Organic arsenic removal from an aqueous solution by iron oxide-coated fungal biomass: An analysis of factors influencing adsorption

A two-level seven-factor (2^7-2) fractional factorial design analysis was conducted to examine the parameters influencing dimethylarsinic acid (DMA) removal from an aqueous solution using iron oxide-coated A. niger biomass. The factors examined were the concentration of DMA in solution, the mass of the adsorbent, the solution temperature, the Ca²⁺ ions in solution, the Fe²⁺ ions in solution, the SO₄²⁻ ions in solution, and the Cl⁻ ions in solution. The magnitude of the influence of the factors considered on DMA removal was observed in the order: presence of Ca²⁺ ions in solution > the DMA concentration > solution temperature > presence of SO₄²⁻ in solution > presence of Fe²⁺ in solution > the mass of adsorbent > the presence of Cl⁻ in solution.     

Effects of dietary defatted squid on cholesterol metabolism and hepatic lipogenesis in rats

Male Sprague-Dawley rats were fed a cholesterol-free (Exp. 1) or cholesterol-supplemented (Exp. 2) diet containing 20% casein (control group) or 15% defatted squid and 5% casein (defatted squid group), as protein, for 14 d. Serum and hepatic cholesterol concentrations were lower in rats fed defatted squid than in those fed casein in both cholesterol-free (−20%, P<0.05 and −15%, P<0.05, respectively) and cholesterol-supplemented (−25%, P<0.05 and −15%, P<0.05, respectively) diets. Hepatic triglyceride concentration was lower in the defatted squid than in the control groups in both cholesterol-free (−51%, P<0.05) and cholesterol-supplemented diets (−38%, P<0.01). The activities of cytosolic fatty acid synthase and the NADPH-generating enzymes, malic enzyme and glucose-6-phosphate dehydrogenase, in the liver were lower in the defatted squid than in the control groups in both cholesterol-free (−21%, P<0.01, −33%, P<0.05, and −33%, P<0.01, respectively) and cholesterol-supplemented diets (−34%, P<0.05, −57%, P<0.05, and −67%, P<0.05, respectively). The activity of mitochondrial carnitine palmitoyltransferase in the liver was comparable between the control and defatted squid groups. The activity of Mg²⁺-dependent phosphatidate phosphohydrolase in the liver cytosol was lower in the defatted squid (−9%, P<0.05) than in the control groups only in the cholesterol-free diet. Fecal excretion of total steroids was stimulated by the feeding of defatted squid in both cholesterol-free (+77%, P<0.005) and cholesterol-supplemented diets (+29%, P<0.01). These results suggest that the nonlipid fraction of squid exerts a hypocholesterolemic effect by increasing the excretion of total steroids in feces. The fraction also induces a triglyceride-lowering activity in the liver by decreasing hepatic lipogenesis.     

Thermal and thermomechanical properties of poly(ethylene oxide) networks produced with silica and organic crosslinking agents

The thermal and thermomechanical properties of two series of poly(ethylene oxide) networks (NPEOs) were investigated as a function of the chain length between crosslink sites (M_c) and the concentration of LiClO₄ (C_L) in the NPEOs. The two series of networks were produced with silica and organic crosslinking agents and, therefore, had crosslink sites of different natures: one was an inorganic silicate network (silica NPEO), and the other was an organic polar group (organic NPEO). The crosslink sites in both series of networks were commonly covalently bonded to the poly(ethylene oxide) (PEO) phase through a urethane group in the NPEOs. The glass‐transition temperatures (T_g's) of the PEO phases in the NPEOs, according to differential scanning calorimetry, increased with a decrease in M_c and were higher in the silica NPEOs than in the organic NPEOs under the same M_c conditions. The difference in T_g between the two series of networks with the same M_c values increased with decreasing M_c. These results suggested that the interaction of crosslink sites with the PEO phase was stronger in the silica NPEOs than in the organic NPEOs. The addition of LiClO₄ to the NPEOs resulted in T_g of the PEO phase in the NPEOs being elevated and increased according to the increase in C_L. The increase of T_g of the PEO phase according to the increase of C_L in the NPEOs was retarded or saturated at high values of C_L, and this indicated that the limit of solubility of the salt in the polymer was attained. The retardation or saturation of the increase of T_g was also observed in dynamic mechanical analyses. The curves of the loss factor tan δ and temperatures from the dynamic mechanical analyses for the NPEOs with high values of C_L showed shoulders or double peaks indicating the existence of the second phase in the polymer networks. In the curves of tan δ for salt‐complexed NPEOs with high values of C_L, silica NPEOs showed a shoulder of low intensity, but organic NPEOs showed a distinguished second peak becoming stronger with increasing C_L. The results of the T_g behavior and tan δ curves suggested that the salt solubility in the NPEOs was limited and that the salt solubility of PEO in the silica NPEOs was higher than that in the organic NPEOs. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 270–277, 2003     

