スメクタイトを含むカドミウム汚染水田土壌の酸処理によるカドミウム溶出特性

概要

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Adsorbed cadmium (Cd) in a smectitic paddy soil was extracted with dilute nitric acid solutions and the factors controlling the extractability of Cd was evaluated with the aid of a simple numerical model to which cation exchange and surface complexation reactions were incorporated. Cd was extracted from a paddy soil containing 6.8 mg kg^<-1> of total adsorbed Cd with 0 to 100 mmol L^<-1> nitric acid solutions at a solution: soil ratio of 50 mL: 10 g. The extraction percentage increased as nitric acid concentration increased, i.e., from 5 % at 5 mmol L^<-1> to 95 % at 100 mmol L^<-1>, whereas extracting time did not significantly affect the extraction percentage. The model predicted the trend of the extraction percentage qualitatively and suggested that the cation exchange sites on layer silicate minerals are the major Cd retention sites particularly when the extracting acid concentration was high. However, the model prediction was far less than the experimental values, indicating possible role of aluminum ions dissolved from soil minerals in Cd-exchange on layer silicate minerals.
日本粘土学会の論文
2002-05-28