Aqueous “polysulfide-ene” polymerization for sulfur-rich nanoparticles and their use in heavy metal ion remediation

Abstract

Elemental sulfur is currently produced as a byproduct of petroleum refining processes, and the overproduction of sulfur has risen as a prominent concern from both industrial and environmental perspectives. Utilization of elemental sulfur, an industrial waste, as a feedstock for functional materials has therefore received keen interest. As a part of an ongoing effort to utilize elemental sulfur or its direct derivatives for polymeric materials, we herein demonstrate the preparation of water dispersible sulfur-rich polymer nanoparticles (PS_nDVS) by developing a precipitation polymerization of aqueous sodium polysulfides, prepared directly from elemental sulfur, with vinyl sulfones. Combination of an anionic surfactant and a neutral steric stabilizer allowed for the preparation of monodisperse, spherical particles, the sulfur content of which could be controlled by varying the rank of the polysulfide used. Through subsequent reduction, densely thiol-functionalized polymer nanoparticles (PS_nDVS-SH) could be obtained. The particles demonstrated well-defined mercury ion uptake kinetics, along with a very high mercury ion capture capacity of 9200 mg of mercury per gram of polymer. Using PS_nDVS-SH, the aqueous mercury ion concentration could be reduced from 11.5 ppm to 0.005 ppm, well below the WHO guidelines for safe drinking water.