Study of the effect of iron and oxidizer on dissolution of galena concentrate in fluoroboric acid

The extraction of Pb from galena concentrate using fluoroboric acid media was studied and optimized as a potentially promising process to replace lead pyrometallurgical producing processes. The lead, zinc and iron content of the galena concentrate investigated were 57.66%, 5.50% and 1.55% respectively. Five control factors, including initial HBF4 concentration, the addition of iron and oxidizer agent, the reaction temperature and reaction time were considered in four different levels using Taguchi technique. L16 orthogonal array and analysis of variance (ANOVA) were applied to determine the optimum conditions and most significant factors affecting the overall lead extraction from galena concentrate. Analysis of variance indicated that the amount of oxidizer agent used and iron usage were the most influential leaching parameters respectively. According to former studies this result can be related to necessity of formation and presence of ferric fluoborate and also oxidation of ferrous ion to ferric in the system. The optimum dissolution condition to maximize lead extraction were; acid concentration = 5 mol/l, additive usage = 46.8 wt. %, oxidizer agent usage = 3 volume percent, temperature = 80 ºC and time = 6 hrs. Lead recovery efficiency in the optimum conditions predicted by Taguchi method successfully reached to 94.651%.