Magnetic metal–organic framework composites for environmental monitoring and remediation

Well-defined Fe3O4@MIL-100(Fe) hollow nanoflower heterostructures for selective dection and monitoring of benzoylurea insecticides from food and water

Developing a platform for the selective detection and effective monitor of toxic contaminants is a major challenge to address organic contaminants contamination in environmental science. Here, for the first time, the thickness-controllable Fe3O4@MIL-100(Fe) heterogeneous materials with special hollow nanoflower (HFs) morphology had been synthesized. The morphology and shell thickness of the nano-petal could be tuned by changing the reaction time. The resultant Fe3O4@MIL-100(Fe) HFs exhibited the hollow nanoflower shapes and exposed abundant accessible active sites. The enrichment performance of Fe3O4@MIL-100(Fe) HFs was approximately 1.4-1.7 times that of spherical Fe3O4@MIL-100(Fe) composite for benzoylurea insecticides (BUs). Furthermore, the optimal sample achieved the wide linearity (0.05-500 ng mL-1) and low limits of detection, (0.003-0.01 ng mL-1) for BUs. The research provides a new strategy for highly sensitive detection and monitoring of harmful pollutant levels in the environment.

Recent advances in metal organic frameworks-based magnetic nanomaterials for waste water treatment

Magnetic nanoparticle-incorporated metal organic frameworks (MOF) are potential composites for various applications such as catalysis, water treatment, drug delivery, gas storage, chemical sensing, and heavy metal ion removal. MOFs exhibits high porosity and flexibility enabling guest species like heavy metal ions to diffuse into bulk structure. Additionally, shape and size of the pores contribute to selectivity of the guest materials. Incorporation of magnetic materials allows easy collection of adsorbent materials from solution system making the process simple and cost-effective. In view of the above advantages in the present review article, we are discussing recent advances of different magnetic material-incorporated MOF (Mg-MOF) composite for application in photocatalytic degradation of dyes and toxic chemicals, adsorption of organic compounds, adsorption of heavy metal ions, and adsorption of dyes. The review initially discusses on properties of Mg-MOF, different synthesis techniques such as mechanochemical, sonochemical (ultrasound) synthesis, slow evaporation and diffusion methods, solvo(hydro)-thermal and iono-thermal method, microwave-assisted method, microemulsion method post-synthetic modification template strategies and followed by application in waste water treatment.

Modulating Photoinduced Electron Transfer between Photosensitive MOF and Co(II) Proton Reduction Sites for Boosting Photocatalytic Hydrogen Production

Photocatalytic hydrogen production via water splitting is the subject of intense research. Photoinduced electron transfer (PET) between a photosensitizer (PS) and a proton reduction catalyst is a prerequisite step and crucial to affecting hydrogen production efficiency. Herein, three photoactive metal-organic framework (MOF) systems having two different PET processes where PS and Co(II) centers are either covalently bonded or coexisting to drive photocatalytic H2 production are built. Compared to these two intramolecular PET systems including CoII -Zn-PDTP prepared from the post-synthetic metalation toward uncoordinated pyridine N sites of Zn-PDTP and sole cobalt-based MOF Co-PDTP, the CoII (bpy)3 @Zn-PDTP system impregnated by molecular cocatalyst possessing intermolecular PET process achieves the highest H2 evolution rate of 116.8 mmol g-1 h-1 over a period of 10 h, about 7.5 and 9.3 times compared to CoII -Zn-PDTP and Co-PDTP in visible-light-driven H2 evolution, respectively. Further studies reveal that the enhanced photoactivity in CoII (bpy)3 @Zn-PDTP can be ascribed to the high charge-separation efficiency of Zn-PDTP and the synergistic intermolecular interaction between Zn-PDTP and cobalt complexes. The present work demonstrates that the rational design of PET process between MOFs and catalytic metal sites can be a viable strategy for the development of highly efficient photocatalysts with enhanced photocatalytic activities.

Uptake of Ethyl Xanthate to Metal Organic Frameworks

As the mining industry spreads to new areas in the arctic regions, the need for re-useable efficient methods for mine chemicals' recycling increases. Especially in the case of xanthates, which are used as collectors for many metals from ore. Xanthates are very toxic to aquatic life either directly or indirectly and cause potentially severe health problems to humans after long-term exposure. In the present work, potassium ethyl xanthate (KEX) was observed to coordinate into metal organic frameworks (MOFs). HKUST-1 and its post-synthetically modified forms were observed to behave most effectively of the studied MOFs at low concentrations of KEX. Differences in the uptake of KEX were detected regarding the synthesis method in the case of MIL-100(Fe) synthetized by solvothermal and mechanochemical methods. Other studied MOFs, UiO-66 and MIL-100(Al)/MIL-96(Al), were not observed to be effective in KEX uptake.

