Photocatalytic degradation of organic pollutants catalyzed by layered iron(II) bipyridine complex–clay hybrid under visible irradiation

An organic–inorganic layered hybrid was prepared by intercalation of Fe(bpy)₃²⁺ into laponite clay. UV–vis diffuse reflectance, X-Ray diffraction, and SEM confirmed the intercalation and the strong host–guest interaction of Fe(bpy)₃²⁺ molecules with the clay matrix. Compared with laponite, the hybrid formed a solid layered structure due to the linking of laponite platelets by Fe(bpy)₃²⁺ molecules. Upon visible light irradiation (λ > 420 nm), the hybrid was found to be highly effective for the degradation of nonbiodegradable cationic organic pollutants such as Rhodamine B (RhB) and N,N-dimethylaniline by activating H₂O₂ at neutral pH values, but inactive toward anionic organic compounds such as Orange II and Sulforhodamine-B. The adsorption and degradation of organics on the hybrid could be controlled by changing the pH value of the suspension. The total organic carbon (TOC) removal yield of RhB was 41%. pH effect trials and the final degraded products further indicate that unless the target is adsorbed onto the clay layers the reaction could not occur. Neither OH nor OOH/O₂⁻ EPR signals were detected during the reaction. The solid support of laponite not only alters the photochemical properties of Fe(bpy)₃²⁺ but also provides a rigid microenvironment for the enrichment of local substrate molecules and thus enhances the interaction of the active center with the substrate.     

The anodic dissolution of iron—V. Some observations regarding the influence of cold working and of annealing on the two anodic reactions of the metal

Under conditions, where two anodic current regions, I₂ and I₂, were distinct in the Tafel plots of the iron electrode, the reaction orders with respect to pH were determined. In solutions containing chloride or bromid, pH ca 3–5, the reaction order for I₁(p_1,pH) was close to 1, while that for I₂(p_2,pH) assumed positive or negative values or even values changing from positive to negative over the pH-range. The numerical values were small, 0·2–0·3. Only lightly cold-worked iron was used in this group of experiments.

In another group of experiments only involving acetate containing solutions both cold-worked and annealed electrodes were employed. Until the influence of acetate became negligible at low pH, the effect of the treatment was largely limited to dissolution rates. The characteristic parameters at pH ca 4 were: for the I₁ reaction: b₁ = 30 mV, p_1,pH = 1·7 and p_1,Ac¹ (the reaction order for Ac) = −0·7; for the p₂ reaction: b₂ = 110 to 130 mV, p_2,pH = 0·2 and p_2,Ac = −0·2 to −0·3.

At lower pH the influence of acetate gradually disappeared, and higher values of b₁ and lower values of p_1,pH were then noted for the annealed metal. The I₂ reaction could not be followed here.

The transition between the I₁ and the I₂ reaction was studied at pH ca 4, and some deviation from earlier experience was noted for strongly cold-worked iron.     

Study of [Fe(bpy)3] complex encapsulated in zeolite Y

Tris complex of Fe^II with 2,2′ bipyridine (bpy) ligand, has been encapsulated in the supercages of zeolite Y and characterized by powder X-ray diffraction, Infrared spectroscopy, ⁵⁷Fe Mössbauer, effect measurements and multinuclear NMR spectroscopy. The complex was prepared in the supercages of Zeolite Y by exchanging the cations of zeolite Y with Fe^II and its subsequent complexing with bpy ligand. Based on the comparison of the results obtained for [Fe^II(bpy)₃](ClO₄)₂ and the [Fe(bpy)₃]Y complexes, it has been inferred that there is significant structural distortion for the encapsulated complex and all Fe is present as Fe^II in low spin state, which is characterized by isomer shift, δ = 0.37 mm s⁻¹ and quadrupole splitting, ΔE_q = 0.81 mm s⁻¹ as revealed by ⁵⁷Fe Mössbauer spectroscopic measurements.     

