Development of Chitosan Based Hybrid Nanocomposite Adsorbent for Removal of Phosphate and Nitrate From Wastewater

ABSTRACT The removal of nitrate and phosphate ions from water bodies is essential to reduce eutrophication and health hazards. In the present study, a hybrid polymer nanocomposite has been developed for the adsorptive removal of nitrate and phosphate from wastewater. The preparation of the nanocomposite has been achieved by microwave irradiation of the aqueous mixture of chitosan (CS), poly(diallyldimethylammonium chloride) (PDADMAC), N‐(2‐hydroxyethyl)acrylamide (HEAAm) and N,N′‐methylenebis(acrylamide) (MBA) in the presence of a radical initiator followed by incorporation of magnetite nanoparticles. A semi‐interpenetrating network (IPN) appears to be formed by the entanglement of PDADMAC chains with the MBA crosslinked network of chitosan‐graft‐poly[N‐(2‐hydroxyethyl)acrylamide] within which Fe 3 O 4 nanoparticles are held. The materials (CS‐g‐PHEAAm)/PDADMAC and (CS‐g‐PHEAAm)/PDADMAC/Fe 3 O 4 were characterized for their physicochemical structures using FTIR, XRD, SEM, EDS, BET, VSM, and TGA techniques. Their utility as adsorbents for nitrate and phosphate removal was evaluated through adsorption studies. The adsorption process was optimized for contact time, solution pH, adsorbent dosage, temperature, and initial adsorbate concentration. The adsorption data showed a close fit with the Freundlich adsorption isotherm and pseudo‐second‐order kinetic models. The presence of Fe 3 O 4 nanoparticles is observed to enhance the adsorption capacity of the parent IPN polymer significantly from a value of 60.97 to 65.35 mg g −1 towards nitrate and from 69.93 to 76.33 mg g −1 towards phosphate. The thermodynamic studies indicated the adsorption to be a spontaneous and endothermic process. The regeneration ability of the hybrid nanocomposite along with its superparamagnetic and biodegradable characteristics makes it a material of choice for absorptive removal of nitrate and phosphate ions from wastewater.