| Due to bentonite reserves are rich in China and many excellent properties it has been widely used in water treatment. However, the adsorption effect of the original bentonite was not ideal, this article modified bentonite by different methods, in order to find an effective adsorbent to remove heavy metal ions, to develop a broader space for the application of bentonite which is efficient and inexpensive and resource-rich.Purified bentonite was used as raw material to prepare Na-bentonite, calcined bentonite, Organo-bentonite and Mn-bentonite, the effects of dosage, adsorption time, pH and temperature on the removal of Cr6+ and Ni2+ was studied by static adsorption tests, the best conditions of adsorption on Cr+ and Ni2+ by various modified bentonite was established. At the same time the results of adsorption isotherm showed that:both Freundlich and Langmuir equation could describe the adsorption isotherm of Cr6+ and Ni2+, but the Freundlich adsorption isotherm model is better, which indicated that the adsorption on Cr6+ and Ni2+ by various modified bentonite is between the single and multi-layer adsorption, and the adsorptive surface of various modified bentonite is uneven. The dynamics of adsorption on Cr6+ and Ni2+ by modified bentonite was studied, Quasi-first order kinetic equation, Quasi-second order kinetic equation and Particle diffusion equation were used to fit the kinetic curves.The results showed that the modified bentonite had a good adsorption performance on Cr6+ and Ni2+, and the Kinetic data met the quasi-second order kinetic equation. Adsorption was controlled by interfacial diffusion and particle diffusion, and this two kinds of adsorption process happened at the same time. Finally, the experiment compared the removal efficiency of Cr6+ and Ni2+ using purified bentonite and several kinds of modified bentonite. The results showed that the adsorption on Cr6+ and Ni2+ using modified bentonite were better than purified bentonite. Na-bentonite had better adsorption on Cr6+ and Ni2+ than purified bentonite, because it had more exchangeable cations than purified bentonite. Bentonite roasted under 450℃and 600℃also had better adsorption effect than purified bentonite, because the bentonite which was being roasted would continue to lose surface water, hydration water and the combination water of institutional framework, which could greatly reduce the water film resistance of adsorption on Cr6+ and Ni2+, thereby enhancing the adsorption properties. Organo-bentonite had great layers spacing which was conducive to Cr6+ presenting in Cr2O72- or CrO42- into the interlayer of organo-bentonite, then it would happen interlayer exchange adsorption, interlayer adsorption and complex precipitation. The common occurrence of these types of function made the adsorption capacity of organo-bentonite greatly improved. Mn-bentonite had high chemical activity and surface adsorption on heavy metals such as Cr6+ and Ni2+, and the adsorption effect of bentonite could be improved greatly through modification and optimization of manganese oxides.Synthesized the experimental data and theoretical analysis, bentonite had great significance in environmental protection, particularly its application in heavy metal wastewater treatment, which will have broad application prospect in environmental pollution control.
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