Loading Control of Metal–Organic Frameworks in Fe3O4@MOFs Series Composite Adsorbents for Optimizing Dye Adsorption

Isotherms, kinetics and thermodynamic mechanism of methylene blue dye adsorption on synthesized activated carbon

The treatment of methylene blue (MB) dye wastewater through the adsorption process has been a subject of extensive research. However, a comprehensive understanding of the thermodynamic aspects of dye solution adsorption is lacking. Previous studies have primarily focused on enhancing the adsorption capacity of methylene blue dye. This study aimed to develop an environmentally friendly and cost-effective method for treating methylene blue dye wastewater and to gain insights into the thermodynamics and kinetics of the adsorption process for optimization. An adsorbent with selective methylene blue dye adsorption capabilities was synthesized using rice straw as the precursor. Experimental studies were conducted to investigate the adsorption isotherms and models under various process conditions, aiming to bridge gaps in previous research and enhance the understanding of adsorption mechanisms. Several adsorption isotherm models, including Langmuir, Temkin, Freundlich, and Langmuir-Freundlich, were applied to theoretically describe the adsorption mechanism. Equilibrium thermodynamic results demonstrated that the calculated equilibrium adsorption capacity (qe) aligned well with the experimentally obtained data. These findings of the study provide valuable insights into the thermodynamics and kinetics of methylene blue dye adsorption, with potential applications beyond this specific dye type. The utilization of rice straw as an adsorbent material presents a novel and cost-effective approach for MB dye removal from wastewater.

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.

Synthesis of strong magnetic response ZIF-67 for rapid adsorption of Cu2+

With the acceleration of industrialization and urbanization, global water resources have been polluted. Among the water pollutants, heavy metals have caused great harm to the environment and organisms. When the concentration of Cu2+ in water exceeds the standard, the intake of the human body will mainly damage the nervous system. We use MOF materials with high chemical stability, specific surface area, adsorption, and other unique properties to adsorb Cu2+. MOF-67 was prepared with various solvents, and a stronger magnetic response MOF-67 with the largest surface area and best crystal form were selected. It quickly adsorbs low-concentration Cu2+ in water to purify water quality. At the same time, it can be recovered promptly through an external magnetic field to avoid secondary pollution, which conforms to the concept of green environmental protection. When the initial concentration of Cu2+ is 50 mg/L for 30 min, the adsorption rate reaches 93.4%. The magnetic adsorbent can be reused three times.

Construction of a 3D Metal-Organic Framework and Its Composite for Water Remediation via Selective Adsorption and Photocatalytic Degradation of Hazardous Dye

In this work, a new bimetallic Na(I)-Zn(II) metal-organic framework (MOF), formulated as [Na₂Zn₃(btc)₂(μ-HCOO)₂(μ-H₂O)₈] _n (1) (H₃btc = benzene tricarboxylic acid), and its composite (ZnO@1) have been successfully synthesized using solvothermal and mechanochemical solid grinding methods. 1 and ZnO@1 were characterized by diffraction [single-crystal X-ray diffraction (XRD) and powder XRD], spectroscopic (ultraviolet-visible diffuse reflectance spectroscopy and Fourier transform infrared spectroscopy), microscopic (transmission electron microscopy), and thermal (thermogravimetric analysis) methods. The surface area and porosity of 1 were determined using a Brunauer-Emmett-Teller analyzer. Single-crystal diffraction of 1 confirms that Na1 and Zn2 have octahedral coordination environments, whereas Zn1 has a tetrahedral coordination geometry. Topological simplification of 1 shows a 3,6-connected kgd net. Na(I)-Zn(II) MOF (1) is crystallized with slight porosity and exhibits good tendency toward the encapsulation of zinc oxide nanoparticles (ZnO NPs). The photocatalytic behaviors of 1 and its composite (ZnO@1) were investigated over MB dye under sunlight illumination with promising degradation efficiencies of 93.69% for 1 and 97.53% for ZnO@1 in 80 min.