Crystal structure of zeolite X nickel(II) exchanged at pH 4.3 and partially dehydrated, Ni2(NiOH)35(Ni4AlO4)2(H3O)46Si101Al91O384

Complete Ni²⁺ exchange of a single crystal of zeolite X of composition Na₉₂Si₁₀₀Al₉₂O₃₈₄ per unit cell was attempted at 73°C with flowing aqueous 0.05 M NiCl₂ (pH=4.3 at 23°C). After partial dehydration at 23°C and ≈10⁻³ Torr for two days, its structure, now of composition Ni₂(NiOH)₃₅(Ni₄AlO₄)₂(H₃O)₄₆Si₁₀₁Al₉₁O₃₈₄ per unit cell, was determined by X-ray diffraction techniques at 23°C (space group Fd , a₀=24.788(5) Å). It was refined using all intensities; R₁=0.080 for the 236 reflections for which F_o>4σ(F_o), and wR₂=0.187 using all 1138 unique reflections measured. At four crystallographic sites, 45 Ni²⁺ ions were found per unit cell. Thirty of these are at two different site III′ positions. Twenty of those are close to the sides of 12-rings near O–Si–O sequences, where each coordinates octahedrally to two framework oxygens, to three water molecules which hydrogen bond to the zeolite framework, and to an OH⁻ ion. The remaining 10 are near O–Al–O sequences; only three members of a likely octahedral coordination sphere could be found. In addition, two Ni²⁺ ions are at site I, eight are at site I′, and five are at site II. Forty six H₃O⁺ ions per unit cell, 24 at site II′ and 22 at site II, each hydrogen bond triply to six rings of the zeolite framework. Each of the 22 H₃O⁺ ions also hydrogen bonds to a H₂O molecule that coordinates to a site III′ Ni²⁺ ion. Six of the eight sodalite cages each contain four H₃O⁺ ions at site II′; the remaining two each contains a tetrahedral orthoaluminate anion at its center. Each tetrahedral face of each orthoaluminate ion is centered by a site I′ Ni²⁺ ion to give two Ni₄AlO₄ clusters. The five site II Ni²⁺ ions each coordinate to a OH⁻ ion. With 46 H₃O⁺ ions per unit cell, the great tendency of hydrated Ni²⁺ to hydrolyze within zeolite X is demonstrated. With a relatively weak single-crystal diffraction pattern, with dealumination of the zeolite framework, and with an apparent decrease in long-range Si/Al ordering likely due to the formation of antidomains, this crystal like others treated with hydrolyzing cations appears to have been damaged by Ni²⁺ exchange and partial dehydration.     

Synthesis and single crystal structure of an AFX-type magnesium aluminophosphate

SAPO-56 (framework type: AFX) has a framework topology slightly different from that of zeolite chabazite (framework type: CHA). While metal substituted aluminophosphate chabazite analogues can be prepared under a variety of experimental conditions with dozens of different amines, the synthesis of SAPO-56 type materials has been more difficult, particularly in non-SAPO compositions. Prior to this work, the growth of large crystals of the AFX-type materials suitable for single crystal diffraction has not been possible in any composition. Here we report the synthesis and single crystal structure of a magnesium aluminophosphate denoted as MAPO-AFX. This represents the first time that the AFX-type topology is made in a metal aluminophosphate composition. The synthesis was accomplished with a novel polyether diamine as the structure-directing agent. Crystal data for MAPO-AFX, (RH₂)_0.10(NH₄)_0.45[Mg_0.65Al_1.35(PO₄)₂](H₂O) where R=O[CH₂CH₂O(CH₂)₃NH₂]₂, space group P-31c (#163), Z=12, MoK radiation, 2θ_max=50°, a=13.8425(6) Å, c=20.204(1) Å, V=3352.7(3) ų, refinement on F², R(F)=7.94% for 131 parameters and 1218 unique reflections with I>2.0σ(I).     

Structure of a cyclopropane sorption complex of dehydrated fully Mn-exchanged zeolite X

The structure of a cyclopropane sorption complex of dehydrated fully Mn²⁺-exchanged zeolite X, Mn₄₆Si₁₀₀Al₉₂O₃₈₄ · 30C₃H₆ (a=24.690(4) Å), has been determined by single-crystal X-ray diffraction techniques in the cubic space group at 21(1)°C. The crystal was prepared by ion exchange in a flowing stream of 0.05 M aqueous Mn(NO₃)₂ for three days, followed by dehydration at 460°C and 2×10⁻⁶ Torr for two days, and exposure to 100 Torr of cyclopropane gas at 21(1)°C. The structure was determined in this atmosphere and was refined to the final error indices R₁=0.065 and R₂=0.071 with 509 reflections for which I>3σ (I). In this structure, Mn²⁺ ions are located at two crystallographic sites. Sixteen Mn²⁺ ions fill the octahedral site I at the centers of the hexagonal prisms (Mn–O=2.290(9) Å). The remaining 30 Mn²⁺ ions are at site II; each extends 0.41 Å into the supercage (an increase of 0.27 Å upon C₃H₆ sorption as compared to fully dehydrated Mn₄₆Si₁₀₀Al₉₂O₃₈₄) where it coordinates to three trigonally arranged framework oxygens at 2.148(8) Å and complexes weakly and facially to a cyclopropane molecule by a primarily quadrupolar interaction. The carbon atoms of each cyclopropane molecule are equivalent and equidistant from its Mn²⁺ ion (Mn–C=2.95(9) Å). Because of high thermal motion, the C–C bond length is inaccurately determined; the value found, 1.21(8) Å, is too small.     

