Multifunctional amphibious superhydrophilic-oleophobic cellulose nanofiber aerogels for oil and water purification

Aerogels are of a popular choice for oil-water separation and water purification due to their attractive properties, such as lightweight, large surface area, and high porosity. Developing robust aerogels with multifunctional characteristics is highly desirable but remains challenging nowadays. Herein, we develop a facile one-pot condensation strategy for the fabrication of superhydrophilic-oleophobic (SHI-OP) composite aerogels using cellulose nanofibers (CNF), 3-glycidy-loxypropyl trimethoxysilane (GPTMS), polyethyleneimine (PEI) and fluorine-contained compound (FS-60). The resulted aerogels exhibit a directional lamellar structure with interconnected macropores, super-lightweight with high porosity of 98.30 % and low density of 0.0256 g·cm-3. Also, the aerogels are mechanically durable against repeated compression. Meanwhile, the amphibious SHI-OP feature of the composite aerogels in both air and water states enables them to not only absorb trace amount of water from contaminated oils, but also separate oil-water mixtures with separation efficiency of over 99 % and high permeation flux of over 9060 L/m2·h. Moreover, the aerogels also show excellent dye adsorption capability and reusability toward anionic dyes with a maximum adsorption capacity of 1245.68 mg/g. Such robust and multifunctional aerogels with special surface wettability provide good opportunity for liquid purification and dye-containing wastewater treatment.

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.

Bimetallic PCN-333 with Modulated Crystallization and a Porosity Structure for a Highly Efficient Removal of Congo Red

Bimetallic metal-organic frameworks (BMOFs) have garnered significant attention in the field of environmental remediation due to their more diverse adsorption sites compared to monometallic metal-organic frameworks (MOFs). Different energy barriers must be overcome for different metal ions and organic linkers to form MOFs. However, the impact of the synthesis temperature on the crystallization and porosity structure of BMOFs has been rarely studied. In this work, PCN-333 series-based BMOFs with different Fe/Al ratios were prepared by a solvothermal method at temperatures of both 135 and 150 °C. The synthesis temperature and Fe/Al ratio have significant effects on the crystal structure and specific surface area of bimetallic PCN-333, leading to the different adsorption performance of the PCN-333 for Congo red (CR). The Fe/Al-PCN-333-135(3:1) and Fe-PCN-333-150 exhibited the maximum CR adsorption capacities of 3233 and 3933 mg/g, respectively, surpassing the capacities of most previously documented adsorbents. The Langmuir model and pseudo-second-order kinetics can well describe the adsorption process of CR on Fe/Al-PCN-333-135(3:1) and Fe-PCN-333-150. Combining the isotherm adsorption behavior with the thermodynamic parameters, CR adsorption on BMOFs is a single-layer endothermic chemical adsorption. Furthermore, Fe/Al-PCN-333-135(3:1) and Fe-PCN-333-150 exhibited regenerability and reusability for three cycles with reasonable efficiency. This work is of great significance in the field of engineering BMOF materials to treat dye wastewater.

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.

Green Synthesis of Cerium-Based Metal-Organic Framework (Ce-UiO-66 MOF) for Wastewater Treatment

Green synthesis of metal-organic frameworks (MOFs) in aqueous solutions under ambient conditions with reduced production costs and environmental effects is an efficient technique to transfer lab-scale production to industrial large scale. Hence, this work proposes a green, low-cost, sustainable, rapid, and innovative synthetic strategy to produce cerium-based (Ce-UiO-66) MOFs under ambient conditions in the presence of water as a green solvent. This synthetic strategy exhibits great potential compared to conventional solvothermal synthetic techniques, and it does not need external activation energy and organic solvents, which can achieve the standards of green chemistry. Ce-UiO-66 MOF was synthesized successfully and utilized as a green adsorbent to efficiently eliminate anionic Congo Red (CR) dye from dye-containing wastewater. The experimental adsorption results were well matched to the pseudo-second-order kinetic and Langmuir isotherm models, in which the maximum CR adsorption capacity was measured to be about 285.71 mg/g. To evidence the applicability of Ce-UiO-66 MOFs in CR adsorption, the CR adsorption reaction was performed in the presence of interfering pollutants [e.g., salts (NaCl, KCl, and MgCl2) and cationic organic dyes (Malachite Green (MG) and Methylene Blue (MB)], where the results prove the promising adsorption performances of Ce-UiO-66 MOFs toward CR dye. Interestingly, the synthesized adsorbent exhibited high structural stability during repeated adsorption-desorption cycles, where the surface area of MOFs decreased from 555 to 376 m2/g after three cycles, while its CR adsorption capacity decreased by only 10% compared to that of the fresh adsorbent. All these outstanding properties indicate that the Ce-UiO-66 MOFs will be an effective adsorbent for water and wastewater treatment applications.