Fe3O4-doped silk fibroin-polyacrylamide hydrogel for selective and highly efficient absorption of cationic dyes pollution in water

Overuse of organic dyes has caused serious threats to the ecosystem and human health. However, the development of high-efficient, environmentally friendly, selective, and degradable cationic dye adsorbents remains a huge challenge. In this work, a novel Fe₃O₄nanoparticles doped silk fibroin-polyacrylamide magnetic hybrid hydrogel (Fe₃O₄@SF-PAAM) was successfully fabricated by combining free radical polymerization to prepare hydrogels andin situco-precipitation to prepare nanoparticles. The obtained Fe₃O₄@SF-PAAM hydrogel shows strong magnetic performance with saturated magnetic of 10.2 emu mg^-1and excellent swelling properties with a swelling ratio of 55867%. In addition, Fe₃O₄@SF-PAAM can adsorb cationic dyes such as methylene blue (MB), crystal violet, and Rhodamine B, but has no adsorption effect on anionic dyes such as methyl orange, congo red, and carmine, indicating that Fe₃O₄@SF-PAAM has good selective adsorption properties for cationic dyes. Interestingly, the adsorption capacity of Fe₃O₄@SF-PAAM was approached 2025 mg g^-1for MB (MB, a typical cation dye) at 25 °C and neutral. Meanwhile, the hybrid hydrogel is reusable, the removal rate for MB is still over 90% after the five adsorption-desorption cycles. The fabricated magnetic hybrid hydrogel is a kind of a highly-efficiency and eco-friendly adsorbent and presents great potential applications in water purification and environmental protection.

Fabrication of Stable MIL-53(Al) for Excellent Removal of Rhodamine B

Adsorptive purification of organic dyes in wastewater is significant to protect the water environment. Herein, MIL-53(Al) was successfully fabricated through a facile and versatile solvothermal strategy. The stability of MIL-53(Al) under high temperature, acid, base, and peroxide conditions was investigated. The porous MIL-53(Al) had high chemical stability, and the thermal stability reached up to 500 °C, which provided a good foundation for dye removal. MIL-53(Al) showed excellent adsorption performance. The maximum adsorption capacity of MIL-53(Al) for rhodamine B (RhB) can reach 1547 mg g^-1 under 303 K, and the corresponding removal efficiency exceeded 90% at the equilibrium time (120 min). The Langmuir model and pseudo-second-order model can well fit RhB adsorption on MIL-53(Al). Thermodynamic study and activation energy values over the range of 298-323 K revealed that the adsorption of RhB was a spontaneous and endothermic physical process in nature. The batch experimental results, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared (FTIR) spectroscopy analyses suggested that the hydrogen bonding and electrostatic interactions between the hydroxyl/carboxyl groups of MIL-53(Al) and RhB were the primary adsorption mechanisms. Besides, MIL-53(Al) had a higher selectivity to RhB than the coexisting ions in aqueous solution and a superior adsorption performance after five cycles.

Cu-Doped Boron Nitride Nanosheets for Solid-Phase Extraction and Determination of Rhodamine B in Foods Matrix

Cu-doped boron nitride nanosheets (Cu-BNNS) were first reported as promising adsorbents for the solid-phase extraction and determination of rhodamine B (RhB) dye in a food matrix. Different characterizations, including XRD, FTIR, XPS, SEM, and TEM, were performed to confirm the formation of the adsorbent. Then, the adsorption performance of Cu-BNNS was investigated by adsorption kinetics, isotherms, and thermodynamics. Multiple extraction parameters were optimized by single-factor experiments. Under optimized conditions, the recoveries in the food matrix were in the range of 89.8–95.4%, with the spiked levels of 100 ng/mL and 500 ng/mL, respectively. This novel system was expected to have great potential to detect RhB in a wide variety of real samples.

