Showing papers in "Microporous and Mesoporous Materials in 2016"
TL;DR: In this paper, the metal organic framework UiO-66-NH 2 has been post-synthetically modified to introduce thiourea, isothiocyanates and isocyanate functionalities without compromising the structural and thermal stability of the parent framework.
Abstract: The metal organic framework UiO-66-NH 2 has been post-synthetically modified to introduce thiourea, isothiocyanate and isocyanate functionalities without compromising the structural and thermal stability of the parent framework. 1 H NMR and IR spectroscopies have been used to monitor the extent of framework functionalization. UiO-66, UiO-66-NH 2 and the new functionalized frameworks UiO-66-NHC(S)NHMe, UiO-66-NHC(S)NHPh, UiO-66-NCS and UiO-66-NCO have been studied as adsorbents for the capture of a range of heavy metals from homoionic aqueous solution, with a view towards applications in environmental remediation. Functionalization markedly improved metal removal efficiency up to 99% with calculated maximum adsorption capacities of 49, 117, 232 and 769 mg/g for Cd 2+ , Cr 3+ , Pb 2+ and Hg 2+ respectively for UiO-66-NHC(S)NHMe.
TL;DR: In this paper, the authors presented the stability of metal organic frameworks with respect to acids, bases, air, water, and peroxides in a stress test and showed that the major part of the MOFs examined in this study show a good hydrothermal stability except for UiO-67, NH 2 -MIL-101 (Al), and CuBTC.
Abstract: In this work, the hydrothermal and chemical stability towards acids, bases, air, water, and peroxides of Metal Organic Frameworks, that are commonly considered to be stable, is presented. As a proof of stability both the crystallinity and porosity are measured before and after exposure to the stress test. The major part of the MOFs examined in this study show a good hydrothermal stability except for UiO-67, NH 2 -MIL-101 (Al) and CuBTC. The chemical stabilities towards acids and bases show a similar tendency and an ordering can be proposed as: MIL-101(Cr) > NH 2 -UiO-66 > UiO-66 > UiO-67 > NH 2 -MIL-53 > MIL-53(Al)>ZIF-8 > CuBTC > NH 2 -MIL-101(Al). In the tests with H 2 O 2 most materials behaved poorly, only the UiO-66 and NH 2 -UiO-66 frameworks show a good stability.
TL;DR: In this paper, the bulk crystal of black phosphorus was exfoliated by liquid exfoliation method for a duration of 8h using N-Methyl-2-Pyrrolidone as the solvent.
Abstract: The bulk crystal of black phosphorus was exfoliated by liquid exfoliation method for a duration of 8 h using N-Methyl-2-Pyrrolidone as the solvent. The exfoliated sample was centrifuged at different rpm such as 3000, 5000 and 10,000 to separate out the 2D black phosphorus nanosheets with different thickness and length. The as synthesized black phosphorus nanosheets collected at these rpm values were characterized with TEM, AFM, Raman spectroscopy and Vis-NIR spectroscopy. Further, we investigated the humidity sensing behaviour of the devices fabricated by using these samples. The results obtained show that the device fabricated with black phosphorus nanosheets and nanoparticles obtained by filtration of the sample collected after 10,000 rpm exhibited better performance as compared to the nanosheets collected at 3000 and 5000 rpm. The response and recovery times of devices are found to be promising and better than those of the black phosphorus gas sensor reported earlier. The present investigations open up a new avenue for further studies in improving the performance of black phosphorus nanosheets based gas sensing devices.
TL;DR: ZIF-8 and ZIF-67 were prepared by using mixed-base ammonium hydroxide and triethylamine (TEA) to promote the ZIF synthesis, and the yields significantly improved.
Abstract: ZIF-8 and ZIF-67 were prepared by using mixed-base ammonium hydroxide and triethylamine (TEA). These two bases could promote the ZIF synthesis, and the yields are significantly improved. The texture structure and morphologies of ZIF prepared with mixed-base also have obvious changes. Three typical dyes, neutral rhodamine B (RB), anionic methyl orange (MO) and cationic methylene blue (MB), were examined for the dye adsorption by using various ZIFs. ZIF-8 and ZIF-67 prepared with TEA have enhanced RB adsorptions that are 2.3–3.8 times of those prepared without TEA, and ZIF-8 exhibited better adsorption performance than ZIF-67. For MO adsorption, ZIF-67 crystals have better adsorption performance than ZIF-8, and ZIF-67 prepared with TEA has a decreased MO adsorption. For MB adsorption, the addition of TEA does not change the MB adsorption for both ZIF-8 and ZIF-67.
TL;DR: In this article, a facile, low cost and novel method was used as non-noble-metal catalyst for reduction of 4-nitrophenol (4-NP) to 4-aminophenol(4-AP) by NaBH 4.
