Application of amino-hypophosphite polyampholyte for purification of wastewater containing Ni(ii) ions

This study investigated the sorption of Ni(ii) ions from an aqueous solution using novel, synthetic amino-hypophosphite polyampholyte resin (AHP) in a batch adsorption system. The removal of Ni(ii) ions was determined as a function of pH (2.0-8.0), initial concentration of Ni(ii) ions (2.0-20.0 mM), resin dosage (1.0-10.0 g dm^-3), contact time (0.04-24 h), and temperature (298-318 K). Moreover, continuous fixed-bed column sorption was also studied using model solutions and actual wastewater from the galvanising plant. The batch sorption experimental data showed that the maximum pH for efficient Ni(ii) ion removal was about 5.0. An equilibrium was reached after about 24 hours. The kinetics results were fitted using pseudo-first-order (PFO), pseudo-second-order (PSO), liquid film (LFD), and intraparticle diffusion (IPD) models. Freundlich and Langmuir isotherm models were applied for sorption equilibrium data. The maximum sorption capacity was obtained from the Langmuir equation to be 2.39, 2.52, and 2.62 mmol g^-1 at 298, 308, and 318 K, respectively. The thermodynamic parameters for the sorption of Ni(ii) ions on AHP imply the endothermic and spontaneous character of the process. The experimental results demonstrated that amino-hypophosphite polyampholyte resin could be used to effectively remove Ni(ii) ions from model solutions and real wastewater.