Immobilization of 2-amino pyridine onto poly(acrylonitrile-co-N,N´-methylenebisacrylamide) nanoparticles for the removal of Hg(II), Cd(II) and Cr(III): Batch and column techniques

New nano chelating resin 2-amino pyridine−functionalized polyacrylonitrile (CPN-AP) (≈ 70 nm) was prepared by precipitation polymerization of acrylonitrile with N,N′-methylenebisacrylamide followed by treatment with 2-amino pyridine. The physicochemical properties of the nano chelating resin were characterized by FTIR, SEM, TEM, BET, XRD, thermal analysis and water regain (W%). Batch technique was used to estimate the effects of some factors that control the adsorption of Hg(II), Cd(II) and Cr(III) including pH, concentration, contact time and temperature. The maximum adsorption capacities at 25 °C were 3.3, 0.94 and 0.43 mmolg−1resin for Hg(II), Cd(II) and Cr(III), respectively. The sorption kinetics and equilibrium data fitted well to the pseudo-second-order model and Langmuir isotherm model, respectively. The intraparticle diffusion model shows three-linear portions. Hence, more than one-step may control the adsorption process. Thermodynamic parameters at different temperatures (25, 35 and 45 °C) revealed that the adsorption of all metal ions was endothermic and (i) Hg(II) sorption was spontaneous (ii) Cd(II) sorption was non-spontaneous at 25 °C and spontaneous at 35 and 45 °C, (iii) Cr(III) sorption was non-spontaneous. Additionally, the removal of Hg(II) was studied using column method. Thomas and Yoon-Nelson models were applied to predict the breakthrough curves and to determine the characteristic parameters of the column that are helpful for process design at a real scale. The prepared nanoparticles were used successfully for six times.