Fabrication of bimetallic-doped materials derived from a Cu-based complex for enhanced dye adsorption and iodine capture

In this work, we used Cu(II) ions, a bis-pyridyl-bis-amide ligand [N,N'-bis(4-pyridinecarboxamide)-1,2-cyclohexane (4-bpah)], and an aromatic dicarboxylic acid [1,4-cyclohexanedicarboxylic acid (H2CHDA)] to construct a 1D binuclear Cu-based complex, namely {[Cu3(4-bpah)(CHDA)3(H2O)]·2H2O}n (1). Moreover, we also developed a facile method to synthesize two monometallic/bimetallic-doped materials which were derived from the Cu complex (C-N-1 and C-V-1, which were doped with nitrogen and vanadium, respectively). The as-synthesized derived materials were fully characterized and the iodine sorption/release capabilities were investigated in detail. We performed iodine adsorption experiments on the two monometallic/bimetallic-doped materials and found that C-N-1 and C-V-1 possess highly efficient adsorption activities for the adsorption of iodine from solution. The C-N-1 and C-V-1 complexes exhibited remarkable adsorption capacities of 1141.60 and 1170.70 mg g-1, respectively, for iodine from a cyclohexane solution. Moreover, the dye adsorption properties of C-N-1 and C-V-1 were also investigated in detail. The obtained C-N-1 and C-V-1 exhibit effective dye uptake performances in water solution. The adsorption of Congo red (CR) on a single metal carbon material C-N-1 doped with heteroatoms reached equilibrium within 240 min and reached an adsorption capacity of 1357.00 mg g-1 and the adsorption capacities of C-V-1 for methylene blue (MB), gentian violet (GV), rhodamine B (RhB), and CR at room temperature were found to be 187.60, 190.60 and 108.10 and 1501.00 mg g-1 in 180 min, respectively. By comparison, we found that doping vanadium could play an important role in the adsorption processes. The adsorption capacity of C-V-1 (containing the vanadium in its structure) was relatively higher than that of C-N-1, which indicated that the introduction of non-noble metals may effectively tune the adsorption kinetics activity and the introduction of noble metals can change the surface electronegativity of porous carbon materials, thus leading to significantly improved adsorption capabilities.

MOF-Derived Ni/ZIF-8/ZnO Arrays on Carbon Fiber Cloth for Efficient Adsorption-Catalytic Oxidation

The catalytic oxidation of toxic organic pollutants in water requires enhanced efficiency for commercial applications. A ZnO nanorod array grown on a carbon fiber cloth (CFC) serves as the zinc source to ensure that the Ni/ZIF-8/ZnO nanoreactor is constructed. The Ni/ZIF-8/ZnO/CFC nanoreactor efficiently activates peroxymonosulfate (PMS) for bisphenol A (BPA) degradation owing to its high density of active sites, high adsorbability, and dispersibility structure, which concentrates catalytic and adsorptive sites within a confined space. Experimental and theoretical calculations clearly show that the introduction of Ni is beneficial for improving the adsorption of BPA and the activation of PMS. The synergistic mechanism of BPA adsorption-PMS activation is also investigated, and the degradation pathway of BPA is examined. Moreover, a filter catalytic unit is constructed using Ni/ZIF-8/ZnO/CFC to achieve a continuous zero discharge of BPA, which is convenient for nanocatalyst recycling. This study aims to develop a new strategy for the removal of emerging organic pollutants from water using a system with strong adsorption and catalytic capabilities.

Iron-Iron Oxide Core-Shell Nanochains as High-Performance Adsorbents of Crystal Violet and Congo Red Dyes from Aqueous Solutions

