Degradation of amoxicillin in aqueous solution using nanolepidocrocite chips/H2O2/UV: Optimization and kinetics studies

Degradation of amoxicillin (AMX) by nanolepidocrocite chips/H₂O₂/UV method as a new photo-Fenton like process was investigated and optimized by response surface methodology (RSM). The optimal conditions were initial AMX concentration of 10 mg l⁻¹ and initial H₂O₂ concentration of 60 mg l⁻¹ at pH of 2 under UV radiation for 120 min. The general photo-Fenton process mechanism was applied to propose a new kinetic model for AMX degradation. According to this model, the reaction constant between AMX and OH was obtained 4.55 × 10⁵ M⁻¹ s⁻¹. Also, nanolepidocrocite showed good catalytic activity even after four successive degradation cycles.     

Broadband dielectric spectroscopy of PbMg1/3Nb2/3O3–PbSc1/2Nb1/2O3 ceramics

Broadband dielectric spectroscopy results of various ordered and disordered (1 ? x)Pb(Mg_1/3Nb_2/3)O₃–(x)Pb(Sc_1/2Nb_1/2)O₃ (PMN–PSN) ceramics are investigated in the temperature range from 80 K to 300 K and frequency range from 20 Hz to 2 THz. Dielectric dispersion is very broad and in the ferroelectrics case (x = 1, 0.95) consists of two parts: low-frequency part caused by ferroelectric domains and higher frequency part caused by soft mode. The relaxational soft mode exhibits pronounced softening close to phase transition temperature, as it is typical for order–disorder phase transitions. By substituting Sc³⁺ by Mg²⁺ in PMN–PSN ceramics relaxation slows down, and for relaxors (x = 0.2) the most probable relaxation frequency decreases on cooling according to Vogel–Fulcher law.     

Chemical oxidation of residual carbon from ZnAl2O4 powders prepared by combustion synthesis

The removal of carbon residue from ZnAl₂O₄ nanopowders by annealing at 500–800 °C leads to a decrease of specific surface area from 228.1 m²/g to 47.6 m²/g. At the same time, the average crystallite size increased from 5.1 nm to 14.9 nm. In order to overcome these drawbacks, a new solution for removing the carbon residue has been suggested: chemical oxidation using hydrogen peroxide. In terms of carbon removal, a H₂O₂ treatment for 8 h at 107 °C proved to be equivalent to a heat treatment of 1 h at 600 °C. The benefits of chemical oxidation over thermal oxidation were obvious. The specific surface area was much larger (188.1 m²/g) in the case of the powder treated with H₂O₂. The average crystallite size (5.8 nm) of ZnAl₂O₄ powder treated with H₂O₂ was smaller than the crystallite size (8.2 nm) of the ZnAl₂O₄ powder annealed at 600 °C.     

Microstructure and mechanical properties of Al2O3–YSZ and Al2O3–YAG directionally solidified eutectic plates

Plates of Al₂O₃–YSZ and Al₂O₃–YAG eutectic composition with a thickness from 0.1 to 1 mm were prepared by directional solidification using a diode laser stack. The melt processed regions of plates exhibited colony microstructure consisting of finely dispersed phases. Due to the curved shape of the melted pool, the growth rate depends on the distance to the surface plate, decreasing from top to bottom. In this way, the microstructure characteristic length changes as a function of the distance to the plate surface. Vickers indentations and piezo-spectroscopy measurements were done on longitudinal and transverse cross-sections of the samples at different depths. From these measurements, we concluded that the Vickers hardness (H_V), indentation fracture toughness (K_IC) and residual stresses (σ_h) of the plates were mainly independent from the distance to the surface. The mean values that we obtained in the Al₂O₃–YSZ plates were H_V = 16 GPa, K_IC = 4.2 MPa m^1/2 and σ_h = −0.33 GPa, and in the Al₂O₃–YAG plates were H_V = 16 GPa, K_IC = 2.0 MPa m^1/2, and σ_h = −0.1 GPa. These values are similar to those found in directionally solidified eutectic rods.     

