N2 Adsorption-desorption Isotherm Analysis Research Articles

Mesoporous bouquet-like Co 3 O 4 nanostructure for the effective heterogeneous activation of peroxymonosulfate

Abstract A facile hydrothermal and subsequent calcination method is proposed for the synthesis of mesoporous bouquet-like Co3O4 nanostructure. The prepared Co3O4 nanostructure is efficient for the activation of peroxymonosulfate (PMS). Morphological observation clearly indicates that the micron-scale bouquet-like structure is composed of numerous regular Co3O4 nano-rods. X-ray diffraction (XRD), X-ray photo-electron spectroscopy (XPS), and fourier transform infrared spectroscopy (FTIR) spectra indicate the high purity and crystallinity of the prepared Co3O4 nanostructure. The N2 adsorption-desorption isotherm analysis shows that the bouquet-like Co3O4 nanostructure possesses a moderate specific surface area (37.0 mg−2) and mesoporous property. The fluoroquinolone antibiotics (nofloxacin, NOR and ofloxacin, OFX) can be effectively degraded in the Co3O4/PMS oxidation system under ambient conditions. In addition, the extremely low metal leaching (no more than 0.07%) indicates that the heterogeneous activation mechanism plays a much significant role in the activation process. By using the radical scavengers, the sulfate radical is found to be the dominant oxidative species in the degradation process. These results reveal that the designed Co3O4 nanostructure exhibit promising capability for the environmental remediation.

Effective removal of Cr(VI) from aqueous solution by diamino-functionalised mesoporous MCM-48 and selective oxidation of cyclohexene and ethylbenzene over the Cr containing spent adsorbent

Adsorptive removal of Cr(VI) by N-3-trimethoxysilylpropylethylenediamine (AEAPTMS) functionalised MCM-48 prepared via grafting method was investigated with respect to contact time, adsorbent dose, initial metal ion concentration, pH, amine loading and temperature. The synthesized samples were characterized by X-ray diffraction (XRD), fourier transform infrared (FTIR) spectrocopy, scanning electron microscopy (SEM), N2 adsorption-desorption isotherm and thermogravimetric analysis (TGA). 1.5mmol AEAPTMS functionalised MCM-48 sample showed highest adsorption among the modified samples under similar conditions. Adsorption kinetics was successfully fitted by pseudo second-order kinetic model. The experimental data fitted well to the Langmuir adsorption isotherm model with a calculated maximum adsorption capacity of 166.67mg/g. The overall adsorption was a spontaneous and endothermic process as signified by the thermodynamic parameters. Another aspect of the work was the high catalytic efficiency of chromium containing spent adsorbent obtained by adsorption of Cr(VI) from the aqueous solution. The catalytic activity of the obtained catalyst was found to depend on the amount of adsorbed chromium. The spent adsorbents behaved as efficient catalysts for oxidation of cyclohexene (81.0% conversion) and ethylbenzene (94.6% conversion) with 96.7% and 100% selectivity towards desired product when 70% tert-Butyl hydroperoxide (TBHP) was used as oxidant.

Dual-functionalized porous organic polymer as reusable catalyst for one-pot cascade C[sbnd]C bond-forming reactions

A porous dual-functional acid-base covalent organic polymer catalyst (CBAP-1(EDA-SO3H)) was prepared using a facile Friedel-Crafts reaction of triphenylbenzene and terephthaloyl chloride to prepare the polymer backbone (CBAP-1) followed by functionalization with ethylenediamine (EDA) and a simple chlorosulfonic acid treatment. The resultant polymeric catalyst and its functional moieties were characterized by Fourier transform infrared (FTIR), elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), and N2 adsorption-desorption isotherm analyses. The catalytic activity of CBAP-1(EDA-SO3H) was then assessed for one-pot cascade CC bond-forming reactions involving deacetylation-Knoevenagel condensation and Henry reactions. Compared with the homogeneous catalyst and CBAP-1 functionalized with just acid or base, CBAP-1(EDA-SO3H) showed superior catalytic activity and selectivity, and was found to be reusable for up to seven consecutive runs. A catalytic mechanism for CC bond-forming reactions over CBAP-1(EDA-SO3H) was proposed.