The main aim of this work was to use the iron-iron oxide nanochains (Fe NCs) as adsorbents of the carcinogenic cationic crystal violet (CV) and anionic Congo red (CR) dyes from water. The investigated adsorbent was prepared by a magnetic-field-induced reduction reaction, and it revealed a typical core-shell structure. It was composed of an iron core covered by a thin Fe₃O₄ shell (<4 nm). The adsorption measurements conducted with UV-vis spectroscopy revealed that 15 mg of Fe NCs constituted an efficient dose to be used in the CV and CR treatment. The highest effectiveness of CV and CR removal was found for a contact time of 90 min at pH 7 and 150 min at pH 8, respectively. Kinetic studies indicated that the adsorption followed the pseudo-first-order kinetic model. The adsorption process followed the Temkin model for both dyes taking into account the highest value of the R² coefficient, whereas in the case of CR, the Redlich-Peterson model could be also considered. The maximal adsorption capacity estimated from the Langmuir isotherms for the CV and CR was 778.47 and 348.46 mg g^-1, respectively. Based on the Freundlich model, both dyes adsorbed on the Fe NCs through chemisorption, but Coulombic interactions between the dye and adsorbent cannot be excluded in the case of the CV dye. The obtained results proved that the investigated Fe NCs had an excellent adsorption ability for both dye molecules within five cycles of adsorption/desorption, and therefore, they can be considered as a promising material for water purification and environmental applications.

Green synthesize of nano-MOF-ethylcellulose composite fibers for efficient adsorption of Congo red from water

Two novel MOF- ethyl cellulose (EC)- based nanocomposites have been designed and synthesized in water by electrospinning and applied for adsorption of congo red (CR) in water. Nano- Zeolitic Imidazolate Framework-67 (ZIF-67), and Materials of Institute Lavoisier (MIL-88A) were synthesized in aqueous solutions by a green method. To enhance the dye adsorption capacity and stability of MOFs, they have been incorporated into EC nanofiber to prepare composite adsorbents. The performance of both composites in the absorption of CR, a common pollutant in some industrial wastewaters, has then been investigated. Various parameters including initial dye concentration, the dosage of the adsorbent, pH, temperature and contact time were optimized. The results indicated 99.8 and 90.9% adsorption of CR by EC/ZIF-67 and EC/MIL-88A, respectively at pH = 7 and temperature at 25 °C after 50 min. Furthermore, the synthesized composites were separated conveniently and successfully reused five times without significant loss of their adsorption activity. For both composites, the adsorption behavior can be explained by pseudo-second-order kinetics, Intraparticular diffiusion and Elovich models demonstrated that the experimental data well matched to the pseudo-second-order kinetics. Intraparticular diffiusion model showed that the adsorption of CR on EC/ZIF-67 and EC/MIL-88a took place in one and two steps, respectively. Freundlich isotherm models and thermodynamic analysis indicated exothermic and spontaneous adsorption.

Magnetite Metal-Organic Frameworks: Applications in Environmental Remediation of Heavy Metals, Organic Contaminants, and Other Pollutants

Due to the increasing environmental pollution caused by human activities, environmental remediation has become an important subject for humans and environmental safety. The quest for beneficial pathways to remove organic and inorganic contaminants has been the theme of considerable investigations in the past decade. The easy and quick separation made magnetic solid-phase extraction (MSPE) a popular method for the removal of different pollutants from the environment. Metal-organic frameworks (MOFs) are a class of porous materials best known for their ultrahigh porosity. Moreover, these materials can be easily modified with useful ligands and form various composites with varying characteristics, thus rendering them an ideal candidate as adsorbing agents for MSPE. Herein, research on MSPE, encompassing MOFs as sorbents and Fe₃O₄ as a magnetic component, is surveyed for environmental applications. Initially, assorted pollutants and their threats to human and environmental safety are introduced with a brief introduction to MOFs and MSPE. Subsequently, the deployment of magnetic MOFs (MMOFs) as sorbents for the removal of various organic and inorganic pollutants from the environment is deliberated, encompassing the outlooks and perspectives of this field.

Efficient capture of U(VI) by magnetic Zr(IV)-ethylenediamine tetramethylene phosphonic acid inorganic-organic hybrid

The separation of magnetic adsorbents from aqueous solutions is made simple by using an external magnetic field. Herein, magnetic Zr(IV)-ethylenediamine tetramethylene phosphonic acid (EDTMPA) hybrids (MZrOP-x-T, x, and T were the different quality of Fe₃O₄@C and temperature in the synthesis process, respectively). A study was conducted on the uses of MZrOP-x-T in the capture of U(VI). The influences of pH, adsorption period, initial concentration, and temperature were all investigated. Furthermore, the desorption and reusability of the materials were explored. The optimal values of x and T were 0.2 g and 100 °C, respectively. At 298.15 K, the maximum adsorption capacity of MZrOP-0.2-100 was 330.30 mg·g^-1. The current research demonstrates that MZrOP-0.2-100 is a potentially effective material in removing U(VI) from radioactive solution.