A comparative study on the performance of different advanced oxidation processes (UV/O3/H2O2) treating linear alkyl benzene (LAB) production plant's wastewater

A detailed investigation on photooxidation of linear alkyl benzene (LAB) industrial wastewater is presented in this study. The process analysis was performed by varying four significant independent variables including two numerical factors (initial pH (3–11) and initial H₂O₂ concentration (0–20 mM)) and two categorical factors (UV irradiation and ozonation). The experiments were conducted based on a central composite design (CCD) and analyzed using response surface methodology (RSM). To assess the process performance, two parameters viz. TCOD removal efficiency and BOD₅/COD were measured throughout the experiments. A maximum reduction in TCOD was 58, 53, 51, and 49%, respectively for UV/H₂O₂/O₃, H₂O₂/O₃, UV/O₃ and UV/H₂O₂ processes at the optimum conditions (initial pH of 7, initial H₂O₂ concentration of 100 mM, and reaction time of 180 min). A considerable increase in BOD₅/COD ratio was obtained in the combined processes (0.46, 0.51, 0.53, and 0.55 for UV/H₂O₂, UV/O₃, H₂O₂/O₃ and UV/H₂O₂/O₃, respectively) compared to the single oxidant process (0.35). The results showed that mineralization of the LAB industrial wastewater in neutral pH is more favored than in acidic and basic pH. Gas chromatography–mass spectrometry (GC–MS) was applied to show the fate of organic compounds. In conclusion, the photooxidation process (UV/H₂O₂/O₃, H₂O₂/O₃, UV/O₃ and UV/H₂O₂) could be an appropriate pretreatment method prior to a biological treatment process.     

Oxidative dehydrogenation of ethane to ethylene over V2O5/Nb2O5 catalysts

V₂O₅/Nb₂O₅ catalysts with various V₂O₅ contents were prepared by impregnation and characterized by various techniques in detail. Oxidative dehydrogenation of ethane was carried out in a fixed bed quartz reactor at 500–600 °C. XPS analysis indicated a clear enrichment of vanadium on the near-surface-region and UV–vis diffuse reflectance spectroscopy revealed the nature of VO_x structures formed. 10 wt.% V₂O₅/Nb₂O₅ catalyst has displayed the best performance (X = 28%, S = 38% at 600 °C) due to enrichment of vanadium in the near-surface-region and formation of optimum amount of monomeric/oligomeric VO_x species.     

Direct H2-to-H2O2 oxidation over highly active/selective Br–F–Pd/Al2O3 catalyst in aqueous acidic medium: Influence of process conditions on the H2O2 formation

The influence of the O₂/H₂ mole ratio in the gaseous feed and also those of other reaction conditions [viz. concentration of H₃PO₄ (0–5 mol/dm³), temperature (5–50 °C), gas (H₂ and O₂) space velocity (5.8–23.4 h^?1) and reaction time (0.1–8 h)] on the H₂O₂ formation in the H₂-to-H₂O₂ oxidation over the Br(1 wt%)–F(1 wt%)–Pd(5 wt%)/Al₂O₃ catalyst in an aqueous acidic (H₃PO₄) medium have been thoroughly investigated. The effects of the O₂/H₂ ratio, reaction temperature and acid concentration on the destruction of H₂O₂ by its decomposition and/or hydrogenation reactions over the catalyst in the acidic reaction medium have also been studied. The net H₂O₂ formation (H₂O₂ yield) over the catalyst passed through a maximum with increasing the acid concentration, the temperature or the O₂/H₂ feed ratio. However, it decreased markedly with increasing the gas space velocity or the reaction period. The H₂O₂ decomposition and hydrogenation activities of the catalyst increased appreciably with increasing the reaction temperature and decreased with increasing the acid concentration. The H₂O₂ destruction during the H₂-to-H₂O₂ oxidation increased with increasing the concentration of H₂ (relative to that of O₂) due to the increased H₂O₂ hydrogenation rate over the catalyst. The net H₂O₂ formation in the H₂-to-H₂O₂ oxidation decreased sharply with increasing the initial amount of H₂O₂ present in the reaction mixture. The presence of H₂O₂ and the higher H₂/O₂ ratios have detrimental effects on the net formation of H₂O₂.     

Catalytic gasification of lignin with Ni/Al2O3–SiO2 in sub/supercritical water

Lignin has been gasified with a Ni/Al₂O₃–SiO₂ catalyst in sub/supercritical water (SCW) to produce gaseous fuels. XRD pattern at 6θ angle shows characteristic peaks of crystalline NiO, NiSi, and AlNi₃, suggesting that Al₂O₃–SiO₂ not only offers high surface area (122 m² g) for Ni, but also changes the crystal morphology of the metal. 9 mmol/g of H₂ and 3.5 mmol/g of CH₄ were produced at the conditions that 5.0 wt% alkaline lignin plus 1 g/g Ni/Al₂O₃–SiO₂ operating for 30 min at 550 °C. A kinetic model was also developed, and the activation energies of gas and char formation were calculated to be 36.68 ± 0.22 and 9.0 ± 2.4 kJ/mol, respectively. Although the loss of activity surface area during reuse caused slight activity reduction in Ni/Al₂O₃–SiO₂, the catalyst system still possessed high catalytic activity in generating H₂ and CH₄. It is noted that sulfur linkage could be hydrolyzed to hydrogen sulfide in the gasification process of alkaline lignin. The stable chemical states of Ni/Al₂O₃–SiO₂ grants its insensitivity to sulfur, suggesting that Ni/Al₂O₃–SiO₂ should be economically promising for sub/supercritical water gasification of biomass in the presence of sulfur.     

