Mechanistic insights into selective adsorption and separation of multi-component anionic dyes using magnetic zeolite imidazolate framework-67 composites

Portable smartphone-assisted amperometric immunosensor based on CoCe-layered double hydroxide for rapidly immunosensing erythromycin

Herein, we have manufactured a newly designed bifunctional impedimetric and amperometric immunosensor for rapidly detecting erythromycin (ERY) in complicated environments and food stuffs. For this, bimetallic cobalt/cerium-layered double hydroxide nanosheets (CoCe-LDH NSs), which was derived from Co-based zeolite imidazole framework via the structure conversion, was simultaneously utilized as the bioplatform for anchoring the ERY-targeted antibody and for modifying the gold and screen printed electrode. Basic characterizations revealed that CoCe-LDH NSs was composed of mixed metal valences, enrich redox, and abundant oxygen vacancies, facilitating the adhesion on the electrode, the antibody adsorption, and the electron transfers. The manufactured impedimetric and amperometric immunosensor based on CoCe-LDH has showed the comparable sensing performance, having a wide linear detection range from 1.0 fg mL-1 to 1.0 ng mL-1 with the ultralow detection limit toward ERY. Also, the portable, visualized, and efficient analysis of ERY was then attained at the smartphone-assisted CoCe-LDH-based SPE.

Heterogeneous MIL-88A on MIL-88B hybrid: A promising eco-friendly hybrid from green synthesis to dual application (Adsorption and photocatalysis) in tetracycline and dyes removal

Herein, the green synthesis of heterogeneous dual functional MIL88A-on-MIL88B hybrids (MIL: Materials InstituteLavoisier) with different amounts of MIL88B compared to MIL88A, including 1:2, 1:1, and 2:1, has been carried out. The photocatalytic degradation of tetracycline and adsorption of tetracycline and dyes (Direct Red 80, Direct Red 23, Acid Blue 92, and Reactive Orange 14) were investigated. Although the ratio of MIL88A-on-MIL88B (1:1) hybrid displayed the best activity, there is a slight difference in the photocatalytic performance of the other mass ratios studied. The result revealed that after 70 min of forming MIL88A on MIL88B, the best pollutant removal performance is obtained. During the limited synthesis time, the lopsided growth of MIL88A on the MIL88B surface limits the formation of sufficient functional groups and new pores between MIL88B as the substrate and MIL88A, which are effective and decisive in the performance. In the photocatalytic studies, the synthesized composite had good compatibility with the zero-order kinetics, and hydroxyl radicals were recognized as the most active species in the photocatalytic reaction. In the adsorption process, the MIL88A-on-MIL88A composite followed pseudo-second-order kinetics and the Langmuir isotherm. Besides, mechanisms such as π-π interaction/stacking, hydrogen bonding, and π-metal interaction were proposed for the pollutant adsorption process.

Fast and effective removal of textile dyes from the wastewater using reusable porous nano-carbons: a study on adsorptive parameters and isotherms

In the present study, recyclable porous nano-carbons (PNCs) were used to remove textile dyes (mainly methylene blue, methyl orange, and rhodamine B) from an aqueous environment. Due to their high surface area and mesoporous nature, PNCs exhibited extremely fast and efficient adsorption behavior. PNCs synthesized at an elevated temperature of 1000 °C are used in batch experiments, as they showed maximum dye removal with high surface area. Batch mode was used to optimize operational parameters such as initial dye concentration, contact time, adsorbent dose and pH as a function of time. Within ~7 minutes of treatment, PNCs achieved a maximum removal efficacy of ~99 percent for methylene blue. The recyclability of PNCs was investigated, and it retained its efficiency even after seven cycles. The efficacy of PNCs in treating industrial water contaminated with methylene blue dye was assessed. Different adsorption isotherms were carried out to determine maximum amount of dye that can be adsorbed on to surface of PNCs. The maximum adsorption capacity attained using Langmuir isotherm for methylene blue was around 1216.54 mg g^-1. Adsorption kinetics were applied on experimental data to identify the rate of adsorption. It was confirmed that novel onion peel-based porous PNCs were successful in removing methylene blue dye effectively with short duration in comparison with other dyes mainly rhodamine B and methyl orange.