Abstract: Porous carbon supported copper composite (Cu/Cu 2 O/C) was synthesized with a facile, low cost and novel method and used as non-noble-metal catalyst for reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH 4 . In the synthetic strategy, metal organic framework Cu 3 (BTC) 2 (also denoted as HKUST-1) was used as both sacrificial template and copper precursor, and phenol formaldehyde resin as carbon precursor. The catalytic Cu/Cu 2 O nanoparticles (Cu/Cu 2 O NPs) about 40 nm-in-diameter distributed uniformly both on the internal and external surface of the porous carbon flakes, and took up 33.38–37.56 wt% of the Cu/Cu 2 O/C composite. Compared with noble metal catalysts, the prepared composite showed comparable high catalytic activity, which was mainly due to their porous structure facilitating diffusion of reactants and products, and the high dispersion of accessible catalytic Cu/Cu 2 O NPs on porous carbon. Moreover, the synthesized catalyst can be reused for at least five cycles due to its good stability. These results confirmed that the as-prepared Cu/Cu 2 O/C is promising candidate to replace noble metal for catalytic application.
TL;DR: The modifications performed, so far, on mesoporous silica nanoparticles to imprint them a stimulus responsive behavior in order to allow their application in cancer therapy are highlighted.
Abstract: The application of nanocarriers as selective drug delivery platforms, as imaging or as diagnostic agents has been evaluated in several studies in the area of biomedicine, namely for cancer therapy. Such systems have the potential to perform a controlled and site-specific delivery of therapeutic agents leading to a reduction of side effects and, ultimately, to an improved therapeutic outcome. Among the different nanocarriers developed so far, mesoporous silica nanoparticles have attracted the attention of the scientific community for being applied as drug delivery systems that are capable of controlling, both in space and time, the drug release. In this review, the modifications performed, so far, on mesoporous silica nanoparticles to imprint them a stimulus responsive behavior (namely, pH, redox potential, adenosine triphosphate, enzyme or temperature) in order to allow their application in cancer therapy are highlighted.
TL;DR: In this article, the electrochemical properties of solvothermally synthesized Cu-1,3,5-benzenetricarboxylate MOF as a novel anode material for lithium-ion battery (LIB) were examined.
Abstract: Versatility and diversity in the nature of bonding between metal ions and polyfunctional organic molecules render metal organic frameworks (MOFs) as interesting materials for a variety of applications. In this work, we have examined the electrochemical properties of solvothermally synthesized Cu-1,3,5-benzenetricarboxylate MOF as a novel anode material for lithium-ion battery (LIB). At a current density of 96 mAg −1 , reversible capacity of 740 mAhg −1 is achieved, the highest ever reported for a MOF. Even at a high current density of 383 mAg −1 , specific capacity of 474 mAhg −1 is observed with no apparent fading up to 50 cycles. Ex-situ studies on the electrode material in the charged and discharged state by X-ray diffraction, Fourier transformed infra-red spectroscopy and X-ray photoelectron spectroscopy suggest that Li storage in Cu 3 (BTC) 2 MOF might not be fully explained by the conventional conversion mechanism that involves reduction into corresponding metal and subsequent oxidation. Rather, redox participation of the organic moiety is indicated. The present results would help in designing new MOFs for LIB applications.
TL;DR: In this article, different morphologies of hollow silica were introduced, including hollow spheres, hollow tubes, hollow cubes, etc., and some perspectives on the future research and development of hollow Silica were put forward.
Abstract: Hollow silica is a special type of novel inorganic material with one or more cavities inside. In addition to the excellent properties as with its solid counterparts, hollow silica exhibits unique characteristics, such as low density, high specific surface and good adsorption performance. Researchers have developed many routes to prepare mono-dispersed hollow silica with regular morphology. However, most studies focused on hollow silica spheres, ignoring the structural superiority of other hollow structures. Template synthesis is highly prominent due to its flexibility and versatility. What's more, it is suitable for the preparation of hollow silica with various morphologies. In this article, the research progress of template synthesis was firstly provided. Then different morphologies of hollow silica were introduced, including hollow spheres, hollow tubes, hollow cubes, etc. To better demonstrate the advantages and potential value of hollow silica materials, their performance in diverse applications were discussed. Finally, some perspectives on the future research and development of hollow silica were put forward.
TL;DR: In this article, a chitosan/activated charcoal (or carbon) composite was obtained in one step, characterized several techniques such as by Fourier transform infrared spectroscopy, scanning electron microscopy and dynamic light scattering, Brunauer-Emmet-Teller, thermogravimetric analysis/differential thermal analysis and differential scanning calorimetry techniques.