Constructing functional metal-organic frameworks by ligand design for environmental applications

Metal-organic frameworks (MOFs) with unique physical and chemical properties are composed of metal ions/clusters and organic ligands, including high porosity, large specific surface area, tunable structure and functionality, which have been widely used in chemical sensing, environmental remediation, and other fields. Organic ligands have a significant impact on the performance of MOFs. Selecting appropriate types, quantities and properties of ligands can well improve the overall performance of MOFs, which is one of the critical issues in the synthesis of MOFs. This article provides a comprehensive review of ligand design strategies for functional MOFs from the number of different types of organic ligands. Single-, dual- and multi-ligand design strategies are systematically presented. The latest advances of these functional MOFs in environmental applications, including pollutant sensing, pollutant separation, and pollutant degradation are further expounded. Furthermore, an outlook section of providing some insights on the future research problems and prospects of functional MOFs is highlighted with the purpose of conquering current restrictions by exploring more innovative approaches.

Overview on recent advances of magnetic metal-organic framework (MMOF) composites in removal of heavy metals from aqueous system

Developing a novel, simple, and cost-effective analytical technique with high enrichment capacity and selectivity is crucial for environmental monitoring and remediation. Metal-organic frameworks (MOFs) are porous coordination polymers that are self-assembly synthesized from organic linkers and inorganic metal ions/metal clusters. Magnetic metal-organic framework (MMOF) composites are promising candidate among the new-generation sorbent materials available for magnetic solid-phase extraction (MSPE) of environmental contaminants due to their superparamagnetism properties, high crystallinity, permanent porosity, ultrahigh specific surface area, adaptable pore shape/sizes, tunable functionality, designable framework topology, rapid and ultrahigh adsorption capacity, and reusability. In this review, we focus on recent scientific progress in the removal of heavy metal ions present in contaminated aquatic system by using MMOF composites. Different types of MMOFs, their synthetic approaches, and various properties that are harnessed for removal of heavy metal ions from contaminated water are discussed briefly. Adsorption mechanisms involved, adsorption capacity, and regeneration of the MMOF sorbents as well as recovery of heavy metal ions adsorbed that are reported in the last ten years have been discussed in this review. Moreover, particular prospects, challenges, and opportunities in future development of MMOFs towards their greener synthetic approaches for their practical industrial applications have critically been considered in this review.

MOF@biomass hybrids: Trends on advanced functional materials for adsorption

This contribution aims to demonstrate the scope of new hybrids between biomass and metal-organic frameworks (MOF@biomass) used in the adsorption process of pollutants. After a brief presentation of the use of the main series of MOFs as efficient adsorbents for different types of pollutants, the limitations of these structures related to particle size and hydrodynamic problems during their application are highlighted. Lignocellulosic biomasses are also recognized as an alternative adsorbent, mainly due to their high natural abundance and their low environmental impact during and after their application. The limited capacity of bioadsorbents becomes important in this research. Consequently, the largest amount of information existing in the last ten years on MOF-Biomass functionalization as a hybrid and improvement technology for adsorption processes is compiled, analyzed, compared and contrasted. So far, there is no evidence of works that exploit the concept of functionalization of adsorbents of different nature to give rise to new hybrid materials. Through this review it was found that the hybrids obtained show a higher adsorption capacity (Qe) compared to their precursors, due to the increase of organic functional groups provided by the biomass. Thus, for heavy metals, dyes, Arsenium anions and other organic and pharmaceutical compounds, there are increases in Qe of about 100 mg g^-1. The possibility of the new hybrid being studied for desorption and reuse processes is also raised, resulting in a new line of research that is attractive for the industry from an economic and environmental point of view. The functionalization methods and techniques used in the studies cited in this article are outlined. In conclusion, this research brings a new horizon of study in the field of adsorption and mentions the main future challenges related to new sustainable applications.

Hexagonal boron nitride nanosheets based magnetic solid phase extraction for the extraction of phenoxy carboxylic acid herbicides from water samples followed by high-performance liquid chromatography-tandem mass spectrometry

High-efficiency caption of pesticide residue is of vital significance for environmental safety monitoring. Herein, a hexagonal boron nitride nanosheets-based magnetic composite (Fe₃O₄@h-BNNSs) was synthesized and applied for the magnetic solid phase extraction (MSPE) of five phenoxy carboxylic acid (PCA) herbicides from water samples. Based on the π-π interaction, hydrogen bond and halogen bond, the Fe₃O₄@h-BNNSs composite showed excellent adsorption ability towards PCA herbicides. Several main variables that influenced the extraction efficiencies of PCA herbicides were investigated and optimized via single-factor experiment. Combining this Fe₃O₄@h-BNNSs composite-based MSPE with high-performance liquid chromatography-tandem mass spectrometry, a novel sensitive method for the analysis of PCA herbicides was developed. Under the most favorable conditions, the proposed method displayed good linear ranges (20.0-10000.0 ng L^-1), low limits of detection (5.6-10.3 ng L^-1), satisfactory precisions (1.1-6.8%) and recoveries (76.6-107.2%). Overall, the present work can be a versatile and worthy utility for the determination of PCA herbicides from different water samples.

