LAUSR

Abstract The present study reflects the efficiency of Mentha piperita waste (MP) as an environmental friendly and cost-effective novel adsorbent for the sequestration of Cd(II), Co(II), Cr(VI) and Pb(II) from synthetically prepared wastewaters through batch adsorption experiments. MP was characterized and identified using SEM (Scanning Electron Microscopy), EDS (Energy Dispersive Spectroscopy), TEM (Tanning Electron Microscopy, FTIR (Fourier Transform Infrared Spectroscopy), XRD (X-Rays Diffraction) and TGA (Thermogravimetric analysis). The efficacy of MP adsorbent for the removal of Cd(II), Co(II), Cr(VI) and Pb(II) was investigated by varying MP dose (15–75 mg), solution pH (2–12), initial adsorbate concentration (0.2–0.6 mg L − 1), ionic strength of KNO3 (0 – 0.1 M) and temperature (298 K – 328 K). On increasing MP dose, the metal percent removal increased. The equilibrium time for the adsorption of Cd(II), Co(II), Cr(VI) and Pb(II) onto MP was found at 90, 90, 60 and 60 min, respectively. The adsorption capacity was found to increase with increasing pH of the metal solutions up to a value of 8.0 for Cd(II), 6.0 for Co(II), 2.0 for Cr(VI) and 6.0 for Pb(II) on MP. Moreover, it remains unchanged with additional increase of pH. Equilibrium data were best fitted by linear Freundlich isotherm model, which indicates multilayer adsorption. Kinetic study showed that the adsorption process of metal ions follows pseudo-second-order kinetics, suggesting chemisorption. Thermodynamic calculations suggested endothermic reactions for Cd(II), Co(II) and Cr(VI), while exothermic reactions for Pb(II) and spontaneous nature for all the metal ions adsorption onto MP adsorbent. MP showed a satisfactory adsorption performance due to its nano range particle size (13.4 nm to 51.7 nm) and good adsorption capacity. As a result, this study concluded that Mentha piperita wastes could be used as low-cost potential sorbent for the removal of Cd(II), Co(II), Cr(VI) and Pb(II) from aqueous solutions.