Highly Persistent Lignocellulosic Fibers for Effective Cationic Dye Pollutant Removal

Due to concerns about environmental pollution and the depletion of fossil resources, research on the utilization of woody biomass, such as lignin and cellulose, has consistently increased. This study examined the possibility of lignin as an adsorption material for water restoration and the dye removal behavior. For fiber wet spinning with continuous preparation of lignin-based adsorbents, polyvinyl alcohol (PVA) was chosen as the additive polymer. To enhance the water stability of the lignin/PVA fibers, a natural crosslinking agent based on woody biomass, bio-aldehyde cellulose, was utilized via a chemical crosslinking reaction. Moreover, Fourier transform infrared data confirmed that the crosslinking site of the bio-aldehyde crosslinker with lignin/PVA fiber was the hydroxyl group of PVA. The fiber remains stable under all pH conditions. Lignin/PVA fibers with maximum lignin contents exhibited a methyl orange removal capacity of 16.64 mg/g and a methylene blue removal capacity of 354.61 mg/g. The excellent cationic dye removal ability was attributed to π–π stacking, hydrogen bonding, and powerful electrostatic interactions between the adsorbent and cationic dye caused by deprotonated hydroxyl and carboxyl groups of lignin. In addition, the low pH condition was the most efficient for the desorption process, and a 95% adsorption efficiency was maintained with five regeneration cycles.