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 Cu2+, 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 Cu2+ adsorption data. A good adsorption amount of Cu2+ 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. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.