磷-铅-柠檬酸在红壤胶体上相互作用机理初探

PRELIMINARY RESEARCH ON MECHANISM OF PHOSPHORUS, LEAD AND CITRIC ACID INTERACTION IN RED SOIL COLLOID

以红壤胶体为对象,通过等温平衡试验,研究了柠檬酸对红壤胶体吸附磷的影响,以及吸附磷和柠檬酸后弃去上清液(次级吸附)和保留上清液(共吸附)两种方式对红壤胶体固定铅的影响。结果表明,柠檬酸对红壤胶体磷吸附产生抑制作用,且随着柠檬酸浓度增加而抑制作用增强;用Langmuir方程拟合时,红壤胶体对磷的吸附反应常数K、最大吸附量X m均随柠檬酸初始浓度增加而降低。吸附磷和柠檬酸后,两种处理方式对铅的固定量影响有明显差异,总体上,次级吸附试验中铅的固定量低于共吸附;且两种方式中铅的固定量均随磷初始浓度及磷吸附量的增加而增加,随柠檬酸浓度升高而降低。共吸附中铅固定量在柠檬酸初始浓度为0.1 mmol L-1和磷初始浓度小于0.4 mmol L-1时达到较高值,说明在此浓度下磷和柠檬酸的共同存在促进了红壤胶体对铅的固定。

Batch isothermal equilibrium experiments were conducted to investigate phosphate adsorption by red soil colloids with addition of citric acid, and effects of two different treatments, （A） removing or （B） retaining supernatant after the samples reached equilibrium on lead immobilization by red soil colloids. Results show that citric acid inhibited phosphate sorption on red soil colloids, and the effect intensified with increasing citric acid concentration. When the Langmuir equation was used to fit isothermal adsorption curve of phosphate on red soil colloids, the adsorption reaction constant （K）, the maximum adsorption quantity （Xm） decreased with increasing initial concentration of citric acid. And the two treatments affected differently lead immobilization capacity of red soil colloids. On the whole, lead immobilization capacity was lower in Treatment A than in Treatment B, and increased with increasing initial P concentration and P adsorption rate, but, decreased with increasing citric acid concentration. In Treatment B, Pb immobilization capacity peaked when the initial citric acid concentration was 0.1 mmol L^-1 and initial phosphate concentration was lower than 0.4mmol L^-1, which indicate that in this condition, the coexistence of phosphate and citric acid jointly promote lead immobilization by red soil colloids.