Chelating polyacrylonitrile beads for removal of lead and cadmium from wastewater

Chelating polyacrylonitrile beads were prepared using phase inversion of polymeric drops in water bath, followed by treatment in sodium hydroxide solution. Applicability of these beads was tested to remove lead and cadmium from contaminated stream. The uptake capacity was 145 mg/g for lead and 156 mg/g for cadmium. Morphology showed that the porosity of the beads decreased upon treatment. Rapid weight loss was noticed in the range of 266-568 degrees C, during thermal analysis. Infrared studies showed that the nitrile group was rearranged to carboxyl and amine group due to hydrolysis of polyacrylonitrile beads, attracting the heavy metals electrostatically. Maximum removal of lead and cadmium was obtained at 5 g/L and neutral pH. Adsorption was exothermic and chemisorption in nature. Adsorption kinetics showed that the equilibrium was achieved within 600 min. The uptake capacity of individual heavy metals, i.e., lead and cadmium was reduced in multi component mixture due to competitive adsorption. Maximum desorption was obtained at acidic pH and the regenerated beads were successfully used for three cycles. The prepared beads were also tested using battery industry effluent, from Exide Industries Ltd., Haldia, West Bengal, India.