Coating metal–organic frameworks on plasmonic Ag/AgCl nanowire for boosting visible light photodegradation of organic pollutants

Photoactive metal–organic frameworks, MIL-100(Fe), with controllable thickness are coated on plasmonic Ag/AgCl nanowire, for boosting visible light photodegradation of rhodamine B and tetracycline hydrochloride. The morphology and composition of the obtained nano-heterostructure were investigated in detail by SEM imaging, TEM imaging, XRD patterns, FT-IR spectra, N₂ adsorption–desorption curves and TGA patterns. Photoelectric performance test suggested that a Z-scheme photocatalysis system for efficient transfer of photogenerated charge carriers was established between MIL-100(Fe) and plasmonic Ag/AgCl nanowire.

A photoactive metal–organic framework, MIL-100(Fe), with controllable thickness was coated on plasmonic Ag/AgCl nanowire for boosting the visible light photodegradation of rhodamine B and tetracycline hydrochloride.

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.

Photocatalytic Performance of the MOF-Coating Layer on SPR-Excited Ag Nanowires

The photoactive metal-organic frameworks (MOFs) were controllably coated on the surface plasmon resonance-excited Ag nanowires in a layer manner to adjust the photocatalytic activity. The influence of the thickness of the MOF coating layer on the photocatalytic activity was investigated. A thicker MOF coating layer not only facilitated the photogenerated electron-hole separation efficiency but also provided a larger Brunauer-Emmett-Teller surface area, thus enhancing the photocatalytic activity. This work provided a new way to adjust the photocatalytic activity of the photoactive MOF.

Effective Adsorptive Removal of Methylene Blue from Water by Didodecyldimethylammonium Bromide-Modified Brown Clay

In the present investigation, brown clay (BC) was modified with didodecyldimethylammonium bromide (DDAB) to produce a sorbent (DDAB-BC), which was characterized and applied for sorption of methylene blue (MB) from aqueous media. BC was functionalized using DDAB by cation exchange of the DDAB moiety with positive ions existing inside the interlayer spaces of the BC. X-ray diffraction (XRD) studies confirmed that the d-spacing of DDAB-BC became wider (3.39 Å) than that of BC (3.33 Å). Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were exploited to explore the functional groups and morphological structure of sorbents, respectively. The Brunauer-Emmett-Teller (BET) surface area, pore volume, and pore diameter of DDAB-BC were determined as 124.6841 m²/g, 0.316780 cm³/g, and 8.75102 nm, respectively. Batch sorption investigations were carried out to determine the optimum experimental conditions, using the one-factor one-time procedure. The sorption of MB on DDAB-BC strongly obeyed the Langmuir isotherm and agreed well with pseudo-second-order kinetics. Sorption of MB onto DDAB-BC showed maximum efficiency (∼98%) and maximum sorption capacity (∼164 mg/g) at optimal values of pertinent factors: dye concentration (100 mg/L), pH (7), and temperature (55 °C). Sorption isothermal studies predicted that removal of MB on DDAB-BC follows multilayer sorption at higher MB dye concentrations and monolayer sorption at lower MB dye concentrations.

Controlling crystal growth of MIL-100(Fe) on Ag nanowire surface for optimizing catalytic performance

Ag/MIL-100(Fe) core/sheath nanowire with controllable thickness of the MIL-100(Fe) sheath was prepared by controlling the crystal growth of MIL-100(Fe) on the Ag nanowire surface. The evolution of the MIL-100(Fe) sheath monitored by transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermogravimetric analyses (TGA), X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FT-IR), and N₂ adsorption–desorption analysis indicates that the thickness of the MIL-100(Fe) sheath increases with the increasing number of crystal growth cycles of MIL-100(Fe) on the Ag nanowire surface. Catalytic reaction over Ag/MIL-100(Fe) core/sheath nanowire suggests that the thickness of the MIL-100(Fe) sheath largely influences the catalytic performance and it is quite important to control the crystal growth of MIL-100(Fe) on the Ag nanowire surface for optimizing catalytic performance.

Ag/MIL-100(Fe) core/sheath nanowire with controlled crystal growth of MIL-100(Fe) on the Ag nanowire surface was prepared for optimizing catalytic performance.