A facile fabrication of MOF for selective removal of chromium (III) from aqueous solution

A simple method for fabricating a metal organic framework (MOF: HKUST-1) as sorbent for selective removal of chromium (III) from aqueous solution is discussed. The structure and morphology of HKUST-1 was identified by fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), the powder X-ray diffraction (XRD) and N₂ adsorption-desorption (BET) analysis. Its removal process of chromium (III) and chromium (VI) on HKUST-1 was assessed systematically under various conditions such as pH value, shaking time and initial concentration of chromium (III). At pH 6.0–8.0, HKUST-1 were selective towards chromium (III) but hardly chromium (VI). Kinetic parameters fitted well with pseudo-second-order model and adsorption progress was described by Langmuir isotherm equations and spontaneous and endothermic according to the results of thermodynamics studies (?G?<?0, ?H?>?0, ?S?>?0).     

EC STM investigations of corrosion due to chloride solutions on thin CrN coatings

The focus of the investigations presented is to evaluate local alterations caused by chloride ions affecting thin, magnetron-sputtered CrN layers. Scanning-probe microscopy and analysis techniques are used for this estimation. Thin CrN layers were deposited by reactive magnetron sputtering. They were investigated in electrochemical scanning tunnelling microscopy (EC STM) by cyclic voltammetry in 1 mol L(-1) NaCl. Simultaneously, the surface topography changes were recorded with STM.Above 100 mV the anodic oxidation leads to formation of chromium(III) hydroxide and at sample potentials above 350 mV oxidation of Cr(OH)(2) and Cr(OH)(3) towards chromium(VI) as a soluble chromate starts. Transpassive dissolution of the coating takes place above 900 mV. Yellow colour of the electrolyte is a visible sign for the formation of chromium(VI). Changes of the surface topography indicate the formation of surface layers at anodic potentials. At cathodic potentials increase in current is measured due to the reduction of chromium(III) hydroxide to divalent chromium and metallic chromium. Roughness of surface topography increases.Follow-up explorations with scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), atomic-force microscopy (AFM), scanning tunnelling microscopy/scanning tunnelling spectroscopy (STM/STS) and X-ray photoelectron spectroscopy (XPS) not only evidence the formation of various chromium oxides, but also indicate the existence of chromium hydroxide.     

Molecular and crystal structure of (E)-4-chloro-N-(3,4-dimethoxybenzylidene)aniline

The reaction of 3,4-dimethoxybenzaldehyde with 4-chloroaniline (1:1 molar ration) leads to the formation of a new Schiff base (E)-4-chloro-N-(3,4-dimethoxybenzylidene)aniline (1) that is successfully obtained and characterized by elemental analyses, FT-IR and ¹H NMR spectroscopy, and single crystal X-ray diffraction. The strong absorption band at 1620 cm⁻¹ in the FT-IR spectrum and a singlet signal at 8.32 ppm in the ¹H NMR spectrum of 1 clearly proves the presence of the C=N (azomethine) group. Single crystal X-ray analyses reveal that the title compound adopts an E configuration with respect to the C=N bond.     

Heterogenization of a molybdenum Schiff base complex as a magnetic nanocatalyst: An eco-friendly,efficient, selective and recyclable nanocatalyst for the oxidation of alkenes

A Schiff base ligand derived from 5-bromo-2-hydroxybenzaldehyde and 2,2′-dimethylpropylenediamine (H₂L) and its corresponding dioxomolybdenum(VI) complex (Mo(O)₂L) has been synthesized and characterized by spectroscopic methods. The adsorption of Mo(O)₂L on the surface of silica-coated magnetite nanoparticles via hydrogen bonding led to the formation of (α-Fe₂O₃)–MCM-41–Mo(O)₂L as a heterogeneous catalyst. FT-IR and atomic absorption spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize and investigate the new nanocatalyst. A practical catalytic method for the efficient and highly selective oxidation of a wide range of olefins with hydrogen peroxide and tert-butyl hydroperoxide in ethanol over the prepared molybdenum nanocatalyst was investigated. Under reflux conditions, the oxidation of cyclooctene with tert-butyl hydroperoxide or hydrogen peroxide led to the formation of epoxide as the sole product. The catalyst was reused at least six times without a significant decrease in catalytic activity or selectivity, and without detectable leaching of the catalyst.     

Synthesis and characterization of VO–vanillin complex immobilized on MCM-41 and its facile catalytic application in the sulfoxidation reaction,and synthesis of 2,3-dihydroquinazolin-4(1H)-ones and disulfides in green media

In this work, a vanillin complex is immobilized onto MCM-41 and characterized by FT-IR, X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, thermogravimetric analysis, and BET techniques. This supported Schiff base complex was found to be an efficient and recoverable catalyst for the chemoselective oxidation of sulfides into sulfoxides and thiols into their corresponding disulfides (using hydrogen peroxide as a green oxidant) and also a suitable catalyst for the preparation of 2,3-dihydroquinazolin-4(1H)-one derivatives in water at 90°C. Using this protocol, we show that a variety of disulfides, sulfoxides, and 2,3-dihydroquinazolin-4(1H)-one derivatives can be synthesized in green conditions. The catalyst can be recovered and recycled for further reactions without appreciable loss of catalytic performance.     

