This work studies the hydrothermal synthesis of zeolitic materials from three types of industrial waste (granite cutting sludge; slate cutting sludge and aggregate washing sludge), which are regarded as low-cost materials. The synthesis was carried out through 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 h. Characterization of the three synthesized zeolite materials by X-ray fluorescence, X-ray diffraction, Fourier-transform infrared spectroscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopy confirmed that the methodology used induced the formation of LOS (Losod) zeolite (Na12Al12Si12O48·xH2O) as the predominant phase in all products, regardless of the waste used as the 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 they 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 reduced CO2 adsorption capacities at room temperature (0.50–0.55 mmol g–1) compared to commercial zeolites such as 13X (3.45 mmol g–1).