Synthesis,characterization and kinetics properties of chromium(III) complex [Cr(3-HNA)(en)2]Cl · H2O · CH3OH

The reaction of chromium(III) chloride, 3-hydroxy-2-naphthoic acid (3-HNA) and ethylenediamine (en) led to the formation of complex [Cr(3-HNA)(en)₂]Cl · H₂O · CH₃OH, Bis(ethylenediamine-κ²N,N′)(3-hydroxy-2-naphthoic acid-κ²O,O′) chromium(III) monochloride monohydrate monomethanol. The kinetics of transfer of Cr(III) from the title compound to the low-molecular-mass chelator EDTA and to the iron-binding protein apoovotransferrin (apoOTf) were carried out by means of UV–Visible (UV–Vis) and fluorescence spectra in 0.01 M Hepes at pH 7.4. The second-order rate constants were calculated, respectively. The results show that Cr(III) can be transferred from the complex to apoovotransferrin.     

Fine grained Nd3+:Lu2O3 transparent ceramic with enhanced photoluminescence

Fine-grained Nd³⁺:Lu₂O₃ transparent ceramic was developed by a two-step sintering method in flowing H₂ atmosphere at T₁ = 1720 °C for 15 min and T₂ = 1620 °C for 10 h. The initial nanopowders were synthesized by a wet chemical processing with a uniform particle size of about 40 nm. The average grain size of the obtained 3 at.% Nd³⁺:Lu₂O₃ ceramic was 406 nm, which is ∼150 times smaller than the coarse-grained ceramic by normal H₂ sintering. The emission intensity of the fine-grained transparent ceramic is 3 times of its coarse-grained counterpart, indicating higher Nd concentration without serious quenching in fine-grained transparent ceramic is possible, which agreed well with the prediction of an atomistic modeling work with YAG. EXAFS research demonstrated that with decreasing grain size, higher degree of disorder factor of the local environment of doped Nd atoms was discovered.     

A sinusoidal chain constructed from decorated Keggin clusters and {Cu(enMe)2}2+ bridging groups in [Cu(enMe)2(H2O)] [{Cu(enMe)2}{Cu(enMe)2(H2O)W12O40(H2)}] · nH2O

A novel organic–inorganic hybrid material, [Cu(enMe)₂(H₂O)][{Cu(enMe)₂}{Cu(enMe)₂(H₂O)W₁₂O₄₀(H₂)}] · nH₂O (n = 0.33, enMe = 1,2-diaminopropane), has been prepared under mild hydrothermal conditions and characterized by single-crystal X-ray diffraction, IR and magnetic susceptibility measurements. It is revealed that the one-dimensional [{Cu(enMe)₂}{Cu(enMe)₂(H₂O)W₁₂O₄₀(H₂)}]²⁻ chain in the structure shows a unique sinusoidal ruffling, which is constructed from decorated Keggin clusters and {Cu(enMe)₂}²⁺ bridging groups through sharing one terminal and one doubly-bridging oxygen atoms of a cluster. The magnetic measurements show that the compound possesses well-separated Cu²⁺ centers. It was indicated that the hybrid exhibits a good catalytic activity in H₂O₂ decomposition.     

Densification and biocompatibility of sintering 3.0 mol% yttria-tetragonal ZrO2 polycrystal ceramics with x wt% Fe2O3 and 5.0 wt% mica powders additive

The densification and biocompatibility of sintered 3.0 mol% yttria-tetragonal zirconia polycrystal (3Y-TZP) ceramics, with X wt% Fe₂O₃ and 5.0 wt% mica powders (denoted by 3Y-TZP: X-5.0 wt% mica) have been studied. When the pellets of 3Y-TZP: X-5.0 wt% mica were sintered at 1300 °C for 1 h, the relative shrinkage increases from 19.20–19.43% with the X increased from 0.3 to 1.0. The relative shrinkage of pellets containing 1.0 wt% Fe₂O₃ (X=1.0) increased from 19.43–19.59% when sintering temperatures were raised from 1300 °C to 1450 °C. X-ray diffraction results show that the pellets of 3Y-TZP: X-5.0 wt% mica sintered at 1400 °C for 1 h only contained single phase of tetragonal ZrO₂ (t-ZrO₂). When the sintering temperature was higher than 1400 °C, the Vickers microhardness was greatest in the pellets with X=0.5. Within pellets with the same Fe₂O₃ content, the dominant wavelength (λ_d) was only slightly different for pellets sintered at 1300 °C and those sintered at 1450 °C. The results of the materials were evaluated in vitro cytotoxicity tests reveals that the powders and sintered pellets are safe materials. The oral mucosa irritation tests did not find erythema or histopathological change including normal epithelium, and was free from leucocyte infiltration, vascular congestion and oedema.     

