Modified natural loofah sponge as an effective heavy metal ion adsorbent: Amidoxime functionalized poly(acrylonitrile-g-loofah)

Natural loofah sponge is a low cost adsorbent, but its adsorption property needs to be improved. A grafted copolymer of poly(acrylonitrile-g-loofah) [poly(AN-g-loofah)] was prepared using cericammonium nitrate (CAN) as initiator. The poly(AN-g-loofah) was further functionalized into a amidoxime-modified poly(AN-g-loofah), which was characterized through FT-IR, X-ray diffraction, and thermogravimetric analysis. The adsorption capacity of amidoxime-modified poly(AN-g-loofah) was investigated under different adsorption conditions. Amidoxime-modified poly(AN-g-loofah) with approximately 70% conversion of the nitrile group could adsorb 51.40   mg/g Cu 2+ , which is more than two times higher than that obtained by previous studies. The modified Langmuir isotherm model and pseudo-second-order model fitted well with the Cu 2+ adsorption data. A good adsorption amount of Cu 2+ was obtained after five adsorption–deadsorption cycles. Hence, amidoxime-modified poly(AN-g-loofah) could be used as a novel substance for waste water treatment in industrial level.