Abstract: In this study, a chitosan/activated charcoal (or carbon) (CTN/AC-Fe 3 O 4 ) composite was obtained in one step, characterized several techniques such as by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, dynamic light scattering, Brunauer-Emmet-Teller, thermogravimetric analysis/differential thermal analysis and differential scanning calorimetry techniques. The sorption the composite were investigated as kinetically and thermodynamically for removal of methylene blue (MB) and reactive blue4 (RB4) from aqueous solution. Effects of several parameters, such as initial temperature and initial concentration on removal of MB and RB4 from aqueous solution by the composite were investigated as a function of contact time. Maximum adsorption capacity (Q max ) was found to be 500 mg g −1 at and 250 mg g −1 at 318 K for MB, 298 K for RB4 respectively. Also, thermodynamic parameters such as ΔH 0 , ΔG 0 and ΔS 0 were calculated by Langmuir adsorption isotherm model. Negative Gibbs free energy (ΔG 0 ) implies that the adsorption is spontaneous and positive adsorption enthalpy (ΔH 0 ) demonstrates the process is endothermic for MB while negative adsorption enthalpy (ΔH 0 ) demonstrates the process is exothermic for RB4, respectively.
TL;DR: In this paper, the performance of MCM-41, amidoxime (AMD) and carboxyl (CA) groups modified particles was studied and the experimental equilibrium data fit the Langmuir model well for all the tested adsorbents.
Abstract: The uranium ion adsorption on the pristine MCM-41, amidoxime (AMD) and carboxyl (CA) groups modified particles was studied. The amounts of adsorbed U(VI) ions onto the pristine MCM-41, CA and AMD modified MCM-41 particles were found to be 58.9, 296.7 and 442.3 mg/g, respectively. The experimental equilibrium data was found to fit the Langmuir model well for all the tested adsorbents. The pristine, CA and AMD modified particles can be regenerated using 10 mM HNO 3 solution with more than 95% recovery. Hence, AMD and CA modified particles are stable, and easily regenerated. Particularly, AMD modified MCM-41 particles with high adsorption capacity seems to be a promising adsorbent for removal of U(VI) ions from aqueous solutions.
TL;DR: In this paper, the current status of MOFs MMMs for pervaporation is reviewed, including polymer (hydrophobicity/hydrophilicity, structure stability), MOFs (stability, hydrophobic/ hydrophilic, surface functional structure, particles morphology and pores size), mass transfer, and applications (dehydration of organic solvents, removal of dilute organic compounds from aqueous streams, separation of organic-organic mixtures, and membrane reactor).
Abstract: Metal-organic frameworks (MOFs)/polymer mixed matrix membranes (MMMs) have great potential in pervaporation separation due to the ease of design and modification of MOFs, along with the compatibility between MOFs and polymer matrix. This article reviews the current status of MOFs MMMs for pervaporation, including polymer (hydrophobicity/hydrophilicity, structure stability), MOFs (stability, hydrophobicity/hydrophilicity, surface functional structure, particles morphology and pores size), mass transfer, and applications (dehydration of organic solvents, removal of dilute organic compounds from aqueous streams, separation of organic-organic mixtures, and membrane reactor). The perspectives and suggestions of MOFs MMMs are given.
TL;DR: In this article, a composite of MCM-41 silica with rice husk was synthesized under hydrothermal conditions using cetyltrimethylammonium bromide (CTAB) as an organic template, aqueous ammonia solution (NH4OH) and Rice husk.
Abstract: Composite of MCM-41 silica with rice husk was synthesized under hydrothermal conditions using cetyltrimethylammonium bromide (CTAB) as an organic template, aqueous ammonia solution (NH4OH) and rice husk. Rice husk served as not only a silica source but also as a substrate for the deposition of MCM-41. The synthetic hybrid composites were characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) and tested as sorbents for phosphate from aqueous solution. Kinetic data and equilibrium uptake isotherms were measured. The effects of different experimental parameters such as contact time, initial phosphate concentration, solution pH, adsorbent mass, and the presence of competitive ions on phosphate uptake were investigated. The phosphate uptake kinetics were found to be fast and equilibrium was achieved after 30 min. The phosphate uptake was found to be highly pH dependent. Studies on the effects of competing ions, without keeping the initial pH constant, indicated that phosphate uptake and Kd values decreased in the presence of CO 3 2 − and NO 3 − , but SO 4 2 − ions showed little or no effect. With keeping the initial pH constant at 6, the presence of these competing ions had no clear effect on the uptake of phosphate. The phosphate uptake by composite of rice husk with MCM-41 could be described well by the Langmuir isotherm equation. Adsorption kinetic data correlated well with pseudo-second-order model, which suggested that the uptake process might be chemical sorption.
