Efficient adsorptive removal of Congo red from aqueous solution by synthesized zeolitic imidazolate framework-8

Unveiling the remarkable simultaneous adsorption-photocatalytic potential of Ag nanoparticles-anchored phosphotungestic acid loaded ZIF-8 for Congo red removal

This research paper presents a direct approach to synthesize AgNPs deposited on polyoxometalate/ZIF-8 on-site (referred to as AgNPS@PW@ZIF-8) to develop a highly efficient photocatalyst in the water treatment. Phosphotungestic acid (PW) serves a multi-purpose in this context: it acts as a bridge layer between AgNPs and Zeolitic Imidazolate Framework-8 (ZIF-8), a local reducing agent, and a catalyst for electron transfer during the photocatalysis process. A comprehensive characterization of the resulting nanostructure was performed utilizing an array of techniques, such as XRD, FTIR, EDX, TEM, BET, Raman, and TGA. The nanostructure that was created exhibited effective removal of Congo red at different pH levels via a combination of simultaneous adsorption and photocatalysis. After 60 min at pH 7, the dye molecules were completely eliminated in the presence of 0.5 g/L AgNPS@PW@ZIF-8 at room temperature. The charge transfer can be facilitated by the PW bridge layer connecting AgNPs and ZIF-8, owing to the photoactive characteristics and strong electron transfer capabilities of PW molecules. Strong electron transferability of PW between Ag nanoparticles and ZIF-8 facilitates charge transfer and significantly improves the photocatalytic performance of ZIF-8. Moreover, the nanostructure demonstrated great structural stability and recyclability, sustaining a high efficiency of removal throughout five consecutive cycles through the implementation of a simple procedure. Widespread applications of the developed nanostructure in aquatic environments for adsorption and photocatalytic reactions are possible.

Valorization of spent brewery yeast biosorbent with sonication-assisted adsorption for dye removal in wastewater treatment

The effluent of textile industries containing synthetic dyes contributed to substantial pollution to water bodies. The biosorption process of Congo Red dye was successfully performed by integrating ultrasonication in the adsorption step with spent brewery yeast as a novel and renewable biosorbent. The adsorption process was hindered when ultrasonication was employed together with the biosorbent, indicating that desorption process had occurred. The adsorption process showed that 4 g/L of biosorbent was the optimum dosage for adsorption of 50 mg/L of Congo Red dye, and that the adsorption equilibrium fitted to the Langmuir model, with kinetics best fitted with pseudo-second order model. The maximum capacity of the adsorption was 52.6 mg/g, showing the potential of spent brewery yeast to aid in removing wastewater pollutants. Maximal Congo Red dye recovery (100%) was achieved in the sonication-assisted desorption studies using 0.01M NaOH as the eluting agent. The ultrasonication effects contributed to the efficient recovery of dye and good conversion of spent brewery yeast to biosorbent can be beneficial for treating pollution from textile wastewater.

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.

Effect of the synthesis pH, the nature of the divalent cations and the metal salt concentration on the formation of layered double hydroxides for removal of Cochineal Red A dye from aqueous solutions

In this research work, removal of Cochineal Red A dye from aqueous solution was studied using layered double hydroxide materials prepared by a coprecipitation method at variable pH. The effects of the synthesis pH, the nature of the divalent cations and the total metal salt concentration on the formation of layered double hydroxides and their application to the removal of Cochineal Red A dye from aqueous solution were investigated. The structure of the materials prepared was characterized by X-ray diffraction and Fourier transform infrared. It was found that the nature and content of the bi- and trivalent metal ions in the layered double hydroxide influenced the adsorption. Ni–Fe had 0.96 to 1.70 times more adsorption capacity before reaching its equilibrium adsorption than Zn–Fe prepared at pH 7–9 with 2.2 M of total metal salt concentration. No difference was observed in the amount of Cochineal Red A dye adsorbed onto Zn–Fe prepared at both pH 7–9 and pH 10–11 in the range 1.1–3.3 M of total metal salt concentration. The results show that the increase in the precipitation pH leads to decreasing adsorption capacity. The Cochineal Red A dye adsorption follows the Temkin model for the Ni–Fe and Zn–Fe prepared at pH 7–9 and follows the Langmuir model for the Zn–Fe synthesized at pH 10–11 with high coefficient correlation. The adsorption kinetics data fitted the pseudo-second-order model. A thermodynamic study indicates that the adsorption process is both spontaneous and endothermic in nature.

Separation and remediation of environmental pollutants using metal-organic framework-based tailored materials

Metal-organic frameworks (MOFs) are a polymer hybrid family of compounds comprising metal ions that have been deliberately incorporated in organic ligands to form several multi-dimensional structures with unique structural and functional attributes. They have the typical properties of brittleness, major porosity, and randomly crystalline. These three factors hampered their potential incorporation into modern technologies. However, with the discovery of their polymers, hope was rekindled. Polymers, unlike their counterparts, are versatile and malleable and can be tailored into solids with a wide range of technical applications. MOFs can be effectively incorporated into polymer structures, resulting in polymers with enhanced properties and increased demand, according to recent studies. This review focuses on the synthetic procedures of MOFs used to create hybrid materials, as well as their potential environmentally related applications. Desalination, hazardous heavy metal removal and mitigation, gas and liquid separations and purifications, and dye removal will all be extensively discussed as applications. To assemble this review, we will add insight from recent papers and discoveries, as well as seminal reports from experts on the advancement of MOF-polymers.

