黄土性土壤对Cr(Ⅵ)的吸附还原动力学研究

Studies on Absorptionand Reduction Dynamics of Cr(VI)in Loessial Soil

通过研究黄土性土壤中Cr(Ⅵ)的吸附和还原动力学,揭示了黄土性土壤对Cr(Ⅵ)的吸附还原机制,从而确定出影响黄土性土壤溶液中Cr(Ⅵ)减少的主要因素。研究结果表明:黄土性土壤中Cr(Ⅵ)的还原反应基本上可由两个一级反应来表示,其还原反应速率常数主要取决于有机质的数量和可氧化性;黄土性土壤对Cr(Ⅵ)的吸附量与游离氧化铁的含量呈正相关,土壤中游离氧化铁是吸附Cr(Ⅵ)的主要成分;黄土性土壤对Cr(Ⅵ) 的吸附过程可用Elovich方程和双常数速率方程描述,其中粘化层对Cr(Ⅵ) 的吸附速率最快;黄土性土壤中Cr(Ⅵ)的减少在初期以吸附反应为主,随着时间延长,还原反应占据优势。

According to the study,the mechanisms of the absorption and reduction dynamics of Cr(VI) in loessial soil are revealed , and the major processesthat caused the Cr(VI)decrease in soil solution are ascertained. The results show that the reduction processof Cr(VI)consists of two first-order reaction in loessial soil, and the rate of the reaction is closely related to the soil organic matter and oxidizability. The amountof absorbed Cr(VI) is positively correlated to contents of free ferric oxide, and free ferric oxide is the importantcomponent of absorbing Cr(VI). The absorption curves may be well fitted by Elovich equation and two-constant rate equation. The rate of Cr(VI)absorption in claying horizon is the biggest among soil layers. The processof removalCr(VI) in loessial soil solution is in charge of absorption in initial stage, and reduction occupiesgradually a dominant positionwith extending time.