Titanium dioxide and halloysite loaded polylactic acid-based membrane continuous flow photoreactor for 17α-ethinylestradiol (EE2) hormone degradation: Optimization, kinetics, mechanism, and reusability study

Abstract

Exposure to endocrine-disrupting chemicals (EDCs) has been linked to harmful effects in biota due to their widespread chemical persistence. In this paper, we report on the fabrication of electrospun polylactic acid (PLA) based nanofibers functionalized with TiO2 nanoparticles. The PLA-based TiO2 nanofibers were further stabilized with the incorporation of halloysite (HNT) particles. The nanofibers were fabricated in varied concentrations of HNT (5, 10, 15%), while TiO2 was kept at 10% for all the prepared samples. The fabricated samples were evaluated for elimination of synthetic 17α-ethinylestradiol (EE2) hormone as a model EDC pollutant. By using combined adsorptive and photocatalytic processes, the as-prepared samples were evaluated in a continuous flow system under dark and UV-light irradiation for EE2 removal. The best-performing sample with an optimized concentration of PLA/TiO2/HNT (85, 10, 5%) was able to eliminate 71.6% of EE2 hormone under UV irradiation at a hormone concentration of 0.1 mg/L. The maximum removal capacity obtained was 1.26 mg/g in 2 h, which best fitted the pseudo-first-order kinetics model. The sample was further utilized for additional experiments by changing experimental parameters, such as contact time, solution pH, and flow rate. To elucidate the actual degradation of the EE2 hormone, LCMS analysis was carried out to monitor the formation of by-products, which indicated that EE2 was fragmented into different potentially benign molecules. Finally, the best-performing sample was utilized for ten cyclic runs under optimized conditions for which the sample maintained sufficiently high degradation without any loss in structural integrity. Overall, the results showed that the developed PLA/TiO2/HNT nanofibers have a high potential to target persistent organic pollutants.