Extraction of zinc from dross generated due to galvanizing in manufacturing industries

Abstract

Zinc dross, a byproduct of the Continuous Galvanizing line at Roofing's Rolling Mills, is currently exported to India for zinc recovery. This practice incurs significant transportation and processing costs, reduces operational efficiency, and presents potential environmental risks due to improper handling of dross. This project aimed at developing a local, cost-effective method for extracting zinc from dross, thereby addressing these challenges. The study involved analyzing the chemical composition of zinc dross, evaluating various extraction methods, and then suggesting a sustainable recovery process. The zinc dross used in this project was obtained from Roofings Rolling Mills, and it included both top and bottom dross. Analysis was carried out on the dross using a spectrometer, and it revealed that the bottom dross possesses a high potential of zinc recovery since it has a higher percentage of zinc residue (63.4%), unlike the top dross (48.1%). The ICP-MS revealed a 51% in zinc content, hence the samples had a high potential for zinc recovery. Extraction methods of acid leaching and alkaline leaching were carried out on the crushed samples, and analysis carried using AAS which revealed a 21% and 5% purity levels of the zinc extracted. Finally, a techno-economic analysis was done to find out which one is more viable in the Ugandan setting and the acid leach dominated. By enabling local zinc extraction, the project contributes to improved resource utilization, cost savings, and sustainable industrial practices. This study helped to pave the way for identification of appropriate recovery methodologies and to economize the process if adopted on an industrial scale. The findings are expected to benefit Roofings Rolling Mills and other steel manufacturing industries in the region.