| Bentonite is a non-metallic mineral with the main component of montmorillonite,currently bentonite is reported in the literature as a purifying agent,but most studies just focus on adsorption of cation and ignore the adsorption of anion in water purification. The hexavalent chromium and fluoride were chosen as the typical representatives of anion.The two pollutants caused much concern for their toxicity and accumulation in the environment.Natural bentonite are widespread in the nature,Safety and environmentally friendly.Bentonite has large specific surface area and cation exchange capacity.Chromium and fluoride can be absorbed effectively after bentonite suitable modified.In order to improve the adsorption and application properties of bentonite,the granular poly(acrylic acid-sodium acrylate) bentonite composite was synthesized by suspension polymerzation using acrylic acid as polymerization monomer in the reserach.Iron hydroxy polycation was applied to synthesize modified poly acrylic acid-sodium acrylate bentonite composite with hydroxy Fe. The characteristics of natural and modified montmorillonite were determined with X-ray diffraction(XRD),fourier transform infrared spectrum(FTIR) and Scanning electron microscope analysis(SEM).Adsorption isotherms and kinetics were also studied.The results shows that the modifying agents has entered the interlayer or adsorbed on the surface. The interlayer spacing of modified bentonite and the adsorption purification capacity of modified bentonite to chromium and fluoride varying degrees of increase.Among them,poly acrylic acid-sodium acrylate bentonite composite modified with hydroxy Fe and CTAC had the best adsorption capacity and regeneration properties to Cr(VI).When 0.15 g of iron-organic pillared bentonite was used to treat 50 mL of Cr(VI)-containing solution at the concentration of 10 mg/L,its equilibrium adsorption capacity to Cr(VI),and their removal rate were 3.13 mg/g and83.69% respectively.The adsorption equilibrium data of Cr(VI) were consistent with the Freundlich isotherm equations. Poly acrylic acid-sodium acrylate bentonite composite modified with hydroxy Fe had excellent adsorption and regeneration properties to F-,When 0.5g of modified poly acrylic acid-sodium acrylate bentonite composite with hydroxy Fe was used to treat 50 mL of F--containing solution at the concentration of 16.3mg/L, its equilibrium adsorption capacity to F-, and theirremoval rate were 1.52 mg/g and 92.8% respectively.The adsorption equilibrium data of F- were consistent with the Freundlich isotherm equations.To study the dynamic adsorption process and regeneration of Iron-organic pillared bentonite for Cr(VI),fixed bed experiments were Carried out.It resultsthat under the conditions of bed height of 16 cm,flow rate of 10mL/min,the capacity of Cr(VI)with initial concentration of 10mg/L was10.2L,the lowest concentration of bed export was 0.22mg/g, the removal rate was 97.7%. The adsorption process was corresponding with Thomas model and Yoon-Nelson model. |
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