Preparation and characterization of a newly constructed multifunctional Co(ii)–organic framework: proton conduction and adsorption of Congo red in aqueous medium

The efficient adsorption of CR over Co-MOF 1 as well as the pH-dependent proton-conducting mechanism of the composite Co-MOF–Nafion membrane.

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.

Comment on "The solvent and zinc source dual-induced synthesis of a two dimensional zeolitic imidazolate framework with a farfalle-shape and its crystal transformation to zeolitic imidazolate framework-8" by C.-X. Jin et al., 2020, 49, 2437

In a recently published article Jin et al. described a new farfalle-shaped zeolitic imidazolate framework (ZIF-F) and its transformation into the well-known ZIF-8 in methanol. However, the shown powder diffraction patterns of ZIF-F are similar to another ZIF polymorph called ZIF-8dia, which has previously been synthesized from synthesis mixtures of different compositions.

One-Step Fabrication of Three Metals Zif and its Application for Adsorption of Levofloxacin in Aqueous Solution

Background:

Zeolitic imidazolate frameworks with three metals Zn, Co and Ag (ZIF-3M) and ZIF-67 were synthesized at room temperature and characterized with different techniques such as FESEM, BET, EDX and XRD. Then, the synthesized nanoparticles were successfully applied for the removal of levofloxacin from aqueous solutions.

Methods:

To optimize the significant factors (i.e., pH, adsorbent dose and contact time), the response surface methodology (RSM) was implemented based on Box-Behnken design (BBD) in each step, an appropriate amount of adsorbent was added to 30 ppm of a solution containing levofloxacin and the pH was adjusted to the desired value with 0.1 M HCl or 0.1 M NaOH. The mixture was stirred at room temperature and then centrifuged at 7500 rpm for 3 min.

Results:

The optimal conditions for each variable were performed using Box-Behnken design. Results revealed that ZIF-3M nanoparticles more efficiently remove levofloxacin than ZIF-67 in aqueous solution.

Conclusion:

In this research, new three metals ZIF (ZIF-3M) nanoparticles were synthesized with Ag, Zn and Co in aqueous solution and characterized by different techniques. Results indicated successful synthesis with preserving ZIF framework. Results indicated that ZIF-3M has more ability for the removal of levofloxacin than ZIF-67. Isotherm studies showed that the most suitable model for the adsorption of levofloxacin onto ZIF-3M has a good agreement with the Langmuier model.

Reusable ZIF-8@chitosan sponge for the efficient and selective removal of congo red

A light ZIF-8@chitosan sponge was prepared by an in situ method for the efficient and selective removal of congo red from aqueous solution.

Kinetics, Isotherm, Thermodynamics, and Recyclability of Exfoliated Graphene-Decorated MnFe2O4 Nanocomposite Towards Congo Red Dye

Herein, we described the use of exfoliated graphene- (EG-) decorated magnetic MnFe2O4 nanocomposite (EG@MnFe2O4) for the removal and adsorption of Congo red (CR) dye from wastewater. Firstly, the precursors (EG, MnFe2O4) and EG@MnFe2O4 were fabricated, characterized using several physical analytical techniques such as X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), and N2adsorption/desorption isotherm measurement. For the adsorption experiments, the effect of contact time (0–240 min), concentration (10–60 mg/L), solution pH (2–10), adsorbent dosage (0.03–0.07 g), and temperature (283–313 K) was rigorously studied. To elucidate the adsorption mechanism and behaviour of CR over EG@MnFe2O4 and MnFe2O4 adsorbents, the kinetic models (pseudo-first-order, pseudo-second-order, Elovich, and Bangham) and isotherm models (Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich) have been adopted. The kinetic results indicated that models adhered to the pseudo-second-order equation, exhibiting the chemisorption mechanism in heterogeneous phrase. Meanwhile, the isotherm results revealed the adsorption of CR over EG@MnFe2O4 obeyed the monolayer behaviour (Langmuir model) rather than multilayer behaviour (Freundlich equation) over MnFe2O4. The thermodynamic study also suggested that such adsorption was an endothermic and spontaneous process. With high maximum adsorption capacity (71.79 mg/g) and good recyclability (at least 4 times), EG@MnFe2O4 can be a potential alternative for the adsorptive removal of CR dye from water.

Chemically Active, Porous 3D-Printed Thermoplastic Composites

Metal-organic frameworks (MOFs) exhibit exceptional properties and are widely investigated because of their structural and functional versatility relevant to catalysis, separations, and sensing applications. However, their commercial or large-scale application is often limited by their powder forms which make integration into devices challenging. Here, we report the production of MOF-thermoplastic polymer composites in well-defined and customizable forms and with complex internal structural features accessed via a standard three-dimensional (3D) printer. MOFs (zeolitic imidazolate framework; ZIF-8) were incorporated homogeneously into both poly(lactic acid) (PLA) and thermoplastic polyurethane (TPU) matrices at high loadings (up to 50% by mass), extruded into filaments, and utilized for on-demand access to 3D structures by fused deposition modeling. Printed, rigid PLA/MOF composites display a large surface area (SA_avg = 531 m² g^-1) and hierarchical pore features, whereas flexible TPU/MOF composites achieve a high surface area (SA_avg = 706 m² g^-1) by employing a simple method developed to expose obstructed micropores postprinting. Critically, embedded particles in the plastic matrices retain their ability to participate in chemical interactions characteristic of the parent framework. The fabrication strategies were extended to other MOFs and illustrate the potential of 3D printing to create unique porous and high surface area chemically active structures.