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•AC@MOF composite was synthesized for removal of pollutants from water.•The absorption half-time was 3 min for adsorption of direct dye on AC@MIL-101(Cr).•The direct dye removal ...process well described by Langmuir absorption model.•The absorption of organic dyes followed the pseudo-second-order kinetics model.
Activated carbon (AC) is an inert adsorbent material that has widely been used in water treatment or removing of environmental pollutants from water. In order to improve the adsorption of AC, which highly depends on its pore size and surface area, we prepared highly porous adsorbent composites of activated carbon (AC)/chromium-based MOF (MIL-101(Cr)). The composite has a high specific surface area of 2440 m2 g−1 and total pore volume of 1.27 cm3 g−1. To show the efficiency of the composite as an adsorbent, the removal kinetics of anionic dyes (Direct Red 31 and Acid Blue 92) from aqueous solutions dependent on the amount of composite, adsorption time, concentration of dye and pH is demonstrated. It is shown that the kinetics of organic dye removal by AC@MIL-101(Cr) composite is faster than MIL-101(Cr) under near neutral pH conditions. The half-time of removal is about 3 min while about 85% of the dye is removed after 5 min. This study provides new idea into the design and synthesis of highly efficient nanoporous adsorbent based on MOFs for removal of pollutants as well as organic dyes from wastewater.
Developing highly sensitive flexible piezoelectric sensor for wearable electronic devices have received considerable attention due to their promising application in physiological monitoring. ...Therefore, many research studies are conducted to enhance the piezoelectric response of poly(vinylidene fluoride) (PVDF)-based membrane. In this work, we present a novel flexible piezoelectric PVDF-based sensor with high-pressure sensitivity induced by the incorporation of microporous metal–organic framework (MOF) particles. Scanning electron microscopy images indicated the formation of uniform and bead-free PVDF/MOF nanofibrous composite with an average diameter of 173–241 nm. In this design, the microporous MOF crystals extremely enhanced the polar β-phase content of PVDF nanofibers by 20% without significant loss in its flexibility and synergistically promoted the piezoelectric performance of PVDF-based sensor. The PVDF nanofibers containing 1 wt% MOF crystals showed a peak-to-peak voltage of 3.84 V under an applied force of 2.5 N, which was superior to that of pristine PVDF nanofibers by 32%. Furthermore, the practical application of the developed PVDF/MOF nanofiber-based piezoelectric sensor was demonstrated for detecting human activities, showing a maximum output voltage of 2.08 V (for finger tapping), 5.92 V (for hand punching), and 20.66 V (for heel strike). The self-powered and highly sensitive PVDF/MOF nanofiber-based piezoelectric sensor also exhibits excellent long-term working stability with no obvious responsivity attenuation. The results of this work provide new insights for the development of next-generation piezoelectric sensors and energy harvesting systems.
Graphical abstract
A novel flexible piezoelectric PVDF-based nanogenerator with high-pressure sensitivity induced by the incorporation of microporous MOF particles. The piezoelectric response of the developed PVDF/MOF nanogenerator indicated superior output voltage and sensitivity than most of the reported PVDF-based nanogenerators.
The mechanical and biological properties of polylactic acid (PLA) need to be further improved in order to be used for bone tissue engineering (BTE). Utilizing a material extrusion technique, ...three-dimensional (3D) PLA-Ti6Al4V (Ti64) scaffolds with open pores and interconnected channels were successfully fabricated. In spite of the fact that the glass transition temperature of PLA increased with the addition of Ti64, the melting and crystallization temperatures as well as the thermal stability of filaments decreased slightly. However, the addition of 3-6 wt% Ti64 enhanced the mechanical properties of PLA, increasing the ultimate compressive strength and compressive modulus of PLA-3Ti64 to 49.9 MPa and 1.9 GPa, respectively. Additionally, the flowability evaluations revealed that all composite filaments met the print requirements. During the plasma treatment of scaffolds, not only was the root-mean-square (Rq) of PLA (1.8 nm) increased to 60 nm, but also its contact angle (90.4°) significantly decreased to (46.9°). FTIR analysis confirmed the higher hydrophilicity as oxygen-containing groups became more intense. By virtue of the outstanding role of plasma treatment as well as Ti64 addition, a marked improvement was observed in Wharton's jelly mesenchymal stem cell attachment, proliferation (4',6-diamidino-2-phenylindole staining), and differentiation (Alkaline phosphatase and Alizarin Red S staining). Based on these results, it appears that the fabricated scaffolds have potential applications in BTE.