A stable and highly luminescent 3D Eu(III)-organic framework for the detection of colchicine in aqueous environment

The metal-organic framework materials have an important application as sensors. In this work, a microporous three-dimensional (3D) Eu(III)-organic framework (Eu-MOF), [Eu₂(3,5-bct)(phen)₂(ox)₂(H₂O)]·H₂O, was constructed from 3,5-bis(3'-carboxyphenyl)-1,2,4-triazole (3,5-H₂bct), oxalate (ox) and 1,10-phenanthroline (phen) as a luminescent sensor. The free volume was found to be 15.7% per unit volume ignoring the free water molecules. The Eu-MOF showed bright red light due to the emission at 622 nm (⁵D₀ → ⁷F₂ transition) of the Eu(III) with high quantum yield (QY, 52.51%). The Eu-MOF exerted high luminescence stability in common organic solvents as well as aqueous solutions within a wide pH range from 4 to 11. Based on the luminescent Eu-MOF, the sensing behavior for colchicine in the aqueous environment was studied. Highly selective and sensitive detection (LOD = 2.43 × 10^-5 mol L^-1) of colchicine was observed by the Eu-MOF even in the presence of potential interfering components. The sensing mechanism for colchicine was investigated by experimental and theoretical results. It is worth noting that a film (Film@Eu-MOF) prepared by loading Eu-MOF showed intense characteristic red light emission under UV light. The luminescence color changed immediately from red to colorless when the Film@Eu-MOF came in contact with colchicine. Highly sensitive and rapid detection of colchicine in wastewater was achieved using this Film@Eu-MOF, which could be identified by the naked eye. The experimental results suggest that the synthesized Eu-MOF has potential application as a luminescent sensing material for pollutants in the environmental system.

Preparation of amine-functionalized lignins for the selective adsorption of Methylene blue and Congo red

Research on low-cost bio-adsorbents for the removal of harmful substances from effluents has recently attracted significant attention. In this study, three types of amino-silane-modified lignins (ASLs) with primary, secondary, and tertiary amine groups were prepared, and their adsorption behavior toward cationic and anionic dyes was investigated. Chemical structural analyses indicated that the three amino-silane reagents resulted in different molecular self-assembly structures on the lignin surface. The ASLs exhibited enhanced thermal stabilities and increased surface areas with different surface charges in different pH ranges. Owing to the high density of primary, secondary, and tertiary amine groups, the ASLs exhibited excellent adsorption capacities for cationic and anionic dyes. Additionally, they selectively adsorb anionic and cationic dyes according to the pH conditions. The ASL with primary amine had the highest adsorption capacity for Methylene blue and Congo red, reaching 187.27 and 293.26 mg·g^-1, respectively, followed by ASLs with the secondary amine and tertiary amine. All adsorption processes followed the Langmuir and Temkin isotherms and had pseudo-second-order kinetics. The hypothesized adsorption mechanism mainly involves electrostatic interaction, NH-π interaction, hydrogen bonding interaction and π-π interaction.

Using recycled coffee grounds for the synthesis of ZIF-8@BC to remove Congo red in water

Around 6.6 million tons of spent coffee is produced per year, resulting in resources loss and potential environmental risks. Hence, a green technique is required to reuse the spent coffee grains. In this study, coffee grounds were burnt at 900 °C to generate the biochar (BC) for the synthesis of the porous adsorbent (ZIF-8 @BC) by growing ZIF-8 on the surface of BC. We applied the well-prepared ZIF-8 @BC to remove Congo red (CR) in water. The maximum adsorption capacity of ZIF-8 @BC on Congo red in water was up to 1080.4 mg/g, which was significantly higher than that of many different types of BCs reported in previous studies. The reasons for its highly efficient adsorption of CR probably was attributed to metal ions and coordinatively unsaturated sites in the material. Also, BC enabled the less aggregation of ZIF-8 to provide sufficient specific surface area for CR adsorption. From the analysis of the pseudo-second-order kinetic model and Langmuir model, the adsorption of ZIF-8 @BC on CR was a homogeneously chemical adsorption process regulated by electrostatic interaction, π-π stacking and metal coordination.

