Heterogeneous photo-Fenton processes using zero valent iron microspheres for the treatment of wastewaters contaminated with 1,4-dioxane

• 1,4-Dioxane was successfully degraded by heterogeneous photo-Fenton on Fe0 microspheres.
• Influences of radiation source, pH and reagent dose were studied on synthetic waters.
• Excellent results were achieved in neutral conditions without any iron leaching.
• Efficient treatment of industrial wastewaters was performed.
• Major reaction intermediates of 1,4-dioxane were identified.

The use of zero valent iron (Fe0) microspheres for the degradation of 1,4-dioxane by photo-Fenton processes was optimized in terms of pH and reagent dosage for the successful treatment of industrial wastewaters. In addition, reaction intermediates of 1,4-dioxane degradation were studied. In UV photo-Fenton treatment of synthetic waters, complete removal of 1,4-dioxane was reached in 5 min, significant biodegradability enhancement (up to 60%) was achieved in 10 min, and an almost total COD removal was obtained after 30 min of treatment (⩾90%), whereat the presence of bicarbonate buffer (pH ⩾ 7) prevented iron leaching. At different H2O2/COD0 ratios the degradation of organics by UV-catalysed Fenton was in a following order: 2.625 > 2.125 > 4 > 1.625. On the other hand, solar photo-Fenton removed above 90% of 1,4-dioxane after 180 min, whereas H2O2/Fe0 ratio of 60 was found optimum. In the treatment of industrial wastewater, ⩾99% and 60% of COD were removed by UV and solar photo-Fenton respectively. Ethylene glycol and formic acid were identified as primary intermediates for the 1,4-dioxane decomposition in heterogeneous photo-Fenton. The opportunity to avoid sludge production and pH adjustments makes the Fe0 microspheres an efficient catalyst for the treatment of relatively alkaline wastewaters containing 1,4-dioxane. The solar driven process could be an important economical alternative to the UV catalysed process. When considering the consumption of energy and chemicals, if partial COD reduction for biodegradability enhancement was the purpose, both heterogeneous photo-Fenton processes appear to be more energy and cost-efficient than ozonation and electro-oxidation treatments.

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