Synthesis, Properties and Photocatalytic Activity of CaTiO3-Based Ceramics Doped with Lanthanum

The aim of this work is to study the effect of lanthanum doping on the phase formation processes in ceramics based on CaTiO3, as well as to evaluate the effectiveness of the ceramics as photocatalysts for the decomposition of the organic dye Rhodamine B. The methods used were scanning electron microscopy to evaluate the morphological features of the synthesized ceramics, X-ray diffraction to determine the phase composition and structural parameters, and UV-Vis spectroscopy to determine the optical properties of the ceramics. During the experiments it was found that an increase in the lanthanum dopant concentration from 0.05 to 0.25 mol leads to the formation of the orthorhombic phase La0.3Ca0.7TiO3 and the displacement from the ceramic structure of the impurity phase TiO2, which presence is typical for the synthesized ceramics by solid-phase synthesis. On the basis of the data of the X-ray phase analysis the dynamics of phase transformations depending on concentration of lanthanum was established: CaTiO3/TiO2 → CaTiO3/La2TiO5 → CaTiO3/La0.3Ca0.7TiO3 → La0.3Ca0.7TiO3. During the determination of photocatalytic activity it was found that the formation of La0.3Ca0.7TiO3 phase leads to an increase in the decomposition rate as well as the degree of mineralization.

Magnetic Solid-Phase Extraction of Carbamate Pesticides Using Magnetic Metal-Organic Frameworks Derived from Benzoate Ligands, Followed by Digital Image Colorimetric Screening and High-Performance Liquid Chromatography Analysis

Magnetic sorbents based on iron-aluminum-mixed metal hydroxides composited with metal-organic frameworks (MOFs) were designed and synthesized using different benzoate ligands, including terephthalic acid, 2-aminoterephthalic acid, 2,5-dihydroxyterephthalic acid, 1,3,5-benzenetricarboxylic acid, and 1,2,4,5-benzenetetracarboxylic acid. The magnetic MOF derived from terephthalic acid ligand exhibited an excellent extraction efficiency, with adsorption capacities in the range of 2193-4196 mg kg^-1, and was applied for magnetic solid-phase extraction (MSPE) of carbamate pesticides, that is, bendiocarb, carbosulfan, carbofuran, carbaryl, propoxur, isoprocarb, and promecarb. Simple digital image colorimetry based on the diazotization reaction and high-performance liquid chromatography (HPLC) were utilized for fast screening and quantification purposes, respectively. A good analytical performance for a simple screening approach using portable equipment was obtained with detection limits in the range of 1.0-18.0 μg L^-1. Under the optimized MSPE-HPLC conditions, the entire developed procedure provided a wide linear range between 0.015 and 1000 μg L^-1, low limits of detection, and limits of quantitation ranging from 0.005 to 0.090 and 0.015-0.300 μg L^-1, respectively. Enrichment factors up to 184 were achieved. The intra- and interday relative standard deviations were below 6.7 and 9.4%, respectively. The proposed MSPE-digital image colorimetry and MSPE-HPLC methods were successfully applied for screening and determining carbamate pesticides in fruits and vegetables. The recoveries were obtained in a satisfactory range of 71.5-122.8%. This discovery has led to the development of integration methods using newly synthesized sorbent materials for the enrichment of carbamate pesticides prior to their analysis in complicated samples. The developed MSPE coupled with digital image colorimetry was efficient for fast carbamate contamination screening, while MSPE-HPLC offered a sensitive analytical methodology for quantifying contaminated samples.

Magnetic UiO-66 functionalized with 4,4'-diamino-2,2'-stilbenedisulfonic as a highly recoverable acid catalyst for the synthesis of 4H-chromenes in green solvent

According to 4H-chromenes importance, we synthesized a novel magnetic UiO-66 functionalized with 4,4′-diamino-2,2′-stilbenedisulfonic as an efficient and reusable solid acid catalyst for synthesizing 4H-chromene skeletons via a one-pot three components reaction in a green solvent. The structure of the synthesized catalyst was confirmed by various techniques including FT-IR, XRD, BET, TGA, TEM, EDX, and SEM, and also the product yields were obtained in 83–96% of yields for all the reactions and under mild conditions. The reported procedure presents an environmentally friendly approach for synthesizing a significant number of 4H-chromene derivatives. Correspondingly, MOF-based catalyst makes it easy to separate from reaction media and reuse in the next runs.

Design of an antenna effect Eu(III)-based metal-organic framework for highly selective sensing of Fe3

Highly selective sensing of Fe³⁺ is very important due to its great effect on biological systems. A novel ligand [1,1':4',1'':4'',1''':4''',1''''-quinquephenyl]-2,2'',2'''',5''-tetracarboxylic acid (H₄qptca) was designed and successfully obtained for the first time via three steps in high total yields according to the absorption spectrum of Fe³⁺. The europium(III)-based metal-organic framework derived from H₄qptca, {[Eu(qptca)_1/2(H₂qptca)_1/2(H₂O)₂]·DMF}_n (referred to as SLX-1), was then synthesized and used as a water-stable and highly selective luminescent sensor for Fe³⁺ in aqueous solution with a comparable detection limit using Ln-MOF probes (6.45 μM) through the antenna effect of SLX-1. Furthermore, the luminescence quenching mechanism was also proposed as a competitive absorption mechanism.

