Removal of selected endocrine-disrupting compounds using Al-based metal organic framework: Performance and mechanism of competitive adsorption

Hollow multi-shelled MOF derivative adsorbent for efficient magnetic solid-phase extraction of several typical endocrine disrupting compounds from water

Bisphenols and benzophenones are two typical kinds of endocrine-disrupting compounds (EDCs) that have been extensively detected in water environments, posing unanticipated risks to aquatic organisms and humans. It is urgent to develop efficient sample pretreatment methods for precise measurement of such EDCs. In this study, a magnetic and multi-shelled metal-organic framework derivative material has been prepared to extract and enrich trace bisphenols and benzophenones from water. Via a solvothermal reaction induced by sodium citrate followed by a carbonization treatment, a ZIF-67@ZIF-8 derived CoZn-magnetic hierarchical carbon (CoZn-MHC) material has been synthesized as a high-performance magnetic solid-phase extraction (MSPE) adsorbent. This adsorbent exhibited a good specific surface area (213.80 m2⋅g-1) and a saturation magnetization of 63.2 emu·g-1. After the optimization of several parameters (including adsorbent dosage, extraction time, pH, ionic strength, desorption solvent, and solvent volume), an efficient MSPE method for several EDCs (comprising bisphenols and benzophenones) was developed with a good linear range (R2 ≥ 0.990), a high sensitivity range (LODs: 0.793-5.37 ng⋅L-1), and good reusability (RSD ≤4.67 % in five consecutive tests). Furthermore, the material exhibited commendable resistance to matrix interference in natural water samples with the recovery rates of target compounds ranging from 74.8 % to 107 %. We envision that the preparation strategy of this functional metal-organic framework (MOF)-based adsorbent for EDCs may provide insights for relevant research in the future.

Removal of trivalent chromium ions in model contaminated groundwater using hexagonal boron nitride as an adsorbent

The feasibility of using hexagonal boron nitride (h-BN) to treat heavy metal Cr(III) from model contaminated groundwater was evaluated in this study by adsorption experiments and characterizations. To the best of our knowledge, this study is the first attempt to conduct the adsorption of Cr(III) by h-BN under various experimental conditions such as exposure time, ratio of adsorbates and adsorbents, solution pH, background ions with different ionic strength, and the presence of humic acids (HA) in model contaminated groundwater. The optimized h-BN showed excellent maximum adsorption capacity (i.e., 177 mg ∙ g-1) when the concentrations of Cr(III) and h-BN were 10 and 10 mg ∙ L-1, respectively. Subsequently, we confirmed there was a negligible change in the adsorption performance of Cr(III) by h-BN in the presence of co-ions (i.e., K and Mg) in concentrations in a range from 50 to 1000 mg ∙ L-1. Furthermore, the adsorption performance of Cr(III) gradually improved with HA concentrations from 2.5 to 25 mg ∙ L-1. Interestingly, the maximum adsorption performance of Cr(III) by both HA and h-BN increased until 500 mg ∙ g-1 in the presence of 25 mg ∙ L-1 HA. The adsorption mechanism was clarified by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Additionally, we successfully confirmed that h-BN could be reused until five cycles. On the basis of the adsorption performance results and characterizations, h-BN can be utilized as an efficient and practical adsorbent to treat Cr(III) in groundwater treatment.

A review on titanium oxide nanoparticles modified metal-organic frameworks for effective CO2 conversion and efficient wastewater remediation

Environmental pollution has been increasing since last decade due to increasing industrialisation and urbanisation. Various kinds ofenvironmental pollutants including carbon dioxide (CO2), dyes, pharmaceuticals, phenols, heavy metals along with many organic and inorganic species have been discovered in the various environmental compartments which possess harmful impacts tox human health, wildlife, and ecosystems. Thus, various efforts have been made through regulations, technological advancements, and public awareness campaigns to reduce the impact of the pollution. However, finding suitable alternatives to mitigate their impacts remained a challenge. Metal-organic frameworks (MOFs) are one of the advanced materials with unique features such as high porosity and stability which exhibit versatile applications in environmental remediation. Their composites with titanium oxide nanoparticles (TiO2) have been discovered to offer potential feature such as light harvesting capacity and catalytic activity. The composite integration and properties have been confirmed through characterization using surface area analysis, scanning electron/transmission electron microscopy, atomic force microscopy, fourier transformed infrared spectroscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, thermogravimetric analysis, and others. Thus, this work rigorously discussed potential applications of the MOF@TiO2 nanomaterials for the CO2 capture and effective utilization in methanol, ethanol, acetone, acetaldehyde, and other useful products that served as fuel to various industrial processes. Additionally, the work highlights the effective performance of the materials towards photocatalytic degradation of both organic and inorganic pollutants with indepth mechanistic insights. The article will offer significant contribution for the development of sustainable and efficient technologies for the environmental monitoring and pollution mitigation.

Engineered lignocellulosic based biochar to remove endocrine-disrupting chemicals: Assessment of binding mechanism

The safety and health of aquatic organisms and humans are threatened by the increasing presence of pollutants in the environment. Endocrine disrupting chemicals are common pollutants which affect the function of endocrine and causes adverse effects on human health. These chemicals can disrupt metabolic processes by interacting with hormone receptors upon consumptions by humans or aquatic species. Several studies have reported the presence of endocrine disrupting chemicals in waterbodies, food, air and soil. These chemicals are associated with increasing occurrence of obesity, metabolic disorders, reproductive abnormalities, autism, cancer, epigenetic variation and cardiovascular risk. Conventional treatment processes are expensive, not environment friendly and unable to achieve complete removal of these harmful chemicals. In recent years, biochar from different sources has gained a considerable interest due to their adsorption efficiency with porous structure and large surface areas. biochar derived from lignocellulosic biomass are widely used as sustainable catalysts in soil remediation, carbon sequestration, removal of organic and inorganic pollutants and wastewater treatment. This review conceptualizes the production techniques of biochar from lignocellulosic biomass and explores the functionalization and interaction of biochar with endocrine-disrupting chemicals. This review also identifies the further needs of research. Overall, the environmental and health risks of endocrine-disrupting chemicals can be dealt with by biochar produced from lignocellulosic biomass as a sustainable and prominent approach.

