Abstract E-waste has become a global risk to the environment and humans due to the improper disposal. Recently, a novel approach has been reported to effectively extract copper (Cu) from waste printed circuit boards (WPCBs) using environmentally friendly glycine solutions, with the co-extraction of other base metals. This process step is ideally positioned after the bulk of the aluminium, copper and iron is removed using conventional dry physical processes, but before hydrometallurgical recovery of precious metals. To recover Cu and other minor base metals from glycine leachate of WPCBs and release the glycine for reuse, this study investigates three options, i.e. hydrazine reduction, sulphide precipitation, and solvent extraction. During the hydrazine reduction, it was found that Cu recovery was sensitive to the leachate pH, and copper recovery increases with the increase of initial pH, Cu concentration and temperature. The obvious co-precipitation of lead and tin was also found while no co-precipitation of nickel, zinc and aluminium was observed. At the Cu/hydrazine molar ratio of 1:0.7 and 1:1, the products were identified as cuprite (Cu2O) and native Cu with 96.9% and 98.6% recoveries, respectively. During sulphide precipitation, ≥99.5% Cu could be easily precipitated at Cu/HS− molar ratio ≤ 1:1.2 in only 5 min. Lead, tin and zinc in the alkaline glycinate leachate also precipitated to a significant extent (>65%), whereas aluminium and nickel co-precipitation was limited (≤3%) in the sulphide. XRD analysis of precipitates verifies that Cu was recovered as covellite (CuS). During solvent extraction from the polymetallic leachate, Mextral 84H showed better performance than Mextral 54–100 but requires higher H2SO4 concentration for stripping. Mextral 84H also showed higher selectivity than Mextral 54–100 with no zinc, aluminium and nickel co-extractions detected. The overall Cu recoveries of 91.6% for 15% Mextral 84H extraction followed by 200 g/L H2SO4 stripping, and 86.7% for 30% Mextral 54–100 extraction followed by 80 g/L H2SO4 stripping were achieved. Finally, discussion and comparison of the three methods were made with a suggested conceptual process of WPCBs recycling.

中文翻译：

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从废印刷电路板 (WPCB) 产生的碱性甘氨酸浸出液中回收铜和去除其他贱金属

摘要 电子垃圾由于处置不当，已成为对环境和人类造成全球性威胁。最近，已经报道了一种使用环境友好的甘氨酸溶液从废印刷电路板 (WPCB) 中有效提取铜 (Cu) 的新方法，并与其他贱金属共提取。该工艺步骤理想地位于使用常规干物理工艺去除大部分铝、铜和铁之后，但在贵金属湿法冶金回收之前。为了从 WPCB 的甘氨酸浸出液中回收 Cu 和其他次要贱金属并释放甘氨酸以供再利用，本研究研究了三种选择，即肼还原、硫化物沉淀和溶剂萃取。在肼还原过程中，发现铜回收率对浸出液 pH 值敏感，铜回收率随着初始 pH、铜浓度和温度的增加而增加。还发现了明显的铅和锡共沉淀，而未观察到镍、锌和铝的共沉淀。在 Cu/肼摩尔比为 1:0.7 和 1:1 时，产物被鉴定为赤铜矿 (Cu2O) 和天然铜，回收率分别为 96.9% 和 98.6%。在硫化物沉淀过程中，当 Cu/HS− 摩尔比≤ 1:1.2 时，只需 5 分钟即可轻松沉淀出≥99.5% 的 Cu。碱性甘氨酸盐浸出液中的铅、锡和锌也大量沉淀 (>65%)，而硫化物中的铝和镍共沉淀有限 (≤3%)。沉淀物的 XRD 分析证实铜以铜钴矿 (CuS) 的形式回收。在从多金属浸出液中提取溶剂时，Mextral 84H 表现出比 Mextral 54–100 更好的性能，但需要更高的 H2SO4 浓度进行汽提。Mextral 84H 还显示出比 Mextral 54-100 更高的选择性，没有检测到锌、铝和镍的共萃取物。15% Mextral 84H 萃取后用 200 g/L H2SO4 汽提的总铜回收率为 91.6%，30% Mextral 54–100 萃取后 80 g/L H2SO4 汽提的总铜回收率为 86.7%。最后，通过建议的 WPCB 回收概念流程对这三种方法进行了讨论和比较。30% Mextral 54–100 萃取后 80 g/L H2SO4 汽提达到 86.7%。最后，通过建议的 WPCB 回收概念流程对这三种方法进行了讨论和比较。30% Mextral 54–100 萃取后 80 g/L H2SO4 汽提达到 86.7%。最后，通过建议的 WPCB 回收概念流程对这三种方法进行了讨论和比较。