pH对砖红壤和黄棕壤Cu~(2+)吸附与解吸的影响

对砖红壤和黄棕壤在不同浓度、不同pH下吸附和解吸Cu2+进行了测定。结果表明, 2种土壤Cu2+吸附量均随平衡液中Cu2+浓度增加而增大,两者关系较好地符合Langmuir吸附方程。Cu2+吸附量随pH升高而增加,Cu2+分配系数的对数与pH呈极显著的线性正相关,吸附一个Cu2+所释放H+的平均数砖红壤(1. 19)大于黄棕壤(1. 01)。可解吸Cu2+的数量随pH升高和吸附Cu2+的数量增加而增加,在pH4~6下,黄棕壤吸附Cu2+及可解吸Cu2+的比例(平均为10. 5% )大于砖红壤(平均为3. 1% )。由此认为, 2种土壤吸附Cu2+虽以专性吸附为主,但砖红壤的表面吸附点位较少,专性吸附点位的比例较高,对Cu2+的亲和性或专性吸附性大于黄棕壤。

Effect of pH on Adsorption and Desorption of Cu2+ in Latersol and Yellow Brown Earth

Adsorption and desorption of Cu~(2 ) in latersol and yellow brown earth under different concentration of Cu~(2 ) and pH of soil solution were measured. The results indicated that the amount of Cu~(2 ) adsorption by these two soils increased with increasing concentration of Cu~(2 ),and the relationship could be described by Langmuir isotherm equation satisfactorily. Although Cu~(2 ) adsorption increased with increasing pH and the logarithm of the distribution coefficient (ratio of Cu~(2 ) sorbed by soil to Cu~(2 ) in soil equilibrium solution) was linear relative with pH significantly in both soils, the amount of H~ released from soil surface after the adsorption each Cu~(2 ) in latersol (1.19) was higher than that of yellow brown earth (1.01) in the same range of pH 4 to 6. Moreover, the ratio of desorption to adsorption of Cu~(2 ) in yellow brown earth (10.5% in average) was greater than that of latersol, which was only 3.1% in average. Thus, the proportion of specific adsorption sites in yellow brown earth was less than that of latersol even total amount of adsorption sites in former soil was higher and adsorption of Cu~(2 ) in both soils was specific adsorption mainly.