Adsorption of uranyl ion on hexagonal boron nitride for remediation of real U-contaminated soil and its interpretation using random forest

Acid leaching has been widely applied to treat contaminated soil, however, it contains several inorganic pollutants. The decommissioning of nuclear power plants introduces radioactive and soluble U(VI), a substance posing chemical toxicity to humans. Our investigation sought to ascertain the efficacy of hexagonal boron nitride (h-BN), an highly efficient adsorbent, in treating U(VI) in wastewater. The adsorption equilibrium of U(VI) by h-BN reached saturation within a mere 2 h. The adsorption of U(VI) by h-BN appears to be facilitated through electrostatic attraction, as evidenced by the observed impact of pH variations, acidic agents (i.e., HCl or H2SO4), and the presence of background ions on the adsorption performance. A reusability test demonstrated the successful completion of five cycles of adsorption/desorption, relying on the surface characteristics of h-BN as influenced by solution pH. Based on the experimental variables of initial U(VI) concentration, exposure time, temperature, pH, and the presence of background ions/organic matter, a feature importance analysis using random forest (RF) was carried out to evaluate the correlation between performances and conditions. To the best of our knowledge, this study is the first attempt to conduct the adsorption of U(VI) generated from real contaminated soil by h-BN, followed by interpretation of the correlation between performance and conditions using RF. Lastly, a. plausible adsorption mechanism between U(VI) and h-BN was explained based on the experimental results, characterizations, and a. comparison with previous adsorption studies on the removal of heavy metals by h-BN.

Adsorption of perfluoroalkyl substances on deep eutectic solvent-based amorphous metal-organic framework: Structure and mechanism

Perfluoroalkyl substances (PFASs) are a class of emerging organic pollutants characterized by high toxicity, environmental persistence, and widespread detection in water sources. The removal of PFASs from water is a matter of global concern, given their detrimental impact on both the environment and public health. Many commonly used PFAS adsorbents demonstrate limited adsorption capacities and/or slow adsorption kinetics. Therefore, there is an urgent need for the development of efficient adsorbents. For the first time, this work systematically investigated the performance of a deep eutectic solvent (DES)-based amorphous metal-organic framework (MOF) for the adsorption of PFASs with different carbon-chain lengths under the state of the mixture in aquatic environments. The adsorption mechanism was probed by a suite of adsorption kinetics studies, adsorption isotherm profiling, spectral characterization, and ab initio molecular dynamics (AIMD) simulations, revealing that PFAS adsorption is driven by synergistic capturing effects including acid/base coordination, CF-π (carbon-fluorine-π), hydrogen bonding, and hydrophobic interactions. Furthermore, the adsorption processes of short-chain and long-chain targets were found to involve different rate-controlling steps and interaction sites. Hydrophobic interactions facilitated the swift arrival of long-chain PFASs at the coordinatively interacting sites between carboxyl termini and Lewis acid Zr unsaturated sites, thanks to their lower reaction barriers. On the other hand, the adsorption of short-chain PFASs primarily relied on a Zr hydroxyl-based ligand exchange force, which would take place at Brønsted acid sites. The existence of massive structural disorder in amorphous UiO-66 led to the development of larger pores, thus improving the accessibility of abundant adsorption sites and facilitating adsorption and diffusion. The presence of multiple types of interactions and flexible structure in defect-rich amorphous UiO-66 significantly increased the exposure of functional groups to the adsorbates. Additionally, this material possessed outstanding regeneration efficiency and outperformed other MOF-based adsorbents with high affinity for targets. It enhances our understanding of the adsorption performances and mechanisms of amorphous materials toward PFASs, thereby paving the way for designing more efficient PFAS adsorbents.

Potential application of 2D nano-layered MXene in analysing and remediating endocrine disruptor compounds and heavy metals in water

With the advancement of technologies and growth of the economy, it is inevitable that more complex processes are deployed, producing more heterogeneous wastewater that comes from biomedical, biochemical and various biotechnological industries. While the conventional way of wastewater treatment could effectively reduce the chemical oxygen demand, pH and turbidity of wastewater, trace pollutants, specifically the endocrine disruptor compounds (EDCs) that exist in µg L-1 or ng L-1 have further hardened the detection and removal of these biochemical pollutants. Even in small amounts, EDC could interfere human's hormone, causing severe implications on human body. Hence, this review elucidates the recent insights regarding the effectiveness of an advanced 2D material based on titanium carbide (Ti3C2Tx), also known as MXene, in detecting and removing EDCs. MXene's highly tunable feature also allows its surface chemistry to be adjusted by adding chemicals with different functional groups to adsorb different kinds of EDCs for biochemical pollution mitigation. At the same time, the incorporation of MXene into sample matrices also further eases the analysis of trace pollutants down to ng L-1 levels, thereby making way for a more cleaner and comprehensive wastewater treatment. In that sense, this review also highlights the progress in synthesizing MXene from the conventional method to the more modern approaches, together with their respective key parameters. To further understand and attest to the efficacy of MXene, the limitations and current gaps of this potential agent are also accentuated, targeting to seek resolutions for a more sustainable application.

Nanoarchitectonics Design Strategy of Metal-Organic Framework and Bio-Metal-Organic Framework Composites for Advanced Wastewater Treatment through Adsorption

Freshwater depletion is an alarm for finding an eco-friendly solution to treat wastewater for drinking and domestic applications. Though several methods like chlorination, filtration, and coagulation-sedimentation are conventionally employed for water treatment, these methods need to be improved as they are not environmentally friendly, rely on chemicals, and are ineffective for all kinds of pollutants. These problems can be addressed by employing an alternative solution that is effective for efficient water treatment and favors commercial aspects. Metal organic frameworks (MOFs), an emerging porous material, possess high stability, pore size tunability, greater surface area, and active sites. These MOFs can be tailored; thus, they can be customized according to the target pollutant. Hence, MOFs can be employed as adsorbents that effectively target different pollutants. Bio-MOFs are a kind of MOFs that are incorporated with biomolecules, which also possess properties of MOFs and are used as a nontoxic adsorbent. In this review, we elaborate on the interaction between MOFs and target pollutants, the role of linkers in the adsorption of contaminants, tailoring strategy that can be employed on MOFs and Bio-MOFs to target specific pollutants, and we also highlight the effect of environmental matrices on adsorption of pollutants by MOFs.

Metal-Organic Framework-Based Composites for the Adsorption Removal of Per- and Polyfluoroalkyl Substances from Water

The increasing health risks posed by per- and polyfluoroalkyl substances (PFASs) in the environment highlight the importance of implementing effective removal techniques. Conventional wastewater treatment processes are inadequate for removing persistent organic pollutants. Recent studies have increasingly demonstrated that metal-organic frameworks (MOFs) are capable of removing PFASs from water through adsorption techniques. However, there is still constructive discussion on the potential of MOFs in adsorbing and removing PFASs for large-scale engineering applications. This review systematically investigates the use of MOFs as adsorbents for the removal of PFAS in water treatment. This primarily involved a comprehensive analysis of existing literature to understand the adsorption mechanisms of MOFs and to identify factors that enhance their efficiency in removing PFASs. We also explore the critical aspects of regeneration and stability of MOFs, assessing their reusability and long-term performance, which are essential for large-scale water treatment applications. Finally, our study highlights the challenges of removing PFASs using MOFs. Especially, the efficient removal of short-chain PFASs with hydrophilicity is a major challenge, while medium- to long-chain PFASs are frequently susceptible to being captured from water by MOFs through multiple synergistic effects. The ion-exchange force may be the key to solving this difficulty, but its susceptibility to ion interference in water needs to be addressed in practical applications. We hope that this review can provide valuable insights into the effective removal and adsorption mechanisms of PFASs as well as advance the sustainable utilization of MOFs in the field of water treatment, thereby presenting a novel perspective.