A Comprehensive Review on the Use of Metal–Organic Frameworks (MOFs) Coupled with Enzymes as Biosensors

Several studies have shown the development of electrochemical biosensors based on enzymes immobilized in metal–organic frameworks (MOFs). Although enzymes have unique properties, such as efficiency, selectivity, and environmental sustainability, when immobilized, these properties are improved, presenting significant potential for several biotechnological applications. Using MOFs as matrices for enzyme immobilization has been considered a promising strategy due to their many advantages compared to other supporting materials, such as larger surface areas, higher porosity rates, and better stability. Biosensors are analytical tools that use a bioactive element and a transducer for the detection/quantification of biochemical substances in the most varied applications and areas, in particular, food, agriculture, pharmaceutical, and medical. This review will present novel insights on the construction of biosensors with materials based on MOFs. Herein, we have been highlighted the use of MOF for biosensing for biomedical, food safety, and environmental monitoring areas. Additionally, different methods by which immobilizations are performed in MOFs and their main advantages and disadvantages are presented.

Magnetic Adsorbents for Wastewater Treatment: Advancements in Their Synthesis Methods

The remediation of water streams, polluted by various substances, is important for realizing a sustainable future. Magnetic adsorbents are promising materials for wastewater treatment. Although numerous techniques have been developed for the preparation of magnetic adsorbents, with effective adsorption performance, reviews that focus on the synthesis methods of magnetic adsorbents for wastewater treatment and their material structures have not been reported. In this review, advancements in the synthesis methods of magnetic adsorbents for the removal of substances from water streams has been comprehensively summarized and discussed. Generally, the synthesis methods are categorized into five groups, as follows: direct use of magnetic particles as adsorbents, attachment of pre-prepared adsorbents and pre-prepared magnetic particles, synthesis of magnetic particles on pre-prepared adsorbents, synthesis of adsorbents on preprepared magnetic particles, and co-synthesis of adsorbents and magnetic particles. The main improvements in the advanced methods involved making the conventional synthesis a less energy intensive, more efficient, and simpler process, while maintaining or increasing the adsorption performance. The key challenges, such as the enhancement of the adsorption performance of materials and the design of sophisticated material structures, are discussed as well.

Multi-functional metal-organic frameworks for detection and removal of water pollutions

Water pollutions have caused serious threats to the aquatic environment and human health, it is of great significance to monitor and control their contents in water. Compared with the traditional...

Dye contaminated wastewater treatment through metal–organic framework (MOF) based materials

A complete discussion of MOFs and MOF composites such as MOF-based membranes, magnetic MOFs, and metal–organic gels (MOGs) used for dye removal along with their adsorption efficiency has been done.

From a Well-Defined Organozinc Precursor to Diverse Luminescent Coordination Polymers Based on Zn(II)-Quinolinate Building Units Interconnected by Mixed Ligand Systems

Introduction of photoactive building blocks into mixed-ligand coordination polymers appears to be a promising way to produce new advanced luminescent materials. However, rational design and self-assembly of the multi-component supramolecular systems is challenging from both a conceptual and synthetic perspective. Here, we report exploratory studies that investigate the potential of [Zn(q)₂]₂[tBuZn(OH)]₂ complex (q = deprotonated 8-hydroxyquinoline) as an organozinc precursor as well as a mixed-ligand synthetic strategy for the preparation of new luminescent coordination polymers (CPs). As a result we present three new 2D mixed-ligand Zn(II)-quinolinate coordination polymers which are based on various zinc quinolinate secondary building units interconnected by two different organic linker types, i.e., deprotonated 4,4'-oxybisbenzoic acid (H₂obc) as a flexible dicarboxylate linker and/or selected bipyridines (bipy). Remarkably, using the title organozinc precursors in a combination with H₂obc and 4,4'-bipyridine, a novel molecular zinc quinolinate building unit, [Zn₄(q)₆(bipy)₂(obc)₂], was obtained which self-assembled into a chain-type hydrogen-bonded network. The application of the organometallic precursor allowed for its direct reaction with the selected ligands at ambient temperature, avoiding the use of both solvothermal conditions and additional base reagents. In turn, the reaction involving Zn(NO₃)₂, as a classical inorganic precursor, in a combination with H₂obc and bipy led to a novel 1D coordination polymer [Zn₂(q)₂(NO₃)₂(bipy)]. While the presence of H₂obc was essential for the formation of this coordination polymer, this ditopic linker was not incorporated into the isolated product, which indicates its templating behavior. The reported compounds were characterized by single-crystal and powder X-ray diffraction, elemental analysis as well as UV-Vis and photoluminescence spectroscopy.

Iron-based metal-organic framework: Synthesis, structure and current technologies for water reclamation with deep insight into framework integrity

Water is a supreme requirement for the existence of life, the contamination from the point and non-point sources are creating a great threat to the water ecosystem. Advance tools and techniques are required to restore the water quality and metal-organic framework (MOFs) with a tunable porous structure, striking physical and chemical properties are an excellent candidate for it. Fe-based MOFs, which developed rapidly in recent years, are foreseen as most promising to overcome the disadvantages of traditional water depolluting practices. Fe-MOFs with low toxicity and preferable stability possess excellent performance potential for almost all water remedying techniques in contrast to other MOF structures, especially visible light photocatalysis, Fenton, and Fenton-like heterogeneous catalysis. Fe-MOFs become essential tool for water treatment due to their high catalytic activity, abundant active site and pollutant-specific adsorption. However, the structural degradation under external chemical, photolytic, mechanical, and thermal stimuli is impeding Fe-MOFs from further improvement in activity and their commercialization. Understanding the shortcomings of structural integrity is crucial for large-scale synthesis and commercial implementation of Fe-MOFs-based water treatment techniques. Herein we summarize the synthesis, structure and recent advancements in water remediation methods using Fe-MOFs in particular more attention is paid for adsorption, heterogeneous catalysis and photocatalysis with clear insight into the mechanisms involved. For ease of analysis, the pollutants have been classified into two major classes; inorganic pollutants and organic pollutants. In this review, we present for the first time a detailed insight into the challenges in employing Fe-MOFs for water remediation due to structural instability.

