Biosorption of copper (II) ions in aqueous solution by microwave-synthesized starch-graft-N-methyl-N-vinyl acetamide

A novel adsorbent starch-graft-N-methyl-N-vinylacetamide (starch-g-NMVA) was synthesized using microwave assisted graft copolymerization. Monomers of N-methyl-N-vinylacteamide (NMVA) was grafted to potato starch using microwave irradiation and potassium peroxydisulfate (KPS) as free radical initiator. The highest % grafting (%G) obtained was 10.03% under the optimum conditions of 0.55 M NMVA and 90 seconds exposure time, keeping the initiator, starch, and microwave power fixed at 0.0014M, 0.1 g, and 1200W respectively. FTIR and SEM analyses confirmed that the monomer was grafted successfully. The graft copolymer was investigated for its efficiency in removing Cu(II) ions from aqueous solutions at different concentrations. Using the Box-Behnken method the most favorable pH, adsorbent dose, and initial Cu(II) concentration generated for the adsorption was 5.5, 100 mg and 100 ppm, respectively. The resulting adsorbent is able to remove 52.9% of Cu(II) ions in an aqueous solution at these conditions. The Langmuir isotherm best described the adsorption property of the system with a correlation coefficient (R2) of 0.9361. On the basis of this model, the maximum adsorption capacity (Qo) of the starch-g-NMVA was calculated to be 46.9749 mg/g. This study indicated that starch-g-NMVA is a good alternative adsorbent for the removal of Cu (II) from aqueous solution. Further desorption and optimization studies will help us know the applicability of this adsorbent in removing metals from a simulated wastewater setup.