Acid-promoted synthesis of UiO-66 for highly selective adsorption of anionic dyes: Adsorption performance and mechanisms

IRTIDP: A simple integrated real-time isolation and detection platform for small extracellular vesicles Glypican-1 in pancreatic cancer patients

Glypican-1 (GPC-1) protein-positive small extracellular vesicles (GPC-1+-sEV) have been proposed as potential biomarkers for early diagnosis of pancreatic cancer. In this study, we present an integrated real-time isolation and detection platform (IRTIDP) to capture and analyze GPC-1+-sEV directly from sera of pancreatic cancer patients. First, CD63 antibody-modified metal-organic framework (MOF) materials were utilized to enrich sEVs with a capture efficiency of 93.93 %. Second, a SERS probe was constructed by Raman reporter 4-MBA and GPC-1 antibody modified SERS active silver nanoparticles (AgNPs), which formed a sandwich complex structure of "MOFs@GPC-1+-sEV@AgNPs-4-MBA" with MOFs-enriched sEVs. The IRTSDP can complete the capture and detection process within 35 min, with a detection limit for 1 GPC-1+-sEV/μL, and linear range between 105∼109 GPC-1+-sEV/mL. Furthermore, this approach has been applied to quantify serum sEV GPC-1 in clinical pancreatic cancer patients. Based on the SERS intensity analysis, pancreatic cancer patients can be distinguished from pancreatic cystadenoma patients and healthy individuals effectively using this innovative platform that provides highly specific and sensitive means for early diagnosis of pancreatic cancer as well as other tumor types.

Engineering the defects of UiO-66 MOF for an improved catalytic detoxification of CWA simulant: methyl paraoxon

Exigency in search of an ideal candidate for an effective detoxification of chemical warfare agents is still continuing. Zirconium-based Metal-organic Framework (MOF) UiO-66 has shown a significant detoxification of such toxic chemicals owing to its tunable physio-chemical properties and profuse catalytic sites. In this context, a series of UiO-66 MOFs synthesized by tuning the acidity constant (pK a) and concentration of the modulator, synthesis temperature and water molecules was tested for their detoxification efficiency against the simulant 'methyl-paraoxon' at room temperature. Amongst, HCl modulated UiO-66 across the considered synthesis temperature have shown competent catalytic performance in virtue of defects generation within its structure. In addition, the role of catalytic features of UiO-66 obtained by tailoring its defects in enhancing the degradation efficiency has been systematically investigated. The detoxification efficiency of 98.5% with a half-life time of 0.23 min has confirmed the effectiveness of engineered defects in enhancing the catalytic activity of UiO-66 in detoxifying the identified simulant.

Hierarchically Porous Structured Adsorbents with Ultrahigh Metal-Organic Framework Loading for CO2 Capture

Metal-organic frameworks (MOFs) have emerged as promising candidates for CO2 adsorption due to their ultrahigh-specific surface area and highly tunable pore-surface properties. However, their large-scale application is hindered by processing issues associated with their microcrystalline powder nature, such as dustiness, pressure drop, and poor mass transfer within packed beds. To address these challenges, shaping/structuring micron-sized polycrystalline MOF powders into millimeter-sized structured forms while preserving porosity and functionality represents an effective yet challenging approach. In this study, a facile and versatile strategy was employed to integrate moisture-stable and scalable microcrystalline MOFs (UiO-66 and ZIF-8) into a poly(acrylonitrile) matrix to fabricate readily processable, millimeter-sized hierarchically porous structured adsorbents with ultrahigh MOF loadings (∼90 wt %) for direct industrial carbon capture applications. These structured composite beads retained the physicochemical properties and separation performance of the pristine MOF crystal particles. Structured UiO-66 and ZIF-8 exhibited high specific surface areas of 1130 m2 g-1 and 1431 m2 g-1, respectively. The structured UiO-66 achieved a CO2 adsorption capacity of 2.0 mmol g-1 at 1 bar and a dynamic CO2/N2 selectivity of 17 for a CO2/N2 gas mixture with a 15/85 volume ratio at 25 °C. Furthermore, the structured adsorbents exhibited excellent cyclability in static and dynamic CO2 adsorption studies, making them promising candidates for practical application.

Using eugenol scaffold to explore the explosive sensing properties of Cd(II)-based coordination polymers: experimental studies and real sample analysis

Eugenol, the major constituent of clove oil, has been explored as an essential natural ingredient for ages owing to its versatile pharmacological properties. However, to date, the coordination chemistry of eugenol derivatives has not been much explored. In the present work, an eugenol-based Schiff base ligand (HL) was synthesized and structurally confirmed through ESI-MS, NMR, and FT-IR spectroscopy studies. Consequently, the N,O-donor chelating ligand HL was coordinated with Cd2+, in the presence of bridging pseudohalides (thiocyanate, SCN-, and dicyanamide, N(CN)2-) to synthesize two luminescent coordination polymers (CPs 1 and 2): [Cd2(L)2(X)2]n (where HL = 4-allyl-2-(((2-(benzylamino)ethyl) imino)methyl)-6-methoxyphenol and Xs are bridging pseudohalides, i.e., SCN- and N(CN)2-) on a Cd-eugenol scaffold. The CPs depicted structural diversity, bulk-phase purity, thermal stability, and the presence of interlayer supramolecular C-H⋯π interactions together with C-H⋯S (for CP 1) and C-H⋯N (for CP 2) interactions. The CPs further exemplified themselves as selective and sensitive 'turn-off' probes towards trinitrophenol (TNP) (quenching efficiency: 82.02% and 83.86% for 1 and 2) among a pool of hazardous nitroaromatic compounds (NACs). Accordingly, 1 and 2 exhibited an ultralow limit of detection (LOD) of 0.29 and 0.15 μM, with high quenching constants (KSV) of 5.91 × 104 and 17.60 × 104 M-1, respectively. In addition, TNP sensing events were evidenced to be recyclable and exhibited fast response (∼31 s, 1, and ∼40 s, 2), which increased its real-world viability. Vapor phase TNP sensing was also accomplished upon drop-casted CP films. Experimental investigations and theoretical DFT study confirmed the cooperative occurrence of RET-IFE-PET-collisional quenching and non-covalent π⋯π stacking as key factors involved in the TNP sensing performance. The competency of 1 and 2 in the detection of TNP from several complex environmental matrices (CEMs), viz. matchstick powder, river and sewage water, and soil specimens, was also established with good recovery (∼66-86% and ∼68-93% for 1 and 2, respectively) and high KSV values (3.90-11.39 × 104 and 6.17-18.79 × 104 M-1 for 1 and 2, respectively).

