Removal of 17β-Estradiol from water by adsorption onto montmorillonite-carbon hybrids derived from pyrolysis carbonization of carboxymethyl cellulose

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.

Preparation of coated MgFe layered double hydroxide nanoparticles on cement kiln dust and intercalated with sodium dodecyl sulfate as an intermediate layer for the adsorption of estrogen from water

Estrogenic hormones, found as micropollutants in water systems, give rise to grave concerns for human health and marine ecosystems, triggering a cascade of adverse effects. This research presents an innovative manufacturing approach using nanoscale layered double hydroxides of magnesium and iron, with sodium dodecyl sulfate surfactant, to create highly efficient sorbent cement kiln dust (CKD) based beads (CKD/MgFe-SDS-LDH-beads). These beads effectively remove estrone from water. Optimization of the preparation process considered factors like molar Mg/Fe ratio, CKD dosage, pH, and SDS dosage using Response Surface Methodology (RSM). The adsorption process was well-characterized by Langmuir isotherm and pseudo-second-order kinetic models, demonstrating a remarkable 6.491 mg/g sorption capacity. Results proved that the calcite was the main component of the CKD with miners of dolomite, and quartz. Adsorption capacity, surface charges, and the availability of vacant sites may be the main mechanisms responsible of removal process. Experimental tests confirmed the beads' potential for estrone removal, aligning with the Bohart-Adams and Thomas-BDST models. This study introduces a promising, eco-friendly solution for addressing water contamination challenges.

Sequestration of steroidal estrogen in aqueous samples using an adsorption mechanism: a systemic scientometric review

Steroidal estrogens (SEs) remain one of the notable endocrine disrupting chemicals (EDCs) that pose a significant threat to the aquatic environment in this era owing to their interference with the normal metabolic functions of the human body systems. They are currently identified as emerging contaminants of water sources. The sources of SEs are either natural or synthetic active ingredients in oral contraceptive and hormonal replacement therapy drugs and enter the environment primarily from excretes in the form of active free conjugate radicals, resulting in numerous effects on organisms in aquatic habitats and humans. The removal of SEs from water sources is of great importance because of their potential adverse effects on aquatic ecosystems and human health. Adsorption techniques have gained considerable attention as effective methods for the removal of these contaminants. A systemic review and bibliometric analysis of the application of adsorption for sequestration were carried out. Metadata for publications on SE removal utilizing adsorbents were obtained from the Web of Science (WoS) from January 1, 1990, to November 5, 2022 (107 documents) and Scopus databases from January 1, 1949, to November 5, 2022 (77 documents). In total, 137 documents (134 research and 4 review articles) were used to systematically map bibliometric indicators, such as the number of articles, most prolific countries, most productive scholars, and most cited articles, confirming this to be a growing research area. The use of different adsorbents, include activated carbon graphene-based materials, single and multi-walled carbon nanotubes, biochar, zeolite, and nanocomposites. The adsorption mechanism and factors affecting the removal efficiency, such as pH, temperature, initial concentration, contact time and adsorbent properties, were investigated in this review. This review discusses the advantages and limitations of different adsorbents, including their adsorption capacities, regenerative potential, and cost-effectiveness. Recent advances and innovations in adsorption technology, such as functionalized materials and hybrid systems, have also been highlighted. Overall, the bibliographic analysis provides a comprehensive overview of the adsorption technique for the removal of SEs from other sources, serving as a valuable resource for researchers and policymakers involved in the development of efficient and sustainable strategies to mitigate the effects of these emerging contaminants.

Recent advances in new generation nanocomposite materials for adsorption of pharmaceuticals from aqueous environment

With rapid increase in the human population, a large amount of wastewater is generated every year. The availability of fresh water is decreasing at an alarming rate due to rapid industrialization and agricultural development. Pharmaceutical drugs which are credited for improving standards of life worldwide have emerged as major water contaminants, raising global concern about their potential risk to human health and environment. The presence of pharmaceutical compounds is detected in surface water (sea, river, lakes, etc.), groundwater, effluents from municipal, hospitals, and wastewater treatment plants, and even in drinking water. Efficient removal of pharmaceutical pollutants still remains a challenging task. Many techniques, including photodegradation, photocatalysis, oxidation, reverse osmosis, biodegradation, nanofiltration, adsorption, etc., have been used for the remediation of wastewater. Adsorption of pharmaceutical compounds on nanoadsorbents, as a low-cost and feasible technology, has gained immense popularity for wastewater treatment over the last decade. Adsorption techniques can be integrated with wastewater treatment plants to achieve efficient removal on an industrial level. Herein, we review the literature on the remediation techniques used for the pharmaceutical waste treatment using carbon nanotubes, metal oxides, nanoclay, and new-generation MXenes via adsorption. These materials show excellent adsorptive properties owing to their high surface area, low cost, high porosity, easy functionalization, and high surface reactivity. The adsorption mechanism of the nanoadsorbents and their reusability as a factor of sustainability have also been included in the review. The factors affecting the adsorption, including pH, the concentration of adsorbate, ionic strength, and adsorbate dose, have also been discussed.