Uptake of organic nitrogen by eight dominant plant species in Kobresia meadows

¹⁵N-labelled glycine experiments were carried out in both a Kobresia pygmaea meadow and a Kobresia humilis meadow to investigate whether alpine plants can take up organic nitrogen directly from the soil and whether different plant species differ in this respect. Eight plant species were selected in the two meadows, five in the Kobresia humilis meadow and four in the Kobresia pygmaea meadow, with one common species. After 4 h following ¹⁵N injection, atom% excess ¹⁵N in the aboveground parts of Ptilagrostis concinna was about 0.012, higher than in the aboveground parts of the other three species in the Kobresia pygmaea meadow, while that in the aboveground parts of Festuca ovina was higher than in the aboveground parts of the other four species in the Kobresia humilis meadow. After 1 day all the values for atom% excess ¹⁵N were substantially higher, except in the aboveground parts of Gentiana straminea in the Kobresia pygmaea meadow and in the aboveground parts of Festuca ovina and Gentiana aristata in the Kobresia humilis meadow. One day after ¹⁵N injection, atom% excess ¹⁵N in the roots was higher than that in any of the aboveground parts. In the first 4 h, uptake rates of organic nitrogen by the four species in the Kobresia pygmaea meadow were in the range of 0–0.83 µmol g^–1 h^–1, with a value of 1.43 µmol g^–1 h^–1 for the roots. In contrast, those of five species and the roots in the Kobresia humilis meadows varied between 1.34–8.08 µmol g^–1 h^–1. Key species such as Kobresia pygmaea and Kobresia humilis showed a greater capacity to take up organic nitrogen than non-key species over a 5-day period. This implies that alpine plants can take up organic nitrogen from the soil, but uptake capacity varies widely among different species, and for the same species from different Kobresia meadows.     

Concentration dependence of electric conductivity for fluorine-containing sodium borate glasses

The influence of sodium fluoride additives on the physicochemical properties of glasses in the Na₂O-B₂O₃ systems is investigated. The introduction of sodium fluoride into the Na₂O · 2B₂O₃ and Na₂O · 3B₂O₃ glasses leads to an increase in the electric conductivity. The temperature-concentration dependence of the electric conductivity has been investigated. It is shown that, in glasses of the NaF-Na₂O · 2B₂O₃ system, an increase in the volume concentration of sodium ions from 2.4 × 10⁻² to ∼3 × 10⁻² mol/cm³ is accompanied by an insignificant decrease in the activation energy E_σ from 1.44 to 1.38 eV and a sharp (by a factor of ∼30) increase in the electric conductivity. In glasses of the NaF-Na₂O · 3B₂O₃ system, an increase in the concentration of sodium ions from 1.8 × 10⁻² to ∼2.3 × 10⁻² mol/cm³ brings about an increase in the electric conductivity by a factor of approximately 100 and an increase in E_σ from 1.6 to 1.83 eV. A further increase in the concentration of sodium ions (up to 2.5 × 10⁻² mol/cm³) virtually does not affect the electric conductivity and E_σ. At the same concentration of sodium ions (∼2.46 × 10⁻² mol/cm³) in the 9.8NaF · 90.2[Na₂O · 2B₂O₃] and 57.1NaF · 42.9[Na₂O · 3B₂O₃] glasses, the electric conductivity and the activation energy are considerably higher in the glass with a larger fluorine content. The regularities revealed are interpreted in the framework of the microinhomogeneous glass structure.     

