pH fractionated lignin for the preparation of lignin-based magnetic nanoparticles for the removal of methylene blue dye

This study aimed to separate fractionated lignin (L2) containing more hydroxyl and carboxyl groups from black liquor by simple sequential acid precipitation, and then L2 was introduced to the surface of magnetic Fe3O4 nanoparticles (MNPs) to prepare high-efficiency and low-cost fractionated lignin-based magnetic nanoparticles (L2-MNPs) adsorbent. The effects of stirring frequency, pH value, initial concentration, contact time, and cyclic stability on the adsorption performances of methylene blue (MB) dye in wastewater were investigated in detail. The adsorption kinetics and adsorption isotherm showed that the adsorption process conformed to the pseudo-second-order kinetic model and the Langmuir isotherm adsorption model, respectively. It indicated that this process was chemical adsorption and a single layer adsorption. The maximum adsorption capacity of MB dye on L2-MNPs was 234.27 mg/g. Overall, this work indicated the L2-MNPs could be an eco-friendly, cost-effective and recyclable adsorbent for the removal of MB dye from wastewater.