Carboxymethyl cellulose sodium gel: A modified material used to suppress coal dust pollution

To reduce the environmental pollution caused by coal dust, a new type of dust inhibitor with a wide application range, high efficiency, and production simplicity was synthesized by modifying sodium carboxymethylcellulose (CMC-Na) with acrylamide (AM). Through molecular dynamics simulations and experiments, the surfactant composition and concentration were optimized. The experimental results showed that the graft copolymer of CMC-Na and AM (CMC-Na-co-AM) had more pores on the microscopic surface and a unique fiber network structure, which greatly increased its contact area with coal dust. After 14 h of drying at 60 °C, coal samples that were sprayed with the dust suppression agent retained >50% of the water in the spray, which was 9 times greater than the water retention of coal samples sprayed with just water. Additionally, the ability of the dust suppression agent to resist wind erosion was 6 times that of water. The CMC-Na-co-AM dust suppression agent showed that it could effectively inhibit the spread of coal dust under strong winds, offering a solution to the problem of coal dust pollution in coal production and storage.

Biochar from fungiculture waste for adsorption of endocrine disruptors in water

The agricultural residues are ecofriendly alternatives for removing contaminants from water. In this way, a novel biochar from the spent mushroom substrate (SMS) was produced and assessed to remove endocrine disruptor from water in batch and fixed-bed method. SMS were dried, ground, and pyrolyzed. Pyrolysis was carried out in three different conditions at 250 and 450 °C, with a residence time of 1 h, and at 600 °C with a residence time of 20 min. The biochar was firstly tested in a pilot batch with 17α-ethinylestradiol (EE2) and progesterone. The residual concentrations of the endocrine disruptors were determined by HPLC. The biochar obtained at 600 °C showed the best removal efficiency results. Then, adsorption parameters (isotherm and kinetics), fixed bed tests and biochar characterization were carried out. The Langmuir model fits better to progesterone while the Freundlich model fits better to EE2. The Langmuir model isotherm indicated a maximum adsorption capacity of 232.64 mg progesterone/g biochar, and 138.98 mg EE2/g biochar. Images from scanning electrons microscopy showed that the 600 °C biochar presented higher porosity than others. In the fixed bed test the removal capacity was more than 80% for both endocrine disruptors. Thus, the biochar showed a good and viable option for removal of contaminants, such as hormones.

Fenton Degradation of Ofloxacin Using a Montmorillonite–Fe3O4 Composite

In this work, FeM composites consisting of montmorillonite and variable amounts of Fe3O4 were successfully synthesized via a facile co-precipitation process. They were characterized using X-ray photoelectron spectroscopy (XPS), a field emission scanning electron microscope (FESEM), energy-dispersive X-ray spectroscopy (EDX), a transmission electron microscope (TEM), N2 adsorption–desorption, and Fourier transform infrared spectroscopy (FTIR) techniques to explain the effect of Fe3O4 content on the physicochemical properties of the Fe3O4–montmorillonite (FeM) composites. The FeM composites were subsequently used as heterogeneous Fenton catalysts to activate green oxidant (H2O2) for the subsequent degradation of ofloxacin (OFL) antibiotic. The efficiency of the FeM composites was studied by varying various parameters of Fe3O4 loading on montmorillonite, catalyst dosage, initial solution pH, initial OFL concentration, different oxidants, H2O2 dosage, reaction temperature, inorganic salts, and solar irradiation. Under the conditions of 0.75 g/L FeM-10, 5 mL/L H2O2, and natural pH, almost 81% of 50 mg/L of OFL was degraded within 120 min in the dark, while total organic carbon (TOC) reduction was about 56%. Although FeM composites could be a promising heterogeneous catalyst for the activation of H2O2 to degrade organic pollutants, including OFL antibiotic, the FeM-10 composite shows a significant drop in efficiency after five cycles, which indicates that more studies to improve this weakness should be conducted.