Fixed-bed adsorption studies of endocrine-disrupting compounds from water by using novel calcium-based metal-organic frameworks

The presence of emerging water pollutants such as endocrine-disrupting compounds (EDCs), including 17-ethynylestradiol (EE2), bisphenol A (BPA), and perfluorooctanoic acid (PFOA), in contaminated water sources poses significant environmental and health challenges. This study aims to address this issue by investigating the efficiency of novel calcium-based metal-organic frameworks, known as mixed-linker calcium-based metal-organic frameworks (Ca-MIX), in adsorbing these endocrine-disrupting compounds. This study analyzed the influence of influent concentration, bed height, and flow rate on pollutant removal, with bed height emerging as a crucial factor. From the breakthrough curves, it was determined that the column maximum adsorption capacities followed the order of 17-ethynylestradiol (101.52 μg/g; 40%) > bisphenol A (99.07 μg/g; 39%) > perfluorooctanoic acid (81.28 μg/g; 32%). Three models were used to predict the adsorption process, with the Yan model outperforming the other models. This suggests the potential of mixed-linker calcium-based metal-organic frameworks for removing endocrine-disrupting compounds from water, using the Yan model as an effective predictor. Overall, this study provides valuable insights for the development of effective water treatment methods using mixed-linker calcium-based metal-organic frameworks to remove endocrine-disrupting compounds from contaminated water sources.

Strategies to improve adsorption and photocatalytic performance of metal-organic frameworks (MOFs) for perfluoroalkyl and polyfluoroalkyl substances (PFASs) removal from water: A review

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) represent a category of persistent and hazardous organic pollutants extensively prevalent across aquatic environments. The combination of adsorption and photocatalytic degradation has been identified as an effective approach for removing trace amounts of PFASs from water. Among the various materials explored for this purpose, metal-organic frameworks (MOFs) have structural solid tunability, and suitable modification methods could endow them with rich adsorption capabilities and excellent photocatalytic performance, which has potential for applications involving the treatment of trace, multi-chain-length PFASs in water. The research within this realm is currently in its nascent phase, and a holistic knowledge of modification methods can provide a comprehensive framework for future studies. Therefore, this review intends to (1) summarize the mechanism underlying the adsorption and photocatalytic removal of PFASs by MOFs; (2) present various modification methods aimed at enhancing the adsorption and photocatalytic performance of MOFs in alignment with the goal mentioned above; (3) provide an outlook on the prospects of utilizing MOFs for PFASs removal based on current trends and data. Ultimately, the findings from these studies will contribute to advancing knowledge in this area and facilitate the development of effective strategies for addressing PFASs contamination in water systems.

An overview on human exposure, toxicity, solid-phase microextraction and adsorptive removal of perfluoroalkyl carboxylic acids (PFCAs) from water matrices

Perfluoroalkyl carboxylic acids (PFCAs) are sub-class of perfluoroalkyl substances commonly detected in water matrices. They are persistent in the environment, hence highly toxic to living organisms. Their occurrence at trace amount, complex nature and prone to matrix interference make their extraction and detection a challenge. This study consolidates current advancements in solid-phase extraction (SPE) techniques for the trace-level analysis of PFCAs from water matrices. The advantages of the methods in terms of ease of applications, low-cost, robustness, low solvents consumption, high pre-concentration factors, better extraction efficiency, good selectivity and recovery of the analytes have been emphasized. The article also demonstrated effectiveness of some porous materials for the adsorptive removal of the PFCAs from the water matrices. Mechanisms of the SPE/adsorption techniques have been discussed. The success and limitations of the processes have been elucidated.

Physico-chemical and biological remediation techniques for the elimination of endocrine-disrupting hazardous chemicals

Due to their widespread occurrence and detrimental effects on human health and the environment, endocrine-disrupting hazardous chemicals (EDHCs) have become a significant concern. Therefore, numerous physicochemical and biological remediation techniques have been developed to eliminate EDHCs from various environmental matrices. This review paper aims to provide a comprehensive overview of the state-of-the-art remediation techniques for eliminating EDHCs. The physicochemical methods include adsorption, membrane filtration, photocatalysis, and advanced oxidation processes. The biological methods include biodegradation, phytoremediation, and microbial fuel cells. Each technique's effectiveness, advantages, limitations, and factors affecting their performance are discussed. The review also highlights recent developments and future perspectives in EDHCs remediation. This review provides valuable insights into selecting and optimizing remediation techniques for EDHCs in different environmental matrices.

Remediation of perfluorooctanoic acid (PFOA) with nano ceramic clay: Synthesis, characterization, scale-up and regenerations

Perfluorooctanoic acid (PFOA) in the ecosystem, resulting from industrial effluent and water bodies, has attracted greater concern. An economical treatment is in demand to optimize the current issue. In this research work, Perfluorooctanoic Acid was treated from drinking water sources with nano-ceramic clay. The ceramic clay was synthesized and characterized with Fourier infrared transformation, scanning electron micrograph, transmission electron micrograph, x-ray diffraction, and thermal analysis. An adsorption process was performed in batch and continuous modes for the effective conditions for maximum removal. In batch mode 82 ± 12 nm ceramic clay particle size; 3.0 initial pH; 210 rpm agitation 1.2 mg/L PFOA concentration; 100 mg/L clay dosage; 27 °C temperature, and 20hrs experimental time shows maximum 99.15% adsorption. The experimental data is well fitted with kinetics, isotherms, and thermodynamics calculated data. In fixed bed, continuous column study 10 h treatment time, 10 cm of bed height, and 2 ml/min were adsorbed 99.99% of PFOA. The experimental data from the fixed bed adsorption equipment was correlated using a number of different mathematical models, including the Thomas, Adams-Bohart, Yoon-Nelson, and Clark models. Overall nano ceramic clay was found to potential adsorbent for Perfluorooctanoic acid removal.

