酸性条件下粉砂质壤土对Cd2+的吸附解吸特性研究

摘要

Batch experiments were used to study the adsorption-desorption mechanisms of Cd2+ in a silt loam under acidic con-ditions. The results showed that, the amount of adsorption and the ratio of adsorption of Cd2+ increased with the increasing of pH values. Under different initial concentration, the maximum adsorption rate was 0. 69 ~0. 95. The isotherm sorption of Cd2+ onto loam under acidic conditions fitted best to Freundlich model. The Langmuir model illustrated that the maximum sorp-tion capacity of Cd2+ of the soil was 2 500 mg/kg. The amount of desorption increased with the increasing of adsorption and they were remarkably correlated linerarly. The ratio of desorption to adsorption decreased with pH increase. When pH in-creased from 2 to 6, the average desorption ratios for Cd2+ were 1. 11, 0. 33, 0. 07, 0. 06, and 0. 06, respectively, which implies that Cd2+ easily migrates down and pollute deep soil and groundwater under acid sewage irrigation.%为了解酸性条件下粉砂质壤土对Cd2+的吸附-解吸机制,采用一次平衡法进行了不同pH值条件下壤土对Cd2+的吸附-解吸实验。结果表明：壤土对Cd2+的吸附量和吸附率均随着pH值升高而增加,不同初始浓度下达到的最大吸附率为0．69~0．95,酸性条件下壤土对Cd2+的等温吸附Freundlich方程拟合效果最好,通过拟合的Langmuir方程计算出壤土对Cd2+的饱和吸附量为2500 mg/kg。 Cd2+的解吸量和解吸前的吸附量呈显著正相关线性关系,解吸率随着pH值升高而减小, pH值从2以等间隔1变化到6,平均解吸率依次为1．11、0．33、0．07、0．06、0．06；表明在酸性污水灌溉条件下污灌壤土中的镉易向下迁移,污染深层土壤和地下水。