Preparation of zeolitic imidazolate framework-67/wool fabric and its adsorption capacity for reactive dyes

Zeolitic imidazolate framework-67 (ZIF-67) formed by Co²⁺ and 2-methylimidazole (MIM) is widely used for adsorption and separation of pollutants. However, there are some disadvantages for ZIF-67 powder, such as strong electrostatic interaction and difficulty in recovery from the liquid phase. The available way to solve the above problems is choosing a suitable substrate to load ZIF-67. The amino and hydroxyl of wool fabrics effectively capture and fix ZIF-67, making it easy to separate ZIF-67 by taking out the composite materials from aqueous solution. In this study, ZIF-67/Wool fabric (ZW) was successfully prepared. The results show that ZIF-67 has better adsorption performance for reactive dyes with more sulfonic groups, higher molecular weight and lower steric resistance. The equilibrium adsorption capacity of ZW for reactive red 195 was 4.15 mg g^-1. The adsorption accorded with pseudo-second-order kinetic model and Langmuir isotherm. This study improved the application of ZIF-67, which provided a treatment method for dyeing wastewater and made it possible to recycle waste wool.

Integration of Phosphotungstic Acid into Zeolitic Imidazole Framework-67 for Efficient Methylene Blue Adsorption

To enhance the dye adsorption capacity of zeolitic imidazolate framework-67 (ZIF-67), phosphotungstic acid (HPW) was integrated into ZIF-67 to prepare composite adsorbents. Characterization results demonstrated that the electronegative HPW was uniformly and tightly deposited on the electropositive ZIF-67. Methylene blue (MB) was selected as a model contaminant to evaluate the adsorption performance of hybrid adsorbents. Results showed that HPW@ZIF-67 had excellent adsorption capacity toward cationic MB. The optimal ZIF-67-0.2 HPW sample with a HPW dosage of 9.9 wt % presented an adsorption capacity of 446.4 mg g^-1. ZIF-67-0.2 HPW displayed good reusability, and the adsorption data can be well described by pseudo-second order and Langmuir isotherm models. The adsorption mechanism was ascribed to the preferred electrostatic attraction and π-π stacking between MB and composite adsorbents. This work provides a route to enhance organic dye removal efficiency of ZIF materials through regulation of surface charge property and sheds light on the development of ZIF-based adsorbents.

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.

In situ synthesis of novel peroxo-functionalized Ti3C2Tx adsorbent for aqueous pollutants removal: Role of oxygen-containing terminal groups

A novel peroxo-functionalized Ti₃C₂T_x adsorbent with abundant surface termination groups was facilely prepared in situ to remove aqueous anionic and cationic dyes. The adsorption behavior of methylene blue on peroxo-functionalized Ti₃C₂T_x was systematically investigated by adsorption kinetics, isotherms, and thermodynamics. Compared with Ti₃C₂T_x, the adsorption capacities of peroxo-functionalized Ti₃C₂T_x for cationic dyes methylene blue (558.0 mg g^-1), rhodamine B (524.6 mg g^-1) and anionic dyes methyl orange (292.6 mg g^-1), congo red (258.2 mg g^-1) were increased at room temperature without adjustment of pH, background ions and humic acid, etc of the contaminant solution by 7.9, 5.3, 5.9 and 4.6 times, respectively. In addition, peroxo-functionalized Ti₃C₂T_x could well tolerate the effects of pH, ionic strength, and humic acid. As revealed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, the adsorption mechanism of peroxo-functionalized Ti₃C₂T_x for anionic and cationic dyes was mainly attributed to the electrostatic interaction, hydrogen bonding interaction, and noncovalent surface-π attraction interaction. This study demonstrates a facile modification strategy for Ti₃C₂T_x adsorbent materials and aims to provide insights for the development of excellent Ti₃C₂T_x-based adsorbent materials.

