Synthesis of eco-friendly lignin-betaine and its application for dye wastewater treatment

Lignin-based polymers have great potential for water treatment due to their environmental friendliness, biodegradability, and safety. Herein, lignin-betaine polymer (LB) was synthesized by Steglich esterification. The formation of ester groups between lignin and betaine was corroborated by Fourier transform-infrared spectroscopy (FT-IR), nuclear magnetic resonance hydrogen spectroscopy (NMR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), elemental analysis and thermogravimetric analysis (TGA). The LB was applied in the treatment of the methylene blue -containing wastewater, and demonstrated a dye removal rate of 98 %. Our study indicated that the dye removal was dominated by chemical adsorption. Moreover, the LB exhibited durable dye removal performance and maintained excellent reusability after four cycles. Collectively, the lignin-betaine polymer could provide an effective candidate for wastewater treatment, with specific potency for the removal of cationic dye. •Easy and efficient synthesis of target products by one-step esterification using the hydroxyl group on lignin.•The innovative use of renewable biomass, lignin and betaine, two extremely environmentally friendly raw materials.•Excellent purification capability for cationic dye wastewater, and is recyclable for purification.