Comparison between UVA- and zero-valent iron-activated persulfate processes for degrading propylparaben
2020
Palharim, Priscila H. | Graça, Cátia A. L. | Teixeira, Antonio C. S. C.
Conventional wastewater treatments are not efficient in removing parabens, which may thus end up in surface waters, posing a threat to aquatic biota and human health. As an alternative treatment, persulfate (PS)-driven advanced oxidation technologies have gained growing attention for removing these pollutants. In this study, the degradation of propylparaben (PrP) by UVA- and zero-valent iron (ZVI)-activated persulfate was investigated. The effects of initial PS concentration ([PS]₀) and irradiance or ZVI concentration were explored using the Doehlert experimental design. For the UVA-activated system, the specific PrP degradation rate (k) and percent removal were consistently higher for increasing [PS]₀ and irradiance, varying in the ranges 0.0053–0.0192 min⁻¹ and 37.9–77.3%, respectively. In contrast, extremely fast PrP degradation was achieved through the ZVI/PS process (0.3304 < k < 0.9212 min⁻¹), with removal percentages above 97.5%; in this case, paraben degradation was hindered for a ZVI dosage beyond 40 mg L⁻¹. Regarding toxicity, ECOSAR predictions suggest that the degradation products elucidated by LC-MS/MS are less toxic than PrP toward fish, daphnid, and green algae. In addition, both processes showed to be strongly dependent on the water matrix, being ZVI/PS more impacted for a MBR effluent, although its performance was much better than that exhibited by the UVA-driven process (t₁/₂ of 65.4 and 276.1 min, respectively).
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