Study On Adsorption Of As (Ⅴ) From Simulated Wastewater By Bentonite And Its Compound Material

Adsorption method has been focused on due to the advantages of less secondary pollution, simple and practicable among the conventional treatment methods of arsenic contaminated wastewater. With the excellent adsorption capacities bentonite has been increasingly used in water treatment. In order to promote the industrial application of bentonite for the treatment of arsenic contaminated wastewater, the adsorption of As(Ⅴ) from simulated wastewater by bentonite and its compound material has been systemically investigated, and the related adsorption mechanism of this process has been discussed in this paper. The study results were summarized as follows:1. Powdered bentonite has good effect on adsorption of As(Ⅴ). Namely, the removal rate was high, the adsorption equilibrium time was short, acidic condition was beneficial for adsorption, and the adsorption temperature has few effect on this process. The suitable volume concentration of bentonite slurry was100g/L when the initial concentration of arsenic contaminated wastewater was2mg/L, the adsorption equilibrium time was1h, the optimum initial pH values was2, and the maximal removal rate was99.81%while As(Ⅴ) amount loaded on bentonite came to0.0204mg/g. 2. Compared to powdered bentonite, the adsorption law of the compound material was basically same, however, the adsorption of As(Ⅴ) onto it was declined. The suitable volume concentration of bentonite slurry was600g/L when the initial concentration of arsenic contaminated wastewater was2mg/L, the adsorption equilibrium time was to8h, the optimum initial pH values was2too, and the maximal removal rate was85.68%while As(Ⅴ) amount loaded on compound material was0.0029mg/g.3. When adding CTAC for adsorption together with the compound material, the effect of adsorption was improved significantly. Under the same experimental conditions, the adsorption equilibrium time came to3h, the removal rate upped to95.65%while As(Ⅴ) amount loaded on compound material was0.0032mg/g, and the pH value had little effect on the adsorption of As(Ⅴ) with a suitable dosage of CTAC.4. The Radke-Prausnitz model was suitable to describe the isothermal adsorption experimental data of compound material when adding CTAC together with compound material for adsorption. it was indicated that the sorption was based on the surface adsorption or non-uniform pore adsorption, not monolayer.5. When adding CTAC together with compound material for adsorption, the pseudo-first-order model could described the adsorption process better at low initial concentration of arsenic contaminated wastewater, it was indicate that intraparticle diffusion controlled the adsorption rate; the pseudo-first-order model and the pseudo-second-order model described the adsorption process nearly at high initial concentration of arsenic contaminated wastewater.6. The XRD and FESEM analysis showed that the apparent morphology, mineral composition and montmorillonite layer spacing has not significantly changed before and after compound, bentonite still maintained its natural absorption properties, but the adsorption capacity of compound material would decline due to the quantity of exposed bentonite particles reduced after compound.