Removal of Cr(VI) 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 mg/g 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.