Influence of a Polycarboxylate Based Solution on Stability of Hydrogen Peroxide and Application to E-waste Leaching

Abstract

Hydrogen peroxide with its high oxidising potential is commonly used in hydrometallurgical extraction of metals from ores, anode slimes and waste materials (e.g. WEEE) and treatment of cyanidation effluents. Main detraction to H₂O₂ is its rapid catalytic decomposition leading to prohibitively high consumption. Effect of pH (0-4), Cu(II) (0-10 g.l^-1) and temperature (20-80°C) on H₂O₂ stability was investigated using response surface methodology. Influence of neutral-alkaline conditions (pH 7.3-11.8) and presence of solids (1-20% w/v) was also tested. A polycarboxylate based solution (PBS) was utilised to improve H₂O₂ stabilisation. The significance order of parameters on H₂O₂ decomposition was temperature > pH > Cu(II). Elevating the level of these parameters increased H₂O₂ decomposition. The activation energy (60.7±2.5 kJ.mol^-1) indicated a chemically controlled process. Alkaline conditions (up to pH 11.8) led to higher H₂O₂ decomposition. Presence of solids adversely affected H₂O₂ stability under certain conditions. The addition of PBS significantly improved (up to 54%) H₂O₂ stability in the presence of copper. The presence of PBS in H₂SO₄-H₂O₂ leaching of waste of printed circuit boards (WPCBs) enhanced copper extraction by up to 19%. PBS can be suitably utilised to stabilise and hence reduce H₂O₂ consumption in aqueous solutions particularly in the presence of copper.