TL;DR: In this paper, CoFe-nitrate-layered double hydroxides (LDHs) with Co2+/Fe3+ molar ratios of 2, 3 and 4 were synthesized by a simple co-precipitation method.
Abstract: CoFe-nitrate-layered double hydroxides (LDHs) with Co2+/Fe3+ molar ratios of 2, 3 and 4 were synthesized by a simple co-precipitation method. The as-prepared CoFe-LDHs exhibited a high adsorption activity to the methyl orange (MO) dye and Cr(VI). The adsorption characteristics including adsorption kinetics and isothermals were investigated. Structure analysis of the as-synthesized LDHs before and after adsorption revealed that adsorption proceeds in two processes: external surface adsorption and interlayer anion exchange. The results of MO adsorption experiments showed that LDHs with Co2+/Fe3+ molar ratios of 4 worked best with the largest MO adsorption amount up to 1290 mg/g at an initial concentration of 300 mg/L due to the porous structures. We have also noted that Cr(VI) in a range of 2–25 mg/L can be quickly removed with the maximum adsorption capacity of 27.62 mg/g in the initial 5 min, much faster than other LDH materials. Therefore, CoFe-LDHs are potential cost-effective adsorbents for both MO dye and Cr(VI).
TL;DR: In this article, the potential of steam activated biochar (RHBC) produced from rice husk via slow pyrolysis at 700°C to remove glyphosate from aqueous solution was investigated.
Abstract: Biochar (BC), a carbon-rich solid product of biomass, and its surface activation via steam have been recognized as alternative economically viable strategy to decontaminate wastewaters. Existence of glyphosate, the most extensively used non-selective herbicide, in waters at elevated concentrations has received worldwide attention due to its ill consequences. The main objective of the present study was to investigate the potential of steam activated BC produced from rice husk (RHBC) via slow pyrolysis at 700 °C to remove glyphosate from aqueous solution. Batch adsorption experiments were carried out to evaluate the effects of pH, reaction time and glyphosate loading on the RHBC adsorption process. Results showed that a maximum removal of glyphosate (82.0%) occurred at pH 4, and the adsorption capacity decreased significantly with increasing pH. Both the Freundlich and Langmuir models fitted best to the equilibrium isotherm data suggesting physisorption as well as chemisorption mechanisms governing the glyphosate adsorption. The Langmuir maximum adsorption capacity was 123.03 mg/g. The kinetics of the adsorption process was well described by the pseudo-first order indicating that the glyphosate adsorption onto RHBC would be more inclined towards physisorption depending on the initial glyphosate concentration. Pore diffusion, π–π electron donor–acceptor interaction and H-bonding were postulated to be involved in physisorption, whereas electrophilic interactions led to chemisorption type of adsorption. Overall, steam activated RHBC could be a promising remedy of glyphosate removal from aqueous solution.
TL;DR: The particle size and size distribution of Zeolitic Imidazole Framework-8 (ZIF-8) nanoparticles are influenced by the synthesis temperature during isothermal mixing reactions in methanol as mentioned in this paper.
Abstract: The particle size and size distribution of Zeolitic Imidazole Framework-8 (ZIF-8) nanoparticles are influenced by the synthesis temperature during isothermal mixing reactions in methanol. As the synthesis temperature is increased from −15 °C to 60 °C, the average nanoparticle size decreased from 78 nm to 26 nm, with a simultaneous narrowing of the particle size distribution. Adsorption studies showed an increase in the external surface area of the nanoparticles from 220 m 2 g −1 till 336 m 2 g −1 as the particle size decreases from 78 nm till 26 nm. The increased external surface area of ZIF-8 nanoparticles (nZIF-8) led to a significantly higher catalytic activity when compared to the catalytic activity of commercially available ZIF-8 micro-particles in a Knoevenagel condensation test reaction.
TL;DR: In this article, the feasibility of using nano-zeolite as support material for the provision of nine out of thirteen primary, secondary and micro-nutrients on slow release basis was assessed.
Abstract: The research deals with assessing the feasibility of using nano-zeolite as support material for the provision of nine out of thirteen primary, secondary and micro-nutrients on slow release basis. The nano-zeolite (NZ) and nano-composite (ZNC), synthesized using simple chemical approach, were characterized by different techniques including FT-IR, powder XRD, SEM/EDX, AFM and TGA/DSC. Physical characterization was also performed by using standard methods. The lab studies showed that there is considerable increase in water retention capacity, water absorbency, equilibrium water content and swelling ratio of ZNC as compared to the NZ which is favorable for maintaining water level in the soil. The nano-composite prepared is safe to use as compared to conventional fertilizers as indicated by salt index value. Nutrients slow release studies carried out in water and soil confirmed the long term availability of all the doped nutrients to the plant over the full crop cultivation period that is suitable for promoting germination, growth, flowering and fruiting. Hence, the results obtained showed that the prepared nano-composite materials can be safely used as environment friendly fertilizer.
