RECOVERY OF VALUE METALS FROM SPENT ZINC-CARBON BATTERIES

By

Author

Presented To

Department of Engineering

ABSTRACT
Spent primary batteries are known to contain metallic compounds that could be of value if recycled as well as harmful to man and the environment if not properly disposed. Also, the recovery of these value metals from the used batteries can reduce limited natural resource (ore) depletion. This research was carried out to investigate the recovery potential of Zinc and Manganese from spent zinc-carbon battery paste. Spent battery samples were collected around Samaru area of Sabon-gari LGA of Kaduna State. The samples were crushed, ground, sieved, washed and oven-dried. Quantities of dry samples were taken for x-ray fluorescence (XRF) analysis and chemical digestion. Chemical digestion (leaching) was done by studying some variable parameters: acid concentration, reducing agent concentration, temperature, stirring speed, solid-liquid ratio and time. Leached samples were then filtered and the filtrate taken for quantitative analysis of dissolved metals using atomic absorption spectrophotometer (AAS) analysis. Results show traces of heavy metals (lead, mercury and cadmium) and also significant amount of zinc and manganese in the solution. The optimum conditions for selective dissolution of zinc was found to be 2M nitric acid concentration, 10% hydrogen peroxide, 600C, 400rpm, 1:5 S/L and 1.5hrs, which yielded 4788.323mg/lit. For manganese, it was 1M nitric acid, 5% hydrogen peroxide, 600C, 400rpm, 1:5 S/L ratio and 1.5hrs giving a yield of 18042.67mg/lit while the optimum condition for simultaneous dissolution of zinc and manganese was found to be 1M nitric acid concentration, 5% hydrogen peroxide, 600C, 400rpm, 1:5 S/L ratio and 1.5hrs with a yield of 1225.648mg/lit zinc and 18042.67mg/lit manganese. The study therefore, showed that there is reasonable potential of zinc and manganese recovery from spent zinc-carbon battery.