An iron-based metal-organic framework as a novel dispersive solid-phase extraction sorbent for the efficient adsorption of tetrabromobisphenol A from environmental water samples

For environmental safety, it is important to establish a simple, rapid, and sensitive method for emerging pollutants. Here, a dispersive solid-phase extraction (d-SPE) method based on an iron-based metal-organic framework (Fe-MIL-88-NH₂) combined with high-performance liquid chromatography (HPLC) was developed for tetrabromobisphenol A (TBBPA) in water samples. Fe-MIL-88-NH₂ was synthesized using a solvothermal method and completely characterized. Fe-MIL-88-NH₂ had good water stability and gave a maximum adsorption capacity of 40.97 mg g^-1 for TBBPA. The adsorption of TBBPA on Fe-MIL-88-NH₂ followed Langmuir adsorption models and a pseudo-second-order kinetic model. The bromine ion and the hydroxyl group of TBBPA could form strong hydrogen bond interactions with the amino protons around the cavity of Fe-MIL-88-NH₂, which was in accord with the molecular simulation calculations. Furthermore, several important d-SPE parameters were optimized, such as the amount of materials, extraction time, pH, ionic strength, elution solvent type, and volume. The established method showed good linearity in the concentration range of 0.005-100 μg g^-1 (r² ≥ 0.9996). This method's limits of detection (LOD) and quantification (LOQ) were 0.001 μg g^-1 and 0.005 μg g^-1, respectively. The recoveries in spiked water samples ranged from 87.5% to 104.9%. The proposed method was applied successfully to detect TBBPA in environmental water samples.

A juxtaposed review on adsorptive removal of PFAS by metal-organic frameworks (MOFs) with carbon-based materials, ion exchange resins, and polymer adsorbents

The removal of poly- and perfluoroalkyl substances (PFAS) from the aquatic environment is a universal concern due to the adverse effects of these substances on both the environment and public health. Different adsorbents, including carbon-based materials, ion exchange resins, biomaterials, and polymers, have been used for the removal of short-chain (C < 6) and long-chain (C > 7) PFAS from water with varying performance. Metal-organic frameworks (MOFs), as a new generation of adsorbents, have also been recently used to remove PFAS from water. MOFs provide unique properties such as significantly enhanced surface area, structural tunability, and improved selectivity compared to conventional adsorbents. However, due to various types of MOFs, their complex chemistry and morphology, different PFAS compounds, lack of standard adsorption test, and different testing conditions, there are inconclusive and contradictory findings in the literature. Therefore, this review aims to provide critical analysis of the performance of different types of MOFs in the removal of long-chain (C > 7), short-chain (C < 6), and ultra-short-chain (C < 3) PFAS and comprehensively study the efficiency of MOFs for PFAS removal in comparison with other adsorbents. In addition, the adsorption mechanisms and kinetics of PFAS components on different MOFs, including Materials of Institute Lavoisier (MIL), Universiteit of Oslo (UiO), Zeolitic imidazolate frameworks (ZIFs), Hong Kong University of Science and Technology (HKUST), and other hybrid types of MOF were discussed. The study also discussed the effect of environmental factors such as pH and ionic strength on the adsorption of PFAS on MOFs. In addition to the adsorption process, the reusability and regeneration of MOFs in the PFAS removal process are discussed. Finally, challenges and future outlooks of the utility of MOFs for PFAS removal were discussed to inspire future critical research efforts in removing PFAS.

Competitive removal mechanism to simultaneously incarcerate bisphenol A, triclosan and 4-tert-octylphenol within beta-cyclodextrin crosslinked citric acid used for encapsulation in polypropylene membrane protected-micro-solid-phase extraction

Endocrine disrupting compounds (EDCs) are extensively found in the environment and severely impacting human health. In addressing this issue, the beta-cyclodextrin crosslinked citric acid (BCD-CA) had been previously employed in membrane-protected micro-solid phase extraction for sequestering EDCs from water medium; and the findings revealed that BCD-CA possessed a selectivity property. On that account, the potential of BCD-CA towards competitive adsorption of selected EDCs was investigated in terms of adsorption mechanism and selectivity property. Factors that affected the removal efficiencies such as sample pH, sorbent dosage, contact time and initial concentration were evaluated. The characterization results revealed that the carbon percentage of BCD-CA had increased by 2.04%, while the hydrogen percentage had reduced by 1.83%, signifying the successful crosslinking of BCD-CA. Besides, the amount of active BCD was calculated to be 3.2 × 10^-7 mol, while the amount of carboxyl group was 2.48 × 10^-5 mol per 4 mg of BCD-CA. Moreover, BCD-CA was stable in an aqueous medium with the zeta potential obtained at -36.5 mV and had a high-water retention capacity (∼150%). The competitive adsorption mechanism by BCD-CA with EDCs followed the pseudo-second-order kinetics and Freundlich isotherm, suggesting that the adsorption process was dominated by chemisorption on the heterogeneous surface of the adsorbent. Thermodynamic results revealed that adsorption of 4-tert-octylphenol had the most negative ΔG value, indicating most favorable to be adsorbed by BCD-CA as opposed to triclosan and bisphenol A, which was coherent with the apparent formation constant results. These unique properties manifested the practicality of BCD-CA as a selective adsorbent to detect and remove EDCs from the water medium.

Endocrine disrupting chemicals in the environment: Environmental sources, biological effects, remediation techniques, and perspective

Endocrine disrupting chemicals (EDCs) have been identified as emerging contaminants, which poses a great threat to human health and ecosystem. Pesticides, polycyclic aromatic hydrocarbons, dioxins, brominated flame retardants, steroid hormones and alkylphenols are representative of this type of contaminant, which are closely related to daily life. Unfortunately, many wastewater treatment plants (WWTPs) do not treat EDCs as targets in the normal treatment process, resulting in EDCs entering the environment. Few studies have systematically reviewed the related content of EDCs in terms of occurrence, harm and remediation. For this reason, in this article, the sources and exposure routes of common EDCs are systematically described. The existence of EDCs in the environment is mainly related to human activities (Wastewater discharges and industrial activities). The common hazards of these EDCs are clarified based on available toxicological data. At the same time, the mechanism and effect of some mainstream EDCs remediation technologies (such as adsorption, advanced oxidation, membrane bioreactor, constructed wetland, etc.) are separately mentioned. Moreover, our perspectives are provided for further research of EDCs.

Functional group modified 1D interpenetrated metal-organic frameworks on perfluorooctanoic acid adsorption: Experimental and theoretical calculation study

Functional groups modified metal-organic frameworks (MOFs) was synthesized via a pre-tailor method and served as an adsorbent for perfluorooctanoic acid (PFOA) removal. The material was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction and N₂ sorption-desorption. Monte Carlo simulation and molecular dynamics are derived to predict the possible molecular packing and adsorption mechanism. The Hirshfeld surface with reduced density gradient analysis demonstrates that PFOA is adsorbed on MOF-X mainly affected by van der Waals interactions and steric effects. Adsorption kinetics and isotherms were investigated on the basis of a static experiment. The pseudo-second-order kinetic model and Langmuir isotherm were fitted well to characterize adsorption process. Hereinto, amino-modified MOFs reached the highest adsorption efficiency and the maximum capacity was 185.6 mg/g. Combing the experimental data with theoretical simulation, results indicated that functional group modification is an effective approach to alter the crystal structure and then affect the adsorptive properties of MOFs.

