Adsorption of estrone, 17β-estradiol, and 17α-ethinylestradiol from water onto modified multi-walled carbon nanotubes, carbon cryogel, and carbonized hydrothermal carbon

A critical and comprehensive review of the current status of 17β-estradiol hormone remediation through adsorption technology

Even at low concentrations, steroid hormones pose a significant threat to ecosystem health and are classified as micropollutants. Among these, 17β-estradiol (molecular formula: C18H24O2; pKa = 10.46; Log Kow = 4.01; solubility in water = 3.90 mg L-1 at 27 °C; molecular weight: 272.4 g mol-1) is extensively studied as an endocrine disruptor due to its release through natural pathways and widespread use in conventional medicine. 17β-estradiol (E2) is emitted by various sources, such as animal and human excretions, hospital and veterinary clinic effluents, and treatment plants. In aquatic biota, it can cause issues ranging from the feminization of males to inhibiting plant growth. This review aims to identify technologies for remediating E2 in water, revealing that materials like graphene oxides, nanocomposites, and carbonaceous materials are commonly used for adsorption. The pH of the medium, especially in acidic to neutral conditions, affects efficiency, and ambient temperature (298 K) supports the process. The Langmuir and Freundlich models aptly describe isothermal studies, with interactions being of a low-energy, physical nature. Adsorption faces limitations when other ions coexist in the solution. Hybrid treatments exhibit high removal efficiency. To mitigate global E2 pollution, establishing national and international standards with detailed guidelines for advanced treatment systems is crucial. Despite significant advancements in optimizing technologies by the scientific community, there remains a considerable gap in their societal application, primarily due to economic and sustainable factors. Therefore, further studies are necessary, including conducting batch experiments with these adsorbents for large-scale treatment along with economic analyses of the production process.

Efficient removal of endocrine disrupting compounds 17 α-ethynyl estradiol and 17 β-estradiol by Enterobacter sp. strain BHUBP7 and elucidation of the degradation pathway by HRAMS analysis

Owing to the increased population and their overuse, estrogens are being detected in the environment at alarming levels. They act as endocrine disrupting compounds (EDC's) posing adverse effects on animals and humans. In this study, a strain belonging to Enterobacter sp. strain BHUBP7 was recovered from a Sewage Treatment Plant (STP) situated in Varanasi city, U.P., India, and was capable of metabolizing both 17 α-Ethynylestradiol (EE2) and 17 β-Estradiol (E2) separately as a sole carbon source. The strain BHUBP7 exhibited high rates of E2 degradation as compared to EE2 degradation. The degradation of E2 (10 mg/L) was 94.3% after four days of incubation, whereas the degradation of EE2 (10 mg/L) under similar conditions was 98% after seven days of incubation. The kinetics of EE2 and E2 degradation fitted well with the first-order reaction rate. FTIR analysis revealed the involvement of functional groups like C = O, C-C, C-OH during the degradation process. The metabolites generated during degradation of EE2 and E2 were identified using HRAMS and a plausible pathway was elucidated. It was observed that metabolism of both E2 and EE2 proceeded with the formation of estrone, which was then hydroxylated to 4-hydroxy estrone, followed by ring opening at the C4-C5 position, and was further metabolized by the 4,5 seco pathway leading to the formation of 3-(7a-methyl-1,5-dioxooctahydro-1H-inden-4-yl) propanoic acid (HIP). It is the first report on the complete pathway of EE2 and E2 degradation in Enterobacter sp. strain BHUBP7. Moreover, the formation of Reactive Oxygen Species (ROS) during the degradation of EE2 and E2 was observed. It was concluded that both hormones elicited the generation of oxidative stress in the bacterium during the degradation process.

Polyaniline Entrapped Water-Dispersible 3MPA-ZnSe Quantum Dots and Their Application for the Development of an Enzymatic Electrochemical Nanobiosensor for the Detection of 17β-Estradiol, an Endocrine-Disrupting Compound

17β-estradiol is used as a growth and fertility stimulant in the agronomic sector to induce fertility and manipulate reproductive characteristics in animals. However, unintended or unregulated distribution and exposure to even significant low levels of 17β-estradiol estrogen have detrimental health implication that can lead to reproductive abnormalities and even cancer. This could have severe effect on the ecosystem imbalance, food safety, to such a degree that its health impact necessitates rapid methods to probe for its prevalence and occurrence in the environment. Herein a simple, robust, sensitive and once-off use electrochemical biosensor to detect 17β-estradiol is developed, using 3-mercaptopropionic acid capped zinc selenide quantum dots trapped within the polyaniline (PANI) framework structure. The biosensor's interaction with the substrate was based on the capability of the hemeprotein, horseradish peroxidase (HRP) enzyme (i.e., baroreceptor) to alternatively catalyze phenolic alcohols. The biosensor displayed a significantly low limit of detection limit (LOD) of value 0.2 × 10^-6 M towards 17β-estradiol. The Mechaelis-Menten constant (K_m) with the magnitude of 0.64 × 10^-6 M was obtained; this indicates an outstanding affinity of the biosensing films towards 17β-estradiol. Subsequently, the developed biosensor was able to accurately and efficiently measure successive concentrations of 17β-estradiol from 0.2 × 10 to 4 × 10^-6 M. The fabricated biosensor showed good selectivity towards 17β-estradiol compared to the other estrogenic endocrine-disrupting compounds such as estrone (E1), ethnylstradiol (EE2), and estriol (E3). The biosensor was capable of detecting 17β-estradiol in spiked tap water samples with good recoveries, thus affirming its potential to be applied for real electro-analysis of 17β-estradiol in treated wastewater.

Hydroxypropyl methylcellulose-sugarcane bagasse adsorbents for removal of 17α-ethinylestradiol from aqueous solution and freshwater

Adsorbents made of hydroxypropyl methylcellulose (HPMC) and sugarcane bagasse (BG) microparticles were applied for the separation of 17α-ethinylestradiol (EE2) from aqueous solution in batch, and from aqueous solution and freshwater in fixed-bed columns. HPMC chains and BG microparticles were crosslinked by the esterification with citric acid. The adsorbents presented compression modulus values that increased from 208 ± 20 kPa (pure HPMC) to 917 ± 90 kPa, when the content of BG particles added to HPMC was 50 wt% (HPMC50BG). The porosity (~ 97%), specific surface area (1.16 ± 0.10 m²/g) and swelling degree (20 ± 1 g water/g) values were not affected by the addition of BG particles. The adsorption isotherms determined for EE2 on HPMC and on HPMC50BG fitted to the Langmuir and Freundlich models; the adsorption capacity of HPMC was slightly higher than that of composite HPMC50BG. Nevertheless, the addition of BG particles rendered outstanding mechanical reinforcement and dimensional stability to the adsorbents. The adsorption was driven by (i) hydrophobic interactions between EE2 methylene and aromatic groups and HPMC methyl groups, as evidenced by FTIR spectroscopy, and (ii) H bonds between HPMC and EE2 hydroxyl groups, as revealed by the adsorption enthalpy change (ΔH_ads) of - 45 kJ/mol. Column adsorption experiments of EE2 from aqueous solution on HPMC and HPMC50BG indicated adsorptive capacity (q₀) values of 8.06 mg/g and 4.07 mg/g, respectively. These values decreased considerably for the adsorption of EE2 from river water, probably due to the competition of EE2 with humic substances dissolved in natural water. The HPMC adsorbents could be recycled retaining up to 83% of the original efficiency.