Electronic waste (e-waste) is one of the fastest growing waste segments in the world. This study investigates the use of supercritical CO₂ (scCO₂) and aqueous acid as co-solvent for the treatment of e-waste, specifically for the extraction of copper. Printed circuit board (PCB) was selected as the e-waste of study. In order to perform controlled experiments, melt-pressed Cu foil and polycarbonate sheets were prepared as surrogates for PCBs. It was found that a scCO₂ and acid pre-treatment induced drastic morphological changes in the polymer, creating pores, cracks, and delamination. This finding was translated to the actual waste PCB system. This unique process involved the pre-treatment of the PCB with scCO₂ and aqueous sulfuric acid at 120 °C and 148 atm for 30 min followed by leaching of the treated PCB in a solvent containing 2 M sulfuric acid and 0.2 M hydrogen peroxide at ambient conditions. Experimental results showed that 82% of the copper contained in the PCB was extracted in under 4 h. The characterization of the PCB demonstrated that the pre-treatment with scCO₂ and acid induced the crystallization of the plastics (polymer component), creating pores and weakening the structure of the PCB, thereby enhancing the transport of the solvent to the buried metal interfaces. This novel process using scCO₂ could reduce physical processing (e.g. grinding of the PCB) and acid usage during the extraction of Cu from e-waste, providing a greener alternative for current methods of recycling of metals, which are energy intensive with large environmental footprints.

电子废物（电子废物）是世界上增长最快的废物类别之一。这项研究调查了超临界CO ₂（scCO ₂）和酸水溶液作为共溶剂用于电子废物处理，特别是铜提取的用途。选择印刷电路板（PCB）作为研究的电子垃圾。为了进行受控实验，制备了熔融压制的Cu箔和聚碳酸酯板作为PCB的替代物。已经发现，scCO ₂和酸的预处理引起聚合物中剧烈的形态变化，从而产生孔，裂纹和分层。这一发现被转化为实际的废PCB系统。这个独特的过程涉及用scCO ₂预处理PCB在120℃和148atm下用硫酸水溶液洗涤30分钟，然后在环境条件下在含2M硫酸和0.2M过氧化氢的溶剂中浸出处理过的PCB。实验结果表明，PCB中所含铜的82％在4小时内被提取。PCB的特性表明，用scCO ₂和酸进行预处理会诱导塑料（聚合物成分）结晶，从而形成孔洞并削弱PCB的结构，从而增强了溶剂向掩埋金属界面的传输。使用scCO _2的新颖过程 可以减少从电子废物中提取铜的过程中的物理处理（例如PCB的研磨）和酸的使用，从而为当前的金属循环利用方法提供了更绿色的替代方法，这些方法耗能大，环境足迹大。