Study on the recovery of gallium from phosphorus flue dust by leaching with spent sulfuric acid solution and precipitation

In this work the effect of reaction temperature, sulfuric acid concentration, liquid-to-solid ratio and Fe2+ concentration on sulfuric acid leaching of gallium from phosphorus flue dust was studied. The results showed that gallium extraction increased with the increase of temperature, sulfuric acid concentration and liquid-to-solid ratio. Fe2+ concentration did not significantly affect the recovery of gallium. The acid-soluble gallium could be completely extracted with simulated spent acid containing 20% sulfuric acid and 0 to 50 g/L Fe2+ at temperature of 80 °C, and liquid-to-solid ratio of 10:1. The effect of phosphate concentration, reaction temperature and pH on the precipitation of gallium and ferrous iron was also studied in order to determine the optimum conditions for the recovery of gallium from simulated spent acid leach solution. It was found that under optimum precipitation conditions, when all gallium precipitated from the simulated spent acid leach solution containing 31 g/L ferrous iron and 0.1 g/L gallium, the precipitation of iron was less than 2%, the ratio of iron-to-gallium decreased from 310:1 in the leach solution to 5:1 in the precipitate. Gallium was therefore concentrated in the precipitate.