Crystal structures of fully dehydrated fully Sr-exchanged zeolite X and of its ammonia sorption complex

The crystal structures of fully dehydrated Sr₄₆–X [Sr₄₆Si₁₀₀Al₉₂O₃₈₄; a=25.214(7) Å] and of its ammonia sorption complex, Sr₄₆–X·102NH₃ [Sr₄₆Si₁₀₀Al₉₂O₃₈₄·102NH₃; a=25.127(7) Å], have been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd at 21(1)°C. The Sr₄₆–X crystal was prepared by ion exchange in a flowing stream of aqueous 0.05 M Sr(ClO₄)₂ for 5 days followed by dehydration at 360°C and 2×10⁻⁶ Torr for 2 days. To prepare the ammonia sorption complex, another dehydrated Sr₄₆–X crystal was exposed to 230 Torr of zeolitically dried ammonia gas for 1 h followed by evacuation for 12 h at 21(1)°C and 5×10⁻⁴ Torr. The structures were refined to the final error indices, R₁=0.043 and R_w=0.039 with 466 reflections, and R₁=0.049 and R_w=0.044 with 382 reflections, for which I>3σ(I). In dehydrated Sr₄₆–X, all Sr²⁺ ions are located at two crystallographic sites. 16 Sr²⁺ ions are at the centers of the double six-rings, filling that site (site I, Sr–O=2.592(6) Å). The remaining 30 Sr²⁺ ions are in the supercage (site II); each extends 0.56 Å into the supercage from the plane of its three nearest oxygen atoms (Sr–O=2.469(6) Å). In the structure of Sr₄₆–X·102NH₃, the Sr²⁺ ions are located at three crystallographic sites: 12 are found at site I [Sr–O=2.652(10) Å]; four in the sodalite units (site I′) each coordinated to three framework oxygen atoms at 2.654(9) Å and also to three ammonia molecules at 2.76(8) Å. The remaining 30 Sr²⁺ ions lie at site II. Each extends 1.12 Å into the supercage where it coordinates to three framework oxygen atoms at 2.584(7) Å and also to three ammonia molecules at 2.774(24) Å.     

Water-soluble niobium peroxo complexes as precursors for the preparation of Nb-based oxide catalysts

In the frame of research aimed at developing new synthetic procedures of multimetallic Nb-based catalysts, peroxo complexes of niobium(V) of general formula A^I₃[Nb(O₂)₄] and A^I₃[Nb(O₂)_x(H_yL)]·nH₂O (A^I: NH₄⁺, CN₃H₆⁺ (gu); L: oxalate, tartrate, citrate) have been prepared and characterized on the basis of elemental and thermal analysis, FTIR and ¹³C-NMR spectra. The crystal structure of (gu)₃[Nb(O₂)₄] and (gu)₃[Nb(O₂)₂(C₂O₄)₂]·2H₂O have been determined. The application of the obtained Nb complexes as precursors for the preparation of silica-supported Nb–Mo–O catalysts has been demonstrated. Combining Nb peroxo-carboxylato compounds with analogous Mo(VI) compounds in a silica-impregnation method carried out in aqueous medium leads to the formation of the supported Nb₂Mo₃O₁₄ phase.     

