Resource Recovery of Scrap Gallium Arsenide

• Main Author: 洪崇欽
• Other Authors: 李清華
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/04003184017755003860

碩士 === 大葉大學 === 環境工程學系碩士班 === 91 === As the gallium arsenide (GaAs) production continues to increase, the amount of scrap GaAs generated each year is also noticeable. Due to the hazardous material of As and valuable resource of Ga contained in the scrap GaAs, the discarded GaAs will present hazardous effects to the environments if they are not treated properly. The main objective of this study is to adopt hydrometallurgial methods to recover the valuable metal of Ga from GaAs and to disposal its hazardous material of arsenic properly. In this study, several methods of leaching, solvent extraction, cementation, ion-exchange, crystallization, electric winning are adopted to investigate the recovery of Ga and treatment of As. This study shows that Ga and As can be leached by 0.5 N NaOH with 0.5 vol% H2O2 (solid/liquid: 4g/100ml; leaching time: 1 hours) to obtain a 100% recovery of Ga and As. This optimal leaching solution is then subjected to a series recycling process of a pH adjustment (to 1.8 with H2SO4), a solvent extraction (by using 5 vol% D2EHPA), a back-extraction (by using 6N H2SO4) and Crystallization to obtain a product of gallium sulfuric (H4Ga2(SO4)5．12H2O). The total recovery of Ga by using aforementioned processes is about 70.7% . For the solution containing As, it is first treated by a pH adjustment to 11 with NaOH Then, Fe2(SO4)3 is added at a Fe/As ratio of 6 to precipitate the As as FeAsO4. The remaining As contained in the solution can be further removed by ion-exchange method by using Amberjet 4400 OH. The aforementioned processes can achieve a 99.999% removal of As.