Potential of biocompatible calcium-based metal-organic frameworks for the removal of endocrine-disrupting compounds in aqueous environments

Rapid urbanization, industrialization and population growth have accelerated the amount and variety of emerging contaminants being released into the aqueous environment, including endocrine-disrupting compounds (EDCs). The introduction of these compounds constitutes a threat to human health and the environment, even at trace levels. Hence, new water treatment technologies are urgently required to effectively remove EDCs from water. The currently available technologies used in water remediation processes are expensive and ineffective, and some produce harmful by-products. Calcium-based metal-organic frameworks (Ca-MOFs) are porous synthetic materials that can potentially be applied as adsorbents. These MOFs are hydrolytically stable, biocompatible and low-cost compared with conventional porous materials. The structure of Ca-MOFs is maintained even though calcium metal centers in the structure can easily coordinate with water. Ca-MOFs and their composite derivatives have the potential for use in water purification because these biocompatible adsorbents have been shown to selectively extract a significant quantity of contaminants. This review highlights the potential of Ca-MOFs to adsorb EDCs from aqueous environments and discusses adsorbent preparation methods, adsorption mechanisms, removal capacity, water stability and recyclability. This review will support future efforts in synthesizing new biocompatible MOFs as an environmental treatment technology that can effectively remove EDCs from water, thereby improving environmental and human health.

Endocrine disrupting chemicals (EDCs) in environmental matrices: Occurrence, fate, health impact, physio-chemical and bioremediation technology

Endocrine disrupting chemicals (EDCs) are an emerging category of toxicity that adversely impacts humans and the environment's well-being. Diseases like cancer, cardiovascular risk, behavioral disorders, autoimmune defects, and reproductive diseases are related to these endocrine disruptors. Because these chemicals exist in known sources such as pharmaceuticals and plasticizers, as well as non-point sources such as agricultural runoff and storm water infiltration, the interactive effects of EDCs are gaining attention. However, the efficiency of conventional treatment methods is not sufficient to fully remediate EDCs from aqueous environments as the occurrence of EDC bioremediation and biodegradation is detected in remediated drinking water. Incorporating modification into current remediation techniques has to overcome challenges such as high energy consumption and health risks resulting from conventional treatment. Hence, the use of advanced psychochemical and biological treatments such as carbon-based adsorption, membrane technology, nanostructured photocatalysts, microbial and enzyme technologies is crucial. Intensifying environmental and health concerns about these mixed contaminants are primarily due to the lack of laws about acute concentration limits of these EDCs in municipal wastewater, groundwater, surface water, and drinking water. This review article offers evidence of fragmentary available data for the source, fate, toxicity, ecological and human health impact, remediation techniques, and mechanisms during EDC removal, and supports the need for further data to address the risks associated with the presence of EDCs in the environment. The reviews also provide comprehensive data for biodegradation of EDCs by using microbes such as fungi, bacteria, yeast, filamentous fungi, and their extracellular enzymes.

A critical overview of MXenes adsorption behavior toward heavy metals

In recent years, tremendous interest has been generated in MXenes as a fast-growing and diversified family of two-dimensional (2D) materials with a wide range of potential uses. MXenes exhibit many unique structural and physicochemical properties that make them particularly attractive as adsorbents for removing heavy metals from aqueous media, including a large surface area, abundant surface terminations, electron-richness, and hydrophilic nature. In light of the adsorption capabilities of MXenes at the ever-increasing rate of expansion, this review investigates the recent computational predictions for the adsorption capabilities of MXenes and the effect of synthesis of different MXene on their remediation behavior toward heavy metals. The influence of MXene engineering strategies such as alkalization, acidification, and incorporation into organic and inorganic hosts on their surface properties and adsorption capacity is compared to provide critical insights for designing effective MXene adsorbents. Additionally, the review discusses MXenes' adsorption mechanisms, the effect of coexisting ions on MXenes' selectivity, the regeneration of exhausted MXenes, and provides an overview of MXenes' stability and biocompatibility to demonstrate their potentiality for wastewater remediation. Finally, the review identifies current flaws and offers recommendations for further research.

Nontraditional Aldol Condensation Performance of Highly Efficient and Reusable Cs+ Single Sites in β-Zeolite Channels

Aldol reactions (self- and cross-aldol condensations) for conjugated enone synthesis were efficiently performed on large-sized Cs⁺ single sites (1 wt %) confined in β-zeolite channels in toluene, which showed the highest level of catalytic aldol condensation activity among reported zeolite catalysts. In general, aldol condensation reactions for C-C bond synthesis can proceed by acids (e.g., H⁺), bases (e.g., OH^-), enolate species, and acidic or basic solid catalysts. However, the Cs⁺ single site/β sample without significant acid-base property showed unprecedented, efficient, and reusable catalysis for self-aldol and cross-aldol condensations. Intrinsically inactive Cs⁺ single sites due to the noble-gas electronic structure were transformed to active Cs⁺ single sites in β-zeolite channels. Cs⁺/β has many advantages such as broad substrate scope, eco-friendliness, high product selectivity and yield, and simple work-up procedure. Thus, the Cs⁺ single site/β provides an attractive and useful methodology for practical C-C bond synthesis. On the basis of the Cs⁺/β characterization by X-ray photoelectron spectroscopy (XPS), in situ X-ray absorption fine structure (XAFS) (X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS)), and temperature-programmed desorption (TPD), density functional theory (DFT) calculations of the self- and cross-aldol condensation reaction pathways involving the transition states on the Cs⁺ single site in β-zeolite channel revealed nontraditional concerted interligand bond rearrangement mechanisms.

Facile fabrication and characterization of kenaf core as natural biochar for the highly efficient removal of selected endocrine-disrupting compounds

This study aims to formulate and fabricate the optimum condition of modified kenaf core (MKC) for the removal of targeted endocrine-disrupting compounds in a batch adsorption system. Kenaf core was chemically modified using phosphoric acid as an activating agent, which involved the pyrolysis step. Results indicated a significant difference (p < 0.05) for unmodified and novel modified biochar, observed in characteristic performance analysis via ultimate analysis, Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR) spectrum, and Brunauer-Emmett-teller (BET) surface area. The removal percentage of 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) in individual and binary mixture systems was examined in order to ascertain the highest removal percentage for MKC application in an aqueous solution. The main and interaction effects of three prepared variables such as incorporate of impregnation concentration of an acid catalyst (0.1-1.0 M), particle size (45-1,000 µm), and dosage (1.0-20.0 g/L) were examined and statistically analyzed via design of experiment (DoE) through developed quadratic models. The removal efficiency of E2 and EE2 in an individual system leads to T₂KC > T₁KC > T₃KC, whereas that in the binary mixture system leads to T₂KC > T₁KC > T₃KC and T₁KC > T₂KC > T₃KC for E2 and EE2 adsorption, respectively, through hydrogen bonding and the π-π interaction mechanism. Thus, the findings revealed T₂KC at a moderate level of acid concentration (0.5 M H₃PO₄) to be a potential biochar, with an environmentally safe and sound profile for opposing emerging pollutant issues as well as for the attainment of sustainable development goals.

