粘土矿物吸附镉污染物的基本特征

以我国各地典型粘土矿物制备标准样品,对镉进行吸附实验,得到蒙脱石、伊利石、高岭石三种矿物的吸附等温线,在广泛浓度范围内符合Langmuir型方程式。研究了温度、接触时间、PH值、粒径、矿种等对吸附的影响效应。提出了镉的溶解-吸附-沉淀区域图,吸附急剧增强和开始发生碳酸镉沉淀的PH值是一致的。发现对不同粒径和不同矿种都存在“饱和吸附值加和现象”。 对湘江中游及上游天然底质样品以化学分离法逐级除去碳酸盐、有机物、金属水合氧化物等组分,以各级样品进行镉的吸附实验。根据吸附等温线和饱和吸附值可以判断不同组分在吸附中的贡献,发现这与各组分相对含量直接有关。 应用本文提出的工作方法。有可能建立天然水体中吸附过程的定量化学模式。

ADSORPTION CHARACTERISTICS OF CADMIUM POLLUTANTS ON THE CHINESE CLAY MINERALS

Adsorption experiments of cadmium on prepared samples of Chinese clay minerals were done. The adsorption isotherms of cadmium on montmorillonite, illite and kaolinite were found to be of the Langmuir-type equation in a wide range of Cd concentrations. Effects of temperature, contact time, pH, particle size and mineral types were also studied. A diagram of dissolution-adsorption-precipitation zones was presented. pH values for rapid adsorption enchancement were in agreement with the calculated pH values for precipitation of carbonates. It seems there exists a correlation of "additivity of saturation adsorption capacities" for different particle sizes or different types of the minerals.Some natural sediment samples from Xiangjiang River were prepared by a series of chemical separation processes. Carbonate, organic matter and hydrous oxide of metals were removed in turn. The adsorption isotherms and the saturation adsorption capacities were thus obtained. The contributions of individual components are to be evaluated from the results. It was found that contribution was related to content of the component herein.The methodology and design idea of the research program developed so far in this laboratory can be expected to be applied to quantitation of chemical model of the adsorption processes in natural aquatic systems.