Adsorptive removal of dyes from wastewater using a metal-organic framework: A review

Water pollution from synthetic dyes is a growing environmental concern because many dyes have carcinogenic effects on humans and aquatic life. Adsorption is a widely used technology for the separation and removal of dyes from wastewater. However, the dye removal process using conventional adsorbents is not sufficiently efficient for industrial wastewater. Metal-organic frameworks (MOFs) addresses these drawbacks. MOF showed excellent dye removal and degradation capacity owing to its multifunctionality, water-stability, large surface area, tunable pore size and recyclability. Magnetic MOFs retained excellent performance up to several consecutive cycles. Modified MOFs performed as Fenton-like catalysis process which generated abundant reactive radicals that degraded complex organic dyes into simple and less toxic forms which were further adsorbed onto the MOF. This review systematically compiles in-depth studies on the adsorptive removal of dyes from wastewater, MOF adsorption mechanisms, major influencing factors, to adsorption efficiency of MOFs. While all MOFs adsorb dyes through electrostatic attraction, the type of MOF, presence of functional groups, ligands, and pH significantly control the adsorption mechanism. Before developing an MOF, optimization and upgradation of factors and interaction between available adsorption site and adsorbate is needed. Finally, the prospects and new frontiers of MOFs in sustainable water treatment is discussed.

Molecularly imprinted photoelectrochemical sensor for detecting tetrabromobisphenol A in indoor dust and water

The gradual emissions of tetrabromobisphenol A (TBBPA) from the primitive recycling of E-waste create human health threats, which urgently require to develop an efficient, rapid yet simple detection method. The present study conducts a highly sensitive molecularly imprinted photoelectrochemical sensor (MIPES) containing molecularly imprinted (MI)-TiO₂, Au, and reduced graphene oxide for the trace detection of TBBPA in indoor dust and surface water from an E-waste recycling area. The photocurrent response is used to evaluate the sensing performance of the MIPES toward TBBPA detection. The working potential for amperometry is 0.48 V. The wavelength range for photoelectrochemical detection is 320-780 nm. The sensor shows a detection range of 1.68 to 100 nM with a low limit of detection of 0.51 nM (LOD = 3 s_b/S) and a limit of quantification of 1.68 nM (LOQ = 3.3 LOD). In addition, the MIPES sensor exhibits rapid, excellent reproducibility, selectivity, and long-term stability toward TBBPA detection. The relative standard deviation of three measurements for real samples is less than 7.0%, and the recovery range is 90.0-115%. The surface of molecular imprinting contributes to the high charge separation and sensing photocurrent response of TBBPA, which is confirmed by single-particle photoluminescence spectroscopy. The present study provides a new facile sensor with highly sensitive yet rapid response to detect environmental pollutants in E-waste by using the MIPES.

Sawdust, a versatile, inexpensive, readily available bio-waste: From mother earth to valuable materials for sustainable remediation technologies

Sawdust or wood shaving is a relatively abundant and inexpensive lignocellulosic compound, which is provided by mother nature. It is a waste of industry and agriculture, that is found in large quantities and has disposal problems. Nowadays, waste management (like sawdust) and research on converting it to different compounds for special applications and goals have been receiving tremendous attention. So, introducing sawdust as a kind of interesting bio-waste and turn it into wealth for diverse utilizations can be mentioned as the main goal of this overview. In this regard, in the first part, sawdust structure and properties are considered. It is then followed by highlighting its wide applications in sustainable water remediation technology, production of activated carbon, oil-water separation, and high-performance composites fabrication. Please come on to start a journey on this motivating topic.

Metal-Organic-Framework Based Functional Materials for Uranium Recovery: Performance Optimization and Structure/Functionality-Activity Relationships

Uranium recovery has profound significance in both uranium resource acquisition and pollution treatment. In recent years, metal-organic frameworks (MOFs) have attracted much attention as potential uranium adsorbents owing to their tunable structural topology and designable functionalities. This review explores the research progress in representative classic MOFs (MIL-101, UiO-66, ZIF-8/ZIF-67) and other advanced MOF-based materials for efficient uranium extraction in aqueous or seawater environments. The uranium uptake mechanism of the MOF-based materials is refined, and the structure/functionality-property relationship is further systematically elucidated. By summarizing the typical functionalization and structure design methods, the performance improvement strategies for MOF-based adsorbents are emphasized. Finally, the present challenges and potential opportunities are proposed for the breakthrough of high-performance MOF-based materials in uranium extraction.

