(636b) Water Remediation by Iron/Iron Oxide Nanoparticle Catalyzed Free Radical Reactions In PAA Functionalized PVDF Membranes

Free radical reaction based on iron/iron oxide nanoparticles catalyzed H₂O₂ decomposition has been studied in water remediation. The highly oxidative hydroxyl radicals (OH·) generated via the catalytic decomposition of H₂O₂ on iron oxide surfaces can degraded the recalcitrant organic contaminants such as trichloroethylene (TCE) and chlorinated phenols. Iron oxide nanoparticles with high specific surface area are preferred in this reaction to provide more catalytic sites. To prevent the agglomeration of nanoparticles and reduce the particles loss, functionalized membranes with polymer matrix were used as the binding support.

The stabilized Fe⁰/Fe₂O₃ nanoparticles synthesized by chemical reduction and air oxidation in the aqueous phase were introduced to the catalytic reaction at the near-neutral pH. The final mineralization products of TCE were chloride ions, carbon dioxide and organic acids. Therefore, the chloride concentration was carefully measured to estimate the degradation of TCE and investigate the reaction pathway. TCE was selected as the model contaminant because of its environmental importance. Depending on the ratio of iron and hydrogen peroxide, TCE conversions as high as 100% (with about 91% dechlorination) was obtained.

A novel functionalized Fe-Fe₂O₃/PAA/PVDF membrane was also prepared based on the in situ polymerization, ion exchange, chemical reduction followed by controlled air oxidation. Fe/Fe₂O₃ nanoparticles were immobilized in the membrane pores, where the PAA matrix prevented the aggregation of particles. At the near-neutral pH, the conversion of TCE is 74.7% after 48h while 96.7% of hydrogen peroxide (41.4 mM) was decomposed. TCE mineralization was also achieved in the actual groundwater with the reactive membrane activated by H₂O₂.

This research is supported by NIEHS-SRP Supplement grant and by the DOE-KRCEE programs.