Synthesis of Novel Lignin-Based Ion-Exchange Resin and Its Utilization in Heavy Metals Removal

Abstract

A new lignin-based resin (LBR) was prepared by condensation polymerization of sodium lignosulfonate with glucose under acidic conditions. The physical and chemical properties of LBR were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and 13C cross-polarization magic angle spinning nuclear magnetic resonance (13C CP MAS NMR). Structure analyses revealed that the resulting spherical particles are composed of amorphous cross-linked phenylpropane-based polymers that have a high density of acidic groups and high thermal stability. The adsorption performance of heavy metals (Cr(III), Cu(II), Ni(II), Pb(II), and Cd(II)) onto LBR were investigated. Langmuir, Freundlich, and Dubinin–Radushkevich (D-R) models were applied to analyze the experimental data. The maximum adsorption capacity of LBR for the five metals was in the following order: Pb(II) ≫ Cu(II) > Cd(II) > Ni(II) ≈ Cr(III). The experimental data were also tested by pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetic models. The adsorption process of all metal ions on LBR is well-described by the pseudo-second-order model. Moreover, the regeneration method of LBR was also studied.