可变电荷土壤中铜离子的解吸

DESORPTION OF COPPER IONS ADSORBED BY VARIABLE CHARGE SOILS

研究了我国四种可变电荷土壤红壤、赤红壤、砖红壤和铁质砖红壤以及二种恒电荷土壤黄棕壤和黑土中吸附性铜离子的解吸特征。研究结果表明 ,可变电荷土壤吸附的一部分铜离子可以被去离子水解吸 ,而且在pH～解吸率曲线上在一定pH值时出现解吸率最大值。在最大值时不同土壤中铜离子解吸率的大小与土壤中氧化铁的含量有关。氧化铁的含量越高 ,在最大值时铜离子的解吸率越大。当用中性电解质解吸可变电荷土壤吸附的铜离子时 ,电解质的浓度越大 ,解吸率越低。与此相反 ,恒电荷土壤吸附的铜离子不能被去离子水解吸 ,只能被中性电解质解吸 ,且电解质的浓度越高 ,解吸率越大。这表明 ,可变电荷土壤中吸附性铜离子的解吸规律 ,完全不同于恒电荷土壤中者。

In the present work, desorption of copper ions adsorbed by variab le charge soils was studied. Four variable charge soils, i.e., Ali Haplic Ac ris ol, Ferrali Haplic Acrisol, Rhodic Ferralsol and Hyper Rhodic Ferrasol collect ed from south China, were used. As contrast, two constant charge soils, i.e., Hap lic Luvisoil and Phaeozems collected from Nanjing and Harbin respectively, were also used. The results showed that the copper ions adsorbed by variable charge soils could be desorbed by deionized water. When the adsorbed copper ions were d esorbed at different pH, a pH～desorption rate curve could be obtained. A peak w ith maximum desorption rate could occur on the curve at a certain pH value. Wh e n the pH of soil suspension was higher than this pH value, the desorption rate d ecreased with the increase in pH. When the pH was lower than this pH value, th e desorption rate decreased with the decrease in pH. For different variable cha r ge soils, this pH value was related to the content of iron oxides in soils. Th e higher the content of iron oxides, the higher this pH value. After removal of copper ions which could be desorbed by deionized water, the residual copper ions adsorbed could be desorbed by dilute solution of NaNO 3. For different varia ble charge soils, the higher the content of iron oxides and the higher the concentr ation of electrolyte, the more difficult the desorption of the residual copper i ons adsorbed. On the contrary, the copper ions adsorbed by constant charge soi l s could not be desorbed by deionized water, but could be desorbed by electrolyte solution. The higher the concentration of electrolyte, the greater the abilit y of desorption of electrolyte. It is suggested that the mechanism of adsorptio n of copper ions by variable charge soils was different from that by constant cha rge soils.