YIELD RESPONSE OF LEAD TO MULTI-FACTORIAL OPERATIONAL INFLUENCES DURING PROCESSING OF GALENA CONCENTRATE IN HYDROFLUORIC ACID SOLUTION

Abstract

This paper presents the response of lead yield to multi-factorial influence during hydroprocessing of galena concentrate in hydrofluoric acid solution. X-ray diffractometer (XRD) analysis of the as-mined galena was carried out to ascertain the various compounds present. Various quantities of the galena were leached at different initial pH, resulting in different final leaching solution pH. Some selected residues were examined using Scanning Electron Microscopy (SEM) to ascertain nature of phase distribution at the different pH values. Lead yield response analysis was carried out using a derived and validated model. The response coefficient of the lead yield to multi-factorial influence was evaluated to ascertain the viability and reliability of the highlighted dependence. Results of the investigation revealed that while increasing the initial leaching solution pH, lead yield decreased correspondingly as a result of decreasing H+ (ore attacking specie) concentration per unit mass of the ore. Increase in the initial solution pH resulted to increase in the final pH due to consumption of H+ during the leaching process. It was observed that the final leaching solution pH was slightly lower (more acidic) than the initial pH due to dissolution of little sulphur from the galena during the leaching process. The validity of the model; ln ξ = 4.6 (ϑ /₰) – 0.0198ε  + 0.0016ɤ   was rooted on the core model expression ln ξ - 0.0016ɤ = 4.6 (ϑ /₰) - 0.0198ε where both sides of the expression are correspondingly approximately equal. Regression model generated results showed trend of data point distribution similar to those from experiment and derived model. Standard errors incurred in predicting of lead yield for each value of the variable factors: initial and final leaching solution pH as obtained from experiment, derived model & regression model were 0.3782, 2.7651 & 3.3945 x 10-5 % and 0.4074, 2.5612 & 0.2329% respectively. Furthermore the correlation between lead yield and initial & final solution pH as obtained from experiment, derived model and regression model were all > 0.86. The maximum deviation of model-predicted lead yield from the experimental results was less than 5%. This translated into over 95% operational confidence and response level for the derived model as well as over 0.95 response coefficient of lead yield to the collective operational contributions of the influencing factors.