镉在土壤上的吸附和解吸特性研究

STUDY ON THE CHARACTERISTICS OF ADSORPTION AND DESOPTION OF CADMIUM IN SOILS

本文研究了土壤对镉的吸附及其解吸特性,结果表明:红壤、黄棕壤、黄红壤吸附镉的等温线符合Langmuir方程。吸附常数K为:黄红壤>黄棕壤>红壤,与土壤基本性质(pH、有机质和无定型铁、锰含量)呈正相关;土壤吸附镉的MgCl_2解吸率为:红壤(50.7—91.9％)>黄棕壤(72.2—80.8％)>黄红壤(63.4—65.5％)>黄潮土(39.0—46.5％),Cu(OAc)_2为:黄潮土(30.0—40.0％)>黄红壤(11.7—22.2％)>黄棕壤(6.9—12.6％)>红壤(2.1—8.0％)。土壤对镉的吸附以离子交换为主,兼有络合或沉淀。如果添加石灰、树脂及葡萄糖,会显著影响土壤对Cd的吸附和解吸状况。

Adsorption and desorption of Cd in four kinds of soils were studied in this paper. It was found that the adsorption isotherms of Cd in red soil,yellow-brown soil, and yellow-red soil fitted the Langmuir equation. The constant K related to finding strength was in the following order: yellow-red soil >yellow-brown soil>red soil, and positively correlated with soil pH,and the contents of organic matter and amorphous Fe and Mn. The experiments also indicated that MgCl2 desorption percentage of Cd in soils were 50.7-91.9%, 72.2-80.8%,64.3-65.5% and 39.0-46.5% for red soil,yellow-brown soil, yellow-red soil, and yellow Chaosoll, respectively. The Cu(OAc)2 desorption rate, however, was in the inverse order, yellow Chao soil(30.0-40.0%)> yellow-red soil (11.7-22.2%) >yellow-brown soil (6.9-12.6%) >red soil (2.1-8.0%). This suggested that cation exchange played a more important role in resin and adsorbing Cd than chelation or precipition. Adding CaCO3, glucose evidently influenced adsorption and desorption of Cd in red soil.