Utilizing Reclaimed Petroleum Waste to Synthesize Water-Soluble Polysulfides for Selective Heavy Metal Binding and Detection

Abstract

Many industrial processes produce waste with toxic and precious metal pollutants. Current remediation strategies lack the selectivity needed to effectively eliminate heavy metals. Thus, materials are needed to effectively treat waste streams and contaminated waterways. Sulfur is well known for its ability to selectively bind heavy metals. Additionally, excess sulfur is produced on large scales during petroleum refinement making it inexpensive and abundant. Inverse vulcanization enables surplus sulfur to be repurposed into high sulfur content materials without the need for solvents. These polysulfides have demonstrated many beneficial applications including heavy metal binding. However, they are plagued by low solubility and dominated by hydrophobic monomers. Here, elemental sulfur and charged monomers, including diallyl dimethylammonium chloride (DADMAC), were combined for the first time in a one-step reaction forming water-soluble polysulfides. The water solubility allows for complete interaction of dissolved metal ions with the polymer, rather than surface-level interaction as is the case for traditional inverse vulcanized polymers. Additionally, the charged polysulfides exhibit enhanced solubility in organic solvents, making solution-based characterization such as NMR more accurate. Poly(S-DADMAC) has demonstrated selective binding to gold and silver inducing the formation of a macromolecular complex that precipitates from solution. Additionally, these polymers interact with other heavy metals including lead and copper demonstrating a visible color change at low concentrations that may be used to detect the presence of these metals in wastewater. The low cost, ease of preparation, and scalability make these polysulfides practical as well as functional.