(180ak) Iron-Based Redox Polymerization towards Nanoparticle Synthesis in Hydrogel

This work describes the preparation of a polymer of acrylic acid (AA) and ethylene glycol (EG) by redox polymerization and the use of the exhausted metal based catalysts (ferric ion) of the process to synthesize zero-valent iron nanoparticles for water remediation applications. The polymerization is done by free radicals in a reaction between a catalyst (FeCl₂ or FeSO₄) and an initiator (Potassium persulfate). This redox polymerization is the source of the metal ions that are going to be reduced and immobilized simultaneously in the polymer.

The creation of a support like polymer hydrogel or membrane pore domain for the immobilization of nanoparticles (NPs) prevents their loss and reduction of active surface. For direct solution-phase (no polymers) synthesis, NPs loss and aggregation occurs, making them unable to recover and possibly increasing the costs in the practice. The novelty of this work is that the nanoparticles are synthesized using the metal catalysts from the polymerization to form PAA hydrogel. Previous reported studies involved polymerization by free radicals but the Fe ions are ion exchanged in the COOH functional groups after the hydrogel synthesis which was followed by zero-valent iron formation with sodium borohydride. The amount of iron in the solution phase is measured by Atomic Absorption and the counter ion (Chloride) is quantified by a ion selective probe. By material balance, the amount of iron inside the polymer is calculated. Characterization of the polymer and the presence of iron nanoparticles within are done by SEM and TGA techniques.

The polymer hydrogel-nanoparticles system is also studied for toxic chloro-organic degradation from water. In addition to the direct use of NPs immobilized charged hydrogels,  polymerization was also conducted in  PVDF microfiltration membrane pores to study their functionalization and application towards the pollutant degradation process in batch and convective flow modes. This research was supported by the NIEHS-SRP program.