Recent Advances of Nanoremediation Technologies for Soil and Groundwater Remediation: A Review

Nanotechnology has been widely used in many fields including in soil and groundwater remediation. Nanoremediation has emerged as an effective, rapid, and efficient technology for soil and groundwater contaminated with petroleum pollutants and heavy metals. This review provides an overview of the application of nanomaterials for environmental cleanup, such as soil and groundwater remediation. Four types of nanomaterials, namely nanoscale zero-valent iron (nZVI), carbon nanotubes (CNTs), and metallic and magnetic nanoparticles (MNPs), are presented and discussed. In addition, the potential environmental risks of the nanomaterial application in soil remediation are highlighted. Moreover, this review provides insight into the combination of nanoremediation with other remediation technologies. The study demonstrates that nZVI had been widely studied for high-efficiency environmental remediation due to its high reactivity and excellent contaminant immobilization capability. CNTs have received more attention for remediation of organic and inorganic contaminants because of their unique adsorption characteristics. Environmental remediations using metal and MNPs are also favorable due to their facile magnetic separation and unique metal-ion adsorption. The modified nZVI showed less toxicity towards soil bacteria than bare nZVI; thus, modifying or coating nZVI could reduce its ecotoxicity. The combination of nanoremediation with other remediation technology is shown to be a valuable soil remediation technique as the synergetic effects may increase the sustainability of the applied process towards green technology for soil remediation.

Environmental occurrence, toxicity concerns, and remediation of recalcitrant nitroaromatic compounds

Nitroaromatic compounds (NACs) are considered important groups of chemicals mainly produced by human and industrial activities. The large-scale application of these xenobiotics creates contamination of the water and soil environment. Despite applicability, NACs have been caused severe hazardous side effects in animals and human systems like different cancers, anemia, skin irritation, liver damage and mutagenic effects. The effective remediation of the NACs from the environment is a significant concern. Researchers have implemented physicochemical and biological methods for the remediation of NACs from the environment. Most of the applied methods are based on adsorption and degradation approaches. Among these methods, degradation is considered a versatile method for the subsequent removal of NACs due to its exceptional properties like simplicity, easy operation, cost-effectiveness, and availability. Most importantly, the degradation process does not generate hazardous side products and wastes compared to other methods. Hence, the importance of NACs, their remediation, and supreme attributes of the degradation method have encouraged us to review the recent progress and development for the removal of these perilous materials using degradation as a versatile method. Therefore, in this review, (i) NACs, physicochemical properties, and their hazardous side effects on humans and animals are discussed; (ii) Physicochemical methods, microbial, anaerobic bioremediation, mycoremediation, and aerobic degradation approaches for the degradation of NACs were thoroughly vetted; (iii) The possible mechanisms for degradation of NACs were investigated and discussed. (iv) The applied kinetic models for evaluation of the rate of degradation were also assessed and discussed. Finally, (vi) current challenges and future prospects of proposed methods for degradation and removal of NACs were also directed.

Magnetic zeolitic imidazolate frameworks composite as an efficient adsorbent for arsenic removal from aqueous solution

In this study, magnetic zeolitic imidazolate frameworks (ZIF-8) was prepared by a one-step method, where its evolution involved the coprecipitation reactions concomitant with the self-assembly reactions. Structural characterizations indicated that magnetic ZIF-8 showed irregular polyhedral morphology with a large specific surface area (696.5 m²/g) and saturation magnetization (4.31 emu/g). The as-prepared magnetic ZIF-8 enhanced the adsorption performance of As(III) and As(V), compared with bare Fe₃O₄. The pseudo second-order kinetic model (R² = 0.9627 and 0.9893 for As(III) and As(V), respectively) and the Langmuir model (R² = 0.9441 for As(III) and 0.9851 for As(V)) can fit the adsorption process well, confirming the nature of single-layer homogeneous chemisorption. The adsorption capacity was 30.87 and 17.51 mg/g, and their corresponding values of PC were 2.664 and 1.286 L/g, for As(III) and As(V), respectively. Solution pH showed an adverse effect on As(V) adsorption whereas no obvious effect on As(III). The ionic strength and coexisting ions had not obvious influence on adsorption of As(III) and As(V). The adsorption mechanism was explored and discussed based on the detailed spectroscopy analysis. This adsorbent can be recovered magnetically after use, which is promising for the practical application.

Recent Advances in Covalent Organic Frameworks for Heavy Metal Removal Applications

Covalent organic frameworks comprise a unique class of functional materials that has recently emerged as a versatile tool for energy-related, photocatalytic, environmental, and electrochromic device applications. A plethora of structures can be designed and implemented through a careful selection of ligands and functional units. On the other hand, porous materials for heavy metal absorption are constantly on the forefront of materials science due to the significant health issues that arise from the release of the latter to aquatic environments. In this critical review, we provide insights on the correlation between the structure of functional covalent organic frameworks and their heavy metal absorption. The elements we selected were Pb, Hg, Cr, Cd, and As metal ions, as well as radioactive elements, and we focused on their removal with functional networks. Finally, we outline their advantages and disadvantages compared to other competitive systems such as zeolites and metal organic frameworks (MOFs), we analyze the potential drawbacks for industrial scale applications, and we provide our outlook on the future of this emerging field.

