JAROSITE PRECIPITATION OF IRON FROM LEACH SOLUTIONS OF WASTE PRINTED CIRCUIT BOARDS (WPCBs)

Abstract

ABSTRACT: Waste of printed circuit boards (WPCBs) with its significant content of base and precious metals is of particular interest for the recovery of metals. Sulphate/chloride leaching of WPCBs produces leach solutions in high concentration of copper as well as impurities such as iron. These impurities can adversely affect downstream processes. In this study, removal of iron as ammonium- or sodium-jarosite from leach solutions of WPCBs was investigated. Precipitation tests were carried out using synthetic (30 g/L Cu2+ and 1 M SO42-) and real leach solutions. The effects of initial concentration of iron (1-4.5 g/L Fe3+), [Fe3+]/[NH4+] ratio (1.5-2.4), pH (1.4-1.8), temperature (80-90°C) and seeding (23.3 g/L) were examined. The results showed that precipitation efficiency was high at low iron concentrations and high [NH4+]/[Fe3+] ratios favoured the iron removal. Seeding and temperature also positively influenced the precipitation process. About 68-69 % of iron was found to be removed as sodium-jarosite from sulphate/chloride solutions ([Na+]/[Fe3+]: 16.3-40.8). Precipitation of iron from real leach solutions produced by sulphate (H2SO4-H2O2) and sulphate/chloride leaching (H2SO4-CuSO4-NaCl) of WPCBs were found to be 76 % and 89%, respectively. SEM-EDS analysis detected 3.0-5.7 % copper in the precipitates. 1.