Bacterial inactivation and organic oxidation via immobilized photo-Fenton reagent on structured silica surfaces

A woven inorganic silica fabric loaded with Fe-ions (EGF-Fe) was tested under simulated solar light during hydroquinone degradation. The abatement of hydroquinone was observed to attain about ∼80% within 3 h. The photo-catalyst was also tested to inactive Escherichia coli K12 at “natural” pH and in the presence of a low concentration of H2O2. Addition of H2O2 (10 mg L−1) did not by itself to bacterial inactivation. Total bacterial inactivation was mediated by EGF-Fe fabrics in the presence of H2O2 (10 mg L−1) under solar light irradiation. A sample containing active (culturable) bacteria (∼105 CFU mL−1) decreased to values <1 CFU mL−1 within 3 h reaction. Fe-mediated homogeneous process decreased the bacterial CFU content by about two orders of magnitude within 4 h. During the degradation of hydroquinone only a small amount of iron ions were found in solution of about 1.2 mg L−1, within 90 min decreasing to values ≤0.5 mg L−1 after 180 min. The leaching of Fe-ions did not affect the photo-catalyst performance since EGF-Fe fabric did not deactivate after five or more cycles. The Fe-ions founds in solution mineralized hydroquinone to levels below 37% of its initial content. The present study presents the first report on the beneficial role of a heterogeneous iron supported catalyst leading to efficient bacterial inactivation in aqueous solution with iron leaching <0.1 mg L−1, the detection limit for Fe-analysis in solution. No bacterial re-growth was observed during a post-irradiation period up to 24 h in the dark.