Direct synthesis of H2O2 from H2 and O2 over Pd/H-beta catalyst in an aqueous acidic medium: Influence of halide ions present in the catalyst or reaction medium on H2O2 formation

The influence of different halide ions present in the catalyst or reaction medium on the performance of Pd/H-beta catalyst in the direct H₂O₂ synthesis in an aqueous acidic (0.03 M H₃PO₄) reaction medium at 27 °C and atmospheric pressure has been thoroughly investigated. The results showed a strong influence of both the bulk Pd oxidation state in the catalyst and the halide ions added to the reaction medium on the performance of the catalyst in the H₂ to H₂O₂ oxidation, H₂O₂ decomposition/hydrogenation reactions. The different ammonium halides impregnated reduced Pd/H-beta catalyst calcined in inert (N₂) and oxidizing (air) gaseous atmospheres also revealed that the bulk Pd oxidation state and nature of the halide ions present in the catalyst together control the overall performance of the catalyst in the H₂O₂ formation reaction. The presence of halide ions in reaction medium or in the catalyst significantly changes the selectivity for H₂O₂ formation in the direct H₂O₂ synthesis. Bromide ions are found to remarkably enhance the H₂O₂ selectivity in the direct H₂O₂ synthesis irrespective of the Pd oxidation state in the catalyst. The promoting action of Br⁻ is attributed mainly to the large decrease in the H₂O₂ decomposition and hydrogenation activities of the catalyst and also inhibition for the non-selective H₂-to-water oxidation over the catalyst.     

Montmorillonite as support for peroxide in the melt grafting of maleic anhydride onto polypropylene

Grafting of maleic anhydride onto polypropylene was performed in a Haake torque rheometer, in the presence of organically modified montmorillonite, MMT (used as support for the peroxide), according to a 2³ factorial design, where the maleic anhydride concentration (C_MA), peroxide concentration (C_per) and reaction time (t_r) were varied. For comparison, the reaction in the absence of MMT was also conducted. Polypropylene degradation was assessed by parallel plate rheometry and size exclusion chromatography (SEC) and percentage of reacted maleic anhydride (%MA_g) was obtained by titration and FTIR spectroscopy. The results showed differences in both systems, conventional and in the presence of MMT. The structure of polypropylene grafted with maleic anhydride, PP‐g‐MA, indicates longer branches are formed in the presence of MMT compared to in its absence, demonstrated by FTIR analysis. As in conventional reaction systems, an increase in C_per caused an increase in %MA_g and a reduction in molar mass. The variable C_MA showed to be not significant in the grafting reaction in the presence of MMT, even at high DCP levels, at a 5% significance level. On the other hand, increase in C_MA resulted in significant increase in viscosity. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44134.     

Effect of growth temperature on the positional distribution of eicosapentaenoic acid andrans hexadecenoic acid in the phospholipids of aVibrio species of bacterium

Phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) were isolated from aVibrio species of bacterium, known to produce eicosapentaenoic acid (20∶5n−3) andtrans-hexadecenoic acid (16∶1n−7), and subjected to phospholipase A₂ degradation to determine the positional distribution of component fatty acids. At the two growth temperatures studied (20 and 5°C), both 20∶5n−3 andtrans 16∶1 n−7 were located mainly at positionsn−2 in PE. Increases in the proportions of 20∶5n−3 andtrans 16∶1n−7 in positionsn−2 with decreasing growth temperature were balanced mainly by decreases in the level ofiso-15∶0. In PG,trans 16∶1n−7 was located predominantly in positionsn-1, although the difference between the two positions was not as great as in PE. Eicosapentaenoic acid was preferentially located in positionsn-2 of PG, particularly at 5°C when it comprised 29.9% of the total fatty acids in this position. It is concluded thattrans 16∶1n−7/20∶5n−3 is not a major molecular species of phospholipid in this species ofVibrio and that changes in the levels of molecular species of PE containingiso-15∶0 may feature in thermal acclimation.     

