Competitive Removal of Cu(II) and Cd(II) from Water Using a Biocomposite Hydrogel.

With an objective to improve the adsorption properties of a synthetic hydrogel, potato starch (PS) was incorporated in the ter-copolymer (TP) of acrylic acid (AA), acrylamide (AM), and bicarboxylic itaconic acid (IA) during polymerization of the monomers. The resulting TP-PS composite hydrogels were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), nuclear magnetic resonance (NMR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), and rheological properties. These hydrogels were used for removal of Cu(II) and Cd(II) as single and binary competitive mixtures from water. The effect of PS as well as various physicochemical parameters such as solution pH, adsorbent dosage, contact time of gel with metal ion in water, and concentration of metal ion in water was studied in batch experiments. The adsorption results indicated that the gels could be used as an efficient adsorbent for removal of Cu(II) and Cd(II) from water as single as well as binary mixtures. The TP-PS4 gel containing 4 wt % starch showed a removal % of 85.8 and 77.6 and adsorption capacity (mg/g gel) of 214.5 and 193.9 for Cu(II) and Cd(II), respectively, from water containing 50 mg/L of each of these metal ions in a solution pH of 5.5 and a dose of only 0.2 g/L gel.