Systematic Study on the Removal of Per- and Polyfluoroalkyl Substances from Contaminated Groundwater Using Metal-Organic Frameworks

Harmful per- and polyfluoroalkyl substances (PFAS) are ubiquitously detected in aquatic environments, but their remediation remains challenging. Metal-organic frameworks (MOFs) have been recently identified as an advanced material class for the efficient removal of PFAS, but little is known about the fundamentals of the PFAS@MOF adsorption process. To address this knowledge gap, we evaluated the performance of 3 different MOFs for the removal of 8 PFAS classes from aqueous film-forming foam-impacted groundwater samples obtained from 11 U.S. Air Force installations. Due to their different pore sizes/shapes and the identity of metal node, MOFs NU-1000, UiO-66, and ZIF-8 were selected to investigate the role of MOF structures, PFAS properties, and water matrix on the PFAS@MOF adsorption process. We observed that PFAS@MOF adsorption is (i) dominated by electrostatic and acid-base interactions for anionic and non-ionic PFAS, respectively, (ii) preferred for long- over short-chain PFAS, (iii) strongly dependent on the nature of PFAS head group functionality, and (iv) compromised in the presence of ionic and neutral co-contaminants by competing for ion-exchange sites and PFAS binding. With this study, we elucidate the PFAS@MOF adsorption mechanism from complex water sources to guide the design of more efficient MOFs for the treatment of PFAS-contaminated water bodies.

The role of solvents and oxygen-containing functional groups on the adsorption of Bisphenol A on carbon nanotubes

The wide application of endocrine disruptors (EDs) has recently created great public concerns because of their toxicities. Previous studies have stated that the effect of oxygen-containing functional groups of carbon nanotubes (CNTs) for Bisphenol A (BPA) sorption, but no study has been quantified the exact contribution of the oxygen-containing functional groups. Moreover, the role of solvents on the adsorption of BPA should be considered. Considering the well properties of CNTs, graphitized (MG), carboxylated (MC) and hydroxylated (MH) multi-walled CNTs were selected as model adsorbents, BPA was used as model adsorbate. Solubility and single point adsorption coefficient (logK_d) of BPA were n-hexadecane > water > methanol, suggesting that hydrophobic interaction was the main mechanism for BPA sorption on CNTs. For different functional groups of CNTs, π-π interaction between MH and BPA may be stronger than that of MC, and thus the sorption of BPA on MH was higher than that of MC. Moreover, hydrogen bond resulted in the higher adsorption of BPA on MH when compared with MC. The oxygen-containing functional groups of CNTs played a key role for BPA sorption in methanol because the values of contribution were 20%-45% for -OH and were 5%-25% for -COOH. In n-hexadecane, other factors such as hydrophobic interactions should be considered because the contribution percentages of -OH were ca.15% and the values for -COOH were ca.10%. The results are expected to provide important information on the interaction of EDs and CNTs.

Enhanced removal of bisphenol A using pine-fruit shell-derived hydrochars: Adsorption mechanisms and reusability

We synthesized NaOH-activated hydrochars via hydrothermal carbonization (HTC) of Brazilian pine fruit shells at HTC residence times of 24, 48, and 72 h. The hydrochars were used as adsorbents to remove bisphenol A (BPA) from aqueous solutions. The surface area of the samples can reach up to 2220 m² g^-1, and the maximum adsorption of BPA onto the surfaces was achieved at a pH of 7.0 (708 mg g^-1). Adsorption occurred mainly via monolayer formation with a low retention time of the adsorbate (τ) on the surfaces, indicating that the BPA molecules reached the already occupied active sites and returned after undergoing heat exchange (τ > 0). Adsorption is an endothermic spontaneous process that results in a balance between entropic and enthalpic contributions. In such a reaction, ΔG°< 0, even with ΔH°> 0, the process occurs with an important increase in the entropy. The desorption was more efficient with ethanol and methanol than with HCl, NaOH, and NaCl owing to the dipole-dipole forces between the adsorbate and the alcohols. Additionally, the low desorption efficiency using acid, base, and salts can be attributed to competitive effects between the desorption agents and the active sites of the adsorbents.

Electrochemical adsorption of perfluorooctanoic acid on a novel reduced graphene oxide aerogel loaded with Cu nanoparticles and fluorine

Perfluorooctanoic acid (PFOA) is widely concerned because its serious toxicity to the environment and ecosystems. In order to effectively and conveniently remove PFOA from aqueous solutions, reduced graphene oxide aerogel modified by Cu nanoparticles and fluorine (Cu/F-rGA) was prepared by the microbubble template method as an electrode in electrosorption. The removal capacity of Cu/F-rGA electrode to PFOA was 489% and 45.9% higher at + 0.8 V than that of open circuit and unmodified electrode, respectively. These significant improvements can be attributed to the advantages of Cu/F-rGA in ligand exchange reaction and electrostatic attraction under voltage assistance. The regeneration of Cu/F-rGA electrode maintained 75.51% capacity after 10 times electrosorption-desorption by applying reverse voltage. These properties provided potential for the reuse and application of Cu/F-rGA electrode. The electrosorption isotherm and model results showed that PFOA tended to be parallel to the adsorption site at low temperature and perpendicular at high temperature. The number of PFOA molecules connected to each adsorption site was 0.72-1.76, and the number of adsorption layers of PFOA on the electrode was between 1.46 and 2.87. Findings from this study provide a green and effective strategy to remove PFOA from aqueous solutions with low energy consumption.

Endocrine-Disrupting Compounds: An Overview on Their Occurrence in the Aquatic Environment and Human Exposure

Endocrine-disrupting compounds (EDCs) as emerging contaminants have accumulated in the aquatic environment at concentration levels that have been determined to be significant to humans and animals. Several compounds belong to this family, from natural substances (hormones such as estrone, 17-estradiol, and estriol) to synthetic chemicals, especially pesticides, pharmaceuticals, and plastic-derived compounds (phthalates, bisphenol A). In this review, we discuss recent works regarding EDC occurrence in the aquatic compartment, strengths and limitations of current analytical methods used for their detection, treatment technologies for their removal from water, and the health issues that they can trigger in humans. Nowadays, many EDCs have been identified in significant amounts in different water matrices including drinking water, thus increasing the possibility of entering the food chain. Several studies correlate human exposure to high concentrations of EDCs with serious effects such as infertility, thyroid dysfunction, early puberty, endometriosis, diabetes, and obesity. Although our intention is not to explain all disorders related to EDCs exposure, this review aims to guide future research towards a deeper knowledge of EDCs’ contamination and accumulation in water, highlighting their toxicity and exposure risks to humans.