Synthesis of ordered mesoporous La2O3-ZrO2 composites with encapsulated Pt NPs and the effect of La-dopping on catalytic activity

In this work, we report a feasible approach to synthesize a ternary nanocomposites, Pt/lanthanum doped mesoporous zirconium oxide (Pt/La2O3-ZrO2), via an effective two-step method. Ordered mesoporous La2O3-ZrO2 composites were firstly fabricated with mesoporous silica KIT-6 as a hard template. Subsequently, uniform Pt nanoparticles encapsulated by 4 hydroxyl-terminated poly (amidoamine) (G4-OH PAMAM) dendrimers were deposited on the La2O3-ZrO2 composites. The as-prepared samples were characterized by transmission electron microscope (TEM), N2 adsorption–desorption isotherm analysis, energy dispersion X-ray analysis (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature programmed reduction (H2-TPR). The average size of PtDENs was found to be 1.48nm in diameter. Furthermore, the introduction of La could improve the structure of the supports which was confirmed by XRD and H2-TPR analysis. The reduction of p-nitrophenol to p-aminophenol by NaBH4 was utilized to evaluate the catalytic performances of catalysts. Results indicated that the Pt/La2O3-ZrO2 catalyst calcined in nitrogen at 550°C exhibited the highest catalytic performance and still kept the high catalytic activity even after six cycles. This phenomenon suggests that synergistic effect among Pt-Zr-La could enhance the catalytic efficiency. Finally, reaction mechanism was proposed for the reduction of p-nitrophenol.

Fibrous N-doped hierarchical porous carbon microspheres: Synthesis and adsorption performance

The creation of high surface area and effective active sites is the key problem for the synthesis of high-performance porous carbon materials. In this work, polyacrylonitrile-coated fibrous silica (F-SiO2@PAN) microspheres were prepared by in situ polymerization of acrylonitrile on fibrous mesoporous silica microspheres induced by γ-ray radiation. After F-SiO2@PAN microspheres were carbonized and etched with hydrofluoric acid, uniform fibrous N-doped porous carbon (FNC) microspheres with an average size of 286nm and a molar ratio of C/N of 5.2 were successfully prepared. As revealed by TEM, SEM, and N2 adsorption-desorption isotherms analysis, FNC microspheres have a hierarchal micro-macroporous structure with a particular high surface area of 554.5m2/g. The FNC microspheres also exhibit a good water dispersibility and an excellent adsorption ability to rhodamine B in water. The equilibrium adsorption capacity of FNC microspheres could reach 95.4mg/g, which is 1.6 times as that of the primary silica template microspheres. The adsorption kinetics and thermodynamics of FNC microspheres are in accord with the pseudo-second-order kinetic equation and Freundlich isotherm model, respectively. This work provides a facile synthesis method for novel N-doped hierarchical micro-macroporous carbon microsphere as a potential high-performance adsorbent material.

Synthesis of La doped Bi2WO6 nanosheets with high visible light photocatalytic activity

The La3+ doped Bi2WO6 were synthesized via a facile hydrothermal process. Various characterization techniques, such as X-ray diffraction patterns (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV–Vis diffuse reflectance spectra (UV–Vis DRS), FT-IR, photoluminescence (PL) spectra and N2 adsorption–desorption isotherm analysis, were employed to investigate the as-prepared products. The results indicate that La3+ replacing Bi3+ enters into the Bi2WO6 lattice, producing a degree of Bi2WO6 lattice distortion. It also has an impact on the crystallinity of Bi2WO6 and the band gap was from 2.64 to 2.79 eV. The photocatalytic results show that when the content of La3+ doping becomes 5%, the degradation rate of Rhodamine B (RhB) was above 98% after 25 min irradiation, This enhancement should be ascribed to the slightly increased band gap and the generated defects by La3+ doping, thus resulting in a much lower recombination rate of the photo-induced electrons and holes.

