Fathima Arshia, Tang Jessie Yuk Bing, Giannis Apostolos, Ilankoon I M S K, Chong Meng Nan
School of Engineering, Chemical Engineering Discipline, Monash University Malaysia, Jalan Lagoon Selatan, Bandar Sunway, Selangor Darul Ehsan, 47500, Malaysia.
School of Chemical and Environmental Engineering, Technical University of Crete (TUC), University Campus, 73100, Chania, Greece.
Chemosphere. 2022 Jul;298:134340. doi: 10.1016/j.chemosphere.2022.134340. Epub 2022 Mar 17.
Smart technologies and digitalisation have increased the consumption of scarce metals that threaten the sustainability of intricated industries. Additionally, the growing streams of waste electrical and electronic equipment (e-waste) are significant hazards to public health and the environment. Thus, there is an escalating need to recover metals from e-waste for sustainable management of metal resources. Hydrometallurgical processing of e-waste, involving copper (Cu) leaching and its subsequent recovery from pregnant leach solution (PLS) via electrowinning, has emerged as an efficient strategy to close the recycling loop. Electrowinning from PLS demonstrated higher Cu recovery efficiency and operational feasibility with a lower reagent use and lesser waste generation. Nevertheless, multiple issues challenged its practical implementation, including selective recovery of Cu from PLS containing mixed metals and high energy consumption. This review (1) identifies the factors affecting Cu electrowinning from PLS; (2) evaluates the composition of lixiviants influencing Cu electrowinning; (3) appraises various catalysts developed for enhancing Cu electrodeposition; and (4) reviews coupled systems that minimised process energy consumption. From the literature review, electrocatalysts are prospective candidates for improving Cu electrowinning as they reduced the cathodic reduction overpotentials, enhanced surface reaction kinetics and increased current efficiency. Other catalysts, including bioelectrocatalysts and photoelectrocatalysts, are applicable for dilute electrolytes with further investigations required to validate their feasibility. The coupled systems, including slurry electrolysis, bioelectrochemical systems and coupled redox fuel cells, minimise process energy requirements by systematically coupling the cathodic reduction reaction with suitable anodic oxidation reactions having thermodynamically low overpotentials. Among these systems, slurry electrolysis utilising a single-step processing of e-waste is feasible for commericalisation though operational challenges must be addressed to improve its sustainability. The other systems require further studies to improve their scalability. It provides an important direction for energy-efficient Cu electrowinning from PLS, ultimately promoting a circular economy for the scarce metal resources.
智能技术和数字化增加了对稀有金属的消耗，这对复杂产业的可持续性构成威胁。此外，废弃电子电气设备（电子垃圾）数量不断增加，对公众健康和环境构成重大危害。因此，从电子垃圾中回收金属以实现金属资源的可持续管理的需求日益迫切。电子垃圾的湿法冶金处理，包括铜（Cu）浸出及其随后通过电解沉积从浸出富液（PLS）中回收，已成为一种有效的策略来闭合回收循环。从PLS中进行电解沉积显示出更高的铜回收效率和操作可行性，同时试剂使用量更低且废物产生量更少。然而，多个问题挑战了其实际应用，包括从含混合金属的PLS中选择性回收铜以及高能耗。本综述（1）确定了影响从PLS中电解沉积铜的因素；（2）评估了影响铜电解沉积的浸出剂组成；（3）评估了为增强铜电沉积而开发的各种催化剂；（4）综述了使工艺能耗最小化的耦合系统。从文献综述来看，电催化剂是改善铜电解沉积的潜在候选者，因为它们降低了阴极还原过电位，增强了表面反应动力学并提高了电流效率。其他催化剂，包括生物电催化剂和光催化剂，适用于稀电解质，但其可行性还需要进一步研究来验证。耦合系统，包括矿浆电解、生物电化学系统和耦合氧化还原燃料电池，通过将阴极还原反应与具有热力学低过电位的合适阳极氧化反应系统地耦合，使工艺能源需求最小化。在这些系统中，利用电子垃圾单步处理的矿浆电解对于商业化是可行的，尽管必须解决操作挑战以提高其可持续性。其他系统需要进一步研究以提高其可扩展性。它为从PLS中进行节能铜电解沉积提供了一个重要方向，最终促进稀有金属资源的循环经济。
