Optimizing the Amino Acid Leaching Parameters of Gold from the Mobile Phone Printed Circuit Boards

Technological advances in electronic equipment and the variety-seeking behavior of people in using new equipment and devices have turned the issue of electronic waste (E-waste) into a major dilemma in the world. Electronic waste contains high levels of toxic metals such as lead and cadmium, base metals like aluminum and copper, precious metals such as silver, platinum, and palladium, and non-metallic parts consisting of resin, ceramic, plastic, and glass. There are different methods available to recover precious metals such as gold and platinum from electronic waste. However, the amino acid L-valine was used in this paper as a cheap and non-toxic leaching agent instead of cyanide. The grade of gold and platinum in the sample is 542 and 30 ppm, respectively, In addition, the parameters of L-valine concentration, temperature, pH, pulp solid percentage, and time were assessed by the Design of Experiments (DOE) method using the software. The experiments’ results demonstrated that the parameters of temperature, time, pH, pulp density, and L-valine concentration respectively have greater importance in the gold recovery process due to the lower P and higher F values. The mean percentage of gold recovery was obtained as 81.47% when validating the results under the proposed optimal conditions (L-Valine concentration: 173 g/t, pH: 11, time: 24 hours, temperature: 80 °C, pulp solid percentage: 19%, and constant stirrer speed: 400 rpm).