Zeolite synthesis in the presence of flexible diquaternary alkylammonium ions (C2H5)3N(CH2)nN(C2H5)3 with n=3–10 as structure-directing agents

The use of flexible diquaternary alkylammonium ions (C₂H₅)₃N⁺(CH₂)_nN⁺(C₂H₅)₃ (Et₆-diquat-n with n=3–10) as structure-directing agents for zeolite synthesis in the presence of alkali metal cation is described. Among the organic structure-directing agents studied here, a considerable diversity in the phase selectivity was observed only for the Et₆-diquat-5 ion: this cation can produce five different zeolite structures (i.e., P1, SSZ-16, SUZ-4, ZSM-57, and mordenite), depending on the oxide composition of synthesis mixtures. Analysis of the variable-temperature ¹H CRAMPS NMR spectra obtained from the Et₆-diquat-5 molecules in these five zeolites reveals that the host–guest interactions occurring within the respective materials maintain in a manner different from one another even at 160 °C at which the zeolite hosts crystallize.     

Synthesis of novel chiral poly(methacrylate)s bearing urethane and cinchona alkaloid moieties in side chain and their chiral recognition abilities

Two types of new chiral methacrylates, cinchoninyl(2-methacryloyloxyethyl)carbamate (CIMOC) and cinchonidinyl(2-methacryloyloxy-ethyl)carbamate (CDMOC) were synthesized from 2-methacryloyloxyethyl isocyanate (MOI) and cinchona alkaloid such as cinchonine and cinchonidine, respectively. Radical polymerizations of CIMOC and CDMOC were performed under several conditions to obtain the corresponding polymers whose specific optical rotations ([]₄₃₅²⁵) were 84.0–89.0° and 0.39–0.72°, respectively. From the results of radical copolymerizations of RMOC (CIMOC and CDMOC, M₁) with styrene (ST, M₂) or methyl methacrylate (MMA, M₂), monomer reactivity ratios (r₁, r₂) and Alfrey–Price Q–e were determined: r₁=0.18, r₂=0.48, Q₁=0.53, e₁=0.92 for the CIMOC–ST system; r₁=0.53, r₂=0.26, Q₁=4.91, e₁=1.80 for the CIMOC–MMA system r₁=0.59, r₂=0.47, Q₁=0.86, e₁=0.33 for the CDMOC–ST system; r₁=0.28, r₂=0.59, Q₁=2.15, e₁=1.74 for the CDMOC–MMA system. The chiroptical properties of the copolymers were strongly influenced by co-units. Poly(RMOC)-bonded-silica gel as chiral stationary phase (CSP) was prepared for high performance liquid chromatography (HPLC). The CSPs resolved some racemates such as mandelic acid and trans-2-dibenzyl-4,5-di(o-hydroxyphenyl)-1,3-dioxolane by HPLC. The chiral recognition ability of poly(RMOC) may be due to the interaction between some cinchona alkaloid units and the racemates and/or to secondary and higher-ordered structures of the polymer.     

Hydrothermal synthesis of Ba(Ti, Sn)O3 fine powders and dielectric properties of the corresponding ceramics

Fine powders of submicron-sized crystallites of BaTiO₃ were prepared at 85–130°C by the hydrothermal method, starting from TiO₂.ξH₂O gel and Ba(OH)₂ solution. The products obtained below 110°C incorporated considerable amounts of H₂O and OH⁻ in the lattice. As-prepared BaTiO₃ is cubic and converts to the tetragonal phase after heat treatment at 1200°C, accompanied by the loss of residual OH⁻ ions. Hydrothermal reaction of SnO₂.ξH₂O gel with Ba(OH)₂ at 150–260°C gives rise to the hydrated phase, BaSn(OH)₆.3H₂O, due to the amphoteric nature of SnO₂.ξH₂O which stabilises Sn(OH)₆²⁻ anions in basic media. On heating in air or releasing the pressure in situ at 260°C, BaSn(OH)₆.3H₂O converts to BaSnO₃ through an intermediate, BaSnO(OH)₄. Solid solutions of Ba(Ti,Sn)O₃ are directly formed from (TiO₂ + SnO₂)..ξH₂O gel up to 35 mol% SnO₂. At higher Sn contents, the hydrothermal products are mixtures of BaSn(OH)₆.3H₂O and BaTiO₃, which on annealing at 1000°C result in monophasic Ba(Ti,Sn)O₃. The sintering characteristics and the dielectric properties of the ceramics prepared out of these fine powders are presented. The dielectric properties of fine-grained Ba(Ti,Sn)O₃ ceramics are explained on the basis of the prevailing diffuse phase transition behaviour.     