Preparation,characterisation and catalytic evaluation of MgF2 supported V2O5 catalysts for ammoxidation of 3-picoline

Non-conventional MgF₂ supported V₂O₅ catalysts with different vanadia contents (2–15 wt.%) were prepared by impregnation (using NH₄VO₃), characterised and catalytically evaluated for selective ammoxidation of 3-picoline to nicotinonitrile. Oxygen and ammonia chemisorption uptakes increased continuously from 60 to over 600 μmol g^?1 and 275 to >750 μmol g^?1, respectively, with rise in V₂O₅ proportion indicating that the redox as well as acidic sites are increasing with increase in V₂O₅ content. Thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) analysis revealed endothermic as well as exothermic thermal effects mainly due to liberation of water and ammonia, and also due to structural changes. XRD patterns showed the formation of crystalline V₂O₅ in the fresh solids having 8 wt.% V₂O₅ and above and NH₄VO₃ phase in the spent samples. The conversion of 3-picoline is observed to increase continuously with increase in V₂O₅ loading. However, the selectivity of nicotinonitrile is found to be independent on conversion of 3-picoline. The catalyst with the highest V₂O₅ loading (15.7 wt.%) displayed the best activity (X > 90%) and selectivity (S > 95%) compared to all other catalysts of this series. The 3-picoline conversion of 10% at 548 K is increased to almost 100% with rise in temperature to 663 K. Increase in 3-picoline feed rate and NH₃: 3-picoline ratio exhibited an inhibiting effect on the conversion, while an increase in air: 3-picoline ratio has no significant influence on the performance.     

Synthesis,structural characterization and properties of a novel 1D helical chain arsenomolybdate {[Cu(en)2][Cu(en)(H2O)][(Cu(en)2(H2O)] [AsIIIAsVMo9O34)]} · 2H2O

An organic–inorganic hybrid 1D helical chain arsenomolybdate {[Cu(en)₂][Cu(en)(H₂O)][(Cu(en)₂(H₂O)] [As^IIIAs^VMo₉O₃₄)]} · 2H₂O (1) (en = ethylenediamine) has been hydrothermally synthesized and characterized by elemental analyses, IR, UV and CD spectrum, powder X-ray diffraction, TG-DTA and single-crystal X-ray diffraction. The asymmetric unit of 1 consists of a monocapped trivacant Keggin [As^IIIAs^VMo₉O₃₄]^6 − subunit, a pendant [Cu(en)₂(H₂O)]^2 + cation, a pendant [Cu(en)(H₂O)]^2 + cation, one bridging [Cu(en)₂]^2 + cation and two lattice water molecules. It should be noted that 1 illustrates a one-dimensional (1D) helical chain assembled by {[Cu(en)(H₂O)][(Cu(en)₂(H₂O)][As^IIIAs^VMo₉O₃₄)]}^2 − clusters and [Cu(en)₂]^2 + linkers.     

Highly efficient Ru/Sm2O3-CeO2 catalyst for ammonia synthesis

A series of Ru/Sm₂O₃–CeO₂ catalysts were prepared by using a co-precipitation (CP) method and characterized by XRD, BET, SEM, H₂-TPD-MS, H₂-TPR and CO chemisorption. The activity test shows that ammonia concentration of the catalyst with 7% Sm is 13.4% at 10 MPa, 10,000 h^− 1, 425 °C, which is 21% higher than that of Ru/CeO₂. Such high catalytic activity was due to three effects: the morphology changes of catalyst, electrodonating property of partially reduced CeO_2 − x to Ru metal and the property of easily hydrogen desorption derived from the presence of Sm³⁺ in ceria.     

