In this study, alkali lignin modified by ethylene glycol and lignin nanoparticles was prepared through acid precipitation technology. Lignin nanoparticle-g-polyacrylic acid adsorbent was prepared using copolymerization reactions between lignin nanoparticle and polyacrylic acid in the presence of potassium persulfate as the radical initiator. Then, lignin nanoparticle-g-polyacrylic acid adsorbent was used to remove Safranin-O from an aqueous environment. The adsorbent structures and morphologies of lignin nanoparticle and lignin nanoparticle-g-polyacrylic acid adsorbent were investigated using scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Nanoparticle sizes were assessed using dynamic light scattering. Equilibrium isotherms were compared using the Langmuir, Freundlich, and Temkin adsorption models. Both adsorbent lignin nanoparticle and lignin nanoparticle-g-polyacrylic acid adsorbent showed good agreement with the Langmuir isotherm. The maximum adsorption capacities of lignin nanoparticle and lignin nanoparticle-g-polyacrylic acid adsorbent reached 99 and 138.88 mg g À1 using model-like, pseudo-second-order, and intraparticle diffusion, respectively. Experimental results showed that adsorbent lignin nanoparticle and lignin nanoparticle-gpolyacrylic acid adsorbent followed the pseudo-second order kinetic model.

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Alkali lignin (AL) modified by ethylene glycol and lignin nanoparticles (LN) was prepared through the acid precipitation technology. Lignin nanoparticle/polyacrylic acid (LN/PAA) hydrogel was prepared using copolymerization reactions. LN and LN/PAA hydrogel were investigated using GPC, SEM, FT-IR spectroscopy, and TGA-DTG analysis. The sizes of the nanoparticles were assessed using DLS. LN/PAA hydrogel was used to remove Safranin-O from an aqueous Solution. The optimal conditions for absorption provided at pH 7, an initial concentration of dye of 1.5 gr.L -1 , and an adsorbent dosage of 0.1 gr. Also, the optimal time for LN and LN/PAA hydrogel were 100 min and 450 min, respectively. Both absorbent LN and LN/PAA hydrogel showed good agreement with the Langmuir isotherm. The maximum absorption capacities of LN and LN/PAA hydrogel were determined to be 100 mg.gr -1 and 1666.6 mg.gr -1 , respectively. Both absorbent LN and LN/PAA hydrogel follow the pseudo-second kinetic model and the intraparticle diffusion model.

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