Two-Dimensional Cu-Based MOF for Selective Staining of the Cellular Nucleus through Fluorescence Imaging and Selective Sorption of Dye Molecules in Aqueous Medium

A two-dimensional copper-based metal-organic framework, [Cu(C23H14O6)(C10H8N2)2]·H2O·DMSO, 1, was synthesized using pamoic acid (C23H16O6) and 4,4'-bipyridine (C10H8N2) as an organic ligand and Cu(II) as a metal ion. Single-crystal structure X-ray diffraction studies of the as-synthesized compound showed a two- dimensional structure with free hydroxyl groups. Upon excitation at 370 nm, the aqueous dispersion of [Cu(C23H14O6)(C10H8N2)2]·H2O·DMSO, 1, showed emission centered at 525 nm resulting from the intraligand energy transfer. Fluorescence microscopic experiments using a human epithelioid cervix carcinoma HeLa cell line were carried out, clearly showing that our compound selectively stained the cellular nucleus. To utilize the porous nature of [Cu(C23H14O6)(C10H8N2)2]·H2O·DMSO, 1, its dye sorption behavior in aqueous solution was determined, and a high affinity for methylene blue (MB) dye was confirmed. Our synthesized compound sorbed 88% MB dye with an initial concentration of 32 mg L-1, and its sorption capacity for MB was found to be 29.79 mg g-1. The possible mechanism of the dye sorption behavior was discussed in terms of the size and charge of dye molecules with respect to molecular-level interactions between the framework and the dye molecules.

In situ synthesis of porous metal-organic frameworks NH2-UiO-66 on tea stem biochar and application in odours adsorption

Multiple odour nuisance in livestock farming is a notorious problem that has a significant impact on the living environment of surrounding communities. Adsorbents based on metal-organic framework (MOF) materials show great promise for controlling odour pollution, as they offer a high specific surface area, a controllable structure and an abundance of active sites. However, the MOF formation process is prone to problems such as pore clogging or collapse and reduced porosity, which limits its further application. In this study, a series of odour adsorbents were prepared by in situ growth of NH2-UiO-66 on tea stem biochar (TSBC) using a hydrothermal method and named UiO (Zr)-TSBCx. The physical and chemical properties and composition of UiO (Zr)-TSBCx have been systematically characterized using SEM, TEM, XRD, FT-IR, N2 adsorption-desorption and XPS. The release of odours from the pig farm effluent was monitored using in-situ continuous Proton-Transfer-Reaction Mass Spectrometry (PTR-MS), and the obtained primary compositions were tested for further adsorption. In dynamic adsorption experiments focused on butyric acid, UiO (Zr)-TSBC2 showed a high adsorption capacity of 3.99 × 105 μg/g and exceptional structural stability. UiO (Zr)-TSBC2 showed variable adsorption efficiencies for different odorous gases, with the best performance for the removal of ammonia, toluene and butyric acid. It also demonstrated the ability to rapidly mitigate instantaneous high concentrations of hydrogen sulfide (H2S), methanethiol and toluene resulting from agitation. Additionally, based on the relationship between the adsorption amount and the structural characteristics of the adsorbent as well as the nature of the odours, a possible adsorption mechanism of UiO (Zr)-TSBC2 for a variety of odours released from pig farm effluent was proposed. This work demonstrates a novel approach to promote deodorization applications in livestock and poultry farming environments by the in-situ growth of NH2-UiO-66 on biochar prepared from tea stem.

Defect-enabling zirconium-based metal-organic frameworks for energy and environmental remediation applications

This comprehensive review explores the diverse applications of defective zirconium-based metal-organic frameworks (Zr-MOFs) in energy and environmental remediation. Zr-MOFs have gained significant attention due to their unique properties, and deliberate introduction of defects further enhances their functionality. The review encompasses several areas where defective Zr-MOFs exhibit promise, including environmental remediation, detoxification of chemical warfare agents, photocatalytic energy conversions, and electrochemical applications. Defects play a pivotal role by creating open sites within the framework, facilitating effective adsorption and remediation of pollutants. They also contribute to the catalytic activity of Zr-MOFs, enabling efficient energy conversion processes such as hydrogen production and CO2 reduction. The review underscores the importance of defect manipulation, including control over their distribution and type, to optimize the performance of Zr-MOFs. Through tailored defect engineering and precise selection of functional groups, researchers can enhance the selectivity and efficiency of Zr-MOFs for specific applications. Additionally, pore size manipulation influences the adsorption capacity and transport properties of Zr-MOFs, further expanding their potential in environmental remediation and energy conversion. Defective Zr-MOFs exhibit remarkable stability and synthetic versatility, making them suitable for diverse environmental conditions and allowing for the introduction of missing linkers, cluster defects, or post-synthetic modifications to precisely tailor their properties. Overall, this review highlights the promising prospects of defective Zr-MOFs in addressing energy and environmental challenges, positioning them as versatile tools for sustainable solutions and paving the way for advancements in various sectors toward a cleaner and more sustainable future.

Acidified groundnut cake for enhanced bio adsorption of anionic textile dye Reactive Red 195

This study focuses on the improvement of bioremediation of textile dye Reactive Red 195 using agro-industrial waste, groundnut oil cake (GNOC) obtained after oil-pressing. The treatment of GNOC with 1 N H2SO4 had resulted in physiochemical changes on the insoluble porous adsorbent, which improved their adsorption efficiency. The dye removal efficiency increased from 55% to 94% on acidification of GNOC. The raw groundnut oil cake (RGNOC) and acid-treated groundnut oil cake (AGNOC) were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction, and zeta potential. The rate and efficiency of dye adsorption were examined using adsorption kinetics and isotherm models. The results confirm that acid-treated GNOC eliminates impurities, alter the surface functional groups, and significantly increase porous surface areas of RGNOC. The investigation of key factors such as contact time, initial concentration of dye, static/agitation impact, particle size, and adsorbent dose had significantly influenced adsorption capacity of GNOC. Adsorption of dye fits best into the Langmuir model and equilibrium data of dye on AGNOC was explained by psuedo-second-order reaction with maximum adsorption capacity of 12.65 mg/g. This emphasis AGNOC has a very excellent potential to remove the textile dye Reactive Red dye from industrial effluent.