TL;DR: In this article, a versatile and efficient adsorbent with high adsorption capacity was presented over the Ag modified calcium hydroxyapatite (CaHAp), which was synthesized using facile aqueous precipitation method and the physico-chemical properties of the materials were determined by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Transmission electron microscopy (TEM), UV-Visible spectroscopy, N-2 physisorption and acidity was determined by n-butylamine titration
Abstract: In the present study a versatile and efficient adsorbent with high adsorption capacity for adsorption of Congo red dye in aqueous solution at ambient temperature without adjusting any pH is presented over the Ag modified calcium hydroxyapatite (CaHAp). CaHAp and Ag-doped CaHAp materials were synthesized using facile aqueous precipitation method. The physico-chemical properties of the materials were determined by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Transmission electron microscopy (TEM), UV-Visible spectroscopy, N-2 physisorption and acidity was determined by n-butylamine titration and pyridine adsorption methods. XRD analysis confirmed all adsorbents exhibit hexagonal CaHAp structure with P6(3)/m space group. TEM analysis confirms the rod like morphology of the adsorbents and the average length of the rods were in the range of 40-45 nm. Pyridine adsorption results indicate increase in number of Lewis acid sites with Ag doping in CaHAp. Adsorption capacity of CaHAp was found increased with Ag content in the adsorbents. Ag (10): CaHAp adsorbent showed superior adsorption performance among all the adsorbents for various concentrations of Congo red (CR) dye in aqueous solutions. The amount of CR dye adsorbed on Ag (10): CaHAp was found to be 49.89-267.81 mg g(-1) for 50-300 ppm in aqueous solution. A good correlation between adsorption capacity and acidity of the adsorbents was observed. The adsorption kinetic data of adsorbents fitted well with pseudo second-order kinetic model with correlation coefficients ranged from 0.998 to 0.999. The equilibrium adsorption data was found to best fit to the Langmuir adsorption isotherm model. (C) 2015 Elsevier Inc. All rights reserved.
TL;DR: In this paper, the pore fractal dimension is larger in coal with a greater pore size, and tectonic movement promotes irregularity and fracturing of the original pore.
Abstract: To study the variation in the characteristics of closed pores in coal under tectonic deformation, three coal samples are selected that differ only slightly in metamorphic degree but differ sharply in deformation degree, with vitrinite reflectance range from 0.88% to 0.96% and deformation degrees corresponding to weak brittle, strong brittle and strong ductile deformations. The experimental methods used are small-angle X-ray scattering and liquid nitrogen adsorption, and the pore diameters obtained by combining the two methods are within the mesopore (2–50 nm) size range. The deformation of coal narrows the distribution of pore diameters. Changes in pore shape are described according to fractal theory: the pore fractal dimension is larger in coal with a greater pore size, and tectonic movement promotes irregularity and fracturing of the original pores. The specific surface area of pores is calculated in this paper. We conclude that the proportion of closed pore specific surface area reaches the peak with the increase of the deformation degree, and then falls gradually. Pore diameters greater than 3.2 nm and less than 3.2 nm correspond to the two parts in the liquid nitrogen adsorption data, with the fractal dimension of the former being larger than that of the latter. The results also show that the closed pore volume increases but the proportion of the total pore decreases with increasing deformation degrees.
TL;DR: In this paper, a non-local density functional theory (NLDFT) analysis based on N2 and CO2 composited adsorption isotherms is used to investigate the pore structure of nanopores in marine organic-rich shale and compare with the results from some conventional methods in this paper.
Abstract: Low-pressure gas adsorption is widely used for pore size analysis of porous materials, and has been employed to characterize pore systems in shale. However, the complexity of shale pore structures means that different methods and models may lead to distinct interprets for adsorption data. Non-local-density functional theory (NLDFT) analysis based on N2 and CO2 composited adsorption isotherms is used here to investigate the pore structure of nanopores in marine organic-rich shale and compare with the results from some conventional methods in this paper. The results indicate that (1) The N2 adsorption isotherms of organic-rich shale are a composite of Types I(b), II, and IV(a), according to the IUPAC (2015) classification of physisorption isotherms. The hysteresis loops show similar shapes to Type H2(a). Delayed capillary condensation is observed in the adsorption isotherms, and the desorption step is shifted to the lower relative pressure of ∼0.45 characteristic of the cavitation mechanism, indicating ink-bottle pores with narrow necks. The CO2 adsorption isotherms are similar to Type I(b), but appear to increase without limit when p/p0 = 0.03 because of the occurrence of meso- and macropores in the shales. (2) NLDFT method based on N2 and CO2 composited adsorption isotherms is the most suitable and accurate method for using gas physisorption when considering the entire size distribution of nanopores, which allows a suitable range of critical pore sizes (∼0.33–100 nm) to be explored.
