Development of Recycling System of Gold from Secondary Resources Using Organic Aqua Regius

Abstract

We have developed a novel process for recycling gold (Au) from secondary sources: the leaching of gold using Organic Aqua Regius, e.g. dimethyl sulfoxide (DMSO) or propylene carbonate (PC) solutions containing copper bromide (CuBr₂) and potassium bromide (KBr), which could offer a number of advantages, including eco-friendliness and ease of operation. In this study, we applied PC solution to recover Au from Waste Electric and Electronic Equipment (WEEE). First, the WEEE samples (memory card, mobile phone board and small appliances) were coarsely grinded and finely grinded. Then, thermal activation of semiconductors (TASC) technology using TiO₂ was applied to decompose the polymers and oxidize base metals containing in WEEEs. Next, the leaching of Au from the oxidized samples were conducted in a PC solution with 0.2 M of CuBr₂ and 0.2 M of KBr, at 353-373 K, followed by biphasic separation with sulfuric acid. The dissolved Au in the PC phase was recovered by reduction of ascorbic acid. The recovery ratio of Au was 56.0%, 67.2% and 65.7% from memory card, mobile phone board and small appliances, respectively.