Effects of electrolytes and fractionated dissolved organic matter on selective adsorption of pharmaceuticals on terephthalic acid-based metal-organic frameworks

In this study, we investigated the synergetic effects of coexisting electrolytes and dissolved organic matter (DOM) on Carbamazepine (CBZ) and Ciprofloxacin (CIP) adsorption on the 1D flexible structure of MIL-53(Al) and 3D rigid structure of UiO-66(Zr). The effects of electrolytes on the adsorption of CBZ and CIP on 1D flexible framework of MIL-53(Al) were more significant than those observed from the 3D framework of UiO-66(Zr). The presence of sulfate, nitrate, and phosphate anions indicates high potential to promote the adsorption of CBZ and CIP onto MIL-53(Al) and UiO-66(Zr) because of the decrease of solubility and strengthening of electrostatic interactions by substitution of oxo-anions at the metal complex node via covalent bonding. The lower hydration energy of the potassium ion enhanced CBZ adsorption on MIL-53(Al), while the higher hydration energy of calcium and magnesium ions reduced the adsorption capacity of CBZ and CIP on MIL-53(Al) and UiO-66(Zr). CBZ interacted with fractionated humic acid better than CIP. High-density carboxylic and aromatic functional groups on humic acid ensured that only humic acid larger than 1KDa was adsorbed by MIL-53(Al). Tryptophan-like and humic acid-like DOM were both detected in real hospital effluent, and their effects on CIP and CBZ adsorption onto MIL-53(Al) were investigated. The presence of tryptophan did not affect CBZ adsorption on MIL-53(Al) (except when coexisting with calcium ions). Conversely, tryptophan interfered with CIP adsorption. The presence of humic acid lower than 1KDa promoted the adsorption of CBZ and CIP by increasing the breathing effect of MIL-53(Al)'s 1D flexible framework. The presence of humic acid with molecular size greater than 1KDa enhanced both CBZ and CIP adsorption via a multilayer adsorption mechanism.

Copper Nanoparticle Loading and F Doping of Graphene Aerogel Enhance Its Adsorption of Aqueous Perfluorooctanoic Acid

Perfluorooctanoic acid (PFOA) persists in the environment for a long time due to its stable physical and chemical properties, and it is harmful to the environment and biological system. In order to effectively remove PFOA from aqueous solution, Cu nanoparticles and fluorine-modified graphene aerogel (Cu/F-rGA) were fabricated by the microbubble template method. Compared with unmodified aerogels (rGA), the adsorption rate of PFOA on Cu/F-rGA was enhanced 2.68-fold. These significant improvements were assumed to benefit from the ligand exchange reaction and hydrophobic and F-F interactions. The regeneration of Cu/F-rGA maintained 73.26% with ethanol as the desorption solvent after 10 times adsorption-desorption. The fitting results of the statistical physics model showed that PFOA tended to be parallel to the adsorption site at low temperature and perpendicular at high temperature. The number of PFOA molecules connected to each adsorption site was 0.53 to 1.41, and the number of adsorption layers of PFOA on the Cu/F-rGA was between 1.63 and 2.51. Compared with the response surface methodology and artificial neural network, an adaptive neuro-fuzzy inference system had more accurate analysis and prediction results. These results provide an effective and alternative strategy to remove PFOA from aqueous solution with environment-friendly consumption.

Polymer-assisted modification of metal-organic framework MIL-96 (Al): influence of HPAM concentration on particle size, crystal morphology and removal of harmful environmental pollutant PFOA

A new synthesis method was developed to prepare an aluminum-based metal organic framework (MIL-96) with a larger particle size and different crystal habits. A low cost and water-soluble polymer, hydrolyzed polyacrylamide (HPAM), was added in varying quantities into the synthesis reaction to achieve >200% particle size enlargement with controlled crystal morphology. The modified adsorbent, MIL-96-RHPAM2, was systematically characterized by SEM, XRD, FTIR, BET and TGA-MS. Using activated carbon (AC) as a reference adsorbent, the effectiveness of MIL-96-RHPAM2 for perfluorooctanoic acid (PFOA) removal from water was examined. The study confirms stable morphology of hydrated MIL-96-RHPAM2 particles as well as a superior PFOA adsorption capacity (340 mg/g) despite its lower surface area, relative to standard MIL-96. MIL-96-RHPAM2 suffers from slow adsorption kinetics as the modification significantly blocks pore access. The strong adsorption of PFOA by MIL-96-RHPAM2 was associated with the formation of electrostatic bonds between the anionic carboxylate of PFOA and the amine functionality present in the HPAM backbone. Thus, the strongly held PFOA molecules in the pores of MIL-96-RHPAM2 were not easily desorbed even after eluted with a high ionic strength solvent (500 mM NaCl). Nevertheless, this simple HPAM addition strategy can still chart promising pathways to impart judicious control over adsorbent particle size and crystal shapes while the introduction of amine functionality onto the surface chemistry is simultaneously useful for enhanced PFOA removal from contaminated aqueous systems.

Magnetite doped metal–organic framework nanocomposites: an efficient adsorbent for removal of bisphenol-A pollutant

The removal of bisphenol-A (BPA) from the aqueous environment is a vital issue for public health due to its toxic effect.

A Critical Review on Metal-Organic Frameworks and Their Composites as Advanced Materials for Adsorption and Photocatalytic Degradation of Emerging Organic Pollutants from Wastewater

Water-borne emerging pollutants are among the greatest concern of our modern society. Many of these pollutants are categorized as endocrine disruptors due to their environmental toxicities. They are harmful to humans, aquatic animals, and plants, to the larger extent, destroying the ecosystem. Thus, effective environmental remediations of these pollutants became necessary. Among the various remediation techniques, adsorption and photocatalytic degradation have been single out as the most promising. This review is devoted to the compilations and analysis of the role of metal-organic frameworks (MOFs) and their composites as potential materials for such applications. Emerging organic pollutants, like dyes, herbicides, pesticides, pharmaceutical products, phenols, polycyclic aromatic hydrocarbons, and perfluorinated alkyl substances, have been extensively studied. Important parameters that affect these processes, such as surface area, bandgap, percentage removal, equilibrium time, adsorption capacity, and recyclability, are documented. Finally, we paint the current scenario and challenges that need to be addressed for MOFs and their composites to be exploited for commercial applications.