Concentration dependences of partial activities of components in the tify-Ticx field of the titanium-nitrogen-carbon system

The method of isodefect sections is used to study the concentration dependence of partial activities of components in the TiN_y — TiC_x. field of the titanium-nitrogen-carbon system at 1273 K. The amount of defects in the alloys is expressed in terms of the concentration of valence electrons (CVE). Equations of concentration dependences of partial activities in the boundary systems TiN_y and TiC_x and in the TiN_y — TiC_x field are presented. An attempt to derive an equation of the concentration dependence of the activity of carbon in the TiC_x — TiN_y field using data expressed in terms of the CVE failed.     

CO2 gas-activated sintering of carbonated hydroxyapatites

Sintering compacts of carbonated hydroxyapatite (CHA) nanoparticles (3.4 wt% CO₃²⁻) in a CO₂ flow (4 mL/min) proceeded at a temperature which was more than 200 °C lower than that for hydroxyapatite in air (1150 °C). During heating from RT to 1200 °C (5 K/min) the rate of shrinkage of the CHA compacts showed a maximum thrice as high as that in air at about 929 °C. The shrinkage correlates with a mass loss caused by the release of CO₂ due to the thermal decomposition of CO₃²⁻ ions that substitute PO₄³⁻ ions in the CHA lattice. Firing the compacts in the CO₂ flow at 800 and 900 °C for 2 h resulted in an additional carbonatation on the B-sites and a further decrease in the sintering temperature to 890 °C. The compacts fired in the 900-1000 °C range became almost complete ceramics with high densities and mechanical properties close to those of medical implants. Firing at temperatures above 1000 °C resulted in an additional carbonatation on the A-sites. However, this led to a material with low densities and poor mechanical properties. A supposition has been proposed that the effect of CO₂ gas-activated sintering is a result of the intensification of the diffusion in the nanoparticles caused by CO₂ molecules entering the bulk from the CO₂ atmosphere and (or) releasing from the bulk due to the decomposition of carbonates on the B-sites in the lattice.     

Electronic Polarizability of Vitreous Alloys in the Ge–As–S System

The influence of temperature on the electronic polarizability of vitreous alloys along the (As₂S₃) _x · (GeS₂)_{1 – x} (0 < x< 1) join in the Ge–As–S system is investigated. Numerical values of the coefficients in the expression describing the temperature dependence of the electronic polarizability are determined. It is found that the temperature change in the polarizability with a variation in the composition is governed by the ratio of two contributions, namely, the change in polarizability unrelated to changes in the density and the photoelastic effect.     

Photolytic hydrogenation of the polyynes C6H2, C8H2, C10H2, and C12H2 in n-hexane with 253.6 nm radiation

The polyynes C₆H₂, C₈H₂, C₁₀H₂, and C₁₂H₂ in n-hexane exposed to 253.6 nm radiation “disappear” much faster in air-free solutions than in solutions in equilibrium with air. These observations suggest that the disappearance is due to reaction of the polyyne molecules in the ground state with a photolytically produced chemical species which in solutions in equilibrium with air is overwhelmingly scavenged by dissolved O₂. Although no hydrogenation products were firmly established the most likely chemical is atomic hydrogen.     

Thermogravimetric Studies of Solid-Phase Reactions in the System MgO – Al2O3 – SiO2 and Their Analysis in Terms of Graph Theory

Changes in the phase composition of the MgO – Al₂O₃ – SiO₂ system in the subsolidus region are studied by the thermogravimetric method. Specific features of the DTA curves are correlated with periodic changes in the concentration of phases involved in chemical reversible solid-phase reactions. Critical kinetic effects associated with conjugated solid-phase reactions in the MgO – Al₂O₃ – SiO₂ system are discussed in terms of graph theory. The phase composition of materials with a dissipative structure is shown to form by a self-organization mechanism.     

