pH值对红壤和黄土中铊的吸附-解吸特征的影响

Effects of pH on Adsorption and Desorption Characteristics of Thallium in Red Soils and Loess

研究了不同pH条件下红壤和黄土对毒害重金属铊的等温吸附-解吸行为,结果表明,Tl+在红壤和黄土中的吸附量均受pH值影响明显。红壤中,在pH=2时吸附量最小,吸附率为3%,吸附量和吸附率随着pH的升高而增加,在pH=10时,吸附量为89.93 mg/kg,吸附率为61.3%;黄土中,pH从4增加到6时,吸附率增加明显,从14%骤升至71.2%,pH=10时,最大吸附量为139.67 mg/kg,吸附率最大为83.8%。红壤和黄土的吸附都符合Langmuir和Temkin方程。解吸过程中,pH=2时,红壤和黄土的解吸率最高,并且解吸率随着初始浓度的增加而增大,最大分别达到78.6%和85.2%,同等条件下,黄土的解吸率高于红壤;在pH=4～10,红壤的解吸有一定的滞后现象,而黄土解吸量随吸附量的增加近似线性增加,无明显滞后现象。

The isotherm adsorption and desorption behaviors of thallium in red soil and loess under different pH were studied. Results indicated that the adsorption amount of T1＋ in two soils was significantly affected by pH. In red soil, the adsorption amount of T1＋ was the least of 3% at pH 2, and adsorption amount and adsorption rate were increased with increasing pH. The adsorption amount and adsorption rate were 89.93 mg/kg and 61.3% at pH 10 respectively. In loess, the adsorption rate increased obviously with increasing pH from 4 to 6, and upsurged from 14% to 71.2%. The .maximum absorbance and adsorption rate were 139.67 mg/kg and 83.8% respectively at pH 10. The adsorption of T1＋ in two soils could be described by Langmuir and Temkin isotherm equation satisfactorily. The desorption rate of T1＋ was the most at pH 2 in two soils, and it increased with increasing initial concentration of T1＋ up to the maximum of 78.6% and 85.2% respectively. The desorption rate of T1 ＋ in loess was higher than that in red soil at the same condition. The desorption of T1＋ in red soil exhibited hysteresis at pH 4-10, but in loess without obvious hysteresis, the amount of adsorption and desorption were approximate linear.