| Bentonite is a kind of clay mineral that is abundant in our country. It has unique samdwich structure and powerful adsorption ability. Modification of bentonite can improve its adsorption ability greatly and so makes it adsorb the contaminants such as heavy metal ions and organic substances in wastewater more effectively. Bentonite has lots of advantages in the treatment of wastewater, such as simple process, high efficiency and low cost. The methods of purification of raw bentonite were investigated and the optimized parameters were discussed. The experiment of modifying bentonite have been done, and the optimized parameters were also discussed. The factors that affect the adsorption of heavy metal ion from the wastewater on bentonite were systematically studied and the best conditions for treatment were determined by experiments. The adsorption mechanism of heavy metal ion on the modified bentonite was discussed. This article studied the raw bentonite by means of XRD and SEM, refined it, determined its basic physicochemical properties, and made modification experiment on it.The bentonite used in the experiments was the Ca-bentonite produced in Yangxian, Shanxi. Bentonite in the region is large reserves (nearly 100 million tons) and easy-mining. It was found that (NaPO3)6 solution is the best dispersing agent for the purification of bentonite. The optimum concentration of bentonite is 15%, and the optimum concentration of (NaPO3)6 solution is about 0.2% with the pH value of 7.0. The optimized heated time of the making of microwaved betonite is 7 minutes uder 800W. When the raw bentonite is ion exchanged with NaCl, the optimum microwaved time is 3.5 minutes and the amount of V(ethanol) / m(betonite) is 7.0, as well as the optimum amount of m(NaCl) /m(betonite) is 25/4.The adsorption of raw bentonite and modified bentonite was studied, the result shows that the effect of modified bentonite is better than raw bentonite. The optimum adsorbable condition of m(trivalent chromium)/ m(bentonite) is 10mg/g and oscillation Adsorbable time is 20min with the pH value 7.0.The removal rate of Cr3+ can be changed form 80.5% of raw bentonite up to above 98.5% of modified bentonite with the concentration of Cr3+ below 1.5mg/L。While, The optimum adsorbable conditions of m(nickel)/ m(bentonite) is 10mg/g and oscillation adsorbable time is 15min with the pH value 7.0. The removal rate of Ni2+ can be changed form 78.0% of raw bentonite up to above 99.0% of modified bentonite with the concentration of Cr3+ below 1.0mg/L. After oscillation absorption by both modified bentonite, the remained concentration of Cr3+ and Ni2+ both reach the first level of "Integrated Wastewater Discharge Standard" GB8978-1996. Whether the raw bentonite or modified bentonite was not ideal for the adsorption of Cr6+. The reason might be that Cr6+ is existed as Cr2O72- in water, and aluminium oxygen structure is negatively charged itself, so repulsion phenomenon happened.The properties and mechanisms for bentonite to adsorb heavy metal ion from waste water were investigated in detail. Data of linear regression indicates that the adsorbing process fits both the Langmuir and Freundlich isotherm.The above findings have certain theoretical and practical significances for using the adsorption performance of betonies to treat the heavy metal ion from wastewater. Simultaneously it provides a theoretical data for the development of Yangxian bentonite and a new way to enhance the application value of bentonite has been developed.
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