PROCESSING OF A METAL CONCENTRATE FROM GROUND WASTE PRINTED CIRCUIT BOARDS IN ACIDIC MEDIA USING HYDROGEN PEROXIDE AS OXIDANT

The recovery of precious and base metals of a metal concentrate from ground waste printed circuit boards (PCBs) is described in detail. Samples were treated with NaOHaq. to remove the soldering mask. Experiments were performed in acidic medium (HF, H2SO4, CH3COOH or H3PO4) using H2O2 as oxidant. Base metals were leached in high yields (>99 wt.%) at ~40 ºC after ~1 h (HF), ~2 h (H2SO4), ~4 h (H3PO4) and ~5 h (CH3COOH). Lead precipitated in the presence of H2SO4 and HF. Precious metals were not oxidized. Ceramic/fiberglass components were dissolved in the presence of HF. Silver, palladium and gold were recovered from the insoluble solid, in this order, by a sequential oxidative treatment in aqueous medium. Recovery of leached elements was possible by a combination of solvent extraction and precipitation. The choice of the extractant and the precipitant were essential to recover them with high yields. The leachates from H3PO4 + H2O2 experiments could not be processed above pH 2.5. Leaching of waste PCBs in the presence of a weak organic acid is possible but a multistage separation scheme for elements recovery is unavoidable as PCBs is a complex material in terms of composition.

本研究详细描述了从破碎废弃印刷电路板（PCBs）中回收金属精矿内贵金属与贱金属的完整流程。实验首先采用氢氧化钠水溶液对样品进行处理，以去除阻焊膜。实验在酸性介质（氢氟酸HF、硫酸H₂SO₄、乙酸CH₃COOH或磷酸H₃PO₄）中开展，以过氧化氢H₂O₂作为氧化剂。在约40℃条件下，贱金属可实现高浸出率（>99 wt.%，质量百分比），对应浸出时间依次为：氢氟酸体系约1小时、硫酸体系约2小时、磷酸体系约4小时、乙酸体系约5小时。在硫酸与氢氟酸体系中，铅会发生沉淀析出。贵金属未被氧化。陶瓷与玻璃纤维组分可在氢氟酸存在的体系中被溶解。研究人员可通过水相介质中的分步氧化处理工艺，从不溶固相物料中依次回收银、钯与金。通过溶剂萃取与沉淀法联用的工艺，可实现浸出元素的回收。萃取剂与沉淀剂的选型对于实现元素的高回收率至关重要。磷酸与过氧化氢联用体系的浸出液，无法在pH高于2.5的条件下开展后续处理。以弱有机酸为介质开展废弃印刷电路板的浸出工艺具备可行性，但由于印刷电路板成分复杂，实现元素回收必须采用多级分离工艺方案。