Recovery of Indium From Zinc Oxide Flue Dust

The main purpose of this study was to extract indium from the zinc oxide flue dust (ZOFD), which contained 753 g/t indium. Two-stage leaching process to recover indium from the ZOFD was investigated. The conditions for neutral leaching were optimized at 60 degrees C for a leaching duration of 30 min with sulfuric acid concentration of 0.16 M and a liquid/solid ratio of 10 mL/g. In the neutral leaching, zinc (> 95%) was selectively leached into the solution and indium (> 95%) was concentrated in the residue, which indicated the successful selective separation of zinc and indium. The dissolution rate of indium was more than 88% under the leaching conditions: temperature of 80 degrees C, sulfuric acid concentration of 0.8 M, liquid/solid ratio of 6 mL/g and reaction time of 2 h. The conditions in extraction of indium by di(2-ethylhexly)-phosphoric acid (D2EHPA) were optimized that organic phase: 20% D2EHPA and 80% kerosene, aqueous phase/oil phase ratio (A/O): 4 and initial acid concentration of the aqueous solution: 1-1.5 M, the fraction of extracted indium from solution was more than 95%, which is a significantly increase compared with less than 70% in traditional process. This work would contribute to provide a novel cleaning and efficiently process to separate and recover zinc and indium from zinc oxide flue dust, and prevent heavy metal pollution.