Elastomeric Polyurethane Foam from Elemental Sulfur with Exceptional Mercury Capture Capability

Elemental sulfur-derived polymers are good candidates for remediation materials of heavy metal pollutants especially mercury as sulfur provides an excellent active site for Hg2+. However, the hydrophobic nature and poor processibility of existing sulfur polymers endow the respective absorbents with inferior wetting ability and a limited surface area, which cannot bring Hg2+ into full contact with the active binding site, ultimately resulting in an unsatisfactory absorbing performance. In this work, for the first time, an elastomeric polyurethane foam derived from elemental sulfur is successfully fabricated by engineering sulfur oligomers featuring multi-hydroxyl functionalities into the soft segment while achieving reasonable sulfur utilization yields. The afforded foam exhibits good wetting behavior and an open cell structure with abundant micropores. As a result, the foam delivers a significantly enhanced relative mercury capture capability of 106 mg Hg2+/g sulfur, which stands out distinctively from that of state-of-the-art sulfur polymers. Moreover, the elastomeric foam nature enables the fast absorber separation after usage in a simple squeezing or pumping step, otherwise tedious post-treatments are mandatory for materials displayed in other forms, which greatly simplifies the water remediation process. This strategy not only demonstrates a novel roadmap for advancing the heavy metal uptake capability of elemental sulfur-derived functional materials but also enriches the application scenario of pollutant absorbents.