Determination of best processing route for lead recovery from fire assay slags

Abstract

In Ghana, voluminous amounts of slags are generated by fire assay laboratories. Since lead is a major constituent in fire assay slags, it is possible to find its way into the slag matrix and be released into the geo environment upon disposal. This work ascertains the possible amount of lead in the slags and recovers it using flotation, gravity concentration and acid-leaching methods. The initial samples were chemically characterized using an X-ray fluorescence (XRF) and acid-digested for Atomic Absorption Spectroscopy (AAS) analysis. The results indicate that fire assay laboratories have elevated heavy metal concentrations, especially lead (Pb), which is above the Ghana Environmental Protection Agency (GEPA) and World Health Organization (WHO) permissible levels, demonstrating anthropogenic impacts. The study found the recoveries were 77.83 %, 77.09 % and 75.90 % for flotation, gravity separation and acid leaching respectively. It is concluded that the gravity separation method is the best processing route for lead recovery from fire assay slags since the gravity separation poses little or no environmental dangers whereas flotation and acid leaching processes require chemicals that can cause skin irritation and other adverse effects. Also, the gravity separation process requires less time to perform.