Partitioning of polymers into pores with surface interactions at dilute solution limit

The partitioning of a single polymer chain into a slit in a good solvent with different surface interactions is examined through Monte Carlo simulations from subcritical regime to adsorptive regime. The chain conformation in the subcritical regime is not perturbed by the surface interactions significantly. In the adsorptive regime, the conformation of the chain is strongly perturbed by the surface interactions. The confinement free energy in the two regimes maybe written in a uniform formula, βΔμ_conf∼c₁N(a/D)^xε_w+c₂N(a/D)^1/ν with x∼2.0 or larger in the subcritical regime and ∼1.0 in the adsorptive regime, where ν is the Flory exponent, D is the slit width, N is the chain length, a is the monomer size, and ε_w is the surface interaction energy between the polymer beads and the slit. This formula is valid for a long chain in the narrow slit in the subcritical regime or when the adsorption layer h>D in the adsorptive regime. A critical behavior occurs when ε_w is at the critical adsorption point and x=1/ν, then Δμ_conf will have little dependence on N or D. Higher order terms that are neglected in the above equation, however, may be present that could lead to a weak dependence of K on N and D even in the critical adsorption point.     

Singlet oxygen lifetime in polymer films

Singlet oxygen lifetimes [τ(¹O₂)] in polymer matrices were calculated using the strong exponential correlation between the incremental rate constant (K_xy) of energy transfer from ¹O₂ to terminal oscillators X—Y contained in solvent molecules and the energy (E_xy) of the highest fundamental vibration of the oscillator X—Y. The lifetimes in polymers correspond very well to experimental data in the literature. They depend only on the nature and quantity of molecular oscillators in the medium but not on the state of aggregation. The computed lifetimes in common polymers vary only from 10 to 50 μs. Therefore the lifetime of ¹O₂ in singlet oxygen reactions in polymers is of secondary importance in comparison to the diffusion coefficient.     

Long-term application effects of chemical fertilizer and compost on soil carbon under intensive rice–rice cultivation

From a long-term fertilizer experiment on rice–rice cropping in Typic Endoaquept, established at the Central Rice Research Institute, Cuttack, India in 1969, effects of application of composted manure (5 Mg ha⁻¹ year⁻¹) and chemical fertilizers (N, NP, NK, and NPK twice in a year), in series without compost (C₀) or with compost (C₁) on changes in soil carbon and microbial pools were examined by comparing the soils archived in 1984 and those sampled in 2004. Mean concentrations of soil organic carbon (SOC) varied between 5.5 and 7.6 g kg⁻¹ in 1984, and 6.8 and 10.8 g kg⁻¹ in 2004, respectively. Temporal increases in the total amounts of carbon, which reflect the carbon sequestration potential of the soil followed the order: C₁ + NK > C₁ + NP = C₁ + NPK > C₁ + N = C₁-control > C₀ + NP = C₀ + NK > C₀ + NPK > C₀-control > C₀ + N. Fractions of H₂O–C and K₂SO₄–C were higher in 1984, especially in those soil treated without compost. A reverse trend was observed in case of KMnO₄–C and carbohydrate–C fractions. The continuous application of compost enhanced microbial biomass carbon as well as active microbial biomass carbon in 2004. Long-term application of chemical fertilizers in combination, rather than N alone, had beneficial effects on soil carbon and microbial pools. Compost application, even once a year, invariably led to higher increments in both soil carbon and microbial pools and the combinations of chemical fertilizers with compost generally showed comparable effects in the long-term.     

Electrical conductivity and the nature of charge carriers in glasses of the Tl<Subscript>2</Subscript>O-B<Subscript>2</Subscript>O<Subscript>3</Subscript> system

