title: Recovery of alumina and alkali in Bayer red mud by the formation of andradite-grossular hydrogarnet in hydrothermal process.
abstract: Bayer red mud (RM) is an alumina refinery waste product rich in aluminum oxides and alkalis which are present primarily in the form of sodium hydro-aluminosilicate desilication product (DSP). A hydrothermal process was employed to recover alumina and alkali from "Fe-rich" and "Fe-lean" RM, the two representative species of RM produced in China. The hydrothermal process objective phase is andradite-grossular hydrogarnet characterized by the isomorphic substitution of Al and Fe. Batch experiments were used to evaluate the main factors influencing the recovery process, namely reaction temperature, caustic ratio (molar ratio of Na(2)O to Al(2)O(3) in sodium solution), sodium concentration and residence time. The results revealed that the Na(2)O content of 0.5 wt% and A/S of 0.3 (mass ratio of Al(2)O(3) to SiO(2)) in leached residue could be achieved with Fe-rich RM under optimal conditions. However, the hydrothermal treatment of Fe-lean RM proved less successful unless the reaction system was enriched with iron. Subsequent experiments examined the effects of the ferric compound's content and type on the substitution ratio.
authors: Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, 100190 Beijing, China. zhangran1313@163.com
authors: Ran
authors: R
authors: Zhang
authors: Shili
authors: S
authors: Zheng
authors: Shuhua
authors: S
authors: Ma
authors: Yi
authors: Y
authors: Zhang
mesh_terms: D000535:Aluminum / Q000737:chemistry; D000537:Aluminum Oxide / Q000737:chemistry*; D002681:China; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste; D007501:Iron / Q000737:chemistry; D012037:Refuse Disposal / Q000379:methods*; D012822:Silicon Dioxide / Q000737:chemistry; D012964:Sodium / Q000737:chemistry; D013696:Temperature; D013997:Time Factors; D014873:Water Pollutants / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D007220:Industrial Waste; D014873:Water Pollutants; D012822:Silicon Dioxide; D012964:Sodium; D000535:Aluminum; D007501:Iron; D000537:Aluminum Oxide