Magnetic hydrogel for better adsorption of heavy metals from aqueous solutions

Free radical polymerisation of 2-acrylamido-2-methyl-1-propanesulfonic acid with acrylic acid and maleic acid as monomers, resulted in a magnetic responsive composite hydrogel (Magnetic (PAAAM/PAMPS)) for effective adsorption of heavy metals from aqueous solutions. These materials were characterised by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and magnetic analysis (vibrating sample magnetometer (VSM)). Their swelling properties were studied in detail and compared with its parent hydrogel, PAAAM/PAMPS and was investigated as potential adsorbent for the safe removal of Zn2+ and Cd2+ from aqueous solution. The effect of time, initial metal concentration and temperature on the adsorption capacity of the hydrogel and magnetic nano composite hydrogel were investigated. Results showed that the magnetic composite hydrogel has better adsorption than bare hydrogel and followed the order Cd2+ > Zn2+. The adsorption kinetics and equilibrium data were best fitted by pseudo-second order kinetic model and Freundlich adsorption isotherm. The thermodynamic studies revealed the adsorption of Cd2+ on the hydrogels to be spontaneous and exothermic in nature.