Recent Advances in MOF-Based Adsorbents for Dye Removal from the Aquatic Environment

The adsorptive removal of dyes from industrial wastewater using commercially available adsorbents is not significantly efficient. Metal–organic frameworks (MOFs) offer outstanding properties which can boost the separation performance over current commercial adsorbents and hence, these materials represent a milestone in improving treatment methods for dye removal from water. Accordingly, in this paper, the recent studies in the modification of MOF structures in dye removal from the aquatic environment have been discussed. This study aims to elaborate on the synthetic strategies applied to improve the adsorption efficiency and to discuss the major adsorption mechanisms as well as the most influential parameters in the adsorptive removal of dyes using MOFs. More particularly, the advanced separation performance of MOF-based adsorbents will be comprehensively explained. The introduction of various functional groups and nanomaterials, such as amine functional groups, magnetic nanoparticles, and carbon-based materials such as graphene oxide and CNT, onto the MOFs can alter the removal efficiency of MOF-based adsorbents through enhancing the water stability, dispersion in water, interactions between the MOF structure and the contaminant, and the adsorption capacity. Finally, we summarize the challenges experienced by MOF-based materials for dye removal from water and propose future research outlooks to be considered.

Utilization of shell-based agricultural waste adsorbents for removing dyes: A review

Dye existence in the water body adversely impacts the habitat and the quality of the aquatic system. Considering different physical and chemical methods, adsorption is a propitious substitute for extracting dyes from wastewater specifically due to its performance, high selectivity, less expense, clear operation, and existence in a broad area of experimental circumstances. These benefits are directly linked to the essence of the adsorbent strength used in dye adsorption. In keeping with the principles of green chemistry, the adsorbent materials' accessibility in large amounts that involves easy preparation should boost the effectiveness of the adsorption cycle. Agricultural waste shell-based adsorbent is a novel and better alternative for the expansive adsorbent. This article focuses on the use of a raw and activated adsorbent from agricultural waste shell-based material (on the mitigation of different types of synthetic as well as natural textile dye particles) to find out adsorption capacity based on its operational conditions like pH, dosage, primary concentration of dye, equilibrium time and temperature. Oil palm empty agricultural waste bunch fiber has a maximum adsorption capacity of 393.67 mg/g of Cibacron blue 3G-A dye and Almond shell activated carbon has a maximum adsorption ability of 833.33 mg/g of Methylene Blue dye. Adsorption removal capacity of various raw agricultural wastes and activated agricultural wastes is reviewed. Agricultural waste shell-based adsorbents are a low-cost adsorbent that is a safer alternative to traditional adsorbents.

Dye adsorption of aluminium- and zirconium-based metal organic frameworks with azobenzene dicarboxylate linkers

The high efficiency of metal-organic-frameworks (MOFs) such as the ZIF, MIL and UiO type species in dye adsorption is well established. Recently, an emerging class of photoresponsive azobenzene-based MOFs has found suitable application in gas adsorption. However, there is a dearth of research on their use in the adsorption of dyes and other water pollutants. In this research, two microporous photoresponsive azobenzene dicarboxylate MOFs of Al³⁺ (Al-AZB) and Zr⁴⁺ (Zr-AZB) were synthesized for the adsorption of congo red (CR) dye. The surface and textural properties of the synthesized MOFs were characterized by FTIR, PXRD, SEM, TGA, BET and pore analysis. Both MOFs were crystalline, thermally stable up to 300 °C and stable in aqueous medium at room temperature. The Al-AZB displayed a higher surface area (2718 m²/g) than the Zr-AZB (1098 m²/g), which significantly impacted the higher adsorption of CR. Besides, pore volumes of 0.86 cm³/g and 0.35 cm³/g were obtained for Al-AZB and Zr-AZB, respectively. The maximum adsorption capacity of Al-AZB and Zr-AZB was 456.6 mg/g and 128.9 mg/g, respectively, with the former superior to other potent adsorbents. The pseudo-second-order and Langmuir models were well correlated with the dye uptake on the MOFs. Thermodynamics revealed random and endothermic sorption of CR dominated by chemisorption, while efficient regeneration and reuse of both MOFs were achieved using dimethylformamide as eluent. The results proved the potency of the synthesized photoresponsive MOFs, as highly efficient and reusable materials for dye adsorption.

Magnetic Poly(glycidyl methacrylate) Microspheres with Grafted Polypyrrole Chains for the High-Capacity Adsorption of Congo Red Dye from Aqueous Solutions

In this study, novel magnetic poly(glycidyl methacrylate) (PGMA) microspheres with grafted polypyrrole chains (magnetic PGMA-g-PPy) were developed for the high-capacity adsorption of Congo red (CR) from aqueous solutions. The magnetic PGMA-g-PPy was synthesized by the typical dispersion polymerization method and the ring-opening reaction of epoxy groups, producing abundant hydroxyls for the grafting polymerization of pyrrole in the presence of FeCl3 as an oxidizing agent on the surface of the microspheres. The characterization results showed that magnetic PGMA-g-PPy was successfully fabricated. The adsorption equilibrium data of the adsorbents could be well fitted by the Langmuir isotherm model, showing a high maximum adsorption capacity of 502.5 mg/g for CR. The adsorption followed pseudo-second-order kinetics with a fast speed. The adsorbents had no leaching of Fe in the solution at pH 1.0–11.0 for 24 h. The adsorption process was strongly pH-dependent and weakly ionic-strength-dependent. Furthermore, the magnetic microspheres could be easily regenerated, rapidly separated from the solution, and reused for wastewater treatment. The results suggest that magnetic PGMA-g-PPy microspheres are a promising efficient adsorbent for the removal of CR from wastewater.

