Assessment of fouling mechanisms on reverse osmosis (RO) membrane during permeation of 17α-ethinylestradiol (EE2) solutions

Thermal Degradation Process of Ethinylestradiol—Kinetic Study

The present study reports the results obtained after the analysis of the thermal stability and decomposition kinetics of widely used synthetic derivative of estradiol, ethinylestradiol (EE), as a pure active pharmaceutical ingredient. As investigational tools, Fourier transformed infrared spectroscopy (FTIR), thermal analysis, and decomposition kinetics modeling of EE were employed. The kinetic study was realized using three kinetic methods, namely Kissinger, Friedman, and Flynn-Wall-Ozawa. The results of the kinetic study are in good agreement, suggesting that the main decomposition process of EE that takes place in the 175–375 °C temperature range is a single-step process, invariable during the modification of heating rate of the sample.

Anti-Pectin Fouling Performance of Dopamine and (3-Aminopropy) Triethoxysilane-Coated PVDF Ultrafiltration Membrane

Due to the diversity and complexity of the components in traditional Chinese medicine (TCM) extracts, serious membrane fouling has become an obstacle that limits the application of membrane technology in TCM. Pectin, a heteropolysaccharide widely existing in plant cells, is the main membrane-fouling substance in TCM extracts. In this study, a hydrophilic hybrid coating was constructed on the surface of a polyvinylidene fluoride (PVDF) ultrafiltration (UF) membrane co-deposited with polydopamine (pDA) and (3-Aminopropy) triethoxysilane (KH550) for pectin antifouling. Characterization analysis showed that hydrophilic coating containing hydrophilic groups (–NH₃, Si-OH, Si-O-Si) formed on the surface of the modified membrane. Membrane filtration experiments showed that, compared with a matched group (FRR: 28.66%, Rr: 26.87%), both the flux recovery rate (FRR) and reversible pollution rate (Rr) of the pDA and KH550 coated membrane (FRR: 48.07%, Rr: 44.46%) increased, indicating that pectin absorbed on the surface of membranes was more easily removed. Based on the extended Derjaguin–Laudau–Verwey–Overbeek (XDLVO) theory, the fouling mechanism of a PVDF UF membrane caused by pectin was analyzed. It was found that, compared with the pristine membrane (144.21 kT), there was a stronger repulsive energy barrier (3572.58 kT) to confront the mutual adsorption between the coated membrane and pectin molecule. The total interface between the modified membrane and the pectin molecule was significantly greater than the pristine membrane. Therefore, as the repulsion between them was enhanced, pectin molecules were not easily adsorbed on the surface of the coated membrane.

Combined reverse osmosis and UV/H2O2 treatment of aqueous solutions of bisphenol A and 17α-ethinylestradiol: assessment of estrogenic activity

Bisphenol-A (BPA) and 17α-ethinylestradiol (EE2) are considered endocrine disrupting compounds (EDC) and they may be harmful to the normal functioning of endocrine systems of humans and animals. Moreover, the presence of these compounds in superficial and groundwater may represent serious risks, even in low concentrations like ng·L^-1. The objectives of this study were to remove BPA and EE2 from solutions containing a mixture of these compounds in ultrapure water at low concentrations through reverse osmosis (RO) membrane combined with a UV/H₂O₂ process. Furthermore, to assess the estrogenic activity reduction after such treatments, in vitro recombinant yeast-estrogen screen (YES) assay was used. The removal efficiencies of target micropollutants increased with the increase of H₂O₂ dosage. For RO permeate stream, they enhanced from 91% to 96% for EE2 and from 76% to 90% for BPA while, for the concentrate stream, from 70% to 81% for EE2 and 41% to 84% for BPA as the H₂O₂ concentration were increased from 100 to 1000 µg·L^-1. The OH radicals' generation was the dominant factor in the degradation of EDC during the UV/H₂O₂ treatment since the photolysis itself was not enough to degrade BPA or EE2. The estrogenic activity reduction after UV/H₂O₂ treatment was high, ranging from 92% to 98% for the permeate stream and from 50% to 93% for the concentrate stream. The EE2 was responsible for the whole observed estrogenic activity since BPA does not present estrogenicity, by in vitro YES assay, in the concentrations observed.