Rice husk,a by-product of rice dehulling,is a widely produced agricultural waste resource during agricultural processes.The utilization of this low-added-value rice husk to produce high-efficiency adsorption material carries significant importance.In this study,the rice husk was used as raw material,and polyethyleneimine was successfully grafted onto the surface of rice husk through a simple cross-linking reaction,thus preparing a biomass adsorbent with good adsorption performance for Cr(Ⅵ).The research results indicate that the optimal conditions for the adsorption process as temperature 60 ℃,pH 2.Under optimal adsorption conditions,the maximum adsorption capacity for Cr(Ⅵ)of the modified rice husk was 113.76 mg/g.The results of adsorption isotherm and adsorption kinetics indicate that the pseudo-second-order model and the Freundlich equation provided a better description of the adsorption behavior of Cr(Ⅵ)on rice husk,indicating that the adsorption process is a multilayer chemical adsorption.The thermodynamic parameters of Cr(Ⅵ)adsorption process by modified rice husk show that △G＜0,△H＞0 and △S＞0),which indicates that the adsorption of Cr(Ⅵ)by modified rice husk is a spontaneous,endothermic and entropy increasing process.In addition,XPS analysis showed that a portion Cr(Ⅵ)was reduced to Cr(Ⅲ)during the adsorption process.And after four cycles,the adsorption activity of modified rice husk remained high,and the removal rate of Cr(Ⅵ)can still reach 69.08％.
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