Gallium and Arsenic Recovery from Waste Gallium Arsenide by Wet Refined Methods

This study was focused on the recovery of gallium arsenide (GaAs) from semiconductor fabrication sludge. Wet refined methods were applied to recover gallium (Ga) including acid leaching, purified isolation, electrolysis, and coagulation. The result showed that leaching Ga with nitric acid (HNO3) was more efficient than with sulfuric acid (H2SO4). GaAs could be leached with 4 N HNO3 to obtain 100% Ga+ and arsenic (As-). The pH was adjusted with sodium hydroxide (NaOH). Then, the solution was extracted by di(2-ethylhexyl) phosphoric acid (D(2)EHPA) and was back extracted by H2SO4. In this way, Ga extraction efficiency was 80%. At the end of the process, electrolysis was applied to recover Ga. The resulting electrolysis efficiency with nickel-copper was only 56% and its purity was 92%. To further increase the recovery of Ga, the leaching solution was adjusted to alkaline solution and was then electrolyzed with platinum-stainless steel. In this way, recovery and purity could be as high as 90% and 94%, respectively. The removal of arsenic was 86% when the leaching solution was added with ferrous sulfate heptahydrate (Fe-2(SO4)(3) center dot xH(2)O) to form iron arsenate (AsFeO4).