Characterization of potassium hydroxide modified anthracite particles and enhanced removal of 17α-ethinylestradiol and bisphenol A

The adsorption, kinetics, and interaction mechanisms of various types of estrogen on electrospun polymeric nanofiber membranes

This study focuses on the adsorption kinetics of four highly potent sex hormones (estrone (E1), 17β-estradiol (E2), 17α-ethinylestradiol (EE2), and estriol (E3)), present in water reservoirs, which are considered a major cause of fish feminization, low sperm count in males, breast and ovarian cancer in females induced by hormonal imbalance. Herein, electrospun polymeric nanostructures were produced from cellulose acetate, polyamide, polyethersulfone, polyurethanes (918 and elastollan), and polyacrylonitrile (PAN) to simultaneously adsorbing these estrogenic hormones in a single step process and to compare their performance. These nanofibers possessed an average fiber diameter in the range 174-330 nm and their specific surface area ranged between 10.2 and 20.9 m²g^-1. The adsorption-desorption process was investigated in four cycles to determine the effective reusability of the adsorption systems. A one-step high-performance liquid chromatography technique was developed to detect and quantify concurrently each hormone present in the solution. Experimental data were obtained to determine the adsorption kinetics by applying pseudo-first-order, pseudo-second-order and intraparticle diffusion models. Findings showed that E1, E2 and EE2 best fitted pseudo-second-order kinetics, while E3 followed pseudo-first-order kinetics. It was found that polyurethane Elastollan nanofibers had maximum adsorption capacities of 0.801, 0.590, 0.736 and 0.382 mg g^-1for E1, E2, EE2 and E3, respectively. In addition, the results revealed that polyurethane Elastollan nanofibers had the highest percentage efficiency of estrogens removal at ∼58.9% due to its strong hydrogen bonding with estrogenic hormones, while the least removal efficiency for PAN at ∼35.1%. Consecutive adsorption-desorption cycles demonstrated that polyurethane maintained the best efficiency, even after being repeatedly used four times compared to the other polymers. Overall, the findings indicate that all the studied nanostructures have the potential to be effective adsorbents for concurrently eradicating such estrogens from the environment.

Incredulity on assumptions for the simplified Bohart-Adams model: 17a-ethinylestradiol separation in lab-scale anthracite columns

In this study, the original Bohart-Adams model was employed to analyze the experimental data of 17α-ethinylestradiol (EE2) separation in lab-scale anthracite columns with low initial concentration. Besides, the assumptions for the simplified Bohart-Adams model were calculated and discussed. The results revealed that the breakthrough curves of EE2 separation in anthracite columns under different conditions were asymmetrical N-shaped and could be divided into three parts. The third part of the breakthrough curves was successfully fitted by the original Bohart-Adams model with high R² values (higher than 0.918) and low ARS values (less than 0.141). As expected, the assumptions for the simplified Bohart-Adams model were not tenable during the whole experiment process. As a result, the EE2 separation capacities (N₀° and N₀^s) obtained from the original and simplified Bohart-Adams model were quite different, and most N₀° values were greater than N₀^s values. The N₀° value used to evaluate the pollutant separation capacity in lab-scale column would be more accurate. In addition, physical interception and chemical adsorption simultaneously worked in the EE2 separation in anthracite columns. Physical interception and bed depth in anthracite columns at low flow rate were related in quadratic function (R² > 0.988).