Redox behavior and oxidation catalysis of HnXW12O40 (X = Co2 +, B3 +, Si4 +, and P5 +) Keggin heteropolyacid catalysts

Redox behavior and oxidation catalysis of H_nXW₁₂O₄₀ (X = Co^2 +, B^3 +, Si^4 +, and P^5 +) Keggin heteropolyacid catalysts were investigated. Successful formation of H_nXW₁₂O₄₀ catalysts was confirmed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Reduction potentials of H_nXW₁₂O₄₀ catalysts were determined by electrochemical measurements. First electron reduction potential of H_nXW₁₂O₄₀ catalysts decreased with increasing overall negative charge of heteropolyanion. H_nXW₁₂O₄₀ catalysts were then applied to the liquid-phase oxidation of benzaldehyde to benzoic acid. Yield for benzoic acid increased with increasing first electron reduction potential.     

A novel paradodecatungstate-B compound decorated by transition metal copper,Na2Cu5(H2O)24(OH)2[H2W12O42]·10H2O: Synthesis,structure and antitumor activities

A new paradodecatungstate-B compound decorated by transition metal copper, Na₂Cu₅(H₂O)₂₄(OH)₂[H₂W₁₂O₄₂]·10H₂O (1), has been synthesized by convenient aqueous solution method and structurally characterized by single-crystal X-ray diffraction, IR spectrum, elemental analysis and TGA. The compound crystallizes in the triclinic P-1 space group with a = 10.7140(8) Å, b = 12.9476(9) Å, c = 13.6696(10) Å, α = 73.56°, β = 75.73°, γ = 67.69°, V = 1661.8(2) ų and Z = 1. In compound 1, polyanion of [H₂W₁₂O₄₂]^10 − acts as a dodecadentate ligand that links copper and sodium cations, forming a remarkable three-dimensional framework. The experiment of antitumor activities in vitro shows that the title compound exhibits remarkable inhibitory actions on human cervical carcinoma HeLa cells, ovarian carcinoma SKOV-3 cells, hepatoma HepG2 cells and neuroblastoma SHY5Y cells.     

Activity and deactivation of Au/Al2O3 catalyst for low-temperature CO oxidation

Au/Al₂O₃ catalyst was investigated with respect to its activity for low-temperature CO oxidation. The activity changes of the catalyst were examined after separate treatment in the following different atmosphere: (i) O₂ + N₂ + CO; (ii) O₂ + N₂ heated above 100 °C and (iii) O₂ + N₂ + H₂O vapor. The results show that each of the treatments above may deactivate the catalyst to the different degree. The deactivation by CO oxidation is mainly due to the accumulation of carbonate-like species on the catalyst surface. The addition of H₂O vapor may inhibit the deactivation effectively. The removal of hydroxyl groups at active sites during heating may be responsible for the deactivation by thermal treatment. These two kinds of deactivations are reversible. The irreversible deactivation by H₂O vapor treatment is mainly caused by the growth of gold particles size.     

B6O materials with Al2O3/Y2O3 additives densified by FAST/SPS and HIP

Fully densified B₆O materials with Al₂O₃/Y₂O₃ sintering additives amounts systematically varied between 0 and 15 vol.% and Al₂O₃/(Al₂O₃ + Y₂O₃) molar ratios of 0.05–1 were prepared by FAST/SPS and HIP at sintering temperatures between 1725 °C and 1900 °C. Their densification and microstructure were correlated with measured mechanical properties. The addition of low additive amounts in the range of 2–3 vol.% was found to increase the fracture toughness and strength from 2.0 MPa m^1/2 (SEVNB) and 420 MPa for pure B₆O to about 3.0 MPa m^1/2 and 540 MPa, but it had no effect on the hardness, which remained at a high level of 30–36 GPa (HV_0.4). Higher additive contents did not yield a further improvement in the toughness but resulted in a reduction in hardness and strength.     

A novel transition-metal-linked hexaniobate cluster with photocatalytic H2 evolution activity

A novel transition-metal (TM) complex based on Lindqvist polyoxoniobate K₁₀[(Nb₆O₁₉)Cr^III(H₂O)₂]₂·28H₂O (1) has been synthesized by a new two-pot synthesis strategy and structurally characterized by single crystal X-ray diffraction analysis, IR spectrum, UV–vis spectroscopy, XRPD and TG analysis. Compound 1 crystallizes in the C2/m space group with a = 32.143(19) Å, b = 10.030(6) Å, c = 12.878(8) Å, β = 110.611(9)°, and V = 3886(4) ų. X-ray structure analysis reveals that polyanion [(Nb₆O₁₉)Cr^III(H₂O)₂]₂^10 − (1a) represents the first example of two nuclear dimeric polyoxoniobate, in which two Lindqvist anions [Nb₆O₁₉]⁸ are sandwiched by two {Cr^III(H₂O)₂} groups. Further, 1 exhibits photocatalytic H₂ evolution activity.