Confinement of Mn3+ redox sites in Mn-KIT-6 and its catalytic activity for styrene epoxidation

In the present study, a series of manganese (Mn) containing 3D cubic mesoporous KIT-6 materials with different Si/Mn ratio (100, 50 25 & 10) having Ia3d space group were synthesized for the first time by a facile one-pot hydrothermal process. The synthesized materials were methodically characterized by various analytical techniques including XRD, N2 sorption, HR-TEM, diffuse reflectance UV–vis (DRS-UV-vis), EPR and FT-IR. The well ordered mesoporous nature of Mn incorporated KIT-6 materials are realized by XRD, N2 adsorption-desorption isotherm and HR-TEM analysis. Surface area, pore volume and pore size of Mn-KIT-6 with different Si/Mn ratio are in the range of 451–786 m2/g, 0.57–0.9 cm3/g and 4.5–4.9 nm respectively. The incorporation of Mn3+ in the framework and fine dispersion of Mn2+ species over silica matrix of Mn-KIT-6 are confirmed by the results of UV-DRS, FT-IR and EPR. Further, the presence of higher amount of Mn2+ extra-framework species in Mn-KIT-6(10) is realized by the presence of high amplitude signal and the contraction in H1 hysteresis loop as shown in EPR and BET isotherm respectively. Catalytic behavior of Mn-KIT-6 material was evaluated for the epoxidation of styrene with various oxidants in which t-butyl hydro peroxide (TBHP) promotes the desired formation of styrene oxide under mild liquid phase conditions. Mn-KIT-6 shown to be highly stable and active which mainly depends on the framework substituted Mn3+ sites.

Phenol and/or Zn2 + adsorption by single- or dual-cation organomontmorillonites

Single- or dual-cation organomontmorillonites (OMt) modified by one or two cationic surfactants, respectively and/or cysteamine hydrochloride (CSH) were used to remove Zn2+ and/or phenol from aqueous solutions. The OMt were characterized by XRD, FTIR spectroscopy and N2 adsorption-desorption isotherm analyses. The adsorption results of Zn2+ and phenol showed that OMt had much larger adsorption capacities of phenol than that of Na+-Mt or CSH-Mt in the presence of Zn2+. Experiments with the simultaneous presence of both the contaminants showed that one did not affect the adsorption of the other with all the adsorbents. The uptakes of Zn2+ and phenol onto dual-cation OMt increased with increasing solution pH, contact time, temperature and initial concentration of Zn2+ and phenol. The adsorption equilibrium time was 10min for both contaminants and the maximum adsorption capacities of Zn2+ and phenol were found under alkaline environment. The adsorption of both Zn2+ and phenol can be better described by Freundlich model than Langmuir isotherm. Phenol adsorption onto OMt was caused primarily by partitioning into an organic phase in the interlayers, and the uptakes of phenol increased with increasing alkyl chain length and loading amount of surfactant in single-cation OMt. Zn2+ adsorption onto dual-cation OMt was due to ion exchange, formation of complexes and/or precipitation mechanism depending on the solution pH.

Facile one-step synthesis of Ag@CeO2core–shell nanospheres with efficient catalytic activity for the reduction of 4-nitrophenol

Ag@CeO2 core–shell nanospheres were synthesized by a facile one-step solvothermal route from Ce(NO3)3·6H2O, AgNO3, poly(N-vinylpyrrolidone) (PVP), and ethanol. The structure, composition, BET specific surface area and optical properties of Ag@CeO2 core–shell nanospheres were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, high resolution transmission electron microscopy, N2 adsorption–desorption isotherm analysis, and UV-vis diffuse reflectance spectroscopy. Field emission scanning, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy etching results of the as-synthesized Ag@CeO2 nanospheres revealed that the as-synthesized Ag@CeO2 nanospheres consist of a Ag core and a CeO2 shell. The catalytic results demonstrated that the as-synthesized Ag@CeO2 nanospheres possessed higher catalytic activity than pure Ag (which was synthesized by a similar solvothermal method) in the reduction of 4-nitrophenol. Their enhanced catalytic activity is found to be due to the unique oxidized Ag species induced by the strong interaction between the core surface of Ag nanospheres and surface defects (oxygen vacancies) of the CeO2 shell. The herein proposed Ag@CeO2 core–shell nanospheres are promising catalytic candidates for the reduction of p-nitrophenol because of their simple preparation route and high catalytic activity.