Biochar based sorptive remediation of steroidal estrogen contaminated aqueous systems: A critical review

Remediation of steroidal estrogens from aqueous ecosystems is of prevailing concern due to their potential impact on organisms even at trace concentrations. Biochar (BC) is capable of estrogen removal due to its rich porosity and surface functionality. The presented review emphasizes on the adsorption mechanisms, isotherms, kinetics, ionic strength and the effect of matrix components associated with the removal of steroidal estrogens. The dominant sorption mechanisms reported for estrogen were π-π electron donor-acceptor interactions and hydrogen bonding. Natural organic matter and ionic species were seen to influence the hydrophobicity of the estrogen in multiple ways. Zinc activation and magnetization of the BC increased the surface area and surface functionalities leading to high adsorption capacities. The contribution by persistent free radicals and the arene network of BC have promoted the catalytic degradation of adsorbates via electron transfer mechanisms. The presence of surface functional groups and the redox activity of BC facilitates the bacterial degradation of estrogens. The sorptive removal of estrogens from aqueous systems has been minimally reviewed as a part of a collective evaluation of micropollutants. However, to the best of our knowledge, a critique focusing specifically and comprehensively on BC-based removal of steroidal estrogens does not exist. The presented review is a critical assessment of the existing literature on BC based steroidal estrogen adsorption and attempts to converge the scattered knowledge regarding its mechanistic interpretations. Sorption studies using natural water matrices containing residue level concentrations, and dynamic sorption experiments can be identified as future research directions.

Effects of heteroaggregation with metal oxides and clays on tetracycline adsorption by graphene oxide

Multiple nanoparticles (NPs) often coexist in water with contaminants, which inevitably affect the fate and transport of coexisted contaminants and other types of nanoparticles in actual water. This research was devoted to examine the adsorption of tetracycline (TC) on graphene oxide (GO) in the presence of different amounts of model engineered and natural NPs (m-NPs), including metal oxides (ZnO and Fe₂O₃), clays (kaolin and montmorillonite). The experimental results proved that the existence of m-NPs greatly enhanced the TC adsorption onto GO except for that at Fe₂O₃/GO = 10:1 and lengthened the adsorption equilibrium time. The enhanced adsorption amount of TC with increasing m-NPs/GO ratio was primarily due to the adsorption of TC onto m-NPs. In contrast, the slightly inhibitory effects by 10:1 Fe₂O₃/GO could be attributed to the blockage effect on GO surface by a small amount of Fe₂O₃. Compared with five m-NPs/adsorbents, m-NPs/GO had the greatest promoting efficiency on TC removal. Moreover, the heteroaggregation of GO with different m-NPs was studied in aqueous phase by microscopic, spectroscopic, and computational methods. Analysis showed that the electrostatic attraction between negatively charged GO and positively charged ZnO were likely to first heteroaggregate in binary systems of GO and ZnO, while GO were prone to homoaggregate owing to electrostatic repulsion with the same negatively charged montmorillonite (or kaolin). Besides, Fe₂O₃ tended to first homoaggregate and then heteroaggregate with GO. In summary, this report elucidated complex interactions between GO and m-NPs, which was crucial to fundamentally understand towards a predictive framework for describing the fate and migration of GO and m-NPs in actual water.

Adsorption kinetic models: Physical meanings, applications, and solving methods

Adsorption technology has been widely applied in water and wastewater treatment, due to its low cost and high efficiency. The adsorption kinetic models have been used to evaluate the performance of the adsorbent and to investigate the adsorption mass transfer mechanisms. However, the physical meanings and the solving methods of the kinetic models have not been well established. The proper interpretation of the physical meanings and the standard solving methods for the adsorption kinetic models are very important for the applications of the kinetic models. This paper mainly focused on the physical meanings, applications, as well as the solving methods of 16 adsorption kinetic models. Firstly, the mathematical derivations, physical meanings and applications of the adsorption reaction models, the empirical models, the diffusion models, and the models for adsorption onto active sites were analyzed and discussed in detail. Secondly, the model validity evaluation equations were summarized based on literature. Thirdly, a convenient user interface (UI) for solving the kinetic models was developed based on Excel software and provided in supplementary information, which is helpful for readers to simulate the adsorption kinetic process.