TL;DR: In this article, the heat treatment effect on the adsorption capabilities of nanoporous carbon particles derived from Zeolitic Imidazolate Framework-8 (ZIF-8) was investigated at 600, 1000 and 1200°C.
Abstract: The heat treatment effect on the adsorption capabilities of nanoporous carbon particles derived from Zeolitic Imidazolate Framework-8 (ZIF-8) was investigated at 600, 1000 and 1200°C in this study. The results showed that heat treatment at 1000°C had a significant effect on the adsorption capacity of ZIF-8 (almost 10 times) for the removal of methylene blue (MB) dye from water. Nanoporous carbons were synthesized by direct carbonization of ZIF-8. SEM and TEM images showed that the carbon resulting from ZIF-8 carbonization at various temperatures retained the original structure and morphology of ZIF-8. The carbon nanoparticles carbonized at 1000°C exhibited outstanding adsorption capacities (186.3 mg/g) compared to nanoparticles carbonized at 600°C (49.5 mg/g) and 1200°C (36.7 mg/g) as well as ZIF-8 (19.5 mg/g) due to the change in surface charge and pore size distribution. The surface functionalities of materials were also characterized by Raman Spectroscopy, N 2 adsorption-desorption, FTIR and TGA. The surface charge of the carbon particles changed from positive (ZIF-8) to negative as a result of conversion to carbon confirmed by zeta potential of the samples. The ZIF-8 derived carbon nanoparticles were found to be efficient adsorbents for water treatment purposes due to the satisfactory adsorption properties such as high adsorption capacity and good wettability.
TL;DR: In this paper, UiO-66 nanoparticles have been facilely prepared in a continuous flow microreactor, in which the particle size can be tuned from hundreds to dozens of nanometers by controlling of the residence time.
Abstract: In this paper, UiO-66 nanoparticles have been facilely prepared in a continuous flow microreactor, in which the particle size can be tuned from hundreds to dozens of nanometers by controlling of the residence time. All the products have been completely characterized by FT-IR, PXRD, N 2 sorption, SEM and TEM. Furthermore, NH 2 -functionalized nano-UiO-66 particles have also been prepared and the drug delivery behavior for 5-fluorouracil (5-Fu) was studied in PBS solution.
TL;DR: In this paper, the authors used the grand canonical Monte Carlo (GCMC) simulations to evaluate the surface area of metal-organic frameworks (MOFs) and zeolites.
Abstract: While nitrogen and argon isotherms at their respective boiling points are commonly used for the BET analysis of porous materials, CO2 isotherms at 273 K have been suggested as an alternative option for materials containing very small pores in which nitrogen and argon molecules cannot access at cryogenic temperatures. However, it has been known that the BET surface areas obtained from CO2 isotherms are not really meaningful in an absolute sense due to the strong CO2–CO2 interaction. In this study, CO2 isotherms in metal–organic frameworks (MOFs) and zeolites were predicted by grand canonical Monte Carlo (GCMC) simulations and used to evaluate the BET analysis for these materials. For all the microporous materials with varied pore sizes, the BET surface areas calculated from the simulated CO2 isotherms agreed roughly with their geometric surface areas from the crystal structures. Moreover, a clear selection of a proper BET linear region was possible for the material possessing only ultra-micropores. These results indicate that the BET surface areas determined from CO2 isotherms at 273 K may be considered reasonable for adsorbents containing only ultra-micropores where the BET surface areas based on N2 or Ar isotherms at cryogenic temperatures are not available.
TL;DR: In this paper, the effects of experimental parameters (e.g., reaction temperature, stirring rate and concentration of triethanolamine (TEA)) on the particle sizes of mesoporous silica nanoparticles (MSNs) were investigated.
Abstract: In this work, systematic studies were performed to investigate the effects of experimental parameters (e.g. reaction temperature, stirring rate and concentration of triethanolamine (TEA)) on the particle sizes of mesoporous silica nanoparticles (MSNs). Results revealed that the stirring rate played a key role in the size-controlling of MSNs. Additionally, both the reaction temperature and the concentration of TEA showed relatively obvious influence on the sizes of MSNs. We supposed that the MSNs particles were formed by the aggregation and condensing of silica-surfactant micelles and the diameters of MSNs were dependent on the concentration of silica-surfactant micelles. In order to obtain MSNs with small sizes, low reaction temperature and rapid stirring rate were adopted to reduce the concentration of silica-surfactant micelles and suppress the growth of MSNs. As a surface capping ligand, TEA could suppress the particle growth and prevent the particle aggregation of MSNs. By simply controlling the synthetic parameters, MSNs with adjustable size from 20 to 110 nm were obtained. Moreover, the obtained MSNs displayed narrow size distribution and well dispersity in water, which made them highly promising in biomedical applications.
