Investigating electrodes for the extraction and utilisation of copper from spent etching solutions

Abstract

Today, reagent-based technologies for metal removal from water often fail to achieve the necessary purification efficiency for reuse and result in the accumulation of toxic sludge. This article aimed to test a regenerator for restoring the properties of etching solutions used in printed circuit boards, evaluate the performance of electrodes in depositing dense copper precipitates during etching solution regeneration, and explore the use of recovered copper in repair processes. During the study, an electrochemical process was employed to deposit a copper layer onto the regeneration unit’s electrodes, along with mechanical testing of the electrodes for separating the removed product from the spent solution. This article investigated the electrochemical regeneration of etching solutions in the printed circuit board etching process, leading to the formation of dense copper deposits on electrodes (regenerators) made of copper, stainless steel, and titanium. The mechanical separation of the recovered copper material reveals that titanium cathodes yield superior results, making titanium the preferred electrode material for regenerator design. Additionally, the findings confirm that the copper deposited on titanium cathodes meets the quality standards required for reuse after remelting in the electrical engineering industry. The copper recovered from spent etching solutions, when combined with a bronze coating applied to the copper layer, improves adhesion and can be used in repair work. Additionally, it enhances the antifriction properties of the friction pair. The article identified suitable materials for use as regenerator electrodes in removing copper from spent etching solutions. It also examined the correlation between electrode surface finish quality and the detachment force of copper deposits in the regenerator, considering the surface roughness of titanium electrodes. The proposed methods and regeneration scheme for the used etching solution enable the creation of integrated equipment that incorporates a regeneration unit, with the primary component being a system (electrolyser) where the copper extracted from the used etching solution will be deposited onto the designated electrode. This study facilitates the development of a technological process for recycling aqueous etching solutions, helping to minimise environmental impact.