Toxicity and photosynthetic inhibition of metal-organic framework MOF-199 to pea seedlings

Metal-organic framework (MOF) materials are star materials with unique structures and properties. To ensure safe production and applications, the toxicity and environmental hazards of MOF materials should be thoroughly investigated. However, the environmental impact of MOF materials on plants is completely unknown. Herein, we reported the toxicity and photosynthetic inhibitory properties of MOF-199 to pea plants (Pisum sativum L.). MOF-199 was synthesized by hydrothermal method. MOF-199 was copper containing double-pyramid of high surface area (668 m2/g). MOF-199 accelerated the germination of pea seeds, but the total germination rates were unchanged. MOF-199 inhibited the seedling growth at high concentrations. The net photosynthetic rate increased, while the total photosynthesis capability decreased. Damage to the acceptor side of photosystem II was evidenced by chlorophyll fluorescence. Mechanistically, MOF-199 released Cu2+ in the nutrient solution, led to Cu2+ accumulations in seedlings, and promoted oxidative stress. In addition, the photosynthetic inhibitions of MOF-199 were stronger than equivalent concentrations of Cu(NO3)2, implying that MOF-199 particles also contributed to the environmental hazards. Our results highlighted the potential threat of MOF materials to plant growth and photosynthesis.

Covalent organic frameworks as robust materials for mitigation of environmental pollutants

Today, one of the main leading global problems is the presence of different pollutants in the environment. These pollutants not only affect human health but also overshadow the life of other creatures. Thus, pollutant treatment has become a challenging issue among the researchers and the scientific community. Different adsorbents and catalysts have been applied to the removal of pollutants. However, the associated limitations like poor chemical and physical stability, low surface area and low binding capacity revived researchers' attention to exploring alternative materials. Covalent organic frameworks (COFs) are versatile materials created based on the strong covalent interactions between blocked monomers. Unique features, including high specific surface area, high chemical-physical stability and crystallinity render COFs an intriguing sorbent and catalyst in treating pollutants. This review spotlights the applications of COFs as distinguished adsorbents to remove hazardous pollutants from the environment. At first, COFs and their properties as alternative materials were introduced. Then, different synthesis approaches of COFs and their advantages and disadvantages were discussed. Furthermore, the applications of COFs outlined to remove a wide variety of pollutants based on adsorption and degradation. Finally, the prospects of COFs for the treatment of pollutants were evaluated.

Selective Adsorption of Aqueous Diclofenac Sodium, Naproxen Sodium, and Ibuprofen Using a Stable Fe3O4-FeBTC Metal-Organic Frameworka

The FeBTC metal–organic framework (MOF) incorporated with magnetite is proposed as a novel material to solve water contamination with last generation pollutants. The material was synthesized by in situ solvothermal methods, and Fe₃O₄ nanoparticles were added during FeBTC MOF synthesis and used in drug adsorption. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy characterized the materials, with N₂-physisorption at 77 K. Pseudo-second-order kinetic and Freundlich models were used to describe the adsorption process. The thermodynamic study revealed that the adsorption of three drugs was a feasible, spontaneous exothermic process. The incorporation of magnetite nanoparticles in the FeBTC increased the adsorption capacity of pristine FeBTC. The Fe₃O₄–FeBTC material showed a maximum adsorption capacity for diclofenac sodium (DCF), then by ibuprofen (IB), and to a lesser extent by naproxen sodium (NS). Additionally, hybridization of the FeBTC with magnetite nanoparticles reinforced the most vulnerable part of the MOF, increasing the stability of its thermal and aqueous media. The electrostatic interaction, H-bonding, and interactions in the open-metal sites played vital roles in the drug adsorption. The sites’ competition in the multicomponent mixture’s adsorption showed selective adsorption (DCF) and (NS). This work shows how superficial modification with a low-surface-area MOF can achieve significant adsorption results in water pollutants.

Sustainable plant and microbes-mediated preparation of Fe3O4 nanoparticles and industrial application of its chitosan, starch, cellulose, and dextrin-based nanocomposites as catalysts

Iron oxide nanoparticles (Fe₃O₄ NPs) attracted significant scientific interest, considering their immense diversity of usage and biocompatibility. Perceiving the growing importance of sustainable chemistry, many efforts have been made to prepare these NPs using naturally occurring materials mostly plant extracts and microbes. Magnetic NPs (MNPs) are commonly used as composites and are considered in two matters: synthesis and modification of their functional groups. Biopolymeric nanocomposites are a group of hybrid materials composed of natural polymers and inorganic nanomaterials. Biopolymers such as alginate, cellulose, starch, gelatin, chitosan, etc. have been considered extensively and provided composites with better electrical and mechanical thermal properties. Fe₃O₄ NPs incorporated in a polymer and biopolymer matrix is a good instance of the functional nanostructure, which has been able to enhance the properties of both ingredients. These hybrids can have impressive applications in various scopes such as magneto-optical storage, electromagnetic interference shielding, catalyst, water remediation, biomedical sensing, and so on. In this study, we have tried to briefly introduce Fe₃O₄ NPs, investigate the green and sustainable methods that have been suggested for its synthesis and review recent utilization of their biopolymeric nanocomposite (NC) including starch, chitosan, dextrin, etc. as catalysts and photocatalysts.