A magnetic graphene oxide and UiO-66 based homogeneous dual recognition electrochemical aptasensor for accurate and sensitive detection of aflatoxin B1

Aflatoxin (AFs) contamination is one of the serious food safety issues. Aflatoxin B1 (AFB1) is the most common and toxic aflatoxin, which has been classified as a class 1 carcinogen by the International Agency for Research on Cancer (IARC). It is extremely destructive to liver tissue. Developing a convenient and sensitive detection technique is essential. In this paper, we developed a homogeneous dual recognition strategy based electrochemical aptasensor for accurate and sensitive detection of aflatoxin B1 (AFB1) based on the magnetic graphene oxide (MGO) and UiO-66. The MGO was synthesized for the recognition and magnetic separation of AFB1 from complex samples. UiO-66/ferrocenecarboxylic acid (Fc)/aptamer composites were constructed as both recognition and signal probes. The probes would specifically capture AFB1 enriched by MGO, which enables dual recognition in homogeneous solution, thus further improving the accuracy of AFB1 detection. The electrochemical aptasensor for AFB1 had a linear range from 0.005 to 500 ng mL-1. Additionally, the limit of detection was 1 pg mL-1. It shows a favorable potential for both sensitive and accurate detection of AFB1 in real samples.

A sulfonate ligand-defected Zr-based metal-organic framework for the enhanced selective removal of anionic dyes

In this work, we introduce a novel defective analogue of the representative 6-connected zirconium-based metal-organic framework (MOF-808), by employing 5-sulfoisophthalic acid monosodium salt (H2BTC-SO3Na) as a defect inducer via a mixed-linker approach. The structural integrity and different physicochemical properties were investigated by various characterization techniques, including powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and nitrogen physisorption at 77 K. Additionally, proton nuclear magnetic resonance (1H-NMR), energy-dispersive X-ray (EDX), and inductively coupled plasma optical emission spectroscopy (ICP-OES) were employed to confirm the presence of 6.9 mol% of the 5-sulfoisophthalate ligand within the highly crystalline MOF-808 structure. The defective material exhibited significant enhancements in the removal efficiency of various organic dyes, including approximately 64% and 77% for quinoline yellow and sunset yellow, and 56% and 13% for rhodamine B and malachite green, compared to its pristine counterpart. Importantly, the defective MOF-808 showed a remarkable selectivity toward anionic species in binary-component dyes comprising both anionic and cationic dyes.

Synergistic photoinduced charge transfer resonance from porous ZIF-67 decorated violet phosphorus array for SERS immunoassay of SARS-CoV-2 spike protein

As a rapid, highly sensitive, and user-friendly technique, surface-enhanced Raman scattering (SERS) has an extraordinary appeal to home self-test of COVID-19 during the post pandemic era. However, most of the existing SERS substrates have been still criticized in stability, repeatability, and sample enrichment. To address these obstacles, a novel non-metallic SERS substrate with porous surfaces and array geometry was developed by in-situ growing ZIF-67 particles on two-dimensional violet phosphorus (VP) matrix. Chemical enhancement was prominently promoted by the synergistic photoinduced charge transfer resonance in the hybrid band structure of the ZIF-67@VP substrate, facilitating a noble metal-similar enhancement factor of 6.11 × 107. The biocompatible ZIF-67@VP porous array with attractive enhancement capability and high anchoring efficiency was further utilized to monitoring SARS-CoV-2 spike protein in practical saliva samples based on a sandwich immunostructure, achieving a limit of detection of 1.7 ng/mL assisted by black phosphorus nanosheets. This nonmetallic immunoassay strategy with exceptional sensitivity and specificity is predicted to extend the utilization of SERS obstacle in daily infectious disease screening.

Fabrication of an Fe-Doped ZIF-67 Derived Magnetic Fe/Co/C Composite for Effective Removal of Congo Red

The dyes in printing and dyeing wastewater are harmful to the human body and the environment. It is essential to develop practical and effective adsorbents to deal with them. In this study, an Fe-doped, ZIF-67 derived Fe/Co/C composite material with strong magnetism was successfully synthesized. The effects of pH, initial concentration, and adsorption time on the properties of the adsorbent were investigated. To further improve the removal efficiency and enhance the practicality, potassium peroxymonosulfate (PMS) was added to the system due to its Fenton-like effect. Then, an Fe/Co/C composite was used with PMS to remove Congo red (CR) with a 98% removal of 250 mg·L-1. Moreover, for its high saturation magnetization of 85.4 emu·g-1, the Fe/Co/C composite can be easily recovered by applying a magnetic field, solving the problem that powdery functional materials are difficult to recover and, thus, avoiding secondary pollution. Furthermore, since the composite material was doped before carbonization, this synthetic strategy is flexible and the required metal elements can be added at will to achieve different purposes. This study demonstrates that this Fe-doped, ZIF-67 derived magnetic material has potential application prospects for dye adsorption.

Defective UiO-66-NH2 (Zr) for Simultaneous Adsorption of Phosphate and Pb2+ for Hydrogen Peroxide Purification

Removal of hetero ions from the hydrogen peroxide solution is a crucial step in purifying electronic-grade H2O2. Conventional adsorption materials are challenged to meet the need for the simultaneous adsorption of both anions and cations in solvents. UiO-66 (Zr) modified by acetic acid and amino group for simultaneous adsorption of phosphate and Pb2+ in H2O2 purification was fabricated in this work. The as-prepared defective UiO-66-NH2 (Zr) demonstrated a significant increase in specific surface area and porosity, along with more exposed sites for phosphate and Pb2+ adsorption. The adsorption capacity of De-UiO-66-NH2 for phosphate and Pb2+ in H2O2 solution was 52.28 mg g-1 and 35.4 mg g-1, which is 1.19 times and 1.88 times that of unmodified UiO-66 (Zr), respectively. The trace simultaneous adsorption with both 100 ppb phosphate and Pb2+ showed removal rates of 94.0% and 88.7%, respectively, confirming the practicality of MOF materials in the purification of electronic chemicals. This work highlights the potential of Zr-based MOFs as anionic and cationic simultaneous adsorbents for highly efficient purification of electronic-grade solvents.

Functional UiO-66 for highly selective adsorption of N-nitrosodipropylamine: adsorption performance and mechanisms

N-Nitrosodipropylamine (NDPA) is a class of nitrogenous disinfection by-products (N-DBPs) with high toxicity. Although NDPA present in water bodies is at relatively low concentrations, the potential risk is high due to its high toxicity and bioaccumulation. Metal-organic frameworks (MOFs), a new type of porous material with remarkable functionality, have shown great performance in a wide variety of applications in adsorption. This is the first study investigating the adsorption of MOFs on NDPA. Herein, UiO-66 with -NH2 and imidazolium functional groups were synthesized by modifying UiO-66 after amination. Adsorption kinetics and isotherm models were used to compare the adsorption properties of the two materials for low-concentration NDPA in water. The results showed that the behavior of all the adsorbents was consistent with the Langmuir model and the pseudo-second-order model and that the adsorption was homogeneous chemisorption. The structures of the nanoparticles were characterized by FTIR, zeta potential, XRD, SEM and BET measurements. Based on the characteristics, four adsorption mechanisms, namely electron conjugation, coordination reaction, anion-π interaction, and van der Waals forces, were simultaneously involved in the adsorption. The influencing factor experiment revealed that the adsorption of UiO-66-NH2 and (I-)Meim-UiO-66 involved hydrogen bonding and electrostatic interactions, respectively.