Catalytic wet air oxidation of phenol and acrylic acid over Ru/C and Ru–CeO2/C catalysts

Ru/C catalysts promoted, or not, by cerium were prepared by impregnation of an active carbon (961 m² g⁻¹) with chlorine-free precursors of Ru and Ce. They were characterized by chemisorption of H₂ and of CO and by electron microscopy. TEM and H₂ chemisorption gives coherent results while CO chemisorption overestimates Ru dispersion. In Ru–Ce/C, Ce is in close contact with Ru and decreases Ru accessibility.

Catalytic wet air oxidation (CWAO) of phenol and of acrylic acid (160°C and 20 bar of O₂) was investigated over these catalysts and their performance (activity, selectivity to intermediate compounds) compared with that of a reference Ru/CeO₂ catalyst. Carbon-supported catalysts were very active for the CWAO of phenol but not for acrylic acid. Although high conversions were obtained, phenol was not totally mineralized after 3 h. It was shown that acrylic acid was more strongly adsorbed than phenol. Moreover, the number of contact points between Ru particles and CeO₂ crystallites constitutes a key parameter in these reactions. A high surface area of ceria is required to insure O₂ activation when the organic molecule is strongly adsorbed.     

Theoretical investigation on cyclic reciprocal derivative chronopotentiometry: Kinetic study of totally irreversible electrode processes

Theoretical expressions and mathematical analysis in cyclic reciprocal derivative chronopotentiometry (CRDCP) are presented for totally irreversible electrode processes corresponding to the application of symmetrical and unsymmetrical programmed currents. For two successive unsymmetrical programmed currents, the effect of the currents ratio b (b = |I₂(t)/I₁(t)|) on the (dt/dE)–E curves is discussed. The electrochemical behavior of totally irreversible electrode processes has been studied corresponding to the application of the unique unsymmetrical programmed Φ^m(I₀) proposed recently. CRDCP characteristic parameters obtained for totally irreversible electrode processes are different from those of reversible electrode processes. Therefore, a comparison of CRDCP between both mechanisms is presented. Based on the mathematical derivation, alternative methods for kinetic measuring are described. It is prospected that CRDCP is convenient and applicable for studying the reversibility of the electrode processes in form of CRDCP characteristic parameters.     

Monocyclopentadienyltitanoxanes

By the hydrolysis of C₅H₅TiCl₃ in water and in aqueous sulphuric acid two types of monocyclopentadienyltitanoxane polymers were obtained. The first was a compound of formula (C₅H₅TiClO)₄^† which was characterized by chemical and by x-ray single crystal analysis, and by light scattering. The second compound was a higher polymer, which was examined by chemical analysis, by ionic decomposition in sulphuric acid and by electron micrography; it was considered to be built up of (C₅H₅TiO)ⁿ⁺_n chains joined together by sulphate groups. The material was unusually transparent to electrons, suggesting that it consists of thin laminae curled to form tubular needles like those formed by silicates such as asbestos. Using an ion exchange resin the compound (C₅H₅)₂Ti(COOCF₃)₂^{, †} was prepared from (C₅H₅)₂TiCl₂. It was found to be a stable non-polymeric substance. Attempts made to obtain polymeric compounds of titanium having trifluoromethyl groups and hexachlorocyclo-pentadienyl groups attached to the titanium atom were unsuccessful.     

Extensive intrazeolitic hydrolysis of Zn(II): partial structures of partially and fully hydrated Zn(II)-exchanged zeolite X

