土壤中Cr(Ⅵ)吸附规律试验研究

Study on adsorption of hexavalent chromium in soil

为了研究Cr(Ⅵ)在土壤不同初始pH和初始浓度条件下的吸附规律,以武汉东西湖蔬菜基地的土壤为试验材料进行土柱的动态吸附试验,调节初始溶液的pH和浓度,制备6种不同性质的土样进行动态吸附试验,选用Origin软件来拟合溶质的穿透曲线;并选用惰性离子Cl-进行示踪试验求取弥散系数,结合CXTFTI软件中的化学非平衡模型——两点模型进行数值模拟,求取Cr(Ⅵ)在该土壤中的溶质运移参数,从而对在土壤中Cr(Ⅵ)的吸附过程进行分析及预测.研究结果表明:Cr(Ⅵ)的吸附对pH值非常敏感,通入溶液的初始pH值越低,穿透时间以及达到吸附饱和的时间越早;而初始浓度也会对Cr(Ⅵ)的吸附有一定影响,通入溶液的初始浓度越高,穿透时间以及达到吸附饱和的时间越早.利用两点模型求取的Cr(Ⅵ)在该土壤中的溶质运移参数能很好的解释土柱试验的结果,Cr(Ⅵ)在该土壤的吸附过程中大约60%都是瞬时完成的,40%是受到速率限制作用,满足一阶动力学方程.

In order to study the adsorption rule of chromium(VI)under different initial pH and initial concentration conditions,the dynamic adsorption test of soil column was carried out on the soil of Wuhan Dongxihu vegetable base.Six soil samples with different properties were prepared by adjusting the initial solution pH values and concentrations.Origin software was used to fit the penetration curve of solute.The diffusion coefficient of inertia Cl-was calculated by tracer experiment,and the solute transport parameters of Cr(VI)in the soil were determined by numerical simulation combined with the chemical non-equilibrium model in CXTFTI software.The adsorption process of Cr(VI)in the soil was analyzed and predicted.The results show that the adsorption of Cr(VI)is very sensitive to the pH value.The lower the initial pH value of the solution is,the earlier the penetration time and the adsorption saturation time are.The initial concentration affects the adsorption of chromium(VI),too,specially,the higher the initial concentration of the solution is,the earlier the penetration time and the adsorption saturation time are.The solute transport parameters of Cr(VI)in the soil determined by the two-point model can well explain the results in the soil column experiment.For example,about 60%of the adsorption process of Cr(VI)in the soil completes instantly,and 40%is restricted by the rate,which satisfies the first-order kinetic equation.