Kinetics, Thermodynamic, and Isotherm Modeling for Biosorption of Heavy Metals from Aqueous Environment onto Lignocellulosic Biomass

The present study evaluates the performance of the lignocellulosic fibers Momordica Charantia for the sequestration of lead (II), zinc (II), chromium (VI), and copper (II) ions from a liquid medium. The biomass has been analyzed and depicted by Fourier-transform infrared spectroscopy and scanning electron microscope. The biosorption rate of these toxic metals depended on contact time and pH solution. The maximum biosorption rate was found at pH = 6.0 for the biosorption of divalent metals and for hexavalent chromium the maximum rate was obtained at pH =2.0. At optimal conditions, the experiment results elucidate that metal uptakes are rapid systems at 60 min equilibrium time, and the order of uptake metal ions is lead > Chromium >Zinc> Copper. The adsorption isotherms were studied and modeled using Langmuir, Freundlich, and Temkin equations. The Langmuir isotherm model presents goodness fit for all metals studied by height coefficient of coloration, with a maximum capacity of 8.9, 5.9, 4.67, and 3.9 mg/g for lead (II), chromium (VI), Zinc (II), and Copper (II), respectively. Kinetic modeling elucidates that the biosorption processes followed better the pseudo-second-order model. Furthermore, the thermodynamic factors demonstrated that the biosorption behavior of heavy metals was favorable, spontaneous, and exothermic processes. Finally, this study showed that the M. Charantia threads could be considered an excellent biomaterial to be employed as an effective sorbent for removing heavy metals in the liquid environment.