Simultaneous adsorptive removal of conventional and emerging contaminants in multi-component systems for wastewater remediation: A critical review

The rapid growth of population and industrialization results in pollution of freshwater sources which leads to the water stress conditions on the world in future. Adsorption is a low cost and popular technique for the removal of contaminants from water bodies. Most of the reports till date are on removal of a single component from aqueous solutions using this technique, but the real-world effluent contains multiple contaminants such as dyes, heavy metals, pesticides, antibiotics and many more. Therefore, a study on simultaneous removal of contaminants is highly needed to obtain a suitable adsorbent that can be used commercially. This critical review provides a detailed study on the removal of contaminants in the presence of other contaminant/s i.e., from a multi-component system (MCS). The different possible interaction mechanisms in MCS like synergism, antagonism and non-interaction are discussed. The MCS containing the mixture of conventional contaminants such as heavy metals and dyes, and other emerging contaminants such as antibiotics, organic contaminants, pesticides and personal care products are explained in depth. This review article will be helpful for researchers working in the field of simultaneous removal of contaminants from MCSs for wastewater remediation.

Ultrasound-assisted electrodeposition synthesis of nZVI-Pd/AC toward reductive degradation of methylene blue

A novel composite (nZVI/Pd-AC) was prepared by loading nanoscale zero-valent iron (nZVI) and Pd on activated carbon (AC) electrode under electrodeposition with ultrasound, which was used to reductive degradation of methylene blue (MB). The loading contents of Fe and Pd in composite materials were 15.84% and 2.06%, respectively. XPS results further confirmed that the as-prepared material contained Fe0 and Pd0. Without external conditions, MB could be degraded in the presence of nZVI/Pd-AC and reached equilibrium within 180 min. To investigate the reusability, the re-electrodeposition strategy was effective to refresh the active sites of nZVI/Pd-AC, and the removal efficiency only reduced by 4.51% in five circles indicating the good reusability of nZVI/Pd-AC composites. GC-MS was used to identify possible degradation pathways of MB; the results showed that the degradation products were mainly N, N-dimethylaniline and 2-amino-5-dimethylamino-benzenesulfonic acid. And the S-C, C-N bonds are the sites easier to be attacked.

Adsorption of methylene blue dye from aqueous solution by a novel PVA/CMC/halloysite nanoclay bio composite: Characterization, kinetics, isotherm and antibacterial properties

Here the fabrication of a novel PVA/CMC/halloysite nanoclay membrane for the effective adsorption of cationic dye (methylene blue, MB) from aqueous environment is reported. The membranes were analyzed through scanning electron microscopy (SEM), optical microscopy (OM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), contact angle and universal testing machine (UTM) analysis. The adsorption behavior of the membrane in terms of nanoclay loading, contact time, initial concentration of MB, pH and temperature were also discussed. The membrane exhibits excellent removal efficiency (99.5%) for MB in the optimal conditions such as nanoclay dose = 6 wt%, initial dye concentration = 10 ppm, contact time = 240 min, pH = 10 and temperature = 30 °C. Three isotherm models (Freundlich, Langmuir and Temkin) were employed to analyze the dye adsorption data. The results revealed that the adsorption process could be described well with both Freundlich and Langmuir isotherm model. The kinetics of MB adsorption onto membrane follows pseudo-second-order model while thermodynamic parameter indicate that adsorption is feasible and endothermic in nature. The antibacterial studies revealed that the PVA/CMC/halloysite nanoclay membrane possess notable antibacterial property. Finally, the desorption studies showed that the membrane have good reusability even after four recycles.

Adsorption isotherm models: Classification, physical meaning, application and solving method

Adsorption is widely applied separation process, especially in environmental remediation, due to its low cost and high efficiency. Adsorption isotherm models can provide mechanism information of the adsorption process, which is important for the design of adsorption system. However, the classification, physical meaning, application and solving method of the isotherms have not been systematical analyzed and summarized. In this paper, the adsorption isotherms were classified into adsorption empirical isotherms, isotherms based on Polanyi's theory, chemical adsorption isotherms, physical adsorption isotherms, and the ion exchange model. The derivation and physical meaning of the isotherm models were discussed in detail. In addition, the application of the isotherm models were analyzed and summarized based on over 200 adsorption equilibrium data in literature. The statistical parameters for evaluating the fitness of the models were also discussed. Finally, a user interface (UI) was developed based on Excel software for solving the isotherm models, which was provided in supplemental material and can be easily used to model the adsorption equilibrium data. This paper will provide theoretical basis and guiding methodology for the selection and use of the adsorption isotherms.