Recent trends in wastewater treatment by using metal-organic frameworks (MOFs) and their composites: A critical view-point

Respecting the basic need of clean and safe water on earth for every individual, it is necessary to take auspicious steps for waste-water treatment. Recently, metal-organic frameworks (MOFs) are considered as promising material because of their intrinsic features including the porosity and high surface area. Further, structural tunability of MOFs by following the principles of reticular chemistry, the MOFs can be functionalized for the high adsorption performance as well as adsorptive removal of target materials. However, there are still some major concerns associated with MOFs limiting their commercialization as promising adsorbents for waste-water treatment. The cost, toxicity and regenerability are the major issues to be addressed for MOFs to get insightful results. In this article, we have concise the current strategies to enhance the adsorption capacity of MOFs during the water-treatment for the removal of toxic dyes, pharmaceuticals, and heavy metals. Further, we have also discussed the role of metallic nodes, linkers and associated functional groups for effective removal of toxic water pollutants. In addition to conformist overview, we have critically analyzed the MOFs as adsorbents in terms of toxicity, cost and regenerability. These factors are utmost important to address before commercialization of MOFs as adsorbents for water-treatment. Finally, some future perspectives are discussed to give directions for potential research.

Magnetic Fe3O4@SiO2 study on adsorption of methyl orange on nanoparticles

Magnetic core-shell Fe3O4@SiO2 nanoparticles were synthesized by sol-gel method. Based on the characterization and experimental results, the adsorbent was found to have an average particle size of approximately 120 nm, a pore size range of 2-5 nm and superparamagnetic properties. It exhibited electrostatic and hydrogen bonding interactions during adsorption of methyl orange (MO). The adsorption of MO on the magnetic Fe3O4@SiO2 nanoparticles exhibited pseudo-second-order kinetics, the adsorption process is a spontaneous endothermic adsorption process, which conforms to the Langmuir adsorption isotherm model. he maximum amount of MO was adsorbed at pH = 2, T = 45 °C and t = 30 min, and the highest adsorption capacity was 182.503 mg/g; The unit adsorption capacity of the Fe3O4@SiO2 nanoparticles still reached 83% of the original capacity after 5 cycles, so the material was reusable and met the requirements of environmental protection. This study reveals the great potential of magnetic mesoporous nanoparticles for removal of dyes from wastewater.

New insights on the preparation of amine covalent organic polymer and its adsorption properties

Dye pollution is becoming increasingly severe. This study used the Schiff base reaction to synthesize a polyaromatic ring covalent organic polymer material with amide bonds and high electronegativity named SLEL-9 to adsorb Methylene Blue (MB) and Rhodamine B (RhB). SLEL-9 was characterized by Fourier transform infra-red spectra, X-ray photoelectron spectra, Brunauer-Emmett-Teller (BET), zeta potential analysis, and other techniques. It was found that SLEL-9 material contains C-C, CN, C-N, and CO. SLEL-9 had a zeta potential of about -45 mV under neutral conditions, which proved that the material had been synthesized successfully. The BET and Langmuir surface areas of SLEL-9 were 35.187 m2 g-1 and 56.419 m2 g-1, respectively. The adsorptions of SLEL-9 on low concentration (10 mg L-1) Methylene Blue and Rhodamine B reached equilibrium within 48 h. The results showed that SLEL-9's adsorption of dye molecules are more consistent with pseudo-second-order kinetic and Langmuir isotherm model. The adsorption experiments showed that the adsorption process is a spontaneous endothermic reaction, mainly chemisorption. The maximum adsorption capacity of SLEL-9 for MB and RhB were 132.45 mg g-1 and 101.94 mg g-1. In addition, this study investigated to determine the optimal reaction parameters. The primary mechanisms of SLEL-9 adsorption of two dyes are n→π* interaction, π-π EDA interaction and electrostatic attraction. Selective adsorb ability experiment results showed that SLEL-9 could selectively adsorb MB and RhB to a certain extent. Finally, it was found that SLEL-9 can maintain over 70% adsorption capacity after five reuses and can maintain stability after soaking in different pH water and organic solvents for 120 h. SLEL-9 proved to be a promising organic covalent polymer adsorption material for the removal of Methylene Blue and Rhodamine B in water.

Green preparation of magnetic ferroferric oxide-polyvinyl alcohol-alginate coated UiO-67 nanospheres: Characterization, adsorption properties and adsorption mechanism of methylene blue

In this paper, a kind of magnetic ferric oxide/polyvinyl alcohol/calcium alginate/UiO-67 (Fe3O4/PVA/CA/UiO-67) nanospheres with homogeneous surface interconnecting structures was prepared by using macromolecular polymer polyvinyl alcohol and sodium alginate as carriers and zirconium organic skeleton as nanocrystals. The properties of magnetic nanospheres were studied by SEM, FT-IR, TGA, XRD, BET, VSM and Zeta potential. The impression of diverse temperatures, MB concentrations, interaction time, pH, and magnetic aerogel sphere dose on MB removal was studied. The optimum adsorption temperature and pH of magnetic nanospheres for MB were 298 K, and 10, respectively. Langmuir simulated that the maximum removal of MB by magnetic nanospheres at room temperature (298 K) was 1371.8 mg/g. The removal of MB by magnetic nanospheres complied with the pseudo-first-order kinetic model. The isotherm simulation can infer that the Langmuir model was more comply with MB adsorption on magnetic aerogel spheres. Thermodynamic studies have confirmed that the removal of MB by magnetic nanospheres was exothermic and spontaneous. The interaction mechanism of MB on magnetic nanospheres can be deduced by FT-IR and BET, including hydrogen bond, π-π bond, electrostatic interaction, and mesoporous pore flow. The removal rate of nanospheres for MB still reached 70.06 % after six cycles.