In this study, the graphene-zinc oxide nanocomposite was synthesized by hydrothermal method and used in the preparation of electrospun poly(vinylidene fluoride) (PVDF) nanofibers. For this purpose, ...PVDF nanofibers containing graphene-ZnO nanocomposite (G-ZnO) were prepared and its microstructure and morphology were studied using infrared spectroscopy (FTIR), X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) techniques. The results showed the production of uniform and bead-free nanofibers. The decrease in PVDF nanofiber diameter (about 23%) was observed with addition of synthesized G-ZnO nanocomposite. It was also observed that the incorporation of G-ZnO nanocomposites increased the crystalline and polar β phase of the PVDF nanofibers and consequently its piezoelectric properties. The PVDF/G-ZnO nanofibrous composite exhibits a peak-to-peak voltage of 840 mV under an applied force of 1 N, which found to be superior than the pristine PVDF (640 mV) and PVDF/ZnO (710 mV) nanofibers. The results of this work provide new insight for the development of flexible piezoelectric nanofibrous devices and energy harvesting systems.
In this study, a magnetic metal–organic framework (MMOF) was synthesized and post-modified with poly(propyleneimine) dendrimer to fabricate a novel functional porous nanocomposite for adsorption and ...recovery of palladium (Pd(II)) from aqueous solution. The morphological and structural characteristics of the prepared material were identified by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmet–Teller (BET) isotherm, and vibrating sample magnetometer (VSM). The results confirmed the successful synthesis and post-modification of MMOF. Semispherical shape particles (20–50 nm) with appropriate magnetic properties and a high specific surface area of 120 m
2
/g were obtained. An experimental design approach was performed to show the effect of adsorption conditions on Pd(II) uptake efficiency of the dendrimer-modified magnetic adsorbent. The study showed that the Pd(II) uptake on dendrimer-modified MMOF was well described by the Langmuir isotherm model with the highest uptake capacity of 291 mg/g under optimal condition (adsorbent content of 12.5 mg, Pd ion concentration of 80 ppm, pH = 4, and contact time of 40 min). The adsorption kinetics of Pd(II) ions was suggested to be a pseudo-first-order model. The results revealed a faster adsorption rate and higher adsorption capacity (about 43%) for dendrimer-modified MMOF. Finally, the reusability of the provided adsorbent was evaluated. This work provides a valuable strategy for designing and developing efficient magnetic adsorbents based on MOFs for the adsorption and recovery of precious metals.
We present enhanced electrocatalytic activity of three-dimensional graphene scaffolds by decoration with one-dimensional Co
Ni
MOF nanostructures (0 ≤x≤ 1). The decreased overpotential and fast ...kinetics of the oxygen evolution reaction as compared with the existing materials are shown. The developed bimetallic MOF/3DG composites have great potential to be used in electrocatalytic water oxidation.
Herein, a magnetic chromium-based metal–organic framework (MOF) was successfully synthesized and applied for adsorption and removal of methylene blue MB and methyl orange MO from an aqueous solution. ...To achieve high adsorption capacity and selective removal of organic dyes, rational surface functionalization of synthesized MOF with poly (propylene imine) PPI dendrimer was carried out. The Fe
3
O
4
@MIL-101@PPI composite exhibits a crystalline structure with high thermal stability and magnetic properties. In addition, this framework shows a high specific surface area (116 m
2
/g) and porosity which is beneficial for wastewater treatment. The results indicate that Fe
3
O
4
@MIL-101@PPI composite can remove cationic dye from an aqueous solution more selectively and efficiently than anionic dye. The adsorption experiments revealed high adsorption capacity (93.9 mg/g) and fast adsorption kinetics following the pseudo-second-order kinetic model. Interestingly, the regeneration study showed that the Fe
3
O
4
@MIL-101@PPI composite had appropriate reusability for dye removal with an almost unchanged structure after five regeneration cycles. This research provides new insights for the rational design of hybrid magnetic adsorbents with synergistic functionality and porous structure by combining the advantages of magnetic nanoparticles, MOFs, and dendrimers.
