Alkaline fusion-hydrothermal synthesis of Losod zeolite from industrial waste for CO ₂ capture

This work studies the hydrothermal synthesis of zeolitic materials from three types of industrial waste (granite cutting sludge, GCS; slate cutting sludge, SCS; and aggregate washing sludge, AWS) which are regarded as low cost materials.The synthesis was carried out by acid pretreatment with aqua regia to minimize iron content, followed by alkaline melting at 600 C followed by a hydrothermal crystallization stage at 180 C for 12 hours.Characterization of the three synthesized zeolite materials by XRF, XRD, FTIR, and SEM_EDX, has confirmed that the methodology used induces the formation of LOS (Losod) zeolite, Na 12 Al 12 Si 12 O 48 xH 2 O, as the predominant phase in all products, regardless of the waste used as raw material.The end products have a significant amorphous fraction (33-43 wt%) and a zeolitic crystalline fraction (51-66 wt%) and are enriched in Na and Al, and have Si/Al and Na/Al ratios ranging from 1.27 to 1.39 and from 0.58 to 1.05, respectively, characteristic of low-silica zeolites.The synthetic zeolites showed a reduced CO 2 adsorption