Study On Adsorption And Photocatalytic Properties Of Composite Modified Bentonite

The purpose of this study is to synthesize new functional bentonite composites with simple and low cost to efficiently remove heavy metal ions and organic pollutants from water,and to explore the adsorption and photocatalytic properties of bentonite based materials.The functional bentonite based materials were characterized by Fourier transfrom infrared spectroscopy（FTIR）,X-ray diffraction（XRD）,scanning electron microscope（SEM）,thermal analyzer（TG）,specific surface and pore size analyzer and UV-visible spectrophotometer（UV）.（1）Study on the adsorption properties of polyacrylate modified bentonite（Bent-PAANa）for Pb²⁺Sodium polyacrylate modified bentonite was prepared by in-situ polymerization.The reaction method is simple;the reaction temperature is very low,which close to room temperature.The hydroxyl groups on the surface of bentonite are oxidized by cerium ammonium nitrate to produce free radicals,which initiate the in-situ polymerization of sodium polyacrylate on bentonite surface.Different from the usual intercalation modification,this method does not destroy the interlaminar structure of bentonite.The modified bentonite can remove harmful heavy metal lead ion by cation exchange between layers and adsorption of negative carboxylic acid on the surface.The adsorption results show that under the optimum conditions,the adsorption capacity of the adsorbent for lead ion is as high as 149.62mg/g.The adsorption behavior of the Bent-PAANa adsorbent for Pb²⁺is in accordance with the second-order kinetic model（pseudo-second-order）and the Freundlich adsorption isotherm model.In addition,the composite bentonite still has good adsorption performance after five times of desorption.（2）Study on the adsorption properties of graphene sponge modified bentonite（Bent-GO）for crystal violetIn this chapter,graphite oxide was prepared by modified Hummers method in order to improve the adsorption property of bentonite to CV.Bent-GO with good adsorption effect was prepared by a simple one-pot hydrothermal method with self-made graphite oxide and bentonite.After modification,the interlayer spacing of bentonite is increased,which is favorable for cationic exchange between layers of cationic dyestuff-CV.In addition,the adsorbent is electrically negative,so the adsorption mechanism includes electrostatic attraction and cation exchange of bentonite.The results show that in the best experimental conditions obtained,the adsorption capacity of the composite adsorbent for methylene blue is as high as 270 mg/g,which is obviously better than that of other adsorbents.Bent-GO adsorbents’adsorption behavior for CV is in accordance with the second-order kinetic model of pseudo-second-order-based adsorption isotherm and also accords with the Freundlich equation.（3）Study on the photocatalytic properties of graphene sponge/titanium dioxide/bentite（GO/P25/Bent）coposites for MBA novel photocatalyst for porous graphene sponge supported titanium dioxide and bentonite was successfully prepared by hydrothermal method.In this experiment,the methylene blue was selected as adsorbate.Commercial titanium dioxide（P25）,graphene（GO）,graphene/bentonite（GO/Bent）and graphene/TiO₂/bentonite（GO/P25/Bent）was compared on the degradation of methylene blue.The synergistic action of graphene sponge,titanium dioxide and bentonite not only broadens the range of light response,but also improves the light absorption ability and the effective utilization rate of photogenerated holes.Under the optimum experimental conditions,the degradation of methylene blue by GO/P25/Bent was the best.In the first 30 minutes of dark reaction,the removal rate of methylene blue（10 mg/L）by this adsorbent was as high as 99.7%,the removal rate of methylene blue reached 100%at 70 minutes,which was obviously superior to that of other adsorbents.