Study On Removal Of Dyes From Aqueous Solution By Organic Bentonite

Bentonite is an inexpensive, abundant clay mineral, which has good sorption capacityand friendly to environment, so it can be used as the basis raw materials in cheap bentoniteproducts as adsorbents. In this dissertation, cationic starch (CS), CTMAB and PDMDAACagents were chosen as raw materials to prepare organic bentonites. A series of noveladsorbents with special structure and function derived from bentonite was synthesized andtheir performances on removing dyes from water were studied at the same time. The mainresearch contents and results are as follows:(1) Three adsorbents of organic bentonites were prepared by compositing bentonite withCS, CTMAB and PDMDAAC solution and characterized by FTIR, XRD and BET. Theresults indicated that the organic bentonites were successfully prepared.(2) The organic bentonites were used for the removal of dyes from water. Theazophloxine dye was selected as the representative to consider the optimum adsorptionconditions. In20mL solution containing100mg/L azophloxine, the best amount of CS-Bentand CTMAB-Bent was0.02g, the best adsorption time was30min. In20mL solutioncontaining100mg/L azophloxine, the best amount of PDMDAAC-Bent was0.2g, the bestadsorption time was30min. Bent had no effect on the removal of azophloxine.(3) The adsorption kinetics data fit the pseudo-second-order equation well, whichsuggested that the adsorption process could be a rate-limiting step. The theoretical maximumadsorption capacity of CS-Bent, PDMDAAC-Bent and CTMAB-Bent was89.37,8.814and79.30mg/g, respectively.(4) At different temperatures, adsorption of azophloxine onto CS-Bent andPDMDAAC-Bent all agreed well to the Langmuir isotherm models, which illustrated theadsorption process was monomolecular layer and uniform on the surface. The adsorption ofazophloxine onto CTMAB-Bent agreed well to the Freundlich isotherm models, whichillustrated the adsorption process was nonuniform on the surface.(5) The thermodynamic studies illustrated the adsorption process was endothermic andspontaneous. The increasing of temperature was favorable to the adsorption reaction.(6) The results of removal of actual dye wastewater by organic bentonites as follows: Removal efficiency of color could reach above90%by0.02g CS-Bent,0.02g CTMAB-Bentor0.2g PDMDAAC-Bent, and had a remarkable colour changes at the same time. Thissuggested that organic bentonites had very good treatment effect on the actual dye wastewater.