IL-functionalized Mn(ii)-doped core–shell Fe3O4@Zr-MOF nanomaterials for the removal of MB from wastewater based on dual adsorption/Fenton catalysis

IL-functionalized Mn(ii)-doped core–shell Fe3O4@Zr-MOF nanomaterials were fabricated for the removal of MB from wastewater based on dual adsorption/Fenton catalysis.

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.

Functionally modified metal–organic frameworks for the removal of toxic dyes from wastewater

This review highlights recent advancement in functional modified (FM) MOFs as superior adsorbents for the removal of dyes, classifying them by various modification strategies. The adsorption interactions affected by the FM approach are summarized.

Investigation of hierarchically porous zeolitic imidazolate frameworks for highly efficient dye removal

Treatment of textile water containing organic molecules as contaminants still remains a challenge and has become a central issue for environment remediation. Here, a nucleotide incorporated zeolitic imidazolate frameworks (NZIF) featuring hierarchically porous structure served as a potential adsorbent for removal of organic dye molecules. Adsorption isotherms of organic dyes were accurately described by Langmuir adsorption model with correlation coefficients of 0.98 and kinetic data followed the pseudo-second-order model. The maximum adsorption capacity of NZIF for Congo red (CR) and methylene blue (MB) reached 769 and 10 mg/g, respectively, which were 6 and 5 times higher than that of ZIF-8. The adsorption behavior of sunset yellow and crystal violet was examined for mechanism investigation. Analysis of pore size, molecular size, zeta potential and FTIR measurement together revealed that mesopores in NZIF provided more interaction sites and led to enhanced adsorption capacity. Hydrogen bonding and π-π stacking which resulted from the interaction between introduced nucleotide monophosphate and dyes dominated the driving forces for adsorption, where electrostatic interaction was also involved. Moreover, the introduced nucleoside monophosphate enabled NZIF to function under acidic condition whereas ZIF-8 collapsed. This study opens a new avenue for design of porous materials for environment remediation.

Efficient and selective removal of Congo red by a C@Mo composite nanomaterial using a citrate-based coordination polymer as the precursor

To research the effect of structural diversity on citrate-based coordination polymers (CPs), citric acid (H4cit) was selected to combine with Cu(ii) under hydrothermal conditions. A new CP [Cu2(cit)(H2O)2] (1) was synthesized and structurally characterized. The title complex shows a 3D 2,4,6-connected topology with the point symbol of {43·63}{44·66·85}{4}. Inspired by the decomposition and functional molybdenum component, 1 was used as a catalyst precursor to synthesize a carbon-based material (C-1) and a C@Mo material (C-Mo-1) by the chemical vapor deposition (CVD) method and characterized in detail. The selective removal of a contaminant (Congo red) by complex 1, C-1 and C-Mo-1 in the aqueous phase was also comparatively investigated.

Super adsorption performance of carboxymethyl cellulose/copper oxide-nickel oxide nanocomposite toward the removal of organic and inorganic pollutants

A novel nanocomposite bead based on polymeric matrix of carboxymethyl cellulose and copper oxide-nickel oxide nanoparticles was synthesized, characterized, and applied for adsorptive removal of inorganic and organic contaminants at trace level of part per million (mgL^-1) from aqueous sample. Carboxymethyl cellulose/copper oxide-nickel oxide (CMC/CuO-NiO) adsorbent beads were selective toward the removal of Pb(II) among other metal ions. The removal percentage of Pb(II) was more than 99% with 3 mgL^-1. The waste beads after Pb (II) adsorption (Pb@CMC/CuO-NiO) and CMC/CuO-NiO nanocomposite beads were employed as adsorbents for removing of various dyes. It was found that Pb@CMC/CuO-NiO can be reused as adsorbent for the removal of Congo Red (CR), while CMC/CuO-NiO nanocomposite beads were more selective for removal of Eosin Yellow (EY) from aqueous media. The adsorption of CR and EY was optimized, and the removal percentages were 93% and 96.4%, respectively. The influence of different parameters was studied on the uptake capacity of Pb(II), CR, and EY, and lastly, the CMC/CuO-NiO beads exhibited responsive performance in relation to pH and other parameters. Thus, the prepared CMC/CuO-NiO beads were found to be a smart material which is effective and played super adsorption performance in the removal of Pb(II), CR, and EY from aqueous solution. These features make CMC/CuO-NiO beads suitable for numerous scientific and industrial applications and may be used as an alternative to high-cost commercial adsorbents.

