Toward Sustainability for Recovery of Critical Metals from Electronic Waste: The Hydrochemistry Processes

Critical metals are significantly important in the preparation of high-tech materials associated with applications on, e.g., renewable energy, sustainable materials engineering and cleaner production. This importance together with supply risk to a substantial extent within the European Union (EU) has pushed their recovery from waste being highlighted. Electronic waste, usually from end-of-life electronic products, is a notable secondary resource for this purpose because of its distinctive features. A range of critical metals, including rare-earth metals, indium, cobalt and valuable metals, such as copper, silver and gold, are possibly recovered from electronic waste. On top of the current practices of electronic waste recycling, it requires innovations on technology and breakthroughs on process design in order to promote critical metal recovery or electronic waste treatment (in general) to be green and sustainable. Significant potentials are more and more noticed from hydrochemistry (metallurgy) technologies (processes) that contribute to this development because of its flexibility, relatively high recovery rate and extraction selectivity of critical metals, and possibilities of eliminating secondary waste. In this review, critical evaluation is carried out on the aspects of (1) understanding the features of different hydrochemistry processes for recycling of (critical) metals from electronic waste; (2) identifying the difficulties for a process to be implemented into industrial application which still originate from the high complexity of electronic waste and the secondary waste generation, e.g., wastewater; (3) defining circulability of metals to be recovered and recognizing their potentials to zero waste scheme. According to the evaluation, sustainable even zero waste processing is expected to be achieved for electronic waste treatment in the long term that it is preferred to reduce or prevent the generation of electronic waste and improve material efficiency from the whole life cycle of electronic products.