Iron Oxide Impregnated Membrane for Sulfate Radical-Based Oxidation of Trichloroethene

This study investigates an iron-activated oxidative reaction with sulfate radicals to degrade trichloroethene (TCE) using a composite membrane. The optimization of this degradation pathway was conducted by comparing three different oxidation states of iron (Fe³⁺, Fe²⁺, and Fe⁰), which are possible to incorporate in a variety of Fe nanoparticles. Performance of Fe-NPs was determined by measuring TCE degradation in a solution phase. The membranes consisted of polyacrylic acid (PAA) and graphene oxide (GO), deposited onto a polyvinyl difluoride (PVDF) backing. Diluted acrylic acid was polymerized using a UV initiator. Two types of membranes were made: a “mix” membrane where PAA and GO are deposited simultaneously, and a “sandwich” membrane where PAA is deposited between two GO layers, creating a substrate layer capable of iron deposition. Membrane characterization included permeability, contact angle, salt rejection (NaSO₄ and CaSO₄), pH responsiveness, and persulfate oxidation. Fe(III) systems showed 0.3 mol Cl^- generated per 1mol S₂O₈^2-, which is a measure of TCE degradation efficiency. Efficiencies for systems with iron oxide and zero-valent iron were calculated, but require further analysis. When persulfate was passed through the “mix” membrane and “sandwich” membrane, persulfate concentration was reduced by 22.73% and 26.5%, respectively. In a control experiment, a GO only membrane reduced the concentration by 14.63%. This study demonstrates the successful use of impregnated membranes as a medium for the oxidative sulfate radical-based degradation pathway. This research was supported by NSF KY EPSCoR program and by NIH-NIEHS-SRP.