Biosorption of Aqueous Pb(II), Co(II), Cd(II) and Ni(II) Ions from Sungun Copper Mine Wastewater by Chrysopogon zizanioides Root Powder

Abstract

In this study, a plant-based adsorbent was used in order to remove lead, nickel, cobalt and cadmium metals from a wastewater sample collected from Sungun mine real wastewater. The biosorbent was one of the most abundant native plants of the Sungun region, named Chrysopogon zizanioides (C. zizanioides). The root powder of C. zizanioides was used in order to remove heavy metals from the wastewater sample. The biosorbent was characterized by FTIR, SEM, HR-TEM, EDS, BET and ZPC analyses. The effect of pH, initial metals concentrations, contact time and temperature on the biosorption process were accurately investigated. The metal concentrations were significantly reduced to lower concentrations after the biosorption process, which indicated that the C. zizanioides root powder removal efficiency was more than 95% for the metals from the wastewater sample, with maximum adsorption capacities of 31.78, 21.52, 26.69 and 27.81 mg/g, for Pb(II), Co(II), Cd(II) and Ni(II) ions, respectively. Furthermore, the adsorption kinetic results showed that the pseudo-second-order kinetic model correlated with the experimental data well, with correlation coefficient values of 1 for all metals. Isotherm studies illustrated that the Freundlich and Dubinin-Radushkevich (D-R) isotherm models could describe the obtained equilibrium data well. Moreover, from the D-R model, it was found that the biosorption type was physical. The thermodynamic studies demonstrated that the metals’ biosorption was an exothermic and spontaneous process. Moreover, the reusability of the biosorbent to be used in several successive cycles, and also the percentage of recovery of adsorbed metals from the biosorbent, was investigated. Altogether, being simple and cost-effective and having a high adsorption rate, fast kinetics, easy separation and high reusability prove that C. zizanioides root powder shows significant performance for the removal of heavy metals from waste effluents.