Removal of aqueous cyanide with strongly basic ion-exchange resin

Abstract

The removal of cyanide (CN−) from aqueous solutions using a strongly basic ion-exchange resin, Purolite A-250, was investigated. The effects of contact time, initial CN− concentration, pH, temperature, resin dosage, agitation speed, and particle size distribution on the removal of CN− were examined. The adsorption equilibrium data fitted the Langmuir isotherm very well. The maximum CN− adsorption capacity of Purolite A-250 was found to be 44 mg CN− g−1 resin. More than 90% CN− adsorption was achieved for most CN− solutions (50, 100, and 200 mg CN− L−1) with a resin dose of 2 g L−1. The equilibrium time was ∼20 min, optimum pH was 10.0–10.5, and optimum agitation speed was 150 rpm. An increase in adsorption of CN− with increasing resin dosage was observed. Adsorption of CN− by the resin was marginally affected (maximum 4% variation) within an environmentally relevant temperature range of 20–50 °C. Fixed-bed column (20.5 mm internal diameters) experiments were performed to investigate the effects of resin bed depth and influent flow rate on breakthrough behaviour. Breakthrough occurred in 5 min for 0.60 cm bed depth while it was 340 min for 5.40 cm bed depth. Adsorption capacity was 25.5 mg CN− g−1 for 5 mL min−1 flow rate and 3.9 mg CN− g−1 for 20 mL min−1 flow rate. The research has established that the resin can be effectively used for CN− removal from aqueous solutions.