Effect of Organic Acid Concentration and Leaching Time on the Efficiency of Nickel and Zinc Recovery from Waste Printed Circuit Boards of Mobile Phones

Abstract

Aims: The present work evaluated the effect of organic acid concentration and reaction time on the recovery of Zn and Ni from waste printed circuit boards of cell phone. Study design:  A survey research design was adopted. Place and Duration of Study: Materials and Energy Technology Lab in Projects Development institute (PRODA) Enugu Nigeria, between March 2021 and December 2024. Methodology: Cables and plastics were removed from circuit boards, and metals were extracted using heat, washed, dried, and treated in sodium hydroxide before being crushed and characterized using SEM-EDX and XRD. Acid leaching was then conducted using varying acid concentrations (1M, 2M, 3M, 4M and 5M) and times (2hrs, 3hrs, 4hrs, 5hrs and 6hrs) to compare metal recovery efficiency. Leachates were filtered and analyzed with atomic absorption spectrophotometry to quantify metal content following standard procedures.  Results: The SEM-EDX and XRD result indicates a copper-zinc-nickel alloy, likely a type of brass or nickel silver. The morphology shows an irregular surface, possibly with some porosity or particle clusters with some trace elements as impurities. Zn and Ni were successfully recovered from waste PCB of cell phone when leached with oxalic acid for 2 hours recording the highest recovery efficiency of 14.90% and 37.5% as leaching time was varied. Then citric acid (15.75%), malic acid (12.95%) and the combination of citric, malic and oxalic acids (6.39%) were recorded as highest efficiencies at 2 hours when Ni was leached. At varied concentration, oxalic acid had the highest efficiency in the recovery of Zn and Ni (53.12 % and 88.91 %) as compared to other acids and their combination. Conclusion: The impact of concentration on leaching efficiency was higher compared to the impact observed when time was varied. It is suggested that leaching with different degrees of oxidant be carried out to enhance the efficiency of the other acids.