A Basic Research Of Comprehensive Recovery Valuable Metals From Red Mud By Hydrochloric Acid Leaching

Nowadays metallurgical solid waste recycling has been widespread concerned. Red mud a strongly alkaline solid is the waste generated during aluminum production process. It require a large area to pile, and it can cause serious environmental pollution. Till now, there are no effective treatment for red mud.However, the red mud contains iron, aluminum, titanium, calcium, gallium, rare earth elements and other valuable metals. At present, there are many researches about separate recycling iron, aluminum, titanium, scandium and other elements from red mud. But researches about recovery gallium and other rare earth elements are few. In this paper, analysis of the phase composition of and chemical composition of red mud has been made. For the purpose of recovery valuable metals from red mud, the research is as follows:In hydrochloric acid leaching tests, the optimum conditions of hydrochloric acid leaching of valuable metals in red mud have been determined by orthogonal experiments:temperature:109℃(boiling point); liquid to solid ratio:7:1; hydrochloric acid concentration:8mol/L; time:180min. In the leaching solution purifying test, the first step was using sodium hydroxide to neutralize the leaching solution to acidity0-1.0and then hydrolyze titanium for2hours age the liquid for12hours. Then recover titanium in the solution by filtration. Sulfuric acid was added into the leaching solution, to remove calcium from the solution. The calcium sulfate recovered after filtration can be used to prepare a plaster. Dissolution of aluminum by add sodium hydroxide to the leaching solution until the solution PH=7.5. Then recover the aluminum in the eluate(sodium aluminate solution) Leach the residue again by acid after dissolution. Then add iron powder to the leaching solution to reduce Fe3+of the leaching solution.In the test of recovering gallium, the best conditions of extracting gallium from leaching solution was determined by orthogonal experiment (extraction agent:TBP; extraction agent concentration60%; inorganic phase to the organic phase ratio:1:2.) At the optimum conditions of gallium extraction the extraction rate was97.51%. Best stripping conditions:stripping agent concentration50%; temperature80℃; inorganic phase to the organic phase ratio:1:2. At the optimum conditions of gallium stripping the stripping rate was97.35%. The recovery rate of gallium oxide which obtained by hydrolysis was85.74%In the test of recovering REE, oxidize Fe2+to Fe3+in the solution by adding hydrogen peroxide solution. And then continue to use the TBP to extract Fe3+of the leaching solution to achieve the aim of recycling iron. After above processing, there are lanthanum, cerium, neodymium and other rare earth elements remaining in the lixivium. By adding sodium hydroxide into the lixivium, Re2O3can be obtained after filtering and drying the precipitate. The recovery rate of REE oxide which obtained by hydrolysis were all above83%.Experiments show that by this process leaching rate reached more than90%of gallium and REE; the recovery rates of each value metallic element in this process are more than80%. It can conclude that the process was designed to be feasible.