Removal of hexavalent chromium from electroplating wastewater by ion-exchange in presence of Ni(II) and Zn(II) ions

Abstract

This study presents the ion-exchange elimination of hexavalent chromium [Cr(VI)] from electroplated industrial wastewater. The effects of experimental factors such as pH, contact time, adsorbent dose, temperature, and co-ions on Cr(VI) removal were investigated. The metal ions were maximally removed (up to 96.7 %) and obtained with a resin dosage of 3 g L−1 at pH 2 for 70 min. Thermodynamic parameters, such as the standard Gibbs free energy change (ΔG0), standard enthalpy change (ΔH0),and standard entropy change (ΔS0), were calculated. The negative value of ΔG0(−8.031 kJ/mol K)indicates the spontaneity of the ion exchange process. The Freundlich and Langmuir isotherms fit the adsorption data well. The adsorption kinetics of Cr(VI) on the Amberlite IRA400 resin were analyzed using reversible first-order kinetics. The presence of Zn(II) and Ni(II) increased the efficiency of the adsorption process in the order Zn(II) > Ni(II). Column experiments were conducted to determine the breakthrough point of the packed-bed resin column, and a break-even concentration of 0.1 mgL−1 was deducted after the treatment of 4.5 L of the effluent. The adsorption data from the column studies were fitted using the Adam–Bohart adsorption model and the results fit the model well. A mathematical approach to the regeneration process is described in this study. The reusability of the resin was tested for 30 cycles and its efficiency of the regenerated resin was found to be above 97 % after the 30th cycle.