土壤胡敏酸对Pb的吸附特征与影响因素

Adsorptive Characteristics and Influence Factors of Humic Acid on Lead in Soil

采用Pb离子选择电极研究了Pb离子在胡敏酸上的吸附量和动力学特性,以及溶液pH、温度、离子强度对吸附的影响。结果表明胡敏酸对Pb离子的吸附量随着溶液pH增加而增大。当pH<4.00,符合Linear等温吸附式(r=0.9581～0.9547);当4.00≤pH≤7.00时,符合Langmuir等温吸附式(r=0.9776～0.9998)。温度降低,吸附量增加;离子强度增加,吸附量增加。胡敏酸与Pb离子作用的条件稳定常数随溶液pH增大而增加,但pH<4.00和4.00≤pH≤7.00这两个pH段增长规律明显不一致,说明在这2个pH段,存在不同的反应机制。胡敏酸结合1个Pb离子所释放的H+平均数小于1,且与溶液温度、离子强度有关。

Adsorptive capacity and dynamics characteristics of humic acid on Pb2+ in soil are studied by using a lead ion selective electrode. Influence factors including pH, temperature and ionic strength in the solution were tested. The results showed that adsorptive capacity increased with the increase of pH or ionic strength of the solution, but decreased with the increase of temperature of the solution. It has been found that the adsorption was in accordance with Linear isothermal adsorption (the regression coefficient is 0.958 1 ～ 0.954 7 ), when pH of the solution was under 4.00, while that with Langmuir isothermal adsorption (the regression coefficient is 0.977 6 ～ 0.999 8  ), when pH of the solution is between 4.00 and 7.00. We also discovered that stability of Pb2+ - humic acid complex enhanced with the increase of pH value for the solution, but the increased pattern at pH<4.0 obviously differed from that at 4.00≤ pH≤ 7.00. This may be suggested that there were different reaction mechanisms at the two pH sections. The average H+ released by humic acid with a Pb2+ was less than 1, and affected by both the temperature and ionic strength of the solution.