Novel Z-scheme Ag3PO4/Fe3O4-activated biochar photocatalyst with enhanced visible-light catalytic performance toward degradation of bisphenol A

A novel solid-state Z-scheme heterostructure, Ag₃PO₄/Fe₃O₄ co-doped bamboo-derived activated biochar (Ag-Fe@BAB), was synthesized as an efficient photocatalyst via a co-precipitation method. Ag-Fe@BAB was used as a magnetically recoverable photocatalyst to generate free radical species with peroxydisulfate (PDS) activation under visible-LED-light illumination. The successful synthesis of Ag-Fe@BAB was confirmed by various characterization techniques. Bisphenol A (BPA) was used as a model pollutant to evaluate the photocatalytic activities of the Vis/Ag-Fe@BAB/PDS system. To confirm the photocatalytic performance of the Vis/Ag-Fe@BAB/PDS system, the effects of significant operating parameters such as the contact time, concentration of oxidant, photocatalyst dosage, and solution pH on the degradation of BPA were evaluated. We confirmed that 95.6% BPA was degraded within 60 min in the Vis/Ag-Fe@BAB/PDS system under 1.0 g/L photocatalyst, pH 6.5, and 0.5 mM PDS. The degradation mechanism of BPA in the Vis/Ag-Fe@BAB/PDS system was mainly attributed to O₂^‾ owing to its photocatalytic performances in the presence of p-benzoquinone as a scavenger. Furthermore, the radical species produced in the Vis/Ag-Fe@BAB/PDS system were identified by electron spin resonance. Finally, we demonstrated the recyclability of the Ag-Fe@BAB photocatalyst through its excellent magnetic property.

Ultrasound-assisted Ti3C2Tx MXene adsorption of dyes: Removal performance and mechanism analyses via dynamic light scattering

Herein, ultrasonication (US)-assisted novel nanomaterial Ti₃C₂T_x MXene was utilized as a selective adsorbent for treatment of synthetic dyes in model wastewater. Two types of US frequencies, 28 and 580 kHz, were applied to disperse MXene to evaluate the feasibility of US-assisted MXene for wastewater treatment. The physico-chemical properties of MXene after US were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and zeta potential. According to FTIR and XPS, 28 kHz US-assisted MXene had a greater amount of oxygenated functional groups and dispersion compared to 580 kHz US-assisted and pristine MXene. Subsequently, US-assisted MXene was utilized as an adsorbent for the removal of positively charged methylene blue (MB) and negatively charged methyl orange. Both 28 and 580 kHz US-assisted MXene showed better adsorption performance for only MB compared to stirring-assisted MXene based on kinetics, isotherms, and several water chemistry factors including solution pH, temperature, ionic strength, and humic acid. Advantages of US-assisted MXene for water treatment are its fast kinetics at low dose and high selectivity for positively charged target compounds (i.e., MB). The main adsorption mechanism between MXene and MB was electrostatic interaction (attraction); however, physical properties (i.e., aggregation kinetics and hydrodynamic diameter), measured via dynamic light scattering, were also found to be critical factors in controlling the adsorption performance of the system. Lastly, US-assisted MXene exhibited a high regeneration property, based on 4th adsorption-desorption cycles.

In Situ Polymerization of Polypyrrole @ Aluminum Fumarate Metal-Organic Framework Hybrid Nanocomposites for the Application of Wastewater Treatment

Composite metal–organic frameworks combine large and accessible surface areas with low density and high stability. Herein, we present novel nanocomposites of polypyrrole/aluminum fumarate metal–organic framework (PPy/AlFu MOF), which were synthesized via in situ oxidative polymerization with the aim of MOF functionalization to enhance its thermal stability and increase the specific surface area so that these nanocomposites may be used as potential adsorbents. The synthesized nanocomposites were characterized by various techniques, such as powder X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy (FTIR). The successful functionalization of aluminum fumarate MOF was confirmed by FTIR, and the Brunauer–Emmett–Teller (BET) surface area of the PPy/MOF nanocomposite slightly increased from 795 to 809 m2/g. Thermogravimetric analysis data also show that the weight loss of the composite is up to 30% at temperatures up to 500 ℃. Remarkably, lead (50 ppm) sequestration using the composite was tested, and the atomic absorption spectrometry data demonstrate that PPy/MOF is a super-adsorbent for heavy metal ions. This work shows that the novel polymer–MOF composites are promising materials for the selective removal of lead from wastewater streams.

Insights to perfluorooctanoic acid adsorption micro-mechanism over Fe-based metal organic frameworks: Combining computational calculation with response surface methodology

Adsorption performance, interfacial interaction mechanism and contribution of pores concerning PFOA adsorption to Fe-based metal-organic frameworks (MOFs) including Fe-BTC, MIL-100-Fe and MIL-101-Fe are investigated using experiments and computational calculation at molecular level even electronic level. Fe-BTC (418 mg/g) with more Lewis acid sites demonstrates higher adsorption capacity of PFOA in comparison with MIL-100-Fe (349 mg/g) and MIL-101-Fe (370 mg/g). Adsorption isotherms and kinetics indicate presence of monolayer adsorption and chemisorption in adsorption process. The pH dependence of PFOA adsorption to Fe-based MOFs is statistically revealed by experiments and analysis of variance of response surface methodology (RSM). XPS spectra of MOF-PFOA corroborate that decreasing binding energy of Fe2p and increasing binding energy of F1s, suggesting the presence of Lewis acid/base complexing (LAB) and hydrophobic interaction in adsorption process. Differential charge demonstrates that Fe center and benzene of organic ligands are respectively electron acceptor and donor in adsorption process. Electronic level mechanism finds that LAB complexing dominates adsorption process due to highest overlap of electron cloud. Smaller pores such as triangle and pentagonal pores of Fe-based MOFs contribute to the load of PFOA, while larger hexagonal one enable PFOA to enter into cages, as revealed by computational calculation.

Metal-Organic Framework-Derived Strategy for Improving Catalytic Performance of a Chromia-Based Catalyst in the Chlorine/Fluorine Exchange Reactions for Unsaturated Fluorocarbons

Hydrofluoroolefins (HFOs) and cyclic hydrofluorocarbons (c-HFCs) have been the most favored alternatives of the ozone depletion substances; however, because of the poor performance of the present chlorine/fluorine (Cl/F) exchange catalysts, the development and production of HFOs and c-HFCs are hindered. Here, we first report a novel and facile route to fabricate high-performance Cl/F exchange catalysts via a metal-organic framework (MOF) carbonization method. The MOF-derived catalyst not only has high selectivity but also can significantly lower the reaction temperature. Moreover, benefiting from the stable structure and coke-inhibiting ability, the MOF-derived catalyst has a long service life compared with the traditional precipitation method. Furthermore, the nanoscopic MOF-derived catalyst can greatly reduce the Cr dosage, which would help to minimize the risk of Cr contamination.