“…The maximum permissible limits for Ni(II), Cu(II), and COD in water are 0.2 mg/L, 2 mg/L, and 200 mg/L, respectively (Sponza & Karaoǧlu, 2002). Several methods including coagulation (Shahriari, Bidhendi, Mehrdadi, & Torabian, 2014), advance oxidation processes (Marinho, Cristóvão, Boaventura, & Vilar, 2019), flotation (Deliyanni, Kyzas, & Matis, 2017), ion exchange (Siu, Koong, Saleem, Barford, & McKay, 2016), precipitation (Rabii, Bidhendi, & Mehrdadi, 2012), solvent extraction (Kul & Oskay, 2015), membrane filtration (Yurekli, 2016;Zhu, Sun, Gao, Fu, & Chung, 2014), adsorption (Abbas et al, 2016;Inyang et al, 2016;Jain, Garg, Kadirvelu, & Sillanpää, 2016;Sarma, Gupta, & Bhattacharyya, 2019;Sizirici et al, 2018), and biological processes (Gunatilake, 2015) have been used for the removal of toxic materials from wastewaters. Among them, the adsorption process as an effective economical method has been reported for the removal of heavy metal ions and COD from aqueous solutions (Inyang et al, 2016;Jain et al, 2016).…”