Iron dosage as a strategy to operate the photo-Fenton process at initial neutral pH

This paper deals with repeated iron additions as a strategy to remove recalcitrant pollutants from water using the solar photo-Fenton process at initial neutral pH and at pilot-plant scale. A mixture of five commonly used commercial pesticides was used as the model pollutant. The effect of iron dosage on process performance was initially studied in demineralized water and later evaluated on real wastewater. Different iron dosage combinations were applied, paying special attention to iron concentration per dose and addition time. As a consequence of iron hydrolysis and anions present in the water (carbonates, phosphates), the first iron additions had to be made at each mixing time in the pilot plant (5 min) since longer periods involved a lack of catalyst in the system. Results showed that iron dosage permits the running of the photo-Fenton process at initial neutral pH with similar reaction rates to those when the process is at pH 2.8; and has an analogous mineralization level in completing pesticide removal (20% DOC mineralization).

Results obtained after 1 h of solar photo-Fenton with 50 mg DOC/L and 650 mg H2O2/L at initial neutral pH with five additions of 20–20–10–10–10 mg Fe/L. The arrows point out the time of addition.Figure optionsDownload as PowerPoint slideHighlights
► Iron additions are used as strategy to run the photo-Fenton process at initial pH 7.
► The process is applied to a pesticide mixture in demineralized and real wastewater.
► Results show iron concentration and the time of addition are essential to the process.
► The strategy permits process rates analogous to the conventional operating conditions.