Industrial waste powder for the removal of acid dye from contaminated water

Toxic dyes continuously released into water sources are causing serious health and environmental concerns. The present study reports the use of free of cost available industrial waste material light yellow stone powder (LYSP) and calcinized light yellow stone powder (CLYSP) for removal of acid red dye from water. Dye removal process was explained using various isotherm models (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Harkins-Jura models) and kinetic models (pseudo-first order, and pseudo-second order models). Among isotherm models, the best data fit was obtained for Freundlich equation which precisely correlated to the experimental dye uptake capacity of the materials used in the present study. Dye removal at various time intervals revealed a superior fit for pseudo-second order over pseudo-first order. Experimental variables such as pH, initial concentration, adsorbent dosage, interaction time, and temperature were identified as significant factors in acid red dye removal. Maximum dye removal was observed at pH 7. Calcination process resulted in disappearance of –OH stretching of the phenolic structure and crystal water in FTIR spectrum. After calcination adsorbent became highly porous and attained sponge-like structure due to elimination of gases and other volatile compounds from its surface. Both adsorbents were used without any significant loss in adsorption capacity for five consecutive cycles.