新型螯合型表面活性剂溶解氢氧化铜的机制研究

Mechanism of Cu(OH)_2 Dissolution in the Presence of a Novel Chelating Surfactant

随着工农业的发展,土壤重金属污染日趋严重,重金属氢氧化物是土壤中的常见存在形态,化学淋洗修复是一种有效的重金属污染土壤修复技术,选用了一种新型螯合型表面活性剂N-十二酰基乙二胺三乙酸钠(NLED3A)作为淋洗剂,探讨了其对重金属氢氧化物的螯合溶解能力.采用批平衡实验法,从动力学和热力学方面研究了N-LED3A溶解Cu(OH)_2的性能,并探讨了溶解反应机理.结果表明:N-LED3A可有效溶解Cu(OH)_2,溶解的Cu(Ⅱ)浓度随着N-LED3A浓度和反应温度的增大而增大,N-LED3A溶解Cu(OH)_2为螯合促进溶解机理;NLED3A和Cu(Ⅱ)可形成稳定可溶性螯合物,25℃时N-LED3A与Cu(Ⅱ)的配位稳定常数K_f~Θ为6.9×10^(19);在25℃下Cu(OH)_2在N-LED3A中的溶解行为为自发、吸热的熵增过程;动力学拟合结果表明,一级动力学方程最适合描述N-LED3A对Cu(OH)_2的溶解过程.

The dissolution thermodynamics and kinetics characteristics of Cu（OH）2 in a novel che- lating surfactant solution called sodium N-lauroyl ethylenedediamine triacetate （N-LED3A） have been investigated by using batch equilibrium experimental method. The results showed that N- LED3A solution rate of Cu（OH）2 was significantly enhanced with increasing N-LED3A concentra- tion and temperature. N-LED3A could seize Cu（ Ⅱ ） from Cu（OH）2 through ligand-promoted dis- solution mechanism and then form stable soluble chelate complex with them. The calculated coor- dination equilibrium constant K between N-LED3A and copper ions was 6.9 × 1019at 25 ℃. The dissolution process of Cu（OH）2 was spontaneous, endothermic and entropy increasing process. The data showed that Cu（OH）2 dissolution in N-LED3A solution fitted a pseudo-first-order kinet- ic equation well.