Synthesis of Cd doped ZnO/CNT nanocomposite by using microwave method: Photocatalytic behavior, adsorption and kinetic study

The Cd-doped ZnO/CNT nanocomposites (Cd@ZnO/CNT-NCs) were synthesized by the microwave assisted hydrothermal method. The as-synthesized Cd@ZnO/CNT-NCs was characterized in detail in term of their structural, morphological, chemical and optical properties using XRD; SEM, FE-TEM, BET and UV–Vis methods. The band gap energy measurements confirmed that the addition of Cd ions causes a decrease in the band gap energy of the nanocomposites. The photocatalytic properties of the synthesized nanocomposites were investigated by the measurements of methyl orange (MO) degradation under UV irradiation.The equilibrium adsorption data of all three nanocomposites (i.e. ZnO/CNT, CZC-1, CZC-0.25) were analyzed by Langmuir and Freundlich isotherm models, respectively. The best fit to the data was obtained from the Langmuir model. The decrease in MO dye concentration was examined by UV–Visible spectroscopy at different time intervals under ultraviolet light irradiation, until the dye was completely degraded to colorless end product. Rapid MO dye decomposition was observed with a degradation rate of ∼93, 70 and 44% on the CZC-1, CZC-0.25 and ZnO/CNT within the initial 110min, respectively. The fast degradation rate and high degradation efficiency of CZC-1 and CZC-0.25 is attributed to the porous nature, large specific surface area (162.5 and 136.1m2g−1), narrow pore size distribution (7.46 and 12.98nm) evaluated from N2 adsorption-desorption isotherms analysis and excellent electron accepting features of the engineered porous Cd@ZnO/CNT-NCs. The kinetic results revealed that the degradation rate of MO on the CZC-1 (i.e. Cd0.5Zn0.5O/CNT) and CZC-0.25 (i.e. Cd0.25Zn0.75O/CNT) is approximately 2- and 4-folds larger than the CNT/ZnO that can be explained by the replacement of Cd ions in the ZnO structure. The degradation of the model dyes was observed to follow pseudo first order degradation kinetics.

Multi‐Metal‐Substituted‐Goethite as an Effective Catalyst for Azo Dye Wastewater Oxidation

Different samples of goethite modified with cobalt, manganese, or aluminum were synthesized and characterized by means of X‐ray diffraction, chemical analysis, scanning electron microscopy, zeta potential measurements, and N2 adsorption–desorption isotherm analysis. The goethite oxides were tested as efficient catalysts for the degradation of methyl orange (MO, sodium 4‐[(4‐dimethylamino)phenylazo]benzenesulfonate), a sulfonated azo dye indicator, employing potassium persulfate (PS) in water, at pH 3. The Mn, Co, and Al substitution in goethite gave rise to active sites for PS activation. The most effective catalyst reached 93% of degradation at 120 min of reaction. The increase of temperature led to an expected conversion enhancement, and kinetic parameters were calculated for one of the evaluated catalysts. MO degradation curves best fitted to pseudo‐second order kinetics. The extent of mineralization, measured as total removed organic carbon (TOC), was also monitored. A significant degree of mineralization was achieved and confirmed by TOC analysis. A mechanism for MO oxidation with radicals was discarded and a pathway involving peroxymonosulfate species was proposed. The results indicate that the goethite‐substituted oxides are effective catalysts for the studied azo dye degradation in aqueous solution.

