Nanoparticle Chelate Immobilization and Iron Delivery for the Fenton’s Reaction: Groundwater Remediation Implications

The Fenton’s reaction provides a powerful mechanism for the hydroxyl radical mediated oxidative breakdown of toxic halogenated organic contaminants in aqueous systems. When applied to groundwater remediation, however, problems arise. Firstly, at the near-neutral pH conditions of groundwater Iron III precipitates from solution, breaking the cycle of Iron II regeneration and thus ending hydroxyl radical production and contaminant destruction.

Secondly, in the presence of the ground rock and organic material present in groundwater systems hydroxyl radicals have low selectivity for the oxidation of organic contaminants and are significantly consumed by side reactions. This reduces Fenton’s reaction effectiveness.

The use of ion-exchange nanoparticles for iron immobilization offers distinct advantages in overcoming these problems. These particles provide ion-exchange sites which can be loaded initially with Iron II and, upon reaction with hydrogen peroxide, Iron III. By effectively chelating Iron III, and preventing its precipitation, these ion-exchange sites act as an immobilized chelating agent. This provides a solution to problem (1). Additionally, due to the high porosity of these nanoparticles the bulk of iron is internally immobilized. This works to provide a solution to problem (2) by keeping hydroxyl radicals produced sequestered from the external environment; contaminant destruction occurs through diffusion of groundwater into the nanoparticles themselves. The use of ion-exchange nanoparticles to facilitate the Fenton’s reaction in geochemically-active near-neutral pH systems has significant potential to increase the effectiveness of the Fenton’s reaction for groundwater remediation. This study is a preliminary effort to develop this potential and provides a foundation for future refinement.