Recovery of zinc from electroplating effluent using cationic resins

摘要

In India, a large number of zinc-electroplating industries are producing effluents containing toxic metals viz. zinc, chromium, nickel, copper, cadmium etc. The effluents directly discharged in the sewage cause pollution. In order to reduce environmental pollution and conserve the natural resources, the studies have been carried out for the selective extraction of zinc from the electroplating effluents containing chromium (520 ppm Zn and 26.5 ppm Cr) using ion-exchange process. Different cationic resins viz. Indion BSR, Tulsion T-42, Lewatit VP OC 1026 and Amberlite IR-120 (Na) have been studied for the extraction of zinc from the effluent. On comparing the performance of different resins, Tulsion T-42 found more effective in comparison to other resins. The effect of various parameters viz. contact time, pH, resin dose, concentration of aqueous feed on the extraction of zinc has also been studied. Almost total zinc was extracted in 10 minutes from the aqueous feed containing 0.5 mg Zn/ml at eq. pH 2-4 and aqueous to resin ratio (A/R) ratio 100. The adsorption of zinc with Tulsion T-42 follows Freundlich equilibrium isotherm better than Langmuir isotherm. The kinetics extraction showed the validity of second order rate expression. The elution studies carried out with strong sulphuric acid showed that total zinc could be, eluted effectively from the loaded resin.