Comparative Study of the Absorption Isotherms of Lead by Lignocellulose Nano-Fibers (LCNFS) and Chitin Nano-Fibers (CNFS) from Aqueous Solutions

Multiple isotopes of lead, heavy metal, are introduced into the aquatic environment through industrial wastewater. Absorption process using natural nano-adsorbents is a suitable method to treat water. The aim of this study was to investigate the mechanism of lead absorption by investigating the isotherm of LCNFs and CNFs adsorption. The experimental conditions considered for two absorbents were completely identical. Variables such as pH, initial concentration of lead and adsorbent dose were investigated to determine the absorption of lead. In order to study adsorption isotherms, the Langmuir, Freundlich, Tamkin, and Dubinin-Radushkevich models were compared and the three-parameter models of Redlich Petersen and Sipes were compared and the highest correlation coefficient (R2) was selected as the best lead isotherm model. According to the results obtained from the CNFs, the data were more consistent with the two models of Sipes (R2 = 0.9992) and Langmuir (R2 = 0.9996). Better matching of the data with the two Sipes and Langmuir models, due to the higher coefficient of R2, indicates the homogeneity of the adsorbent structure and the single-layered nature of the absorption of CNFs, and the highest correlation coefficient for the Langmuir model is for the LCNFs (0.9997) and Redlich-Patterson (0.9338). Therefore, the adsorbent data were consistent with both models, but were better described by the Langmuir model, which shows homogeneity of the adsorbent level. The positioning of the RL parameter obtained from the Langmuir model of two adsorbents in the range of 0 and 1 showed that the absorption system of this model is suitable.