Preparation of a Gangue-Based X-type Zeolite Molecular Sieve as a Multiphase Fenton Catalyst and Its Catalytic Performance

In this study, a series of X-type zeolite molecular sieve catalysts, modified with copper (Cu-X), were prepared by an alkali fusion-hydrothermal synthesis using coal gangue from Inner Mongolia. These catalysts were used in the degradation of the methylene blue dye by a Fenton-like reaction. Characterization results showed that Cu is considered to be present in the surface structure of the zeolite in the form of doped Cu ions and metal oxide. It is believed that Cu2+ is the main active site involved in the Fenton reaction. The X-ray photoelectron spectroscopy (XPS) spectra indicated that Cu2+ and Cu+ coexist in the catalysts and participate together in the Fenton reaction. The degradation of methylene blue by the Cu-X catalysts was investigated to determine the optimal catalytic conditions in terms of six aspects: catalyst dosage, initial solution concentration, initial pH of the solution, H2O2 dosage, copper loading, and reaction temperature. The experimental results showed that CX-1.0 had excellent activity and stability for the degradation and decolorization of the methylene blue dye, which could completely degrade the dye within 90 min, and the total organic carbon removal rate reached as high as 97.8%. Electron spin resonance (ESR) and radical capture experiments showed that •OH played a dominant role in the Fenton-like reaction. Combined with XPS, ESR, and catalytic tests, the redox cycle of Cu+/Cu2+ was found to be accelerating the generation of reactive radicals in the Fenton system.

Boosting Ammonia Uptake within Metal-Organic Frameworks by Anion Modulating Strategy

Ammonia with toxic and corrosive features needs advanced protective materials and removal tools, although it is a vital component in human food supply processes. So, to satisfy these requirements, materials with high adsorption capacity and affinity for ammonia should be developed. The present research has been focused on a series zinc-based metal-organic frameworks (MOF) containing mixed ligands, biphenyl dicarboxylic acid (BPDA) and tris(4-(4H-1,2,4-triazol-4-yl)phenyl)amine (TTPA), which are modulated by different anions including CH₃COO^-, CF₃COO^-, and CF₃SO₃^-. Ammonia uptake capacity was measured via static and dynamic conditions under 50% relative humidity. Among all compounds, CF₃SO₃^- anion could enhance the ammonia uptake capacity of MOFs up to 177.85 and 349 mg/g during static and breakthrough measurements, respectively, so that 83.30% of the total uptake capacity (at P/P_o = 1.0 and 298 K) was achieved at low relative pressure range (up to 0.1). The isosteric heats of ammonia adsorption on PFC-27 and derivatives were calculated in the range of 7.03-10.16 kJ mol^-1 so that they increased upon CF₃SO₃^-, CF₃COO^-, and CH₃COO^- ion incorporation. This is potentially beneficial for enhanced ammonia adsorption. Interestingly, adsorption capacities were retained with only slight changes after five cycles and three regeneration temperatures, 25 °C, 60 °C, and 120 °C, under vacuum. The special affinity for NH₃ adsorption and MOF phase stability after desorption is clearly proved by FTIR spectra and PXRD analysis, respectively. Generally, the results suggest that ion insertion modification is an efficient strategy for enhancement of MOF adsorption performance.

The "Lab4treat" Outreach Experience: Preparation of Sustainable Magnetic Nanomaterials for Remediation of Model Wastewater

The Lab4treat experience has been developed to demonstrate the use of magnetic materials in environmental applications. It was projected in the frame of the European project Mat4Treat, and it was tested several times in front of different audiences ranging from school students to the general public in training and/or divulgation events. The experience lends itself to discuss several aspects of actuality, physics and chemistry, which can be explained by modulating the discussion depth level, in order to meet the interests of younger or more experienced people and expand their knowledge. The topic is relevant, dealing with the recycling of urban waste and water depollution. The paper is placed within the field of water treatment for contaminant removal; therefore, a rich collection of recent (and less recent) papers dealing with magnetic materials and environmental issues is described in the Introduction section. In addition, the paper contains a detailed description of the experiment and a list of the possible topics which can be developed during the activity. The experimental approach makes the comprehension of scientific phenomena effective, and, from this perspective, the paper can be considered to be an example of interactive teaching.

