Adsorption of Cr (III) using an Iranian natural nanoclay: applicable to tannery wastewater: equilibrium, kinetic, and thermodynamic

Adsorption phenomenon is a techno-economically viable solution for eliminating heavy metals from wastewaters. Among all adsorbents, clays are cost effective, high abundance, and most importantly, and they have high sorption capacities. In this work, a local clay was used to remove C r 3 + from aqueous solutions. X-ray fluorescence (XRF), Brunauer–Emmett–Teller (BET) and scanning electron microscopy (SEM) analyses were applied to characterize the adsorbent. The effect of initial pH and concentration, adsorbent dosage, contact time, and temperature was examined and the maximum adsorption capacity was obtained in the following condition: pH of 4 , initial concentration of 140 mg / L , adsorbent dosage of 750 mg / L , contact time of 30 min, and temperature of 20 ∘ C . Experimental data were fitted to equilibrium isotherms. Kinetic models were studied and thermodynamic parameters were calculated. Langmuir isotherm was the best fit to the equilibrium data. Pseudo-first-order kinetic model described the dynamic data and thermodynamic studies showed that the process is exothermic and spontaneous. A review and comparison done among C r 3 + adsorption processes by natural adsorbents showed that this adsorbent provides the highest adsorption capacity.