Complete Zn²⁺ exchange of two single crystals of zeolite X (Na₉₂Si₁₀₀Al₉₂O₃₈₄) was attempted at 80°C from aqueous Zn(NO₃)₂ (pH=5.5 at 23°C). The structures of crystal 1 (partially dehydrated by evacuation at 23°C and 10⁻³ Torr for two days) and crystal 2 (fully hydrated) were determined by X-ray diffraction techniques in the cubic space group Fd at 23°C (a_o=24.750(5) and 24.872(6) Å, respectively). They were refined using all intensities to the final error indices R₁=0.126 and 0.116 based on the 428 and 348 reflections, respectively, for which F_o>4σ(F_o). Each crystal has about 54 Zn²⁺ ions per unit cell, indicating the uptake of eight excess Zn(OH)₂ molecules. In both crystals, further extensive hydrolysis of Zn²⁺ is seen. Many non-framework oxygens were not found. In crystal 1, 34 Zn²⁺ ions per unit cell occupy conventional cationic sites: 10 are at site I^′, 12 at site II, and 12 at site III^′. Three Zn²⁺ ions each coordinate to a framework oxygen at a non-conventional site in the supercages. Three Zn²⁺ ions at the centers of sodalite cavities each coordinate tetrahedrally to four non-framework oxygens to give (likely) Zn(OH)₂(H₂O)₂ which hydrogen bonds multiply to the zeolite framework. At three supercage positions, about 14 Zn²⁺ ions that do not coordinate to the zeolite framework are found. Per unit cell, 37 H₃O⁺ ions are found: 20 at site I^′ and 17 at site II. It is presumed, considering the number of H₃O⁺ ions, that the latter 14 Zn²⁺ ions are hydrolyzed Zn²⁺ ions, likely hydrated Zn(OH)₂ molecules, some likely bridging. In crystal 2, 33 Zn²⁺ ions per unit cell are found at conventional cationic sites: two at site I, 14 at two different sites I^′, seven at site II, and 10 at site III^′. As in crystal 1, three Zn²⁺ ions each coordinate to a framework oxygen at a non-conventional site in the supercage. At three supercage positions, about 18 Zn²⁺ ions that do not coordinate to the zeolite framework are found. Per unit cell, 40 H₃O⁺ ions are found: 18 at site II^′ and 22 at site II. Only about 16 non-framework oxygens were found per unit cell: eight water molecules in the supercages and, in the sodalite cages, eight hydroxide ions which participate in the formation of two nearly cubic Zn₄(OH)₄⁴⁺ clusters.     

Preparation of ITQ-29 (Al-free zeolite A) membranes

Membranes consisting of Al-free ITQ-29 (a zeolite with the LTA-type structure) have been prepared on alumina tubular supports by seeded liquid phase hydrothermal synthesis. A supramolecular organic structure-directing agent (SDA) was used for the synthesis of ITQ-29 that must be removed from the zeolite pores to activate the membrane for permeation. The high temperature needed to decompose SDA from small-pore zeolites could create thermal stresses that affect the final membrane quality. Because of this, the effect of the atmosphere (N₂, O₂, air and O₃/air) and temperature of the membrane calcination process has been studied. An ITQ-29 membrane activated by means of the combination of pyrolytic (at 723 K) and ozonization (at 473–573 K) treatments gave the best results, with N₂/CH₄ and N₂/propane selectivities well above the corresponding Knudsen values.     

Zeolite-mediated removal of NOx by NH3 from exhaust streams at low temperatures

NH₃ stored on zeolites in the form of NH₄⁺ ions easily reacts with NO to N₂ in the presence of O₂ at temperatures <373 K under dry conditions. Wet conditions require a modification of the catalyst system. It is shown that MnO₂ deposited on the external surface of zeolite Y by precipitation considerably enhances the NO_x conversion by zeolite fixed NH₄⁺ ions in the presence of water at 400–430 K. Particle-size analysis, temperature-programmed reduction, textural characterization, chemical analysis, ESR and XRD gave a subtle picture of the MnO₂ phase structure. The MnO₂ is a non-stoichiometric, amorphous phase that contains minor amounts of Mn²⁺ ions. It loses O₂ upon inert heating up to 873 K, but does not crystallize or sinter. The phase is reducible by H₂ in two stages via intermediate formation of Mn₃O₄. The manufacture of extrudates preserving stored NH₄⁺ ions for NO_x reduction is described. It was found that MnO₂ can oxidize NO by bulk oxygen. This enables the reduction of NO to N₂ by the zeolitic NH₄⁺ ions without gas-phase oxygen for limited time periods. The composite catalyst retains storage capacity for both, oxygen and NH₄⁺ ions despite the presence of moisture and allows short-term reduction of NO without gaseous O₂ or additional reductants. The catalyst is likewise suitable for steady-state DeNO_x operation at higher space velocities if gaseous NH₃ is permanently supplied.     