A New Strategy of Chemical Photo Grafting Metal Organic Framework to Construct NH2-UiO-66/BiOBr/PVDF Photocatalytic Membrane for Synergistic Separation and Self-Cleaning Dyes

Photocatalytic membranes are typical multifunctional membranes that have emerged in recent years. The lack of active functional groups on the surface of membranes made of inert materials such as polyvinylidene fluoride(PVDF) makes it difficult to have a stable binding interaction with photocatalysts directly. Therefore, in this study, we developed a simple method to prepare NH2-UiO-66/BiOBr/PVDF(MUB) membranes for efficient dye treatment by grafting benzophenolic acid-functionalized NH2-UiO-66 onto the surface of membranes with photocatalytic properties under visible light irradiation using benzophenolic acid with photoinitiating ability as an anchor. The structural characteristics, photocatalytic properties, antifouling properties, and reusability of the composite membranes were investigated in subsequent experiments using a series of experiments and characterizations. The results showed that the benzophenone acid grafting method was stable and the nanoparticles were not easily dislodged. The MUB composite membrane achieved a higher dye degradation efficiency (99.2%) than the pristine PVDF membrane at 62.9% within a reaction time of 180 min. In addition, the composite membranes exhibited higher permeate fluxes for both pure and mixed dyes and also demonstrated outstanding water flux recovery (>96%) after the light self-cleaning cycle operation. This combination proved to improve the performance of the membranes instead of reducing them, increasing their durability and reusability, and helping to broaden the application areas of membrane filtration technology.

Adsorption and decolorization study of reactive black 5 by immobilized metal-organic framework of UiO-66 and Gloeophyllum trabeum fungus

This study aimed to investigate immobilized metal-organic framework (MOF) UiO-66 and brown-rot fungus Gloeophyllum trabeum (GT) in PVA-SA matrices for adsorption and decolorization of reactive black 5 (RB5). Furthermore, UiO-66/GT@PVA-SA composite was successfully fabricated and obtained by immobilizing UiO-66 and GT mycelia into a mixture of PVA-SA. This composite demonstrated a decolorization ability of 80.12% for RB5 after 7 days. The composite's reusability was assessed for three cycles; at last, it only achieved 21%. This study reported that adsorption of RB5 by the composite followed a pseudo-second-order kinetic model with a correlation coefficient (R2) of 0.9997. The Freundlich model was found to be suitable for the isotherm adsorption. The process was also spontaneous and feasible, as indicated by the negative ΔG value. Subsequently, four metabolite products resulting from decolorization of RB5 by UiO-66/GT@PVA-SA composite were proposed, namely: C24H19N5Na2O13S4 (m/z = 762), C10H13N2O8S2- (m/z = 353), C12H9N4O7S2- (m/z = 384), and C10H13O8S2- (m/z = 325).

Preparation of a Multifunctional and Multipurpose Chitosan/Cyclodextrin/MIL-68(Al) Foam Column and Examining Its Adsorption Properties for Anionic and Cationic Dyes and Sulfonamides

A multifunctional cylindrical hybrid foam column, referred to as the chitosan/cyclodextrin/MIL-68(Al) (CS/CD/MIL-68(Al)) foam column, was prepared for the first time. The prepared foam column could be used for the adsorption/removal of hydrophilic and hydrophobic contaminants by different forms. Here, it was placed in hydrophilic dye solutions to investigate the adsorption behavior of methylene blue and trypan blue. The adsorption process followed the pseudo-second-order kinetic model with R2 ranging from 0.9983 to 0.9998 for methylene blue and from 0.9993 to 1.0000 for trypan blue, and the adsorption process was consistent with the Langmuir isothermal model with R2 greater than 0.96. The RL values for methylene blue and trypan blue were 0.8871 and 0.5366, respectively, which were present between 0 and 1, indicating that the adsorption behaviors of the two dyes onto the CS/CD/MIL-68(Al) foam column were favorable. The maximum adsorption capacities (Qm) of methylene blue and trypan blue were 60.61 and 454.55 mg/g at 298 K, respectively. Also, the CS/CD/MIL-68(Al) foam column was spun into a syringe and used to adsorb trace hydrophobic sulfonamides from water in the form of filtration. The porous structure impeded the need for any external force and equipment, allowing the water sample to pass through the foam column smoothly. The conditions of the CS/CD/MIL-68(Al) foam column were optimized. The adsorption was carried out under the condition of pH = 4, the amount of the adsorbent was two foam columns, and no salt was added. It was found that the removal rate of the CS/CD/MIL-68(Al) foam column for six sulfonamides was 100%, and it could be reused at least five times. Therefore, this CS/CD/MIL-68(Al) foam column had a simple preparation method, offered a flexible and diverse form of use, was nonpolluting, biodegradable, and reusable, and could have a wider application in the field of environmental pollutant removal and adsorption.

Porous amorphous metal-organic frameworks based on heterotopic triangular ligands for iodine and high-capacity dye adsorption

The research on amorphous metal-organic frameworks (aMOFs) is still in its infancy, and designing and constructing aMOFs with functional pores remains a challenge. Two aMOFs based on Co(II) and heterotopic triangular ligands with large conjugated aromatic planes, namely aMOF-1 and aMOF-2, were constructed and characterized by IR, XPS, EA, ICP, XANS and so on. aMOF-1 possesses mesopores, whereas aMOF-2 possesses micropores. The porosity, conjugated aromatic plane and uncoordinated N atoms in the framework allow these aMOFs to adsorb iodine and dyes. The iodine adsorption capacity of aMOF-1 is 3.3 g per g, which is higher than that of aMOF-2 (0.56 g per g), mainly due to the expansion or swelling of aMOF-1 after iodine adsorption. The uptake of cationic dyes by aMOF-2 showed more rapid kinetics and a higher removal rate than that by aMOF-1, mainly due to the difference in the porosity and surface charge. Although the surface charges of aMOF-1 and aMOF-2 are negative, both of them showed significantly faster adsorption kinetics toward anionic dyes, among which methyl orange (MO) and Congo red (CR) can be removed in 5 min. This occurs possibly because the quick adsorption of Na+ ions alters the surface charge of the framework and promotes dye uptake. The adsorption capacities of aMOF-1 for MO and CR reached 921 and 2417 mg g-1, respectively. The correlation data for aMOF-2 are 1042 and 1625 mg g-1, respectively. All adsorption capacities are among the highest compared to many cMOFs. Adsorption in mixed dye solution is found to be charge-dependent, kinetic-dependent, and synergetic in these systems. The porosity, surface charge regulation during adsorption, weak interactions and multiple adsorption processes contribute to the dye adsorption performance.

