Study On Extraction Technology Of Scandium Form The Bayanobo Tailings

Baiyanobo ore is large iron, rare earth and niobium coexistence mineral deposit, and also contains scandium metal. Tailings are solid waste residue which formed during production processes of iron, rare-earths and niobium metals. A lot of emission and accumulation of the residues increase the cost of iron and rare earth production, and it also has brought tremendous environmental problems. As one kind of typical rare rare-earth element which contained in tailings, scandium has not been recovered yet. It has some outstanding characteristics such as high chemical activity, good electrical conductivity, soft enough so as easy to be cut and so on. These advantages make it widely applied materials in essential areas such as electro-optic light, astronavigation, electronics industry, nuclear technology, superconductivity technology and so on. Therefore, recovering scandium from tailings is very significant, and this article studies on the processes of recovering scandium from tailings for the first time.The chemical composition of tailings was analyzed comprehensively and the composition of mineral containing scandium was studied by using the method of XRD、DSC and TG. The results show that the major mineral containing scandium is riebeckite and the aegirine. The content of scandium which distribute at different particle sizes was measured. The distribution of scandium at different particle sizes in the tailings is irregularity. There is no specific enriched phenomenon exist.The physical and chemical properties of riebeckite and aegirine which are silicate minerals were combined, in order to study the process of extracting scandium from tailings by NaOH-HCl leaching method. Three experimental conditions were studied to determine the optimal leaching conditions. They are ratio of concentrate to alkali, NaOH concentration and reaction time. We obtained the optimal scheme of leaching scandium, when the condition·is that:the ratio of concentrate to alkali is1:1.7, NaOH concentration is60%and reaction time is7hr, the leaching rate of scandium is more than85%.Based on considerations of cost and process conditions, the process of extraction scandium from tailings by HCl leaching was studied through orthogonal experiment, we ascertained the order of primary and secondary factors of leaching scandium, obtained the optimal scheme of leaching scandium. When the condition is that:6mol/L HCl, the liquid-solid ratio L/S=4:1, reaction time is8hr and reaction temperature is90℃, the leaching rate of scandium is less than40%.The process of extracting scandium from tailings by activated dissociation-HCl leaching was studied, the optimal scheme of leaching scandium is that: amount of activator is60%, calcination temperature is950℃and calcination time is1.5hr, leaching agent is HCl and leaching time is6hr. The leaching rate of scandium is more than99%.