Abstract
A successful attempt to degrade synthetic estrogen 17α-ethynylestradiol (EE2) is demonstrated via combining photocatalysis employing magnesium peroxide (MgO2)/low-pressure ultraviolet (LP-UV) treatment followed by biological treatment using small bioreactor platform (SBP) capsules. Reusable MgO2 was synthesized through wet chemical synthesis and extensively characterized by X-ray diffraction (XRD) for phase confirmation, X-ray photoelectron spectroscopy (XPS) for elemental composition, Brunauer-Emmett-Teller (BET) to explain a specific surface area, scanning electron microscopy (SEM) imaging surface morphology, and UV-visible (Vis) spectrophotometry. The degradation mechanism of EE2 by MgO2/LP-UV consisted of LP-UV photolysis of H2O2 in situ (produced by the catalyst under ambient conditions) to generate hydroxyl radicals, and the degradation extent depended on both MgO2 and UV dose. Moreover, the catalyst was successfully reusable for the removal of EE2. Photocatalytic treatment by MgO2 alone required 60 min (~1700 mJ/cm2) to remove 99% of the EE2, whereas biodegradation by SBP capsules alone required 24 h to remove 86% of the EE2, and complete removal was not reached. The sequential treatment of photocatalysis and SBP biodegradation to achieve complete removal required only 25 min of UV (~700 mJ/cm2) and 4 h of biodegradation (instead of >24 h). The combination of UV photocatalysis and biodegradation produced a greater level of EE2 degradation at a lower LP-UV dose and at less biodegradation time than either treatment used separately, proving that synergetic photocatalysis and biodegradation are effective treatments for degrading EE2.
Highlights
Endocrine-disrupting chemicals (EDCs) are emerging contaminants that pose a serious threat to the environment, humans, and livestock
We evaluate the role of MgO2 in photocatalytic degradation, small bioreactor platform (SBP) capsule-based biodegradation using
The optical band gap was determined from the UV-Vis absorption spectrum by Tauc plot (Figure 1b):n = A(hν − Eg) where α denotes the absorption coefficient, hν is the discrete photon energy, A is constant, Eg is the band gap, and the exponent n depends on the type of transition
Summary
Endocrine-disrupting chemicals (EDCs) are emerging contaminants that pose a serious threat to the environment, humans, and livestock. It has been estimated that an average of 30,000 kg of natural estrogens, 700 kg of synthetic hormones from humans, and 83,000 kg of estrogens from livestock are released annually into the environment [1]. To the best of our knowledge, there is no cost-effective treatment barrier to prevent chronic exposure to EDCs. The synthetic EDC 17α-ethynylestradiol (EE2), widely used in oral contraceptives and hormone-replacement therapy, has the potential to elicit negative effects in the endocrine systems of humans and wildlife. Advanced oxidation processes (AOPs) are used to oxidize/mineralize organic pollutants in water through the accelerated production of hydroxyl free radical (·OH). AOPs such as ozonation [3], ultraviolet (UV)/hydrogen peroxide (H2 O2 )
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