Functionalized lignin-based-adsorbent derived from black liquor in the paper industry for superior adsorption characteristics.

Abstract Lignin's availability in large amounts from industrial black liquor as waste from the paper industry is still a problem. On the other hand, its utilization potentials as a green low-cost adsorbent for the effective removal of toxic organic dye from industrial wastewater has become a topic of great interest but remains quite challenging. In this sense, this work aimed to evaluate the feasibility of removing the reactive green dye (RGD) onto the functionalized lignin-based adsorbent (FLA) by the acidic method. The kinetic study suggested the adsorption process confirmed to a pseudo-second-order-kinetic and intra-particle diffusion models. Also, the isotherm results showed that the FLA exhibited multi-layer adsorption. Meanwhile, the results of FTIR and SEM showed that the RG-19 adsorption mechanisms were electrostatic interaction, hydrogen bonding, π-π stacking, and physical adsorption. Thermodynamic parameters were also evaluated and their values indicated that adsorption of RG-19 onto FLA is an exothermic process and spontaneous in nature. As a renewable, low-cost, and natural biomass material, FLA has the potential to be used as a promising sustainable and economic application of biomass and will inspire more scholars to investigate solutions to the problem of contaminated water resources.