Simultaneous removal of Cu(II), Ni(II), Pb(II), and Zn(II) ions from aqueous solution using MIL-53(Al) and multi-walled carbon nanotube

Heavy metals in industrial wastewater pose a severe threat to both environmental and human health. The discharged water, particularly in mining, is often acidic and contains hazardous metal ions such as lead, copper, zinc, and nickel. In this study, a metal organic framework (MIL-53(Al)) and multi-walled carbon nanotube (MWCNT) adsorbents were employed for the simultaneous removal of these ions from aqueous solution. The effects of key process variables, adsorbent dosage, pH, initial metal concentration, and contact time were systematically examined. The physicochemical characterization of the adsorbents before and after adsorption in the simultaneous multi-metal removal on MIL-53(Al) and MWCNT was evaluated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM). Additionally, the zeta potential values for MIL-53(Al) and MWCNT were determined as +14.6 and -31.8, respectively, which were used to explain the effect of pH on the process. Langmuir maximum adsorption capacities for Cu(II), Ni(II), Pb(II), and Zn(II) using MWCNTs in the simultaneous multi-metal adsorption were 5.32, 16.05, 14.01, and 7.07 mg/g, respectively. However, lower adsorption capacities were obtained for MIL-53(Al) compared to MWCNT. In both processes, competitive adsorption and electrostatic repulsion between coexisting metal ions negatively affected the adsorption efficiency.