Multiple adsorption properties of aptamers on metal-organic frameworks for nucleic acid assay

Enrichment and detection of circulating free nucleic acids in biological samples have gained great attention for disease diagnosis or prognostic evaluation. Nanoscale metal-organic frameworks (NMOFs) have been used for aptamer-based nucleic acid sensing. In this work, different NMOFs, including ZIF-8, MIL-88, MIL-100, MIL-101, as well as Eu-TDA and Tb-TDA [prepared by the coordination of 2,2'-thiodiacetic acid (TDA) and Eu³⁺ or Tb³⁺], were investigated in nucleic acid sensing by employing their aptamer adsorption ability and fluorescence quenching capacity for the labeled dyes. Two types of dye aptamer, FAM-labeled aptamer (FAM-Ap) and TexasRedaptamer (TexasRed-Ap) were designed, and their adsorption properties on NMOFs-were compared. It was found that the TexasRed-Ap can be well used for nucleic acid (miR-21) extraction and sensing by linking with a pH-responsive nucleotide chain (TexasRed-Ap-pH) or with an additional random chain ssDNA-1' (TexasRed-Ap-a). After interacted with the target miR-21 in biosamples, the TexasRed-dsDNA + NMOFs composites can be collected, and the formed TexasRed-dsDNA can be released by changing pH value or addition of ssDNA-1, which is matched with ssDNA-1'. A linear relationship from 0.1 to 200 pM for miR-21 detection was obtained. The results show that the NMOFs can be used as promising platforms for nucleic acid extraction and fluorescent sensing.

Metal-Organic Framework@Carbon Hybrid Magnetic Material as an Efficient Adsorbent for Pollutant Extraction

The preparation of a hybrid magnetic metal-organic framework (MOF)@carbon from a MOF-derived porous carbon is reported. MOF-74(Co) is used as a precursor for the synthesis of a magnetic carbon with homogeneous cobalt particle distribution (C-MOF-74) by a direct carbonization step. The cobalt particles present in the carbon are partially converted to zeolitic imidazolate framework (ZIF)-67 by reaction with 2-methylimidazole to obtain a core-shell ZIF-67@C-MOF-74. The effect of the reaction time and 2-methylimidazole concentration in the conversion procedure is studied by X-ray diffraction and scanning microscopy. Because of its high surface area, dual porosity, and magnetic properties, ZIF-67@C-MOF-74 exhibits high extraction capacity (180 mg g^-1), fast adsorption rate, and excellent recyclability for Congo red adsorption. In addition, the prepared material shows high efficiency in the extraction of different phenolic compounds. The developed procedure can be easily adapted to different carbons and MOFs, thus potentially enabling the preparation of a wide number of new hybrid materials.

Triggering Lewis Acidic Nature through the Variation of Coordination Environment of Cd-Centers in 2D-Coordination Polymers

The rational design and successful synthesis of novel functional metal-organic frameworks relies on careful selection of metals and versatile organic ligands. A newly designed pyrazole-based dicarboxylate ligand, 5-(3,5-dimethyl-1H-pyrazol-1-yl) 1,3-benzenedicarboxylic acid (H₂L), was utilized to obtain two new Cd-based coordination polymers I [Cd(L)(H₂O)]·H₂O and II [Cd(L)] under similar reaction conditions via solvothermal strategy. Single-crystal X-ray data confirmed that compound I exhibits a two-dimensional (2D) skeleton comprising pentagonal bipyramidal Cd-ions and an organic ligand moiety. Compound II has also formed a two-dimensional layer arrangement with the connectivity between trigonal bipyramidal Cd-ions and the organic ligand. Topological analysis revealed that compound I has formed unique 4³.6³ net topology while compound II has displayed a 4⁴.6² sql net topology with 2D frameworks. The Lewis acidic nature of both I and II containing a Cd²⁺ metal center has been correlated with the coordination number through dye adsorption-desorption and catalysis studies. The selective adsorption of anionic dye and the extent of adsorption are interrelated with the Cd-ion geometry. For the first time, the role of coordinated water molecule has been analyzed through heterogeneous catalysis reaction (i.e., cyanosilylation) with Cd-based 2D-coordination polymers (CPs). The plausible mechanisms have been proposed to explain the subsequent role of coordination number and environment in CPs.