TL;DR: In this paper, the effects of slag addition and molar ratio of alkaline solution on the microstructure and mechanical strength of mesoporous materials were investigated and evidenced by XRD analysis, compressive strength and nitrogen adsorption tests.
Abstract: The present study investigates the synthesis of mesoporous geopolymers containing different nano-crystalline zeolite phases. A hydrothermal treatment procedure was utilized to synthesize the mesoporous geopolymers using fly ash, slag and alkaline solution. The effects of slag addition and molar ratio of alkaline solution on the microstructure and mechanical strength of the geopolymers were investigated and evidenced by XRD analysis, compressive strength and nitrogen adsorption tests. The test results showed that the geopolymers incorporating fly ash and slag consisted of Na-P1 and Sodalite zeolite phases, and had the characteristic of mesoporous materials (2 nm
TL;DR: In this paper, hybrid nanocomposites of zeolitic imidazolate framework-8 (ZIF-8) and graphene oxide (GO) were prepared in a methanol system at room temperature.
Abstract: Hybrid nanocomposites of zeolitic imidazolate framework-8 (ZIF-8) and graphene oxide (GO) were prepared in a methanol system at room temperature. The ZIF-8/GO composites exhibited tunable nanoscale morphology and porosity, both determined by the GO content. A series of characterization techniques confirmed the formation of strong interactions between ZIF-8 and GO in the synthesized composites. The as-synthesized ZIF-8/GO composites were composed of aggregated nano-sized particles, and exhibited a higher volatile organic compounds (VOCs) uptake capacity than normal ZIF-8 crystal owing to the synergistic effect between ZIF-8 and graphene oxide(GO). Also an increase in the content of GO resulted in enhancing in the VOCs adsorption capacity, and the maximum adsorption capacity for VOCs was up to 240 mg/g on ZIF-8/GO with the GO content of 15 wt%. The synergistic interactions of ZIF-8 and GO may provide a new path to fabricate novel ZIFs/GO composites for a wide range of applications such as adsorption.
TL;DR: In this paper, the authors used GCMC simulations to study the adsorption behavior of CH 4, CO 2, and their mixture in Na-, Cs-, and Ca-montmorillonite clays in the presence of water.
Abstract: Using grand canonical Monte Carlo (GCMC) simulations, we study the adsorption behavior of CH 4 , CO 2 , and their mixture at 298.15 K and pressures up to 50 bar in Na-, Cs-, and Ca-montmorillonite clays in the presence of water. Montmorillonite clays in the presence of preadsorbed water, preferentially adsorb CO 2 over CH 4 during both pure component and mixture adsorption. The atomistic model we have used, gives good agreement with available single-component experimental adsorption isotherms, for CH 4 and CO 2 molecules adsorbed onto montmorillonite clays in the presence of water. We observe the general trend that the presence of increasing preadsorbed water content in the clay interlayers, reduced adsorption amounts of pure CH 4 and CO 2 molecules. With a relatively large basal spacing (d = 30 A), the favorability of adsorption of CO 2 by montmorillonite at relatively low pressures and intermediate water contents has been demonstrated using simulations. GCMC simulation is also used to assess the effect of water on the adsorption of N 2 /CH 4 , H 2 S/CH 4 , CO 2 /N 2 , and CO 2 /H 2 S binary mixtures in Na-montmorillonite clay. The ideal adsorbed solution theory is shown to agree well with the observed adsorption capacities and selectivities of mixtures in Na-montmorillonite clay.
TL;DR: In this paper, the compressive strength of geopolymer concrete has been studied against the percentage of oxides (i.e., SiO2, Al2O3, FeO 3, CaO etc.) present in the raw material which were employed in the production of the concrete.
