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.