Synthesis a graphene-like magnetic biochar by potassium ferrate for 17β-estradiol removal: Effects of Al2O3 nanoparticles and microplastics

A graphene-like magnetic biochar (GLMB) was synthesized using lotus seedpod and potassium ferrate with simple step and applied for E2 adsorption. GLMB was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), Raman, X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and BET surface area. Several common (solution pH, ionic strength, humic acid and foreign ions) and new (Al₂O₃ nanoparticles and microplastics (MPs)) water experiment conditions were investigated. Characterization results demonstrated that the sample was fabricated successfully and it possessed some graphene-like properties and a large surface area (828.37 m²/g). Adsorption results revealed that the pseudo-second-order kinetics and Langmuir isotherm models could provide a better description for E2 uptake behavior. The E2 adsorption capacity could be influenced by solution pH, ionic strength and SO₄^2- ions, and the effect of humic acid and background electrolyte (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl^-, NO₃^-, PO₄^3-) could be neglected. The presences of Al₂O₃/MPs significantly decreased the time to reach adsorption equilibrium for E2 adsorption on GLMB, but had no obvious improvement or inhibiting effects on E2 removal when the adsorption reached equilibrium. The adsorption mechanism for E2 adsorption on GLMB was multiple, which involving π-π interactions, micropore filling effects, electrostatic interaction. The regeneration experiments showed that GLMB possessed a good regeneration performance. Based on the experimental results and comparative analysis with other adsorbents, GLMB was an economical, high-efficiency, green and recyclable adsorbent for E2 removal from aqueous solution.

Surface Functionalization of Montmorillonite with Chitosan and the Role of Surface Properties on Its Adsorptive Performance: A Comparative Study on Mycotoxins Adsorption

Understanding surface and interfacial information, which has a close relationship to the structures and properties of materials, helps guide the design of materials for specific applications. This study focuses on the surface functionalization of montmorillonite (Mt) with chitosan (CTS) and exploring the role of surface properties on its adsorptive performance. Two prototypical products, namely, 180-Htc@Mt and 250-Htc@Mt, were fabricated via the hydrothermal method at 180 and 250 °C, respectively. Field emission scanning electron microscopy revealed that hydrothermal carbon (Htc) derived from CTS anchored on the surface of Mt uniformly with a spherical morphology. The introduction of Htc endowed the surface of Mt with abundant hydroxy, amine, and amide groups; organic carbon; developed porosity; and hydrophobic interfacial property. Hydrothermal temperature has huge impacts on the surface system, and smaller particles (average size of 27 vs 53 nm) with deeper carbonization, higher content of carbonaceous and nitrogenous functional groups, more developed porosity (66.149 vs 39.434 m²/g of specific surface area, 0.115 vs 0.090 cm³/g of pore volume), and slightly decreased hydrophobicity can be readily achieved at a higher temperature. The incoming surface protonated amine and amide functional groups show an ion-dipolar interaction to polar aflatoxin B₁ (AFB₁), and the increased organic carbon content as well as interfacial hydrophobicity generate a hydrophobic interaction to weak polar zearalenone (ZER). Consequently, the surface functionalization affords Mt enhanced adsorption capacity for AFB₁, approximately two times compared with Mt, and superior adsorption ability for ZER (10 mg/g). The present work provides sufficient evidence of "surface directs application" of Mt, which encourages researchers to focus on studies of the surface science of clay minerals.

Function of agricultural waste montmorillonite-biochars for sorptive removal of 17β-estradiol

Agricultural wastes of cow manure and wheat straw were used to prepare montmorillonite (Mt)-biochars (CMt and WMt) for sorptive removal of 17β-estradiol (E2) from aqueous solution. The E2 adsorption performance of the two Mt-biochars was investigated using systematic adsorption kinetics and isotherms. The results exhibited that the maximum E2 adsorption amount of CMt was 41.02 mg/g, while it was 62.89 mg/g for WMt. Meanwhile, intraparticle diffusion model demonstrated that intraparticle diffusion was not the only rate-limiting step, both film diffusion and intraparticle diffusion were involved in the diffusion process. Higher pH levels (>10) decreased the adsorption capacities of Mt-biochars for E2. However, the ionic strength and the background electrolytes did not significantly affect adsorption process. Moreover, the two Mt-biochars both exhibited excellent regeneration and reusability. These results provided a potential solution to the recycling of agricultural wastes and the problem of estrogen contaminant.