Study On Enrichment And Leaching Of Gallium From Coal Ash

With the development of the electronic communications industry, the demand ofgallium is increasing. As a dissipated metal, gallium is very dispersive and never forman independent ore the earth’s crust. Coal ash will become a new source of galliumbecause of its broad source and large storage.We extracted gallium from coal ash in this experiment. Firstly, the gallium wasenriched by flotation test. At the same time, we studied influence of pH, foaming agentand collecting agent. Then, the coal ash which had been enriched was lixiviated to findthe influence of acid or alkali concentration, leaching time, leaching temperature,liquid-solid ratio and microwave preheating. Lastly, according to orthogonalexperiments, the best technological condition was determined. The main results wereas follows.(1) Octadecylamine was one of the best collecting agents in flotation test. Wefound that addition of octadecylamine, sodium silicate and terpenic oil in roughingexperiment was300g/t,100g/t and70g/t. When addition of octadecylamine andterpenic oil was100g/t and70g/t, the recovery of gallium was90%which was thehighest. In this process, the pH of serifux must be controlled to about7.(2) The highest leaching rate of conventional acid leaching test was74.08%, andthe reaction condition was as follows: hydrochloric acid concentration was10%,leaching temperature was60℃, leaching time was4h, and liquid-solid ratio was5:1.When the concentration of sodium hydroxide was40%, leaching temperature was80℃,leaching time is4h and liquid-solid ratio was5:1, the leaching rate of gallium was79.81%.(3) According to the single-factor and orthogonal experiments, we found that thehighest leaching rate of acid and alkali leaching test under microwave can be reachedup to87.9%and88.5%. The optimum condition of acid leaching test was below:microwave preheated under medium–low heat for10min, hydrochloric acidconcentration was10%, temperature was65℃, leaching time was15min andliquid-solid ratio was5:1, and that of alkali leaching test was as follows: microwavepreheated under medium–low heat for10min, sodium hydroxide concentration was40%, temperature was80℃, leaching time was40min and liquid-solid ratio was5:1.