Graphical Abstract
We present a rapid and surfactant-free temperature-assisted synthesis route to prepare γ-cyclodextrin-based metal–organic framework (γ-CD-MOF). The cubic crystals of the CD-MOF with an average edge ...length of 10–15 µm, specific surface area of 775 m
2
g
−1
and total pore volume of 0.229 cm
3
g
−1
were synthesized in much shorter time than conventional CD-MOFs. To show the efficiency of the synthesized CD-MOF as adsorbent of gas, the uptake of CO
2
at different temperature and pressure was investigated. It is shown that the CO
2
uptake increases with increasing pressure and decreasing temperature. Further microgravimetric investigation on gas adsorption at low pressure demonstrated superior gas uptake (ca. 147 mg g
−1
) than previous reports. At the maximum equilibrium pressure, the uptake amounts of CO
2
were found to be 326 and 268 mg g
−1
at 303 and 323 K, respectively. The synthesized CD-MOF has great potential to be used in gas storage and separation applications.
The present study aimed to optimize the electrospinning parameters for polyacrylonitrile (PAN) nanofibers containing MgO nanoparticle to obtain the appropriate fiber diameter and mat porosity to be ...applied in air filtration. Optimization of applied voltage, solution concentration, and spinning distance was performed using response surface methodology. In total, 15 trials were done according to the prepared study design. Fiber diameter and porosity were measured using scanning electron microscopic (SEM) image analysis. For air filtration testing, the nanofiber mat was produced based on the suggested optimum conditions for electrospinning. According to the results, the lower solution concentration favored the thinner fiber. The larger diameter gave a higher porosity. At a given spinning distance, there was a negative correlation between fiber diameter and applied voltage. Moreover, there were curvilinear relationships between porosity and both spinning distance and applied voltage at any concentration. It was also concluded that the developed filter medium could be comparable to the high-efficiency particulate air (HEPA) filter in terms of collection efficiency and pressure drop. The empirical models presented in this study can provide an orientation to the subsequent experiments to form uniform and continuous nanofibers for future application in air purification.
Implications: High-efficiency filtration is becoming more important, due to decreasing trends air quality. Effective filter media are increasingly needed in industries applying clean-air technologies, and the necessity for developing the high-performance air filters has been more and more felt. Nanofibrous filter media that are mostly fabricated via electrospinning technique have attracted considerable attention in the last decade. The present study aimed to develop the electrospun PAN-containing MgO nanoparticle (using the special functionalities such as absorption and adsorption characteristics, antibacterial functionality, and as a pore-forming agent) filter medium through experimental investigations for application in high-performance air filters.
In this study, the sound absorption performance of warp-knitted spacer fabrics (WKSFs) was investigated. WKSFs with different angles of connecting yarns between two surfaces and different numbers of ...layers were fabricated. The effect of porosity and the number of layers on the sound absorption coefficient (SAC) of WKSFs were measured by the impedance tube method at the frequency range of 0–6100 Hz. The results indicated that increasing the angle of connecting yarns and the number of layers will enhance the SAC of WKSFs. An artificial neural network (ANN) model was also used to predict the effect of knit structure and the number of layers on the SAC of WKSFs at different frequencies. It is found that the ANN model provided an accurate and reliable prediction of SAC for different WKSF structures with a high value of correlation coefficient (more than 0.99%). The obtained results showed that the developed high-precision ANN model would be a helpful and powerful tool for modeling and predicting sound absorption performance of fibrous acoustic materials.
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