Abstract: Off late, geopolymer concrete has gained significant attention in the construction industry because of the benefits that it brings via, by-product waste utilization, reduction in greenhouse gas emission. Studies reveal that the chemical oxide composition of the raw material (viz., fly ash) strongly influences the mechanical behavior and durability properties of geopolymer concrete. However, not many studies have paid attention towards the influence of an oxide percentage in the raw material on the compressive strength of the geopolymer concrete. In this paper, an attempt has been made to study the compressive strength behavior against the percentage of oxides (viz., SiO2, Al2O3, Fe2O3, CaO etc.) present in the raw material which were employed in the production of geopolymer concrete. In this extensive data has been collected from various earlier research publications. Trends for 7 & 28 day compressive strengths against individual oxide component percentages were developed, and it was observed that the strength of geopolymer concrete differs greatly with the variation in percentage of the individual oxide component. Also, each oxide has shown distinct influence on the compressive strength of geopolymer concrete. Further, it has been noticed that the compressive strength of a sample has been predominantly influenced by the percentage of alumina-silicate oxides, and whereas oxides like CaO and Fe2O3 even though lesser in amount compared to alumina-silicate oxides have shown a distinctive effect on the strength built-up. Also, the oxide molar ratios influence on the compressive strengths has been analysed and it was noticed that compared to individual oxide composition its influence is not major on the compressive strength development. Therefore, knowing the typical range of the major oxides percentage required for achieving superior compressive strength will be beneficial in developing concrete mix proportion.
TL;DR: In this article, two series of Ni (2.5-7.5 ) and Ce (6-wt%) catalysts were used in dry reforming of methane, a promising route for the production of syngas.
Abstract: Two series of Ni (2.5–7.5 wt%) and Ce (6 wt%) containing SBA-15 catalysts were prepared and tested in dry reforming of methane, a promising route for the production of syngas. Both Ni and Ce species were introduced in the organized mesoporous silica support in the form of nitrate salts using the “two solvents” procedure that is known to favor metal dispersion inside the porosity. Samples characterizations by N 2 sorption, SAXS, XRD, SEM and TEM indicate good preservation of the porosities after Ni deposition and calcination as well as formation of NiO nanoparticles entrapped in the porous channels. In the cerium-enriched samples, the CeO 2 nanoparticles are also highly dispersed. After reduction, all the catalysts show high activity and selectivity towards H 2 and CO at atmospheric pressure with full CH 4 conversion below 650 °C. In these conditions, there is no significant promotional effect by ceria. Moreover, prolonged tests performed at 500 °C for 12 h reveal a high stability of the catalysts. The absence of deactivation throughout the catalytic run at this temperature agrees with the low carbon amount detected after test and with the limited sintering of the Ni nanoparticles in the used catalysts. The positive effect of the SBA-15 mesoporous channels towards stabilization of the supported particles is discussed.
TL;DR: In this paper, the effects of some parameters, such as contact time, adsorbent dosage, pH, stirring speed, and concentration, on the removal efficiency of chabazite were taken into consideration.
Abstract: Chabazite, one of the common types of zeolite, was used in our study to remove methylene blue (MB) dye from aqueous solutions. The characterization of chabazite was performed using scanning electron microscope (SEM), Fourier Transform infrared (FTIR), X ray diffraction (XRD), and thermogravimetric-differential thermal analyses TG/DTA. During the experimental study, the effects of some parameters, such as contact time, adsorbent dosage, pH, stirring speed, and concentration, on the removal efficiency of chabazite were taken into consideration. To evaluate the experimental data, Langmuir, Freundlich, and Tempkin isotherm models were used. The experimental data were well fitted to the Langmuir isotherm model, with a correlation coefficient of 0.95. The adsorption kinetics of MB dye on chabazite could be described by a pseudo second-order model.
TL;DR: In this article, a magnetic polymer clay composite was used for removing pharmaceuticals from water, and the optimum ratio of composite adsorbent was found to be clay: chitosan: powdered activated carbon (PAC): magnetic nano particles (MNP).
Abstract: Adsorption of three pharmaceuticals, namely, atenolol, ciprofloxacin and gemfibrozil using synthesized magnetic polymer clay composite was investigated in detail by conducting batch kinetic, equilibrium and desorption experiments. Optimum ratio of composite adsorbent was found to be clay: chitosan: powdered activated carbon (PAC): magnetic nano particles (MNP) as 1:0.5:0.3:0.3. Characterization studies showed the incorporation of modifiers into the clay structure. Surface area of the synthesized pellets was 94.81 m2/g with mesoporous surface. Freundlich model was able to predict the adsorption equilibrium data. Maximum adsorption capacities were estimated to be 15.6, 39.1 and 24.8 mg/g for atenolol, ciprofloxacin and gemfibrozil, respectively. The main driving force of adsorption was electrostatic interaction. The adsorbent performance was affected at lower and higher pH and by the presence of humic acid. Desorption of atenolol and ciprofloxacin were significantly higher in acid and alkaline solution whereas gemfibrozil was desorbed upto 70% in methanol. Magnetically separable clay composite was found to be a suitable adsorbent for removing pharmaceuticals from water.