Selective Recovery of Silver from Cell Phone and Television Printed Circuit Boards via Organic Acids

Abstract

Electronic waste (e-waste) is growing rapidly worldwide and represents a significant environmental threat due to technological advancements. The environmental impacts of e-waste disposal are gaining increasing global attention. Recovery methods used in developing countries often expose people to numerous toxic materials and contaminants. This study aimed to recover silver from waste printed circuit boards (PCBs) of cell phones and televisions using two organic acids. The metallic parts of the waste PCBs from cell phones and televisions were separated, washed with sodium hydroxide, dried, pulverized to 75 µm, and characterized using SEM-EDX and XRD. Leaching experiments were conducted with varying concentrations of oxalic and malic acids, different time intervals, and temperatures. Leaching efficiency was determined by analyzing the leached solution using an atomic absorption spectrophotometer. SEM analysis revealed a magnified view of material's surface and also presence of metal particles in the PCB samples of cell phone and a rough, irregular surface with a combination of smooth and textured areas for waste PCB of television. EDX analysis indicated silver weight concentrations of 1.06% and 3.51% for cell phone and television PCBs, respectively. Silver from cell phone PCBs leached with 3 M oxalic acid achieved the highest yield (83.47%) at 30°C and 3 hours, representing the optimal condition. Malic acid under the same conditions yielded 63.77%. For television PCBs, silver leaching with oxalic acid recorded the highest efficiency of 73.88% at 30°C and 3 hours, while malic acid achieved 35.74% under the same conditions. Kinetic studies showed that both acids fit pseudo-first- and pseudo-second-order models reasonably well, with malic acid providing a better correlation. For television PCBs, oxalic acid exhibited an excellent fit (R² ≈ 0.90). Rate constants (k₁) indicated that malic acid dissolved silver faster from cell phone PCBs. The green leaching of silver from end-of-life PCB panels using organic acids offers an environmentally beneficial approach.