Synthesis and Electrochemical Properties of Li2MnO3 Li4Mn5O12 Binary System As Positive Electrode Materials for Lithium Ion Battery

Synthesis and Electrochemical Properties of Li2MnO3―Li4Mn5O12 Binary System as Positive Electrode Materials for Lithium Ion Battery Masaki Okada and Yuya Sakaguchi Inorganic Materials Research Laboratory, TOSOH CORPORATION Lithium ion batteries are their high energy density compared with other batteries, progressed recently applied to applications requiring large capacity like for electric power storage system and electric vehicle. The positive electrode materials for a lithium ion battery, lithium metal oxide containing a large amount of rare metallic element such as cobalt or nickel are mainly investigated. Positive electrode material containing a large amount of these rare elements is very difficult to achieve both high energy density and low cost. As a positive electrode material that does not contain a rare metallic element, it is being studied of Li2MnO3 with a layered rock-salt structure. Li2MnO3 shows a large discharge capacity of more than 250mAh/g in the first cycle, but the capacity decreases with charge and discharge cycles. [1-3] In this work, we studied the Li2MnO3―Li4Mn5O12 binary system (Li4/3-4X/5Mn2/3O2-2X/5, 0<X<1) of the positive electrode materials based on Li2MnO3. Li4/3-4X/5Mn2/3O2-2X/5 can be suppressed capacity fading as compared with the conventional Li2MnO3. It may be able to achieve both low cost and high energy density. Li4/3-4X/5Mn2/3O2-2X/5 was prepared by reacting of mixture of MnCO3･0.5H2O and LiOH･H2O as raw material. The mixture was fired at 400～600ºC for 32h in air stream. Crystal structure and multilayered particle structure were investigated through TEM and N2adsorption-desorption isotherm analysis, respectively. The electrochemical characterization of positive electrode material was performed on CR2032 coin type cells. From the TEM images of the prepared samples, the presence of two crystal phases was observed. In addition, the electron diffraction pattern is attributed to the rock salt and the spinel phase, the possibility of a two-phase coexistence structure of Li2MnO3 and Li4Mn5O12 having a twin structure has been suggested. The initial charge and discharge capacity of Li4/3-4X/5Mn2/3O2-2X/5 was reduced as compared with Li2MnO3, but cycle stability was improved (X=0.36, 170mAh/g@50th, 50mA/g, RT). In additionally, capacity fading is suppressed by magnesium substitution of a part of manganese, the substituted sample showed stable cycling at about 200mAh/g (X=0.36, Mg 8mol %). In the viewpoint of the crystal structure and multilayered particle structure, the effect of the characters on capacity and cycle ability will be discussed. [1] Denis Y.W. Yu et.al., J. Electrochem. Soc. 2009 156(6) A417-A424 [2] Denis Y.W. Yu et.al. J. Electrochem. Soc. 2010 157(11) A1177-A1182 [3] Denis Y.W. Yu et.al., J. Electrochem. Soc. 2011 158(9) A1015-A1022

Rapid methyl orange degradation using porous ZnO spheres photocatalyst

Porous zinc oxide (ZnO) spheres were synthesized by facile low temperature solution route. The as-synthesized porous ZnO spheres were characterized in detail in terms of their morphological, structural, optical and photocatalytic properties using field-emission scanning electron microscopy (FESEM, equipped with energy dispersive spectroscopy (EDS)), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffractometer (XRD), UV–visible spectroscopy and Raman-scattering measurements. Nitrogen adsorption-desorption analysis was performed to determine pore size distribution from the adsorption isotherm curves using the Barrett-Joyner-Halenda (BJH) method. Morphological and structural characterizations showed porous nature of ZnO spheres with high surface area, good crystallinity, wurtzite hexagonal phase and good optical features. Next, ZnO spheres were studied as photocatalyst for photodegradation of harmful dye, methyl orange (MO). Under ultraviolet light irradiation, the decrease in MO dye concentration was monitored by UV–visible spectroscopy at different time intervals until the dye was completely degraded to colorless end product. Rapid MO dye decomposition was observed with a degradation rate of ~96.3% within the initial 120min, which is attributed to the porous nature, large specific surface area (114.6m2g−1), narrow pore size distribution (~2.5 to 25nm) evaluated from N2 adsorption-desorption isotherms analysis and excellent electron accepting features of the engineered porous ZnO spheres.

