Adsorption of 2-nitrophenol by technical hydrolysis lignin: Kinetics, mass transfer, and equilibrium studies

The potential of technical hydrolysis lignin (THL), a low-cost and abundantly available material, to act as an adsorbent of 2-nitrophenol (2-NP) has been investigated. The extent of mononitrophenol uptake was determined conducting parallel single-component kinetic experiments in standardized batch adsorbers. The effect of the operating parameters, initial sorbate concentration, and mass of adsorbent was tested. The applicability of three kinetic/mass transfer models was estimated on the basis of comparative analysis of the corresponding rate parameters (k(1), k(2), k(i)), equilibrium capacity (q(1)(cal), q(2)(cal)), and correlation coefficients (R-1(2), R-2(2), R-i(2)). Results suggest that chemisorption processes could be the rate-limiting step in the adsorption process. The Langmuir and Freundlich isotherm models were applied to describe the experimental results. The Langmuir model was found to best represent the equilibrium data for 2-NP uptake on THL. The sorption characteristics and the calculated sorption capacity of the lignin proved the feasibility of its use as a potential and alternative sorbent for 2-NP removal.