Experimental Research On The Recovery Of Scandium From Red Mud Of Pingguo Aluminum Plant In Guangxi Province

Red mud is the industrial waste of alumina plant. But scandium content was very high in red mud, reached the industrial level, so the research about scandium extraction process of red mud, not only can make effective use of red mud, but also expanded the sources of raw materials extraction of scandium. This will have a positive impact on the utilization of red mud and the development of the industry of scandium.The study was based on the Bayer red mud from Pingguo Aluminum plant in Guangxi province as the main object. Comprehensive analysis of the chemical composition and phase composition of the red mud was studied. The chemical composition of the red mud was determination by the ICP-MS method. The mainly valuable elements in the red mud were Fe, Al, Ti and rare earth. There was0.016%percent content of Sc2O3in the red mud, showed a high economic taste. The phase composition of red mud was analysis by SEM and XRD method. The results show that there was no independent mineral of scandium in the red mud, mostly scandium exists in the other crystalline minerals by the way of formed isomorphous phase.Based on the properties of red mud from Pingguo Aluminum plant and acid leaching thermodynamics and kinetics, scandium in the red mud was recovered by two-stage acid leaching and extraction process. After the first stage, Na and Ca was leached the most while Sc was leached seldom. In the second stage, the24-1factorial design was used to explore the effect of the hydrochloric acid concentration, leaching temperature, liquid-solid ratio, leaching time to scandium, iron leaching yield in the leaching process. The Design-expert software was used to design the experimental and analysis of the data. The statistically sound regression2FI model of scandium, iron leaching yield was finally obtained. And from the optimization solution obtained the optimum leaching conditions of scandium. In the condition of leaching temperature70℃, leaching time120min, the hydrochloric acid concentration3.49, liquid-solid ratio8, the leaching yield of scandium was73.49%, while the leaching yield of iron was17.12%. Such leaching yield is very satisfactory. In the extraction process, D2EHPA(P204) was used as the extracting agent. Single-factor experiment was used to discuss the effect of the extraction agent concentration, extraction time and acid concentration to the scandium, iron extraction yield. Finally obtained the optimum conditions of the extraction process that is A/O was5, the acidity of the liquid phase was pH0.5, the content of the P204in the organic phase was1%and the extraction time was15min. Under this condition, the extraction yield of scandium reached to96%. Sodium hydroxide solution was used to be the stripping agent. The optimal conditions for the stripping process were obtained. Under the following conditions, phase ratio1, NaOH concentration of2mol/L, the temperature at70℃, the stripping yield of scandium was up to93.68%.