Rapid synthesis of cerium-UiO-66 MOF nanoparticles for photocatalytic dye degradation

An unprecedented synthesis method is used to form a series of Ce-UiO-66-X (X = NH2, OH, H, NO2, COOH) metal-organic frameworks by precipitation from mixed solvents, with instantaneous crystallisation on combining separate solutions of ligands and metal precursors. This allows the first direct synthesis of Ce-UiO-66-OH. Powder X-ray diffraction (PXRD) shows that all materials are pure phase with a broadened profile that indicates nano-scale crystallite domain size. The effect of different functional groups on the benzene-1,4-dicarboxylate linker within the UiO-66 structure has been investigated on degradation of two cationic (methylene blue and rhodamine B) and two anionic (Congo red, and Alizarin red S) dyes under UV and visible light irradiation at room temperature. Analysis of the dye adsorption in the absence of light is accounted for using pseudo-first order kinetics, and the Ce-UiO-66-NH2, Ce-UiO-66-OH, and Ce-UiO-66-H materials display a considerable photocatalytic activity to degrade Alizarin red S and Congo red rapidly between 1 and 3 minutes. The materials show excellent photostability and recyclability under UV and visible light, with no loss of crystallinity seen by PXRD and activity maintained over 5 cycles, with 16 hours photostability for Ce-UiO-66-NH2.

Ultrasonication-Tailored Graphene Oxide of Varying Sizes in Multiple-Equilibrium-Route-Enhanced Adsorption for Aqueous Removal of Acridine Orange

Graphene oxide (GO) has shown remarkable performance in the multiple-equilibrium-route adsorption (MER) process, which is characterized by further activation of GO through an in-situ reduction process based on single-equilibrium-route adsorption (SER), generating new adsorption sites and achieving an adsorption capacity increase. However, the effect of GO on MER adsorption in lateral size and thickness is still unclear. Here, GO sheets were sonicated for different lengths of time, and the adsorption of MER and SER was investigated at three temperatures to remove the typical cationic dye, acridine orange (AO). After sonication, we found that freshly prepared GO was greatly reduced in lateral size and thickness. In about 30 min, the thickness of GO decreased dramatically from several atomic layers to fewer atomic layers to a single atomic layer, which was completely stripped off; after that, the monolayer lateral size reduction dominated until it remained constant. Surface functional sites, such as hydroxyl groups, showed little change in the experiments. However, GO mainly reduces the C=O and C-O bonds in MER, except for the conjugated carbon backbone (C-C). The SER adsorption kinetics of all temperatures fitted the pseudo-first-order and pseudo-second-order models, yet room temperature preferred the latter. An overall adsorption enhancement appeared as sonication time, but the equilibrium capacity of SER GO generally increased with thickness and decreased with the single-layer lateral size, while MER GO conversed concerning the thickness. The escalated temperature facilitated the exfoliation of GO regarding the adsorption mechanism. Thus, the isotherm behaviors of the SER GO changed from the Freundlich model to Langmuir as size and temperature changed, while the MER GO were all of the Freundlich. A record capacity of ~4.3 g of AO per gram of GO was obtained from the MER adsorption with a sixty-minute ultrasonicated GO at 313.15 K. This work promises a cornerstone for MER adsorption with GO as an adsorbent.

Selective adsorption of anionic and cationic dyes on mesoporous UiO-66 synthesized using a template-free sonochemistry method: kinetic, isotherm and thermodynamic studies

In this study, template-free mesoporous UiO-66(U) has been successfully synthesized in shortened time by sonochemical methods and provided energy savings. The synthesized mesoporous UiO-66(U) demonstrated irregular morphology particle around 43.5 nm according to the SEM image. The N2 adsorption-desorption isotherm indicated an irregular, 8.88 nm pore width mesoporous structure. Ultrasonic irradiation waves greatly altered mesoporous materials. A mechanism for mesoporous UiO-66(U) formation has been proposed based on the present findings. Sonochemical-solvent heat saves 97% more energy than solvothermal. Mesoporous UiO-66(U) outperformed solvothermal-synthesized UiO-66(S) in adsorption. These studies exhibited that mesopores in UiO-66 promote dye molecule mass transfer (MO, CR, and MB). According to kinetics and adsorption isotherms, the pseudo-second-order kinetic and Langmuir isotherm models matched experimental results. Thermodynamic studies demonstrated that dye adsorption is spontaneous and exothermically governed by entropy, not enthalpy. Mesoporous UiO-66(U) also showed good anionic dye selectivity in mixed dye adsorption. Mesoporous UiO-66(U) may be regenerated four times while maintaining strong adsorption capability.

Tuning the Dual Active Sites of Functionalized UiO-66 for Selective Adsorption of Yb(III)

The recovery of rare earth elements (REEs) from discharged electronic devices or mineral waste water is highly essential but still facing challenges. In this work, two amino-functionalized carboxyl-UiO-66 (UiO-66-COOH-TETA and UiO-66-(COOH)₂-ED) prepared via the postmodification method were employed as the adsorbents for Yb(III) capture. The experimental results revealed their superior adsorption capacities of 161.5 and 202.6 mg/g, respectively. Meanwhile, their adsorption processes can be described by the pseudo-second-order kinetic model and Langmuir model. Effects of initial pH and temperature on adsorptions were systematically evaluated, affording an optimal operating condition (i.e., pH of 5.5-6, T of 65 °C, t of 10 h). Moreover, the fabricated materials exhibited great reusability after five adsorption-regeneration cycles. UiO-66-COOH-TETA demonstrated good separation selectivity for Yb(III) over light REEs (i.e., 3.98 of Yb/Ce, 3.51 of Yb/Nd). Based on the density functional theory calculations and characterization analysis (XPS, Zeta, mapping, and IR), the adsorption mechanisms were mainly attributed to significant electrostatic attraction and strong surface complexation between N and O sites and Yb(III).

Zr-MOF/NiS2 hybrids on nickel foam as advanced electrocatalysts for efficient hydrogen evolution

As a typical transition-metal sulfides (TMS), nickel disulfide (NiS₂) has attracted great attention in terms of hydrogen evolution reaction (HER). Howbeit, owing to the poor conductivity, slow reaction kinetics and instability of NiS₂, its HER activity is still necessary to be improved. In this work, we designed hybrid structures consisting of the nickel foam (NF) as a self-supporting electrode, NiS₂ derived from the sulfuration of NF and Zr-MOF grown on the surface of NiS₂@NF (Zr-MOF/NiS₂@NF). Due to the synergistic effect between the different constituents, the obtained Zr-MOF/NiS₂@NF demonstrates ideal electrochemical hydrogen evolution ability in acidic and alkalescent environment, reaching a standard current density of 10 mA cm^-2 at overpotentials of 110 and 72 mV in 0.5 M H₂SO₄ and 1 M KOH electrolytes, respectively. What is more, it also maintains excellent electrocatalytic durability for 10 h in both electrolytes. This work could provide a useful guidance on effectively combining metal sulfide with MOF for high-performance HER electrocatalysts.

