Preparation of Ultra-purity Al_2O_3 from Wuhai Coal Gangue

The high purity Al2O3 powder was prepared from Wuhai coal gangue as raw material, the iron removal process was mainly studied. The coal gangue was leached by hydrochloric acid to produce aluminium chloride solution. The techniques of extracting iron from the aluminium chloride solution was investigated to optimize the process conditions. The reaction system for extracting iron was constituted of the organic and inorganic phases. The organic phase was composed of extracting agent(tri-butyl phosphate) and diluents(petroleum ether); the inorganic phase was aluminium chloride solution from the coal gangue. The experiment results showed that, while the composition of the inorganic phase was Al 35.0 g/L, Fe 0.6232 g/L and volume fraction of extracting agent in the organic phase was 40%, the optimum extraction conditions were: phase ratio O/A(volume ratio) was 1 ∶ 1, extracting temperature was 30 ℃ and extracting time was 20 min. Under the optimum conditions, the aluminium chloride solution being extracted one times only, the extraction rate of iron reached 99.82% and separation coefficient of Fe/Al went up to 1.386×104.The recycling of iron-loaded organic phase was investigated, and the results showed that, when stripping agent was pure water, phase ratio A/O was 1 :1, temperature was 60 ℃ and time was 20 min, the stripping rate of iron was 98.85% only using the single-stage stripping, the poor organic phase can be recycled. At last, taking the raffinate as intermediate material, the γ-Al2O3 powder which having a purity of 99.99 wt% and the particle size of 3.09 um(median diameter) was prepared.