to be gentle; the pH value has a great influence on the removal of Cr(VI), and it helps the MCAB to adsorb Cr(VI) under low pH conditions, and the removal rate can reach 99%. The adsorption isotherm equation accords with the Langmuir adsorption model, and the maximum adsorption capacity of the monolayer is 16.67 mgg‒1; the adsorption kinetics of MCAB for Cr(VI) accords with the quasi-secondary kinetic model, and the adsorption process is dominated by chemical adsorption. (3) The reason why MCAB enhances the adsorption performance of Cr(VI) can be summarized as the electrostatic attraction between protonated ‒NH3+ and HCrO4, the redox reaction of HCrO4 itself and the ligand exchange reaction. Synergistic interaction. In this study, the preparation process of MCAB is simple, the raw materials used are economical and environmentally friendly, and the adsorption effect has obvious advantages compared with other adsorbents of the same type. The results show that MCAB has certain application potential in the treatment of wastewater containing Cr(VI).


Take 2.0 g of CAB in 100 mL of deionized water, ultrasonically disperse for 5 min, then slowly add 1.47 g of FeCl3.6H2O and 0.685 g of FeCl2.4H2O, and continue sonication for 10 min. Pour the mixed suspension after sonication into a three-necked flask. After heating to 60 ° C in the microwave, quickly add 10 mL of 25% (wt) ammonia water, stir at constant temperature for 30 min, then add 20 mL of chitosan solution (0.1 g dissolved in 20 mL 1% (wt) glacial acetic acid), and 2 mL of 5% (wt) glutaraldehyde was added dropwise and stirring was continued for 30 min. After the reaction, the magnetic composite was separated by solid-liquid under the action of an external magnetic field, and washed with absolute ethanol and deionized water several times, vacuum dried at 60 ° C for 12 h, ground and passed through a 200 mesh sieve to prepare a MCAB sample.