Adsorption of Cu2+ Ions using Rubber-Based Hydrogel Siti Salihah Jamaluddin, Rozidaini Mohd Ghazi, Nik Raihan Nik Yusoff and Siti Fairus Mohd Yusoff BIO Web Conf., 73 (2023) 05003 Published online: 08 November 2023 DOI: 10.1051/bioconf/20237305003