Interaction of ciprofloxacin hydrochloride with sodium dodecyl sulfate in aqueous/electrolytes solution at different temperatures and compositions

Interactions of ciprofloxacin hydrochloride(CPFH) with sodium dodecyl sulfate(SDS) were investigated by conductivity measurement in H_2O/electrolyte solutions(NaCl, Na_2SO_4 Na_3PO_4) over 298.15–318.15 K temperature range(with 5 K interval) considering the human body temperature. In all cases, two critical micelle concentrations(c~*) were observed which are increased in the presence of drug and decreased in the presence of salts enunciating the presence of interaction amongst the studied components. For(CPFH + SDS) system in the presence of salt, the c~*values at 303.15 K and I = 0.50 mmol·kg~(-1) followed the order: C_(NaCl)C_(Na_2SO_4)C_(Na_3PO_4). The ΔG_(1,m)~0 and Δ G_(2,m)~0values are found to be negative for all systems that show that the micellization process is thermodynamically spontaneous. For(CPFH + SDS) system in water, the Δ H_m~0 Δ S_m~0 values reveal that the micellization processes is both entropy dominated in almost all cases. In the occurrence of electrolytes, Δ H_m~0 and Δ S_m~0 values indicate that micellization processes are both entropy enthalpy restricted at upper temperature but it becomes totally entropy dependent at higher temperature. The higher positive Δ S_m~0 values indicate the enhanced hydrophobic interaction in presence of salts. The enthalpy-entropy compensation was determined from the linear relationship betweenΔ H_m~0 and Δ S_m~0 values in every state. Different transfer energies as well as compensation temperature and intrinsic enthalpy were also evaluated and the behaviors were comparable to other biological system.     

Epoxidation of olefines with PDMS membranes containing zeolite occluded manganese diimine complexes

A new composite catalyst for selective epoxidation of olefins with tert-butyl hydroperoxide (tBHP) is reported. The catalyst contains manganese diimine complexes (cis-Mn bis-2,2′-Bipyridyl), occluded within a NaY zeolite, in turn incorporated in a polydimethylsiloxane membrane (cis-[Mn(bpy)₂]²⁺-NaY-PDMS). The three-step synthesis consists of a Mn²⁺exchange of NaY, ligand sorption to form cis-[Mn(bpy)₂]²⁺-NaY and incorporation of the latter in a PDMS membrane. The major differences between [Mn(bpy)₂]²⁺-NaY as such and occluded in PDMS are observed in the sorption and catalytic characteristics. With the membrane system, the use of a solvent becomes obsolete. Whereas optimal cyclohexene oxidation with [Mn(bpy)₂]²⁺-NaY occurs with hydrogen peroxide in acetone, tBuOOH proves to be a better oxidant for [Mn(bpy)₂]²⁺-NaY-PDMS. The reactions in batch and fed-batch reactors are discussed. A simple regeneration procedure, monitored by FT-IR spectroscopy is proposed.     

Ba2+、MoO42-掺杂对NaCaPO4：Eu3+荧光粉发光性能的影响研究

为提高红色荧光粉的发光强度和色纯度,以硝酸钙、硝酸钠、硝酸铕、磷酸二氢铵、钼酸铵、硝酸钡为原料,采用高温固相法合成了NaCa_1-xPO₄：xEu³⁺、NaCa_1-x（PO₄）_1-y（MoO₄）_y：xEu³⁺、NaCa_1-x-zPO₄：xEu³⁺,zBa²⁺系列红色荧光粉。探讨了Eu³⁺单掺杂和Eu³⁺/MoO₄^2-、Eu³⁺/Ba²⁺共掺杂对荧光粉发光性能的影响。用X射线衍射（XRD）、荧光分光光度计、色坐标等对荧光粉的结构进行表征。研究结果表明：掺杂Eu³⁺、MoO₄^2-、Ba²⁺后NaCaPO₄晶系没有发生变化,但是晶胞参数发生了变化,说明Eu³⁺、MoO₄^2-、Ba²⁺进入NaCaPO₄晶格中。在393 nm紫外光激发下,荧光粉发射光谱图出现两个Eu³⁺比较强的特征发射峰,分别属于Eu³⁺的⁵D₀→⁷F₁和⁵D₀→⁷F₂跃迁。与单掺杂16%Eu³⁺荧光粉相比,共掺杂16%Eu³⁺/3%MoO₄^2-或16%Eu³⁺/6%Ba²⁺荧光粉的发射光谱中⁵D₀→⁷F₂跃迁产生的发射峰强度均高于单掺杂16%Eu³⁺荧光粉的发射峰强度,其⁵D₀→⁷F₂与⁵D₀→⁷F₁发射光强度之比（R）分别为1.76（R_Mo）和1.28（R_Ba）,都大于单掺杂16%Eu³⁺荧光粉的R_Eu（0.99）,共掺杂Eu³⁺/MoO₄^2-荧光粉的色纯度比单掺杂Eu³⁺和共掺杂Eu³⁺/Ba²⁺荧光粉的色纯度更好。