Enhanced removal of Co(II) and Ni(II) from high-salinity aqueous solution using reductive self-assembly of three-dimensional magnetic fungal hyphal/graphene oxide nanofibers

Layer-structured graphene oxide excellent carrier for modifications; however, its poor recoverability and stability preclude its application in wastewater treatment fields. Herein, three-dimensional magnetic fungal hyphal/graphene oxide nanofibers (MFHGs) were assembled by a reductive self-assembly (RSA) strategy for the efficient capture of Co(II) and Ni(II) from high-salinity aqueous solution. The RSA strategy is inexpensive, eco-friendly and easy to scale up. The obtained MFHGs enhanced the dispersity and stability of graphene oxide and exhibited excellent magnetization and large coercivity, leading to satisfactory solid-liquid separation performance and denser sediment. The results of batch removal experiments showed that the maximum removal capacity of MFHGs for Ni(II) and Co(II) was 97.44 and 104.34 mg/g, respectively, in 2 g/L Na₂SO₄ aqueous solution with a pH of 6.0 at 323 K, and the effects of initial pH and ionic strength on Co(II) and Ni(II) removal were explored. Yield residue analysis indicated that the high porosity and oxygen-containing functional groups of MFHGs remarkably improved their Co(II)- and Ni(II)-removal capacities. According to the analysis, hydroxyl groups and amine groups participated in the chemical reaction of Co(II) and Ni(II) removal, and cation-exchange chemical adsorption was dominant during the Co(II)- and Ni(II)-removal process. Based on the attributes of MFHGs, a continuous-flow recycle reactor (CFRR) was proposed for emergency aqueous solution treatment and exhibited satisfactory removal efficiency and regeneration performance. The combination of MFHGs and the proposed CFRR is a promising water treatment strategy for rapid treatment applications.

Surfactant assisted Cr-metal organic framework for the detection of bisphenol A in dust from E-waste recycling area

Due to their highly porous structures, metal organic framework materials are widely used in analytic areas. In this paper, Cr-metal organic framework (MIL-101(Cr)) modified electrode was prepared and then was used as electrochemical sensor for the detection of bisphenol A (BPA). By using one kind of surfactant of cetyltrimethylammonium bromide (CTAB), the analytic performances of MIL-101 (Cr) towards BPA detection were greatly improved. Compared with pure MIL-101 (Cr), the differential pulse voltammetry (DPV) behavior of CTAB/MIL-101 (Cr) was improved 3.0 times in the presence of BPA. The hydrophobic long chain alkanes of CTAB can improve the enrichment and electrochemical oxidation for BPA. The CTAB/MIL-101 (Cr) sensor exhibited a linear range from 20 to 350 nM and a low detection limit of 9.95 nM (LOD = 3s_b/S) and showed good reproducibility, stability and selectivity. Finally, real samples of dusts from E-waste recycling area in South China were collected and the CTAB/MIL-101 (Cr) sensor demonstrated satisfactory results for BPA detection from these dust samples.

Dispersion behaviors of exhaust gases and nanoparticle of a passenger vehicle under simulated traffic light driving pattern

In the present study, the flow structure and pollutants dispersions were investigated by experiment and simulation on a typical passenger vehicle under simulated traffic light driving pattern. Some important findings were achieved: 1) gaseous pollutants diffuse drastically during first 0.3-0.6 m distance depending on wind velocity, at 1.25 m/s wind speed which is the similar level of exhaust gas, the pollutant concentration rises suddenly at ~0.6 m because exhaust plume is twisted by bottom gas flow, and a low velocity zone is produced; 2) as wind speed increases, the vehicle-induced turbulence is more and more important on pollutant dispersion pattern than exhaust plume dynamics. For instance, at 1.25 m/s and 4.17 m/s wind speeds, pollutants decrease to zero at ~1.6 m behind tail pipe, but at 0 m/s condition, pollutant relative fraction is still at ~0.12 level even at very long distance; 3) solid particle has larger attenuation rate than gaseous pollutants, only after ~0.6 m the particle number (PN) and diameter are very close to background values. Solid particle can diffuse to farther distance in vehicle transverse direction, when a car passes through the pedestrians with a 3 m distance, pedestrians expose to 2.6-3 times higher PN relative to atmosphere with diameters of 28-33 nm, this is very hazardous for human health; 4) exhaust pollutants disperse difficultly when followed by a car with a commonly waiting distance. At free dispersion scenario only behind ~0.6 m, PN decreases to 5800 #/cm³ (background value), but in-cabin PN of the following car (behind 0.8 m) rises to 3.5 × 10⁴ #/cm³ (even after 2-3 times decay through ventilation system). This study provides implications for future studies on transport planning.

Fabrication of a functionalized magnetic covalent organic framework composite as an efficient adsorbent for sulfonamide extraction from food samples

A carboxyl group functionalized magnetic covalent organic framework as an adsorbent to extract sulfonamides from meat samples was proposed.