Red mud (RM) is a waste material resulting from alumina production when bauxite ores are subjected to caustic leaching processes. Its mineralogical composition is characterized by the presence of hematite and goethite with minor amount of boehmite and, subordinately, calcium oxides, katoite, sodalite. RM has been used as alumina and iron source for the synthesis of zeolites thus promoting one useful method to reduce the amount of this waste to be deposed of in landfill. In detail, in our previous papers, this alkaline waste was used for the synthesis of LTA and X-type zeolite in combination with fly ash (Belviso et al., 2015), as alternative aluminium source for FAU and GIS types zeolite (Belviso et al., 2018) or as non-conventional Fe source for the synthesis of zeolite A with magnetic properties Belviso et al. (2020a). Red mud treated by sonication was also used to form zeolite-layered double hydroxide composite (LTA-LDH) (Belviso et al., 2020b). In all these experiments, the waste material was alkaline activated by sodium hydroxide. To the best our knowledge, zeolite synthesis from red mud by KOH alkaline activation has not been yet performed. In this new work, the solid waste resulting from bauxite ore (red mud) was converted into useful products consisting in hydrogarnet together with zeolite. RM transformation from disposal material into new source was carried out using potassium hydroxide as activator and hydrothermal process (HY) or vapor phase crystallization (VPC) approach. The results indicate the formation of katoite and zeolite L (LTL topology) with both approaches. All the synthetic products display magnetic properties. In addition, a preliminary investigation on arsenic removal from drinking water (from 68 to 87%), makes the synthetic materials appealing for environmental applications. Finally, the synthesis of large amount of very useful newly-formed phases using vapour molecules confirms the efficiency of the innovative and green VPC process.
Red mud treated with KOH: from disposal material to new resource
Mancinelli M.Secondo
;
2024
Abstract
Red mud (RM) is a waste material resulting from alumina production when bauxite ores are subjected to caustic leaching processes. Its mineralogical composition is characterized by the presence of hematite and goethite with minor amount of boehmite and, subordinately, calcium oxides, katoite, sodalite. RM has been used as alumina and iron source for the synthesis of zeolites thus promoting one useful method to reduce the amount of this waste to be deposed of in landfill. In detail, in our previous papers, this alkaline waste was used for the synthesis of LTA and X-type zeolite in combination with fly ash (Belviso et al., 2015), as alternative aluminium source for FAU and GIS types zeolite (Belviso et al., 2018) or as non-conventional Fe source for the synthesis of zeolite A with magnetic properties Belviso et al. (2020a). Red mud treated by sonication was also used to form zeolite-layered double hydroxide composite (LTA-LDH) (Belviso et al., 2020b). In all these experiments, the waste material was alkaline activated by sodium hydroxide. To the best our knowledge, zeolite synthesis from red mud by KOH alkaline activation has not been yet performed. In this new work, the solid waste resulting from bauxite ore (red mud) was converted into useful products consisting in hydrogarnet together with zeolite. RM transformation from disposal material into new source was carried out using potassium hydroxide as activator and hydrothermal process (HY) or vapor phase crystallization (VPC) approach. The results indicate the formation of katoite and zeolite L (LTL topology) with both approaches. All the synthetic products display magnetic properties. In addition, a preliminary investigation on arsenic removal from drinking water (from 68 to 87%), makes the synthetic materials appealing for environmental applications. Finally, the synthesis of large amount of very useful newly-formed phases using vapour molecules confirms the efficiency of the innovative and green VPC process.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
