Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, 100190 Beijing, China.
J Hazard Mater. 2011 May 30;189(3):827-35. doi: 10.1016/j.jhazmat.2011.03.004. Epub 2011 Mar 9.
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.
拜耳赤泥（RM）是氧化铝精炼厂的废物，富含氧化铝和碱，主要以硅酸钠脱硅产物（DSP）的形式存在。采用水热法从“富铁”和“贫铁”赤泥中回收氧化铝和碱，这两种赤泥是中国生产的两种代表性赤泥。水热过程的目标相是钙铁榴石-钙铝榴石水榴石，其特征是 Al 和 Fe 的同晶取代。批处理实验用于评估影响回收过程的主要因素，即反应温度、苛性比（氢氧化钠溶液中 Na(2)O 与 Al(2)O(3)的摩尔比）、钠离子浓度和停留时间。结果表明，在最佳条件下，富铁赤泥的浸出残渣中可以达到 Na(2)O 含量为 0.5wt%和 A/S 为 0.3（Al(2)O(3)与 SiO(2)的质量比）。然而，贫铁赤泥的水热处理效果较差，除非反应体系中富含铁。随后的实验研究了铁化合物含量和类型对取代比的影响。
