Applicability of gypsum in selective removal of anionic dye molecules from aqueous medium

Abstract This article describes how selectively anionic organic molecules could be removed from aqueous medium using naturally available gypsum (GS) adsorbent. Gypsum (CaSO 4 .2H 2 O) shows strong interactions with dye while it dos not show any affinity towards cationic molecules. We have shown the removal efficiency of taking chlorazole yellow (anionic dye) and methylene blue (cationic as examples adsorbates. The GS has been to even more effective than activated carbon in attaining (CY) removal. Three well-known kinetic equations e.g. pseudo-first-order, pseudo-second order intraparticle diffusion were exploited interpret experimental data. Results best fitting second process excellent regression coefficient ( r = 0.99) for adsorption process. equilibrium data analyzed exploiting some isotherm models. It was apparent that Freundlich model superbly fitted CY And maximum capacity, Q m , obtained 12.85 mg g −1 at room temperature. negative values Gibb’s free energy change (Δ G o ) suggests molecule is spontaneous nature. Moreover, enthalpy H indicates exothermic nature outcome where are required separated, selectively.