Direct synthesis of lignin nanoparticles from palm kernel shell for application in fabricating new chitosan/nano-lignin based composite sorbent

In this study, lignin nanoparticles in the form of hollow spheres were directly prepared from palm kernel shell biomass in a simple and economically viable way using recyclable tetrahydrofuran in an acidified aqueous system without any chemical modification steps. We then fabricated a new chitosan/nano-lignin composite material as highly efficient sorbent, as demonstrated by efficient removal (~83%) of methylene blue (MB) dye under natural pH conditions. The adsorption process obeyed pseudo-second-order kinetics and adequate fitting of the adsorption data using Langmuir model suggested a monolayer adsorption with a maximum adsorption capacity of 74.07 mg g−1. Moreover, thermodynamic study of the system revealed the spontaneous (ΔG° = −2.56 kJ mol−1) and endothermic (ΔH° = 14.40 kJ mol−1) nature of the sorption process. It was found that chitosan reinforced with nano-lignin showed better performance in dye decontamination compared to native chitosan and chitosan/lignin composite. This could essentially be attributed to synergistic effects of size particularity (nano-range) and incorporated functionalities due to LNP. Recyclability study revealed the recyclable nature of the prepared composite after four repeated adsorption/regeneration cycles, whilst adsorption experiments using spiked real water samples indicated recoveries as high as 89%. Based on this study, as-prepared bio-nanocomposite may thus be considered as an effective potential adsorptive platform for the efficient and cost effective decontamination of water supplies.