Fe3O4 supported UiO-66 (Zr) metal-organic framework for removal of drug contaminants from water: fuzzy logic modeling approach

The increase in production and consumption of pharmaceuticals and personal care products causes environmental problems. In this study, naproxen and clofibric acid adsorption were studied using Fe₃O₄-supported UiO-66 (Zr) metal-organic framework (Mag-UiO-66). The adsorption processes were carried out in batch mode at pH value 3.0. The optimum adsorbent quantities, equilibrium periods, pseudo-first-order (PFO), pseudo-second-order (PSO), and intra-particles diffusion kinetic models were calculated. Non-linear Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Sips isotherm equations were applied to experimental data. Thermodynamic analyses of naproxen and clofibric acid adsorption were also carried out in this study. The Langmuir isotherm q_m values were found as 14.15 mg/g for naproxen at 308 K and 41.87 mg/g for clofibric acid at 298 K. Both of the adsorption processes were exothermic. MISO (multi-input single-output) fuzzy logic models for removal of both naproxen and clofibric acid adsorptions were designed based on the experimental data to estimate the removal uptake values. It is noteworthy that the results obtained through designed fuzzy logic models matched well with the experimental data and the findings of this study emphasize the validity of designed fuzzy logic models.

Dibenzothiophene Removal from Fuel Oil by Metal-Organic Frameworks: Performance and Kinetics

Desulfurization of organic sulfur in the fuel oil is essential to cut down the emission of sulfur dioxide, which is a major precursor of the acid rain and PM2.5. Currently, hydrodesulfurization is regarded as a state-of-art technology for the desulfurization of fuel oil. However, due to the stringent legislation of the fuel oil, the deep desulfurization technology is urgent to be developed. Adsorptive desulfurization method is promising due to the high selectivity and easy operation. The development of efficient adsorbent is important to advance this technology into industrial application. In this work, the five types of metal-organic frameworks (MOFs), including Cu-BTC, UMCM-150, MIL-101(Cr), UIO-66, and Cu-ABTC were synthesized for the adsorption of dibenzothiophene (DBT), a typical organic sulfur compound in the fuel oil. The experimental results revealed that the adsorption capacity of the five MOFs followed the order of Cu-ABTC, UMCM-150, Cu-BTC, MIL-101(Cr), and UIO-66, which adsorption capacities were 46.2, 34.2, 28.3, 26.3, and 22.0 mgS/g, respectively. The three types of Cu-based MOFs such as Cu-ABTC, UMCM-150, and Cu-BTC outperformed the Cr-based MOFs, MIL-101, and Zr-based MOFs, UIO-66. Since the surface area and pore volumes of the Cu-based MOFs were not the greatest among the tested five MOFs, the physical properties of the MOFs were not the only limited factor for the DBT adsorption. The π-complexation between DBT and linkers/metal in the MOFs was also important. Kinetic analysis showed that the DBT adsorption onto the five tested MOFs follows the pseudo-second-order kinetics, confirming that the chemical π-complexation was also contributed to the DBT adsorption. Furthermore, the operation parameters such as oil-adsorbent ratio, initial sulfur concentration and adsorption temperature for the DBT adsorption onto Cu-ABTC were optimized to be 100:1 g/g, 1000 mgS/L and 30 °C, respectively. This work can provide some insights into the development of efficient adsorbent for the organic sulfur adsorption.

Removal of methyl orange wastewater by Ugi multicomponent reaction functionalized UiO-66-NS

The efficient and rapid removal of organic dyes from wastewater remains a complex and challenging task. In this study, UiO-66-NH₂ was prepared by solvothermal synthesis, and then, UiO-66-NS was prepared by compounding L-cysteine with UiO-66-NH₂ via the Ugi reaction for the efficient removal of methyl orange. UiO-66-NS was prepared by the addition of 1 mmol L-cysteine and showed good adsorption of methyl orange with 92.00% removal. Pseudo-second-order kinetics and Langmuir isotherms more accurately described the adsorption process of UiO-66-NS on methyl orange, which indicated that the adsorption process was dominated by monolayer adsorption of chemical reactions, and the maximum adsorption amounts of UiO-66-NS on methyl orange were 242.72 mg/g at 298 K. In addition, UiO-66-NS exhibited ultrahigh stability in acidic, neutral, and alkaline media (pH = 3-10), but its adsorption of methyl orange after 5 cycles was only 59.53% of the maximum adsorption amount. The adsorption mechanism is primarily electrostatic adsorption of UiO-66-NS with methyl orange, hydrogen bonding, and π-π interactions. This atomically economical Ugi multicomponent reaction provides new ideas for the preparation of structurally designable adsorbents with excellent performance.

Negatively Charged Composite Nanofibrous Hydrogel Membranes for High-Performance Protein Adsorption

Nanofibrous materials are considered as promising candidates for fabricating high-efficiency chromatography media, which are urgently needed in protein pharmaceuticals purification and biological research, yet still face several bottlenecks. Herein, novel negatively charged composite nanofibrous hydrogel membranes (NHMs) are obtained by a facile combination of electrospinning and surface coating modification. The resulting NHMs exhibit controllable morphologies and chemical structures. Benefitting from the combined effect of the stable framework of silicon dioxide (SiO₂) nanofiber and the function layer of negatively charged hydrogel, as well as good pore connectivity among nanofibers, NHMs exhibit a high protein adsorption capacity of around 1000 mg g^-1, and are superior to the commercial cellulose fibrous adsorbent (Sartobind^®) and the reported nanofibrous membranous adsorbents. Moreover, due to their relatively stable physicochemical and mechanical properties, NHMs possess comprehensive adsorption performance, favorable resistance to acid and solvents, good selectivity, and excellent regenerability. The designed NHMs composite adsorbents are expected to supply a new protein chromatography platform for effective protein purification in biopharmaceuticals and biochemical reagents.