Fabrication of electronspun porous CeO2 nanofibers with large surface area for pollutants removal

The porous CeO2 nanofibers with diameter of 100–140nm were successfully synthesized by single-capillary electrospinning of a Ce(NO3)3·6H2O/PVP precursor solution, followed by calcination. The preparation parameters, including solution parameters and process parameters, affecting the spinnability and the morphology of nanofibers were investigated and discussed systematically. And the effects of different calcination temperatures on the microstructure CeO2 nanofibers were also studied. A plausible mechanism was proposed to explain the formation process of the CeO2 nanofibers. The N2 adsorption-desorption isotherm analysis showed that the specific surface area and average pore size of the nanofibers were 195.75g/m2 and 2.4nm, respectively. Moreover, as absorbent, the porous CeO2 nanofibers adsorbed the MO effectively. The adsorption experiment indicated that the adsorption process can be divided into two stages, including quick adsorption and gradual adsorption. And the adsorption capacities were not only determined by the specific surface area, but closely related to the pore size. Finally, the adsorption data were modeled by the pseudo-first-order and pseudo-second-order kinetics equations. The results showed that the pseudo-second order kinetics could best describe the adsorption of MO onto the porous CeO2 nanofibers.

Detailed characteristics of adsorption of bisphenol A by highly hydrophobic MCM-41 mesoporous molecular sieves

A surfactant structure-directing agent was used to synthesize a hydrophobic mesoporous material (MCM-41-d) at room temperature. As-prepared materials were characterized through X-ray diffraction (XRD) analysis, Fourier-transform infrared (FT-IR) spectroscopy, N2 adsorption–desorption isotherm analysis, and thermogravimetry (TG). The properties of the samples for adsorption of bisphenol A (BPA) from water were also investigated in detail. The results revealed that pH affected BPA adsorption. Equilibrium and kinetic data were consistent with the Langmuir adsorption and second-order kinetic model, respectively. The adsorption capacity of MCM-41-d was considerably higher than that of MCM-41-c because of its higher hydrophobicity and more abundant adsorption sites. The maximum adsorption capacity of MCM-41-d was as high as 416.7 mg/g, indicating that MCM-41-d can serve as an efficient adsorbent to remove BPA from water.

Production of mesoporous materials with high hydrothermal stability by doping metal heteroatoms

SBA-15 and metal doped SBA-15 with different metal special ratios were prepared using Pluronic P123 as a structure-directing agent. SBA-15 and metal doped SBA-15 were extensively characterized via N2 adsorption–desorption isotherm analysis, small-angle X-ray diffraction (SXRD), and Fourier transform infrared (FT-IR) analysis. The hydrothermal stability of the obtained mesoporous materials was tested in a stainless autoclave at 593 K for 1 h. Results of adsorption–desorption isotherm analysis, transmission electron microscopy, and SXRD revealed that metal doping improved the hydrothermal stability of SBA-15. Metal species and their molar ratios also contributed to the enhancement of hydrothermal stability. SXRD results showed that the diffraction peaks of metal doped SBA-15 shifted to higher 2θ degrees possibly because of framework constriction. FT-IR results indicated that the decrease in doped SBA-15 surface hydroxyl groups and hydrophilicity may be responsible for the improvement in hydrothermal stability after the introduction of heteroatoms. This work may serve as a reference for exploiting mesoporous materials with a hydrothermal stability and catalytic performance under aqueous conditions at high temperatures.

Preparation, characterization and catalytic activity of dendrimer-encapsulated phosphotungstic acid nanoparticles immobilized on nanosilica for the synthesis of 2H-indazolo[2,1-b]phthalazine-triones under solvent-free or sonochemical conditions