Characterization of hexavalent chromium interaction with Sargassum by X-ray absorption fine structure spectroscopy, X-ray photoelectron spectroscopy, and quantum chemistry calculation

Hexavalent chromium represents higher toxicity in aqueous solutions. It can be removed by such low-cost biosorbents as Sargassum sp. In this study, X-ray absorption fine structure spectroscopy, X-ray photoelectron spectroscopy, and quantum chemistry (QC) calculation were used to study the interactions between hexavalent chromium and Sargassum sp. during the biosorption. It was found that most of the adsorbed Cr(VI) ions were reduced to Cr(III) after the biosorption. The electrons for the reduction of Cr(VI) were possibly supplied from the Sargassum biomass, some organic compounds of which were oxidized. Cr(III) ions were coordinated with the oxygen atoms from either carboxyl or hydroxyl functional groups to form an octahedral structural metal complex. The coordination numbers of the formed Cr complex were 4-6, and bond length of Cr-O was 1.98?. QC calculation proved the possible formation of the Cr(III) metal complex, and revealed that carboxyl from biomass could be strongly bound with Cr(III). A three-step removal mechanism of Cr(VI) by Sargassum was proposed.     

Plant‐supported silver nanoparticles: Efficient,economically viable and easily recoverable catalyst for the reduction of organic pollutants

Ginger rhizome powder was used for the synthesis of supported metallic nanoparticle catalysts. A simple and novel adsorption method was used for the synthesis of silver nanoparticles loaded on ginger powder (Ag/GP), copper on ginger powder (Cu/GP) and nickel on ginger powder (Ni/GP). Among these, Ag/GP showed selective reduction of methyl orange and was used for further reactions. The prepared nanomaterials were characterized through X‐ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, fourier transform infrared spectroscopy and energy‐dispersive X‐ray spectroscopy. The prepared Ag/GP catalyst was employed in the catalytic reduction of 4‐nitrophenol (4‐NP), 2‐nitrophenol (2‐NP), rhodamine B, methyl red and congo red. Ag/GP showed excellent catalytic reduction activity, the rate constants being 1.26 × 10^?3 and 2.38 × 10^?3 s^?1 for 2‐NP and 4‐NP, respectively. The turnover frequency reached 1.06 min^?1 for 2‐NP and 1.16 min^?1 for 4‐NP when using the Ag/GP catalyst. The prepared Ag/GP catalyst demonstrated outstanding activity for the degradation of a mixed solution of dyes. Also, stability and reusability of the prepared catalyst were investigated, which showed outstanding reusability up to five times and was stable up to five days.     

Crystal structure of Schiff base derivative of gossypol with 3,6,9-trioxa-decylamine

Crystals of the Schiff base derivative of gossypol with 3,6,9-trioxa-decylamine were examined using X-ray diffraction, FT-IR and CPMAS spectroscopy. The Schiff base crystallizes as a racemate in the space group C2/c with a=24.390(5), b=12.026(2), c=14.810(3) Å, β=102.78(3)°, and Z=4. The results of the FT-IR, and CPMAS study of the crystals are in agreement with the X-ray data. The FT-IR spectrum of the crystals shows that the OH groups at position 1,1′ and 6,6′ as well as the N₁₆-H proton are involved in weak intermolecular and intramolecular hydrogen bonds, respectively. The FTIR and CP-MAS spectral behaviour is in agreement with the crystallographic results demonstrating the existence of the enamine-enamine tautomeric form of the Schiff base studied.     

Mg3(VO4)2的环己烷氧化脱氢性能与X射线光电子能谱分析

采用X射线光电子能谱对柠檬酸法制备的Mg3( VO4)2催化剂表面物种进行了研究,并结合X射线衍射(XRD)、扫描电镜(SEM)、傅立叶红外光谱(FT-IR)和氢气程序升温还原(H2 - TPR)对催化剂的表征结果及其在环己烷氧化脱氢反应中的催化性能,进一步探讨了Mg3( VO4)2催化剂表面物种与其催化性能之间的关系...     