In Situ Generated UiO-66/Cotton Fabric Easily Recyclable for Reactive Dye Adsorption

In view of the environmental pollution caused by the widespread use of reactive dyes in the printing and dyeing industry, the modified cotton fabric was loaded with the extremely stable metal-organic frame (MOF) material UiO-66 for removing reactive dyes from colored wastewater. UiO-66/cotton fabric was prepared by in situ synthesis, and its surface morphology and structure were analyzed by XRD, SEM, BET, and XPS. The adsorption performance of UiO-66/cotton fabric on reactive dyes was investigated by adsorbent dosage, adsorption time and temperature, dye concentration, pH, and so on. The results indicated that the adsorption equilibrium time of UiO-66/cotton fabric on reactive orange 16 was 120 min, and the removal rate was about 98%. The adsorption process belongs to simple molecular layer chemisorption and can be regarded as a spontaneous heat absorption reaction, which was consistent with the proposed secondary kinetic model and Langmuir isothermal adsorption model. In addition, the reactive dyes with a higher molecular weight of each sulfonic acid group are more hydrophobic, and the dyes are more likely to aggregate and deposit on the adsorbent surface by electrostatic attraction, hydrogen bonding, and π-π accumulation. Therefore, this work provides a potential UiO-66/cotton fabric application for the effective adsorption of reactive dyes in textile wastewater.

Electrochemical degradation of methylene blue by Pb modified porous SnO2 anode

A significant number of pollutants in wastewater can be electrocatalytically oxidized by SnO₂-Sb, a relatively inactive electrode. However, the arduous process of environmental remediation due to poor electrochemical performance and short service life of the traditional Ti/SnO₂-Sb electrode. In this work the SnO₂ electrode with a micron-sized sphere structure was prepared by in-situ hydrothermal. The results of the study that the electrode (Pb-10%) synthesized from the precursor solution in which the Pb:Sn molar ratio is 10% exhibits excellent electrooxidation properties. Impressiveing, the Pb-10% electrode displayed the small charge transfer resistance (10.71 Ω) and the high oxygen evolution potential (2.26 V vs. SCE). Thus, the electrochemical degradation experiment demonstrates that 100 mg L^-1 MB was degraded by Pb-10% electrode under the condition of initial pH = 5, and the decolorization rate reached 94.6%. Moreover, the influence of different parameters such as Pb doping amount, initial pH value of solution, initial concentration of MB and inorganic ions on degradation efficiency were also explored, in turn the practical application of electrodes in the field of purifying water resources is optimized. It is worth noting that the service life of the optimized electrode (100 mA cm^-2, 0.5 M H₂SO₄, 90 h) is about 12 times longer than that of the bare electrode (Sn-Sb). Therefore, the high-performance Ti/SnO₂-Sb electrode prepared in this work possesses vast application prospects in the electrocatalytic oxidation.

Effective Removal of Tetracycline from Water Using Copper Alginate @ Graphene Oxide with In-Situ Grown MOF-525 Composite: Synthesis, Characterization and Adsorption Mechanisms

For nanomaterials, such as GO and MOF-525, aggregation is the main reason limiting their adsorption performance. In this research, Alg-Cu@GO@MOF-525 was successfully synthesized by in-situ growth of MOF-525 on Alg-Cu@GO. By dispersing graphene oxide (GO) with copper alginate (Alg-Cu) with three-dimensional structure, MOF-525 was in-situ grown to reduce aggregation. The measured specific surface area of Alg-Cu@GO@MOF-525 was as high as 807.30 m²·g^-1, which is very favorable for adsorption. The synthesized material has affinity for a variety of pollutants, and its adsorption performance is significantly enhanced. In particular, tetracycline (TC) was selected as the target pollutant to study the adsorption behavior. The strong acid environment inhibited the adsorption, and the removal percentage reached 96.6% when pH was neutral. Temperature promoted the adsorption process, and 318 K adsorption performance was the best under experimental conditions. Meanwhile, 54.6% of TC could be removed in 38 min, and the maximum adsorption capacity reached 533 mg·g^-1, far higher than that of conventional adsorption materials. Kinetics and isotherms analysis show that the adsorption process accords with Sips model and pseudo-second-order model. Thermodynamic study further shows that the chemisorption is spontaneous and exothermic. In addition, pore-filling, complexation, π-π stack, hydrogen bond and chemisorption are considered to be the causes of adsorption.

Amine-Modified Carbon Xerogels as Effective Carbon-Based Adsorbents of Anionic Dye from Aqueous Solutions

Carbon xerogels were obtained by polycondensation of resorcinol and formaldehyde in a water medium. Their surface was oxidized by ammonium persulfate and then modified with amine groups. Four amines were used: methylamine, ethylamine, propylamine, and ethylenediamine, differing in carbon chain length and number of amine groups. The materials were characterized by low-temperature nitrogen sorption, elemental analysis, thermal analysis, X-ray diffraction, infrared spectroscopy, and determination of the surface oxygen group content with the use of the Boehm method. The final carbon adsorbents had surface areas ranging from 172-663 m²/g and acid-base nature. They were applied for adsorption of thymol blue from water solution. The sorption capacities of the studied adsorbents ranged from 83 to 140 mg/g. The presence of amine groups on the xerogel surface was found to increase its sorption capacity towards the dye studied. The dye adsorption process is endothermic and spontaneous, as indicated by the positive values of ΔH and the negative values of ΔG, respectively. The kinetics of adsorption of thymol blue was established to be described by the pseudo-second-order model. The equilibrium data were analyzed by the Langmuir and Freundlich models. The character of thymol blue adsorption is much better described by the Langmuir isotherm.

Evaluation of Zn Adenine-Based Bio-MOF for Efficient Remediation of Different Types of Dyes

As an eco-friendly material, Zn-adeninate bio-metal-organic framework (bio-MOF) was investigated as an efficient adsorbent for both anionic and cationic dyes. The adsorption capability of the synthesized Zn-adeninate bio-MOF was confirmed by its notable surface area of 52.62 m2 g−1 and total pore volume of 0.183 cm3 g−1. The bio-MOF adsorption profiles of anionic direct red 81 (DR-81) and cationic methylene blue (MB) dyes were investigated under different operating parameters. The optimum dosages of Zn-adeninate bio-MOF were 0.5 g L−1 and 1 g L−1 for MB and DR-81 decolorization, respectively. The pHPZC of Zn-adeninate bio-MOF was 7.2, and maximum monolayer adsorption capacity was 132.15 mg g–1 for MB, which decreased to 82.54 mg g–1 for DR-81 dye. Thermodynamic data indicated the spontaneous and endothermic nature of the decolorization processes. Additionally, the adsorption processes were in agreement with the Langmuir and pseudo-second-order kinetic models. The synthesized Zn-adeninate bio-MOF could be reused several times with high decolorization ability. These findings demonstrated that the synthesized Zn bio-MOF is an effective and promising adsorbent material for the removal of both cationic and anionic dyes from polluted water.