The concentration dependence of the electrical conductivity of glasses in the Tl₂O-B₂O₃ system is studied. The nature of charge carriers in this system is experimentally investigated for the first time. It is demonstrated using the Hittorf, Tubandt, and Hebb-Liang-Wagner techniques and the Faraday law that neither Tl⁺ ions nor electrons are involved in the electricity transport. The verification of the Faraday law does not reveal the presence of thallium in the amalgam of the cathode or a change in the sample weight after electrolysis, to within the experimental error. This allows one to make the inference that protons can be charge carriers in glasses of the Tl₂O-B₂O₃ system. It is shown using extended X-ray absorption fine structure (EXAFS) spectroscopy that Tl³⁺ ions and thallium Tl⁰ reduced to the metallic state are absent in the structure of the glasses under investigation. This means that thallium in glasses of the Tl₂O-B₂O₃ system occurs only in the form of Tl⁺ ions. The analysis of the IR spectroscopic data leads to only a qualitative conclusion that the water content in the glasses insignificantly increases with an increase in the thallium oxide content. An increase in the electrical conductivity of glasses in the Tl₂O-B₂O₃ system with an increase in the thallium oxide content is explained by the increase in the number of protons formed upon dissociation of H⁺[BO_4/2]^? structural-chemical units, because their concentration increases with increasing Tl₂O content. In the structure of boron oxide, impurity hydrogen enters predominantly into the composition of H⁺[O_2/2BO^?] structural-chemical units, for which the dissociation energy is higher than that for the H⁺[BO_4/2]^? structural-chemical units. The increase in the concentration of H⁺[BO_4/2]^? structural-chemical units is accompanied by the increase in the number of dissociated protons, which are charge carriers in glasses of the Tl₂O-B₂O₃ system.     

Dispersion polymerization of styrene in CO2-expanded ethanol

Dispersion polymerization of styrene has been performed in CO₂-expanded ethanol at ≤9 MPa and 70 °C using PVP as stabilizer. The polymerizations proceeded with good colloidal stability, resulting in spherical particles of diameters of ∼2 μm. Pressurization with CO₂ leads to an increase in particle size (∼1 μm in the corresponding CO₂-free system), and a decrease in both polymerization rate and molecular weight. The main effect of CO₂ is proposed to be its influence on the partitioning of monomer between the continuous and the particle phase–the results indicate that CO₂-pressurization causes a reduction in monomer concentration in the particles. Overall, the results are consistent with literature data on the effects of the polarity of the continuous phase in dispersion polymerization of styrene in alcohols and alcohol/water mixtures.     

Synthesis of SiC whiskers by VLS and VS process

This study investigates the mechanisms of SiC whisker formation in the carbothermal reduction of quartz to SiC in different gas atmospheres. Reduction of quartz by graphite was studied in Ar, H₂, and CH₄–H₂–Ar gas mixture in a laboratory fixed bed reactor. The reduction products were characterised by XRD, SEM and TEM. Whiskers were not formed in the carbothermal reduction of quartz in argon. Two types of SiC whiskers were observed in the carbothermal reduction of quartz in H₂ and CH₄–H₂–Ar gas mixture. In the process of reduction at 1400–1600 °C in H₂ and at 1200–1600 °C in CH₄–H₂–Ar gas mixture, whiskers with hexagonal shape with diameter 100–800 nm and length up to tens of microns were formed by the VLS mechanism under catalytic effect of iron. The whiskers with the characteristics of cylindrical shape and high aspect ratio were synthesized in CH₄–H₂–Ar gas mixture at 1400–1600 °C by VS mechanism.     

Anodic dissolution of U, Zr and U–Zr alloy and convolution voltammetry of Zr|Zr couple in molten LiCl–KCl eutectic

The anodic dissolution of U and Zr metal was studied in LiCl–KCl–UCl₃ and LiCl–KCl–ZrCl₄, respectively, at 773 K by cyclic voltammetry and compared with their respective dissolution behaviour in blank LiCl–KCl eutectic. The anodic dissolution of U–Zr alloy in LiCl–KCl–UCl₃ was also studied at 773 K to compare with the dissolution of U and Zr. The transfer coefficients evaluated by Tafel analysis and the method of Allen–Hickling for U and Zr dissolution were found to be in fair agreement with each other. U dissolution in LiCl–KCl–UCl₃ and Zr dissolution LiCl–KCl–ZrCl₄ were also studied by chronoamperometry and the diffusion coefficient value of U³⁺ was calculated to be in the range of 2.9 × 10⁻⁵ to 3.3 × 10⁻⁵ cm² s⁻¹ which is in agreement with those reported in literature. Convolution voltammetric analysis of Zr⁴⁺/Zr²⁺ redox couple in LiCl–KCl–ZrCl₄ was carried out for the first time to have a comprehensive understanding of the electrode kinetics.