膜电解法在线再生酸性蚀刻液及回收铜新技术

New technology for on-line regeneration of acidic etchant and recovery of copper by membrane electrolysis

采用极化曲线法研究了酸性蚀刻液阴、阳极电化学行为，并构建了离子膜电解反应体系，考察了在线再生酸性蚀刻液及回收铜的效果。结果表明，阳极氧化过程发生浓差极化，存在极限电流密度，Cu＋含量越高，极限电流密度越大；阴极还原分4步反应进行，存在极限电流密度；强化溶液传质可有效提高阴、阳极极限电流密度，有利于避免电解过程中析出氯气和氢气；在线实验表明，通过监控阳极液ORP，可避免析出氯气；分步降低电流电解有利于避免析出氢气，形成致密的金属铜块；在电流为9～24A范围内分4步电解23．5h可再生酸性蚀刻液23．5L，同时电沉积回收510g铜，纯度高达99．98％。阴极电流效率达到95．2％，吨铜电耗3251kWh。电解过程中无氯气和氢气析出，无废液排放，表明膜电解法在线再生酸性蚀刻液具有良好的应用前景。

The anodic and cathodic electrochemical behavior of acidic etchant was studied by polarization curve measurement. A system of ion-membrane electrolysis was constructed to evaluate the effectiveness of on-line regeneration of acidic etchant and recovery of copper. The results showed that concentration polarization occurs in the anodic oxidation process, where exists a limiting current density which increases with increasing concentration of Cu ＋ . The cathodic reduction involves four reaction steps, in each of which exist a limiting current density as well. The intensification of mass transfer in electrolyte effectively increases the cathodic and anodie limiting cur- rent densities and facilitates the prevention of Cl2 and H2 evolution. On-line tests showed that the evolution of Cl2 can be avoided by monitoring the ORP of anolyte. The stepwise reduction of current during electrolysis is favora- ble for avoiding the evolution of H2 and forming a compact copper block. A four-step electrolysis at current values decreasing from 9 to 24 A reclaimed 23.5 L of acidic etchant and 510 g of electrodeposited copper with a purity of 99. 98%. The cathodic current efficiency was 95. 2% and the electric energy consumption was about 3 251 kwh per ton of copper. Neither Cl2 nor H2 was emitted and no wastewater was discharged during the elec- trolysis. The on-line regeneration of acidic etchant by membrane electrolysis has a good application prospect.