Mechanism for removing 17beta-estradiol by bio-nanocomposite FJ1@rGO based on integration of adsorption and biodegradation

Abstract

17beta-estradiol (E2) is classified as an endocrine disruptor and it poses a significant threat to the environment. Despite our previous work on the preparation of green-reduced graphene immobilized Ochrobactrum sp. FJ1(FJ1@rGO) to achieve high efficiency in removing E2, the functions of strain FJ1 and rGO, as well as their removal mechanism of E2, remain not well understood. In this study, FJ1@rGO was used to remove E2 to comprehend the removal mechanism where efficiency was found to be 93.74% after 10 days of removal compared to only rGO (43.82%). This indicated that E2 degradation was based on the integration of adsorption using rGO and biodegradation through strain FJ1, as evidenced by HPLC-UV. Additionally, results confirmed that the E2 removal process by FJ1@rGO conforms to first-order degradation kinetics and pseudo-second-order kinetics, further demonstrating the synergistic effect of physical adsorption and biodegradation. LC-Q/TOF-MS analysis identified the primary degradation products as estrone (E1), 4-OH-E1, and catechol. Combining characterization analysis, rGO facilitates the transfer of electrons between cells and E2, improving the strain's tolerance of environmental changes. Finally, the assessment of various wastewaters showed that the removal efficiency was 99.76%, 96.89%, and 78.09%, respectively. Overall, the mechanism by FJ1@rGO to remove E2 was proposed here, providing new insights into green and sustainable technology for treating E2 in wastewater.