Efficient synthesis of β-aminoketones catalyzed by Fe3O4@ quillaja sapogenin/Ni (II) as a novel magnetic nano-catalyst

A new nano-magnetic core–shell Fe₃O₄@quillaja sapogenin/Ni (II) was synthesized and characterized thoroughly using various tests including energy-dispersive X-ray spectroscopy (EDS), Brunauer–Emmett–Teller (BET), thermo-gravimetric analysis (TGA), high-resolution transmission electron microscopy (HR-TEM), vibrating sample magnetometer (VSM), Fourier transform infrared (FT-IR) spectroscopy, inductively coupled plasma (ICP), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The achievements demonstrated that the proposed agents were beneficial to synthesis the derivatives of β-aminoketone. Moreover, it was possible to recover the catalyst by means of simple magnetic decantation quickly. Besides, no reduction in the activity of the catalyst occurred, even though it was utilized in various reactions.     

Synthetic,characterization and catalytic studies of some coordination compounds derived from unsymmetrical quadridentate Schiff base ligand

The stable complexes of VO(IV), Cr(III), Mn(III), Fe(III), MoO₂(VI), and WO₂(VI), with an unsymmetrical tetradentate Schiff base ligand derived from 2-hydroxy-5-methylacetophenone, 2-hydroxy-5-chloroacetophenone and carbohydrazide were synthesized and characterized by the elemental analysis, UV-Vis and IR spectroscopy, magnetic measurements and thermal analysis. The VO(IV) and Mn(III) complexes were tested for the catalytic oxidation of styrene. The conversion of styrene increases with use of VO(IV) catalyst and decreases with use of Mn(III) catalyst.     

DNA interaction and cytotoxicity studies of ruthenium(III) complexes containing 3-(benzothiazol-2-yliminomethyl)-naphthalen-2-ol ligand

A new Schiff base, 3-(benzothiazol-2-yliminomethyl)-naphthalen-2-ol, has been synthesized and characterized by elemental analysis, Fourier transform infrared spectroscopy (FT-IR), UV–vis, nuclear magnetic resonance, and single-crystal X-ray diffraction. Ruthenium(III) complexes of the Schiff base were synthesized and characterized by analytical and spectroscopic (FT-IR, UV–vis, and electron paramagnetic resonance) data as well as magnetic susceptibility measurements. DNA-binding properties of the ligand and its ruthenium(III) complexes have been investigated by electronic absorption spectroscopy. The three ruthenium(III) complexes were tested for DNA cleavage. Further in vitro study of the cytotoxity of the ligand and the complexes on human cervical cancer cell line and human laryngeal epithelial carcinoma cell line were carried out.     

Progress on the Photocatalytic Reduction Removal of Chromium Contamination

Rapid industrialization leads to increased wastewater discharge encompassing hexavalent chromium (Cr(VI)), which leads to serious environmental problems of toxicity and potential carcinogenicity. Removal of these species is normally carried out by ion‐exchange, precipitation, membrane filtration, sorption, photocatalytic reduction, etc. This review mainly focuses on the photocatalytic and photoelectrocatalytic (PEC) reduction of Cr (VI), because of their advantages over other methods such as reduced risk of secondary pollution by non‐reduced Cr (VI), no sludge formation, no need for a large amount of chemical reagents, clean and easy installation. The main factors influencing the photocatalytic reduction efficiency of Cr (VI) such as catalyst activity, solution pH, Cr adsorption on the catalyst and additives, are briefly discussed. Finally, a special emphasis is provided to the photoelectrocatalytic (PEC) reduction of Cr (VI).     

Radiation-induced catalytic reduction of chromium(VI) in aqueous solution containing TiO2, Al2O3 or SiO2 fine particles

Reduction of chromium (VI), Cr(VI) in aqueous neutral or basic solution was promoted by γ-ray irradiation in the presence of oxide particles such as TiO₂, Al₂O₃ or SiO₂. The oxide particles behaved as a catalyst, and the efficiency of the Cr(VI) reduction increased with an increase of the irradiation dose irrespective of the initial Cr(VI) concentration. The insoluble Cr(III) oxide formed through the Cr(VI) reduction also acted as the catalyst.     

Selective oxidation of ethylbenzene to acetophenone over Cr(III) Schiff base complex intercalated into layered double hydroxide

A new heterogeneous catalyst, Cr(III) Schiff base‐containing layered double hydroxide, was synthesized using the intercalation method. The Cr(III) Schiff base complex derived from 2‐hydroxy‐1‐naphthaldehyde and 4‐aminobenzoic acid was intercalated into the layered double hydroxide. The synthesized materials were characterized using inductively coupled plasma atomic emission spectrometry, energy‐dispersive X‐ray analysis, scanning electron microscopy, X‐ray diffraction, Brunauer–Emmett–Teller surface area measurement, Fourier transform infrared spectroscopy, thermogravimetric analysis, diffuse reflectance UV–visible spectroscopy and electron paramagnetic resonance spectroscopy. The catalytic activity was investigated for the oxidation of ethylbenzene with tert‐butylhydroperoxide as an oxidant under solvent‐free conditions as well as with lower chromium concentrations. In the oxidation reaction, ethylbenzene was oxidized to acetophenone and benzaldehyde. The catalyst was recycled ten times without significant loss of catalytic activity. Leaching studies performed with hot filtration experiments showed that the chromium catalyst was heterogeneous in nature and stable under the reaction conditions.     

