Box-Behnken Optimization and Theoretical Study for Copper Leaching from Scrap Laptop Computer Printed Circuit Board by Malonic Acid and Hydrogen Peroxide

Abstract

The hydrometallurgical method of copper leaching from scrap electronics is commonly undertaken using pulverized printed circuit boards. Though studies on the use of organic acids like citric and oxalic acids for copper removal are well documented, those on the use of malonic acid are rare. Herein, we report on the investigation of the efficiencies of mixtures of malonic acid and hydrogen peroxide for copper leaching from unpulverized scrap PCB by the Box-Behnken design and the theoretical determination of the most stable copper-malonic acid complex. The average copper content in each unpulverized printed circuit board was found to be (0.84 ± 0.13) mg/g following aqua-regia digestion and atomic absorption spectrophotometry measurement. The conditions at which the highest leaching efficiency of 51.3% was obtained were a malonic acid concentration of 0.5 M, a hydrogen peroxide concentration of 1.0 M, and a contact time of 75 min. The contact time was the most significant individual parameter that influenced the efficiency of copper leached with a p-value of 0.001. Theoretical calculations show that malonic acid prefers to coordinate with copper in a 2:1 malonic acid: copper ratio. This study shows that appreciable amounts of copper can be leached from the minimally processed unpulverized printed circuit board.