A simple ZVI-Fenton pre-oxidation using steel-nails for NOM degradation in water treatment

The feasibility of a heterogeneous Fenton Process (ZVI/H2O2) using commercial low-carbon-steel nails as the Zero-Valent Iron (ZVI) source was evaluated for the first time for the removal of natural organic matter (NOM) from natural surface waters with distinct physico-chemical characteristics. The synergistic effect of ZVI nails and H2O2 on the process was confirmed. Results showed similar removal efficiencies of NOM in water samples from Thames river and Regent's Park lake (both in London, UK) (under initial pH 3.5 and 100% excess of H2O2 dosage), reaching dissolved organic carbon (DOC) removals of 61.6% +/- 3.0 and 59.6% +/- 4.7, and UV254 removals of 79.9% +/- 0.6 and 77.3 +/- 6.2, respectively with 60 min of batch reaction time. ZVI nail surface characterization by scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), and X-ray photoemission spectroscopy (XPS) revealed the formation of a passivating oxide-hydroxide layer on the nail during the reaction, which reduces its surface activity with 20% in continuous use. Results indicate that ZVI/ H2O2 process using commercial iron nails is a promising pre-oxidation step for drinking water treatment. The low cost of commercial nails together with the facility of separating them from the water are the main advantages for the application of this process in remote regions with limitations in infrastructure and/or finance.

Automated summary

The study evaluated the feasibility of a heterogeneous Fenton Process using commercial low-carbon-steel nails as the source of Zero-Valent Iron for the removal of NOM from natural surface waters, and confirmed the synergistic effect of ZVI nails and H2O2 on the process. Similar removal efficiencies of NOM were observed in water samples with distinct characteristics, reaching up to 61.6% DOC removal and 79.9% UV254 removal with 100% excess of H2O2 dosage and initial pH 3.5.