Removal of Hexavalent Chromium from Mine Effluents by Ion Exchange Resins-Comparative Study of Amberlite IRA 400 and IRA 900

Abstract

Strongly basic anion exchange resins, Amberlite IRA 400 and IRA 900, have been tested to remediate Cr(VI) from a model as well as from the untreated chromite mine effluent samples. For an initial concentration of 50 ppm Cr(VI), IRA 400 was found to adsorb Cr(VI) completely in less than 6 min of contact time and was efficient in a larger range of pH (1–6); however IRA 900 was able to remediate 97% Cr(VI) in the pH range 4.5–5 in less than 10 min. A cumulative loading of 112.9 and 115.2 mg/g of Cr(VI) was obtained with Amberlite IRA 400 and IRA 900, respectively from a feed of 200 ppm Cr(VI). A close adherence to the Freundlich isotherm during the adsorption reflected the strong chemical interaction of Cr⁶⁺ ions with the quaternary functional group on the resins. The adsorption process followed the pseudo second-order kinetics. The experiments were further carried out in glass columns with 10 L chromite mine effluent samples. Almost complete sorption of Cr(VI) from the effluent was achieved using 0.5% (w/v) IRA 400 and 2% (w/v) IRA 900, at a resin bed height of 7 cm and flow rate of 10 mL/min. Desorption studies in column show that 200–500 mL solutions of 15–30% (w/v) NaOH eluted the Cr(VI) completely from the metal laden Amberlite IRA 400 and IRA 900 resins.