Preparation of thiol-functionalized polyurethane foam and its adsorption performance for Hg(ii)

To address the challenges of heavy metal mercury-induced water pollution and the recycling difficulties of polyurethane foam, this study modified waste polyurethane foam (PUF) using γ-mercaptopropyl trimethoxysilane (NQ590) to prepare thiol-functionalized polyurethane foam (PUF-HS). The adsorption mechanism of PUF-HS toward Hg(ii) was investigated via adsorption kinetics and isothermal adsorption models. Results showed that the modified foam surface displayed protruding particles formed by silane condensation, while the matrix foam maintained its highly porous three-dimensional network structure. The adsorption equilibrium time of PUF-HS for Hg(ii) was determined to be 510 min. Kinetics and isothermal analyses revealed that the adsorption process conformed well to the pseudo-second-order kinetics model and the Freundlich isotherm model, respectively. The adsorption was multilayer adsorption dominated by chemical adsorption and controlled by intra-particle diffusion and film diffusion. According to Langmuir isotherm model fitting, the maximum adsorption capacity of PUF-HS for Hg(ii) at 35 °C was 35.96 mg g^-1. This study enabled the resource utilization of waste polyurethane foam and developed a novel adsorbent material for efficient removal of toxic heavy metal ion Hg(ii) from water.