Chlorine-free emission disposal of spent acid etchant in a three-compartment ceramic membrane reactor

Abstract Electrochemical technologies for the on-site treatment of spent acid etchant have received great attention due their ease of operation and economic benefits. On the other hand, a large amount of Cl 2 is generated during the electrolysis process, which leads to potential environmental risks. In the present work, a novel three-compartment ceramic membrane flow reactor, including a cathode chamber, an anode chamber, and a gas absorption chamber was developed. The three chambers were divided by an Al 2 O 3 ceramic membrane and a breathable hydrophobic anode diffusion electrode (ADE). The Cl 2 evolution onset potential of the ADE was increased to 1.19 V from 1.05 V of the graphite felt, effectively inhibiting the chlorine evolution reaction (CER). The anode-generated Cl 2 diffused into the gas absorption chamber through the ADE and was eventually consumed by the H 2 O 2 adsorbent. Cu could be recovered without emitting chlorine due to the special structure of reactor. The current efficiency of copper precipitation and cathode reduction from Cu 2+ to Cu + reached 97.7% at a working current of 150 mA. These results indicated that the novel membrane reactor had high potential for application in the copper recovery industry.