Assessment of a commercial biodegradable iron fertilizer (Fe 3+-IDS) for water treatment by solar photo-Fenton at near-neutral pH

The employ of commercial iron fertilizers based on aminopolycarboxylic chelates for urban wastewater reclamation stands out as a practical circular economy approach for arid/semi-arid regions. A proof -of -principle study of a novel photo -Fenton -like process using the commercial fertilizer ADOB (R) Fe IDHA-9% based on Fe 3 + -IDS (Fe 3 + -IDS/H 2 O 2 /solar) for organic pollutant removal has been performed. The process was tested including the baseline effects of photolysis, H 2 O 2 /solar, Fe 3 + -IDS/solar and Fe 3 + -IDS/H 2 O 2 , in a wide range of target pollutants (0.1-10 mg/L) and reagent concentrations (1-10 and 4-40 mg/L of Fe 3 + -IDS and H 2 O 2 , respectively), in three water matrices (demineralized, natural water and synthetic urban wastewater) and at lab -scale under constant artificial solar radiation. Successful removal of 10 mg/L of imidacloprid (85% in 60 min), was attained by the photo -Fenton -like process with a significant contribution of the Fenton process (52%) and photo-redox activation of the iron chelate (37%). The increase of the water matrix complexity, mainly in bicarbonate ions and organic matter content, leads to a moderate performance decrease (66% removal in 60 min). When increasing the complexity of the water matrix to synthetic urban wastewater, high process performance was attained in 60 min to remove three recalcitrant contaminants of emerging concern: 63%, 81% and 92% for imidacloprid, carbamazepine and trimethoprim, respectively. The results obtained showed a high efficiency of the use of a commercial fertilizer based on iron in the photo -Fenton process, slightly lower than the widely studied Fe-EDDS, but feasible to be an alternative iron source for solar photo -Fenton at near -neutral pH based on its lower cost and environmentally greener characteristics.