Functionalization of acidified multi-walled carbon nanotubes for removal of heavy metals in aqueous solutions

Water pollution is a worldwide issue for the eco-environment and human society. Removal of various pollutants including heavy metals from the environment is a big challenge. Techniques of adsorption are usually simple and work effectively. In the current study, MWCNTs were prepared by chemical vapor deposition (CVD) of acetylene at 600 °C. Fe–Co/CaCO 3 catalyst/support was prepared by wet impregnation method. The crystal size of the catalyst was identified using XRD. Acidified functionalized multi-walled carbon nanotubes (MWCNT) were produced from oxidation of multi-walled carbon nanotubes by mixture of H 2 O 2 + HNO 3 in a ratio of 1:3 (v/v) at 25 °C. The structure and purity of synthesized functionalized CNTs were examined by TEM, N 2 -BET method and thermogravimetric analysis. The functional groups produced at CNTs surface were investigated using FTIR spectroscopy. Acidified functionalized MWCNTs with a high surface area of 194 m 2 g −1 and porous structure (17.19 nm) were used for water treatment from harmful cations (Pb 2+ , Cu 2+ , Ni 2+ and Cd 2+ ), single cation solutions and quaternary solution at different pH values and different times. The results were interesting because in single solutions the catalyst removed Pb 2+ , Ni 2+ , Cu 2+ and Cd 2+ with percentages of 93, 83, 78 and 15%, respectively, in 6 h. While in quaternary solution, adsorption was more complex and the order of the adsorbed metals was as following: Pb 2+ (aq) > Cu 2+ (aq) > Cd 2+ (aq) > Ni 2+ (aq).