四种生物质材料水浸提液淋洗镉污染土壤及其废水处理研究

Cadmium Contaminated Soil Washing by Leaching Liquid of Four Biomass Materials and Their Wastewater Treatment

采用八角金盘、枳椇子、空心莲子草和赤胫散4种生物质材料的水浸提液进行Cd污染土壤的批量淋洗试验,结果表明:4种生物质材料浸提液对污染土壤中的Cd均有一定去除作用,且差异显著(P<0.05)。4种材料的Cd淋洗率随其浸提液浓度的增加呈对数、幂函数或倒数变化;赤胫散的Cd淋洗率随淋洗液p H增加呈线性上升,而其余3种生物质材料Cd淋洗率则随淋洗液p H增加呈线性、倒数或幂函数下降。[0]时间和淋洗量的关系以二级动力学模型(R^2>0.994)和Elovich方程(R^2>0.803)拟合效果较优。液土比增加能够促进Cd的淋洗。淋洗3次后,八角金盘、枳椇子、空心莲子草和赤胫散的Cd累积淋洗率分别达到78.31%、53.88%、47.59%和27.98%。此外,采用4种生物质材料浸提液淋洗后,土壤可交换态、碳酸盐结合态和铁锰氧化物结合态Cd含量显著降低(P<0.05),土壤钾素含量略有增加,其他养分及有机质则下降。浸提残渣能够有效吸附淋洗废水中的Cd,用其处理后的废水达到国家排放标准。由此,兼顾Cd的淋洗率及对土壤性质的影响,八角金盘是一种修复Cd污染土壤的潜力材料。

The leaching liquid of four biomass materials including Fatsia japonica, Hovenia acerba, Alternanthera philoxeroides and Polygonum runcinatum were investigated by batch soil washing experiments. Cd removal efficiencies of four biomass materials varied obviously, and their removal efficiencies increased consistent with logarithm, power function or multiplicative inverse with growing concentrations. From 4 to 9 of solution pH, the removal efficiency linearly increased for the P runcinatum. However, it dropped in liner change, multiplicative inverse or power function respectively for the other three materials. Fitting data between contact time and removal amount were better curved the pseudo second order kinetics （RZ〉0.994） and Elovich model （R2〉0.803）. Liquid to soil ratio increment would improve the removal efficiency. The optimal removal efficiency reached 78.31%, 53.88%, 47.59% and 27.98% respectively when successive washed for three times. In addition, Cd fractions of exchangeable, carbonate and organic matter were decreased （P〈0.05）. Except soil potassium slightly increased （1.69%-13.13%）, other soil nutrients and soil organic matter were decreased by less than 19.59%. Additionally, residues after leaching could adsorb Cd from waste water which was accord with national wastewater emission standard. Therefore, considering both efficiency and influence on soil properties, F.. japonica could be a promising Cd removal material.