(562n) Inverse Vulcanized Polysulfide-Based Foam with Hierarchical Pore Structure for Effective and Efficient Heavy Metal Sequestration

Introduction of inverse vulcanization (IV) led to the development of new class of polysulfides (PS) with interesting properties for various applications. IV involves ring opening reaction of elemental sulfur (i.e. S-S chain scission at T > 159ºC) with organic comonomer. Due to the high sulfur content, PS synthesized via IV show potential as mercury (II) sequestrants. However, almost no reported PS has competitive mercury adsorption performance with capacity only ranging 1-30 mg g^-1. This could be attributed to the hydrophobicity of the materials since PS were synthesized with hydrocarbon- or aromatic-rich comonomers. The low wettability prohibits intimate adsorbent/aqueous feed contact thereby disfavoring Hg²⁺ capture.

In this work, hydrophilic PS was synthesized by copolymerizing elemental sulfur with ethylene glycol dimethacrylate (EGDMA). Different S-EGDMA PS were prepared according to different S:EGDMA molar ratio and were thoroughly analyzed to propose their structure and characterized in terms of morphology and other physico-chemical properties. Their ability to sequester mercury (II) were evaluated via adsorption isotherm, kinetics, and thermodynamics.

The S-EGDMA PS was configured into a macroporous foam. PS were incorporated in poly(vinyl alcohol) (PVA) matrix via blending, cryo-dessication, and chemical cross-linking. This ensured the high quality and convenient loading control of PS in the foam. The composite foams were thoroughly characterized and evaluated in terms of mercury (II) adsorption capacity, kinetics, and thermodynamics. Mechanical durability vis-à-vis reusability was also evaluated. This study features significant advantages not only to the competitive mercury (II) adsorption performance of the materials but also to the cost-effectiveness of the material preparation.

This research was supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (No. 2018R1D1A1B07047503 and No. 2017R1A2B2002109) and by the Ministry of Education (No. 22A20130012051(BK21Plus)).