A general route to prepare one- and three-dimensional carbon nanotube/metal nanoparticle composite nanostructures

Adsorption of polyethyleneimine (PEI)-metal ion complexes onto the surfaces of carbon nanotubes (CNTs) and subsequent reduction of the metal ion leads to the fabrication of one-dimensional CNT/metal nanoparticle (CNT/M NP) heterogeneous nanostructures. Alternating adsorption of PEI-metal ion complexes and CNTs on substrates results in the formation of multilayered CNT films. After exposing the films to NaBH4, three-dimensional CNT composite films embedded with metal nanoparticles (NPs) are obtained. UV-visible spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy are used to characterize the film assembly. The resulting (CNT/M NP)n films inherit the properties from both the metal NPs and CNTs that exhibit unique performance in surface-enhanced Raman scattering (SERS) and electrocatalytic activities to the reduction of O2; as a result, they are more attractive compared to (CNT/polyelectrolyte)n and (NP/polyelectrolyte)n films because of their multifunctionality.     

聚苯胺-改性木质素磺酸钠复合材料基活性炭负载Pd催化剂对甲酸氧化的催化性能

将聚苯胺/改性木质素磺酸钠复合材料在不同炭化温度下进行处理得到活性炭材料，利用红外光谱、拉曼光谱、比表面积分析和扫描电镜等手段对其结构和表面性质进行了表征。通过液相还原方法将Pd纳米颗粒负载在所制备的活性炭材料上，获得Pd/C催化剂用于甲酸氧化，并采用X射线衍射、透射电镜和电化学测试等方法对该Pd/C催化剂进行表征。结果表明，以800℃下炭化得到的活性炭材料为载体所制备的Pd-AC800催化剂其催化性能最优；Pd粒径为5.4 nm，电化学活性面积为53.78 m²/g。由于在该催化剂上甲酸氧化通过直接途径进行，Pd-AC800可用作直接甲酸燃料电池的催化剂。     

LiNO_3改性ZSM-5分子筛催化乳酸制丙烯酸的失活行为研究

采用X射线粉末衍射(XRD)、傅里叶变换红外光谱(FT-IR)、热重-差示扫描量热分析(TG-DSC)、X射线光电子能谱(XPS)对新鲜和再生Li-ZSM-5催化剂在乳酸脱水制丙烯酸反应中的失活原因进行了研究.结果表明,催化剂失活主要是因为乙醛和丙烯酸在酸性位点结焦生成酮类或醛类积碳前驱体、低聚烃类和高聚烃类积碳,导致活性位减少而失活.催化剂经焙烧再生,若碳物种不能脱除干净,将导致积碳速率增加,活性位减少的速度加快,稳定性降低.     

微波溶剂热法制备掺氮石墨烯用于碱性氧还原反应

采用微波处理氧化石墨烯（GO）与乙二醇（EG）、乙二胺（ED）混合液的方法制备氮掺杂石墨烯（NG）,使用旋转圆盘电极对NG催化氧还原在碱性溶液中反应进行研究,并考察了不同微波辐射时间、ED与EG之比对反应性能的影响。采用X射线衍射仪（XRD）、透射电子显微镜（TEM）、拉曼光谱（Raman）和傅里叶变换红外光谱（FT-IR）研究了NG催化剂的结构与性质。相比于未掺氮的石墨烯样品,NG表现出更正的起始电位和接近四电子的转移过程。NG中掺杂氮原子的键合方式通过XPS进行表征,结果表明起始电位的高低取决于石墨氮含量。此外,所有表征结果表明总氮含量与氧还原反应性能没有直接关系。     

微波溶剂热法制备掺氮石墨烯用于碱性氧还原反应

采用微波处理氧化石墨烯(GO)与乙二醇(EG)、乙二胺(ED)混合液的方法制备氮掺杂石墨烯(NG),使用旋转圆盘电极对NG催化氧还原在碱性溶液中反应进行研究,并考察了不同微波辐射时间、ED与EG之比对反应性能的影响。采用X射线衍射仪(XRD)、透射电子显微镜(TEM)、拉曼光谱(Raman)和傅里叶变换红外光谱(FT-IR)研究了NG催化剂的结构与性质。相比于未掺氮的石墨烯样品,NG表现出更正的起始电位和接近四电子的转移过程。NG中掺杂氮原子的键合方式通过XPS进行表征,结果表明起始电位的高低取决于石墨氮含量。此外,所有表征结果表明总氮含量与氧还原反应性能没有直接关系。