Efficient adsorption of nickel and chromium(VI) from aqueous solutions using lignocellulose nanofibers: kinetics, isotherms, and thermodynamic studies

The entry of heavy metals due to industrial activities into the environment is one of the major problems in this century. Nickel and chromium(VI) are the toxin elements that are used in various industries. In this study, lignocellulose nanofiber was purchased from the Nano-Novin Polymer Company and used as an adsorbent for the removal of nickel and chromium(VI) ions from aqueous solutions in a batch system. The effects of pH, initial concentration, adsorbent dose, contact time, and temperature were investigated. The adsorption mechanism was determined by Langmuir, Freundlich, kinetic, and thermodynamic models. Investigation of equilibrium isotherms nickel and chromium(VI) showed that the isotherm fitted well with the Freundlich model. The pseudo-second-order model with the larger correlation coefficient had a greater fitness against experimental data in the kinetic studies. Thermodynamic parameters of both nickel and chromium such as Gibbs free energy, enthalpy, and entropy were calculated which indicated spontaneous, endothermic, and random processes, respectively. Lignocellulose nanofiber can be suggested as a good adsorbent that is highly capable of adsorbing nickel and chromium(VI) from aqueous solutions.