Natural dolomite as a low-cost adsorbent for efficient removal of As(III) from aqueous solutions

Abstract

In the current investigations, physicochemical and adsorption characteristics of natural dolomite has been determined to evaluate its potential for the removal of As(III) from aqueous solutions. The characterization of the adsorbent was made by SEM-EDS, XRD, XRF, TG/DTA, FTIR and PZC. The influence of different adsorption parameters such as time, temperature, pH, concentration and dosage amount were discussed in detail. The absorption affinity of dolomite was observed to increase with increasing As(III) concentration and temperature of the solution. The maximum adsorption capacity (mg.g−1) of the adsorbent was obtained 11.57 mg.g−1 at 333 K showing enormous potential of adsorbent for As(III) removal. The adsorption data was evaluated by non-linear Freundlich and Sips isotherm models to examine the nature of adsorption process. The mean free energy of adsorption calculated from Dubinin-Rasdushkevich model confirmed that the reaction is physisorption in nature. The kinetic study revealed that 92% of the total adsorption capacity was achieved in 180 min of reaction time and adsorption followed the pseudo second order mechanism. The thermodynamic parameters have shown that the adsorption of As(III) on dolomite adsorbent was endothermic and spontaneous in nature. Equilibrium data showed the well fitting for Freundlich adsorption isotherm which indicates the heterogeneity of the adsorbent surface. The results proved that the local Pakistani dolomite can be effectively used for removal of As(III) ions in aqueous conditions.