可变电荷土壤和矿物表面Cu^(2+) 吸附过程中H^+释放动力学

KINETICS OF H+ RELEASING AS Cu2+ ADSORBED ON VARIABLE CHARGE SOILS AND MINERALS

本文以硝酸根离子选择电极为参比电极,低阻pH玻璃电极为指示电极,研究了红壤和高岭石体系Cu^(2+)吸附过程中pH的变化情况,并通过红壤和高岭石的酸碱滴定曲线求得了不同反应时间H^+释放的绝对量,即H^+释放动力学.结果表明,Cu^(2+)吸附过程中H^+释放大部分在反应刚开始时进行,反应进行5min后,两种Cu^(2+)起始反应浓度的高岭石和红壤体系H^+分别释放了92%和82%以上.Cu^(2+)起始反应浓度愈大.H^+ 释放量就愈大.在众多动力学方程中,二级反应动力学方程可以完美地描述Cu^(2+)吸附过程中H^+释放动力学.线性化的二级反应动力学方程与实验观测结果的相关系数平均为0.9989(n>30).反应过程中H^+质子释放量与Cu^(2+)吸附量之比(H^+/Cu^(2+))随反应时间的推移而逐渐上升,说明H^+释放过程与Cu^(2+)吸附过程不是同步的,且H^+释放速度滞后于Cu^(2+)吸附速度.

The changes of suspension pH of red soil and kaolinite suspension at different time after Cu2+ adsorption on red soil and kaolinite was detected by using a low-resistant pH glass electrode as working electrode and a nitrate selection electrode as reference electrode, and the amount of H+ released at different time , that was, the kinetics of H+ releasing was calculated by the combination of the time-dependent data of suspension pH and the acid-base titration curves of red soil and kaolinite. The results showed that the suspension pH of red soil and kaolinite dropped sharply and most of H+ , more than 92 % and 82% in kaolinite and red soil system, was displaced out within the five minute after Cu2+ was added into the suspension and then the amount of H+ released increased gradually. More H+ was released at a higher concentration for a given sample and the amount of H4 released in red soil system was more than that of kaolinite system at a given concentration. The time-dependent data of H+ releasing of red soil and kaolinite at two concentrations could be fitted best by second-order equation among six equations tested , and the average correlation coefficient for the linear form of second-order equation was 0. 9989 (n>30). The ratio of the amount H+ released to amount of Cu2+ adsorbed, H+/ Cu2'1', increased with time, which suggested that the speed of H+ releasing and the speed of Cu2+ adsorption were not synchronous, but the releasing of H+ was hysteretic to the adsorption of Cu2+.