Synthesis of lignin-containing polymer hydrogels with tunable properties and their application in sorption of nickel(II) ions

Abstract

Polymer hydrogels with lignin in the form of microspheres have been synthesized and their properties were evaluated. Prior to the polymerization, hardwood lignin (Eucalyptus grandis) was modified with methacryloyl chloride, and unmodified lignin (L-N) and its methacrylic derivative (L-M) were polymerized with 2-hydroxyethyl methacrylate (HEMA) and divinylbenzene (DVB) in different ratios using suspension polymerization. The presence of characteristic functional groups in the synthesized hydrogels was confirmed using attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FT-IR) and NMR. Thermal properties were determined by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Swelling was studied in common organic solvents and distilled water. The shapes of the hydrogels were confirmed by scanning electron microscopy (SEM) and optical microscopy. The addition of lignin significantly increased the swelling ability of the hydrogels in water and acetone. The incorporation of methacrylated lignin into the structure of HEMA-DVB hydrogels increased their sorption of Ni(II) ions by 30 % showing that these hydrogels are a promising material for use in nickel removal and recovery, as well as contributing to a better utilization of lignin.