Poly(urethane Methacrylate)-Lignin (PUM-Lig) Microspheres: Synthesis, Characterization, and Their Application in Metal Ions and Dye Adsorption.

In this study, poly(urethane methacrylate) (PUM)-lignin (Lig) polymeric adsorbent in the form of microspheres was synthesized and evaluated for the removal of metal ions such as Cu(II), Ni(II), Zn(II), and C.I. Basic Yellow 40 (BY40) dye from aqueous solutions. The performance of the PUM adsorbent without lignin was also described. PUM and PUM-Lig were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TG), attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FT-IR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), to confirm the successful incorporation of lignin and to assess their thermal stability, chemical structure, morphology, and surface properties. Equilibrium uptake of Cu(II), Ni(II), Zn(II), and BY40 was described by the Freundlich isotherm model rather than the Langmuir, Temkin, or Dubinin-Radushkevich ones with the following affinity: Cu(II) > Zn(II) > BY40 > Ni(II). The experimental equilibrium sorption capacities ranged from 78.0 to 152.2 mg/g. The effect of NaCl, Na2SO4, and surfactants CTAB, TX100 on Cu(II), Ni(II), Zn(II), and BY40 was investigated. The effective desorption of Cu(II) and BY40 from adsorbents was performed using 1 M HCl, 1 M H2SO4, 1 M HNO3, and 1 M HCl or 1 M NaCl in 50% v/v methanol.