study of kinetics, isotherms and thermodynamics of lead adsorption from aqueous solutions using lignocellulose nano-fibers (lcnfs)

The surface adsorption of heavy metals in effluents with nanoparticles is today a suitable method for effluents treatment. in the present study, lignocellulose nano-fibers (lcnfs) were used as natural adsorbent for lead adsorption. the aim was to evaluate lead adsorption using adsorption isotherms, kinetics and thermodynamics. fourier transform-infrared spectroscopy (ft-ir) and transmission electron microscopy (tem) were employed to determine the chemical and structural properties of this adsorbent. to study the adsorption isotherm, two-parameter models of langmuir, freundlich, temkin, and dubinin–radushkevich were compared and three-parameter models of redlich-peterson and sips and maximum correlation coefficient (r²) were selected as the best isotherm model for lead adsorption, which was obtained for the langmuir model at 0.9997 and the redlich-peterson model at 0.9338. therefore, the data were consistent with both models but were better described by the langmuir model, indicating homogeneity of the adsorbent surface. in addition, reaction kinetic models, including pseudo-zero-order, pseudo-first-order, pseudo-second-order and pseudo-third-order as well as the diffusion kinetic models including intra-particle diffusion and elovich were investigated for adsorption reaction. the maximum correlation coefficient (r²=1) was related to the pseudo-second-order model; therefore, the lead adsorption by lcnfs was of a chemical type. the results obtained from the calculation of thermodynamic parameters such as gibbs free energy (δg), enthalpy (δh◦), and entropy (δs◦) respectively showed spontaneity, exothermicity, and increased irregularities of the reaction. this study showed that lcnf is suitable for the adsorption of lead and as such could be used as a cost-effective adsorbent in the process of industrial wastewater treatment.