In this paper, we adopt a facile method to prepare a type of porous silica nanoparticles (n-SiO2) from tetraethyl orthosilicate as the source of silica. Then, dendritic polymer supported on nanosilica with surface amino groups was fabricated. Finally, H3PW12O40 nanoparticles (PWAn) were synthesized by the treatment of H3PW12O40 powder with n-Octane as solvent by a solvothermal method and then immobilized onto the dendrimer polymer functionalized nanosilica. The synthesized nanostructures were characterized by fourier transform infrared (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), dynamic light scattering (DLS), N2 adsorption–desorption isotherm analysis, UV–Vis and elemental analysis. The morphology of the catalyst was characterized using transmission electron microscopes (TEM). The acidity of the catalyst was determined by FTIR pyridine adsorption spectroscopy. Then, this catalytic system was used as an efficient catalyst for the synthesis of 2H-indazolo[2,1-b]phthalazine-triones via multi-component and one-pot reactions of various aldehydes, phthalic anhydride, hydrazinium hydroxide, and dimedone under thermal solvent-free conditions or ultrasound irradiation at room temperature. Also, the catalyst can be easily recovered and reused for six consecutive reaction cycles without significant loss of activity.

Palladium Nanoparticles Supported on MIL-101 as a Recyclable Catalyst in Water-Mediated Heck Reaction.

Pd nanoparticles supported on the chromium terephthalate metal organic framework, Pd0.9/MIL-101, was prepared by simple Pd-acetate adsorption on MIL-101 followed by reduction in acetone. The material was characterized by XRD, N2 adsorption-desorption isotherm, TEM and ICP analysis. Pd0.9/MIL-101 was found to be an effective heterogeneous catalyst for the water-mediated Heck cross-coupling reaction of various aryl iodides and alkenes under mild reaction conditions with product yields of 81 to 97%. The electron-withdrawing group attached to aryl iodide reacted faster than the electron-donating one, and the activity increased in the sequence of 4-methoxy-1- iodobenzene << iodobenzene < 1-iodo-4-nitrobenzene. The catalyst could be reused several times without losing its initial catalytic activity, and XRD and TEM confirmed that the crystallinity of Pd0.9/MIL-101 had been retained during the reaction with no metal leaching or agglomeration observed.

Modeling and thermodynamics of methylene blue and acid blue 80 adsorption onto potato residue based activated carbon

A study was made on the adsorption kinetics and thermodynamics of methylene blue(MB) and acid blue 80(AB80) onto powder of activated carbon(PAC) prepared by chemical method from dry potato residue(DPR). The PAC was characterized by N2 adsorption-desorption isotherms analysis and scanning electron microscopy. The maximum adsorption capacities of PAC for MB and AB80 at 303 K are 532.19 and 156.22 mg/g, respectively. The results indicate that the adsorption kinetics of the selected dyes on PAC is well-described by the pseudo-second order model. And their thermodynamic data were analyzed via the isotherms of Langmuir, Freundlich, Redlich-Peterson, Toth and Sips, and the thermodynamic parameters were calculated. The results show that PAC is a fast and effective adsorbent for removing the cationic dyes from aqueous solutions.

Fabrication of porous hollow γ-Al2O3 nanofibers by facile electrospinning and its application for water remediation

In this paper, we fabricated porous hollow γ-Al2O3 nanofibers by the facile single-capillary electrospinning of an aluminum nitrate (Al(NO3)3)/polyacrylonitrile (PAN) precursor solution, followed by sintering treatment. The nanofibers were characterized by scanning electron microscopy, thermogravimetric analysis, X-ray diffraction. N2 adsorption–desorption isotherm analysis showed that the specific surface area and average pore size of the nanofibers were 67.17 m2 g−1 and 17.3 nm, respectively. A possible mechanism based on the Kirkendall effect was proposed to explain the formation process of the hollow structure. The pore size and diameter of the nanofibers can be tailored by changing the weight ratio of Al(NO3)3·9H2O to the PAN. Moreover, the prepared porous hollow γ-Al2O3 nanofibers were used as adsorbents to eliminate three model dyes (i.e., Congo red, methyl blue, and acid fuchsine) from aqueous solutions. The material exhibited excellent dye adsorption efficiency at a removal ratio greater than 90% in 50 mg L−1 dye solutions after 60 min of adsorption. Kinetic studies were performed and pseudo-first order, pseudo-second order were carried out. The nanofibers also exhibited desired adsorption cycle performance and the ability to regenerate easily. By virtue of the facile electrospinning method, it provides possibilities to fabricate other porous hollow nanofibers with potential applications in the environmental remediation, catalysis, and biomedical fields.