Application of Waterborne Polyurethane Dispersion for Selective Removal of Heavy Metals from Acidic Wastewater

Waterborne polyurethane (WBPU) dispersion, originally synthesized as an intermediate material for aerogel fabrication, was investigated as a polymeric extractant for the removal of divalent metal ions such as Cu(II), Co(II), Mn(II), and Ni(II) through a biphasic extraction approach. The produced WBPU exhibited notable extraction performance toward these metal ions, achieving up to 59.2% Cu(II) extraction at a 1:1 mass/volume ratio, pH 3, and under mild low-temperature conditions. Competitive extraction studies involving different divalent metal ions were performed together with extraction and selectivity experiments. The results demonstrated that Cu(II) was extracted with the highest selectivity (39.6%) with the WBPU matrix. The resulting WBPU–M(II) materials were characterized by FT-IR and UV–Vis spectroscopy. Additionally, a potential molecular structure based on density functional theory (DFT) calculations was proposed to explain the WBPU–Cu(II) interaction in the organic phase. The resulting molecular structure is characterized by square-planar complex formation between Cu(II) metal ions and the urethane units within the WBPU structure.