Adsorption of 17β-estradiol onto humic-mineral complexes and effects of temperature, pH, and bisphenol A on the adsorption process

The long-term use of animal manure in agriculture has resulted in estrogen pollution, which poses risks to facility vegetable soils. Owing to the complex soil composition, estrogen may exhibit a variety of behaviors at the water/soil interface. This study demonstrated the role of humic acid (HA) on the 17β-estradiol (E2) adsorption by clay minerals (montmorillonite, kaolinite, and hematite). The interfacial behaviors were investigated using adsorption kinetics and isotherms data. Then, the effects of temperature, pH, and bisphenol A (BPA) on the interactions between humic-mineral complexes and E2 were explored. The adsorption of E2 is an exothermic and spontaneous process, and the addition of HA to minerals significantly promoted their E2 adsorption capacities. Higher pH levels (>10) and the presence of BPA decreased the adsorption capacities of minerals and mineral complexes for E2. Moreover, intercalation, hydrophobic partitioning, π-π interactions and hydrogen bonding could dominate the E2 adsorption onto complexes. These results provided insight into the interfacial behaviors of E2 on the surfaces of humic-mineral complexes and promoted the understanding of the migration and transport of estrogens in soils.

Adsorption characteristics of nitrite on natural filter medium: Kinetic, equilibrium, and site energy distribution studies

Nitrite is one of the world's major contaminants in drinking water resources, and granular anthracite is often used as filter medium in water treatment. In this study, the adsorption characteristics of nitrite on granular anthracite under various temperatures were investigated through adsorption kinetic, isotherm models, and site energy distribution theory. The adsorption of nitrite on granular anthracite was an endothermic reaction, while intraparticle diffusion was not the only rate control step. The adsorption could be well described by using pseudo-second-order and Langmuir-Freundlich equations. The adsorption capacity was 402.51 mg NO₂^--N kg^-1 at 298 K, which could be significantly improved to 1380.1 mg NO₂^--N kg^-1 when the temperature reached 308 K. Furthermore, nitrite ions first occupied the high-energy adsorption sites and then diffused to the low-energy adsorption sites on granular anthracite. There were more sites, including high-energy sites and low-energy sites, for nitrite adsorption at 308 K. Besides, the thickness of the boundary layer increased with the adsorption capacity improved at a higher temperature, and nitrite ions were adsorbed mainly through chemical mechanisms. Moreover, the neutral pH was helpful for the adsorption. The presence of co-existing ions could limit the adsorption and the effect followed the order of PO₄^3- > CO₃^2- > SO₄^2- > NO₃^- > Cl^-. The saturated anthracite could be effectively regenerated by 0.2 mol L^-1 HCl solution. Therefore, the granular anthracite used as filter medium also has a possible application as a nitrite scavenger at the same time.

Analysis of 17α-ethinylestradiol and bisphenol A adsorption on anthracite surfaces by site energy distribution

17α-Ethinylestradiol (EE2) and bisphenol A (BPA) are highly toxic and widely detected endocrine-disrupting compounds (EDCs) throughout the world in surface waters. Adsorption is an effective way to remove EE2 and BPA from water. However, it is difficult to clearly explain the mechanism of adsorption theoretically only through classic adsorption models. In order to insight into the adsorption of EE2 and BPA, site energy distribution (SED) theory was introduced to investigate the adsorption of EE2 and BPA on heterogeneous surfaces. EE2 and BPA were adsorbed on un-anthracite (unmodified anthracite) and 4K anthracite (4 mol L^-1 KOH-modified anthracite) in single- and bi-component systems under various temperatures and pHs. The results suggested that EE2 and BPA molecules first occupied the high-energy adsorption sites and then spread to low-energy adsorption sites. There were more high-energy sites on 4K anthracite, resulting in a higher adsorption capability for EE2 and BPA. Besides, increasing temperature and acidic environment were conducive to the EE2 and BPA adsorption. SED analyses indicated that, in neutral solutions, π-π electron donor-acceptor (EDA) interaction might be the primary mechanism for BPA adsorption, while ligand exchange, hydrogen bonds, and π-π EDA interaction might simultaneously work in the adsorption of EE2. It was possible that EE2 molecule was near perpendicular to surface, while BPA molecule was parallel to surface, resulting in the higher adsorption capacities of EE2. However, compared with EE2, BPA had outstanding competitive advantages in bi-component system because of the stronger π-π EDA interaction between BPA and anthracite.