Environmentally Friendly Technology for Separating Gold from Waste Printed Circuit Boards: A Combination of Suspension Electrolysis and a Chlorination Process

Regarding waste printed circuit boards (WPCBs) as a secondary resource for recycling precious metals such as gold has become a worldwide consensus to conserve mineral resources, sustainably utilize resources, and prevent pollution. The dissolving of gold is the most important part for gold recycling because this process determines the maximum gold recovery efficiency. However, aqua regia and cyanide are dominantly used in the abovementioned process, causing serious environmental contamination and human health damage. This paper reports an environmentally friendly technology combining electrolysis and the chlorination process to extract gold from WPCBs. A response surface methodology called central composite design was employed to optimize the parameters. The results showed that the response surface quadratic model was significant (p-value = 0.0107), and the interaction of current density and time (p-value = 0.0335) and the interaction of temperature and time (p-value = 0.0034) were recognized as significant model terms. The leaching rate of gold reached 98.96% under the optimal conditions of 1.4 mol/L sodium chloride concentration, 643.54 A/m(2) current density, 40 degrees C, and 3 h. In this reaction system, the electrolyte was only composed of NaCl which was used as the chlorinating agent, and the electron was used as an oxidizing agent for potential controlling. Compared with the traditional approaches, the present strategy shows the major advantage of using fewer, nontoxic, and noncorrosive chemicals, which contributes to cleaner production and environmental protection.