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ISSN 1811-0231 / ISEIS Publication Series Number P002
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Paper EIA05-036, Volume 3 (2005), Pages 278-285 = complimentary
Recovery of High-Purity Gallium from Wafer Grinding Wastes
Y. F. Chen*, J.-S. Jean and F.-R. Yang
Center for Environmental, Safety and Health Technology Development, Industrial Technology Research Institute, Chutung, Hsinchu, Taiwan, 310. *Corresponding author: Y_FChen@itri.org.tw.
Abstract
Wafer grinding wastes that contained GaAs were dissolved in 5N aqua regia to prepare extraction solution. During extraction, the liquid to solid ratio was fixed at 10. The pH of the extraction solution was adjusted to 4.0~5.0 with sodium hydroxide to obtain gallium and arsenic hydrate precipitates. Thermal treatment at 300℃for 15 hours removed around 87% of arsenic compounds from the precipitate. Then, the Ga-rich precipitate was dissolved using 2.5N nitric acid (at a liquid/solid ratio of ten) and 45 g/L ferric hydroxide was added as the extractant to remove the residual arsenic compounds. The percentage of arsenic removed (RAs) exceeded 99%. The pH value was adjusted to 12 to remove ferrous and aluminiferous compounds. At a gallium concentration of 4250 ppm, an NaOH concentration of 4N, an electric density of 1 A/dm2 and a temperature of 30℃, 99.99% pure gallium metal was obtained with copper as the anode and nickel as the cathode. Following six hours of electrodeposition, the percentage of gallium recovered was around 99.06 %.
Keywords: Recovery, gallium, arsenic, extraction, electrodeposition