Process optimization and kinetic evaluation for biosynthesis of D-isoascorbyl stearate.

The synthesis of D-isoascorbyl stearate from D-isoascorbic acid and stearic acid with immobilized lipase (Novozym(®)435) as catalyst was studied. Response surface methodology and Box-Behnken design with six variables and three levels were employed to evaluate the effects of processing conditions on the conversion of D-isoascorbic acid. The results confirmed that the response surface method and statistical analysis were proved to be useful in developing optimal conditions for D-isoascorbyl stearate synthesis. The optimum conditions were predicted as follows: reaction temperature 48 °C, reaction time 17.7 h, immobilized lipase amount 50.0 % (w/w, of D-isoascorbic acid), substrate molar ratio 9:1 (stearic acid to D-isoascorbic acid), D-isoascorbic acid concentration 0.14 mol/L (based on solvent), 4A molecular sieve addition 200 g/L (based on solvent), and the optimal conversion was 90.6 %. Through the kinetics model fitting of the esterification, it was considered that the esterification conformed to a Ping-Pong bi-bi kinetic model with D-isoascorbic acid inhibition, and the obtained kinetic constants showed that the inhibition of D-isoascorbic acid and the enzyme affinity to substrate were abate with the increase of the reaction temperature.

Copper-mediated direct alkoxylation of arenes using an N,O-bidentate directing system.

Highly effective CuCl-mediated C-H alkoxylation of arenes and heteroarenes has been developed by using a 2-aminopyridine 1-oxide moiety as an N,O-bidentate directing group. The reaction proceeds smoothly using a broad range of substrates to afford o-alkoxylated benzoic and heteroaromatic amide products. Moreover, the reaction system shows remarkable compatibility when hexafluoroisopropanol is used as a coupling parter; halogen, nitro, ether, alkoxy, ester, and sulfonyl functional groups are all tolerated. The directing group can be easily removed by base hydrolysis, affording o-alkoxylated benzoic acids.

The effect of UV365/Fenton process on the removal of gaseous ethylbenzene in a bubble column reactor.

As volatile organic compounds (VOCs), gaseous ethylbenzene has adverse effects on human health and ecology. Therefore, an effective degradation process is highly desirable. The Fenton process under UV 365 nm was selected as the first option to remove gaseous ethylbenzene in a bubble column reactor. The main parameters for the batch experiments were systematically studied, including H2O2 concentration, [H2O2]/[Fe2+], pH, UV wavelength, UV intensity, gaseous ethylbenzene concentration, gas flow rate, and process stability towards removal efficiency. The optimum conditions were found to be H2O2 concentration of 100 mmol·L-1, [H2O2]/[Fe2+] of 4, pH of 3.0, UV wavelength of 365 nm, UV power of 5 W, gas flow rate of 900 mL·min-1, and gaseous ethylbenzene concentration of 30 ppm, resulting in a removal efficiency of 76.3%. The study found that the Fenton process, when coupled with UV 365 nm, was highly effective in removing gaseous ethylbenzene. The degradation mechanism of gaseous ethylbenzene was proposed in the UV365/Fenton process based on EPR, radical quenching experiments, iron analysis, carbon balance, and GC-MS analysis. The results indicated that •OH played a crucial role in the process.

Facile decoration of Au nanoparticles on CdS nanorods by polyoxometalate with enhanced photocatalytic activities toward hydrogen evolution.

The tri-component hybrid CdS nanorods (NRs)/Au nanoparticles (NPs)@polyoxometalate (POM) was successfully prepared by a facile, efficient and green method. The structural properties and component analysis were studied by Transmission electron microscopy (TEM), X-ray Diffraction (XRD) and UV-Vis spectra. The POMs sever as not only reductant and bridge molecules, but also as co-catalyst to play an important role in the photocatalytic process. The as-prepared nanohybrid shows obviously enhanced photocatalytic activity toward photocatalytic evolution of hydrogen.

Effective Absorption of Dichloromethane Using Carboxyl-Functionalized Ionic Liquids.

Dichloromethane (DCM) is recognized as a very harmful air pollutant because of its strong volatility and difficulty to degrade. Ionic liquids (ILs) are considered as potential solvents for absorbing DCM, while it is still a challenge to develop ILs with high absorption performances. In this study, four carboxyl-functionalized ILs-trioctylmethylammonium acetate [N1888][Ac], trioctylmethylammonium formate [N1888][FA], trioctylmethylammonium glycinate [N1888][Gly], and trihexyl(tetradecyl)phosphonium glycinate [P66614][Gly]-were synthesized for DCM capture. The absorption capacity follows the order of [P66614][Gly] > [N1888][Gly] > [N1888][FA] > [N1888][Ac], and [P66614][Gly] showed the best absorption capacity, 130 mg DCM/g IL at 313.15 K and a DCM concentration of 6.1%, which was two times higher than the reported ILs [Beim][EtSO4] and [Emim][Ac]. Moreover, the vapor-liquid equilibrium (VLE) of the DCM + IL binary system was experimentally measured. The NRTL (non-random two-liquid) model was developed to predict the VLE data, and a relative root mean square deviation (rRMSD) of 0.8467 was obtained. The absorption mechanism was explored via FT-IR spectra, 1H-NMR, and quantum chemistry calculations. It showed a nonpolar affinity between the cation and the DCM, while the interaction between the anion and the DCM was a hydrogen bond. Based on the results of the study of the interaction energy, it was found that the hydrogen bond between the anion and the DCM had the greatest influence on the absorption process.

Quantum Chemistry Study on the Structures and Electronic Properties of Bimetallic Ca2-Doped Magnesium Ca2Mgn (n = 1-15) Clusters.

Here, by utilizing crystal structure analysis through the particle swarm optimization (CALYPSO) structural searching method with density functional theory (DFT), we investigate the systemic structures and electronic properties of Ca2Mgn (n = 1-15) clusters. Structural searches found that two Ca atoms prefer to occupy the external position of magnesium-doped systems at n = 2-14. Afterward, one Ca atom begins to move from the surface into the internal of the caged skeleton at n = 15. Calculations of the average binding energy, second-order difference of energies, and HOMO-LUMO gaps indicated that the pagoda construction Ca2Mg8 (as the magic cluster) has higher stability. In addition, the simulated IR and Raman spectra can provide theoretical guidance for future experimental and theoretical investigation. Last, further electronic properties were determined, including the charge transfer, density of states (DOS) and bonding characteristics. We hope that our work will provide theoretical and experimental guidance for developing magnesium-based nanomaterials in the future.

Enhanced adsorption of copper ions by phosphoric acid-modified Paeonia ostii seed coats.

Novel adsorbent, phosphoric acid-modified Paeonia ostii seed coats (PA-PSC) were successfully prepared by low-temperature pyrolysis to effectively remove Cu(II) from aqueous solution. The results revealed that equilibrium adsorption capacity (qe) of PA-PSC for Cu(II) was notably enhanced up to 4-folds compared with the raw PSC. FT-IR and XPS analyses suggested that the adsorption of Cu(II) by PA-PSC was primarily ascribed to electrostatic forces and complexing effects. Besides, equilibrium and kinetic studies demonstrated that Freundlich and pseudo-second-order models were the actually fairly good approximations of Cu(II) adsorption. Thermodynamic analysis revealed that the adsorption of Cu(II) onto PA-PSC was a chemical, endothermic, and spontaneous process. Lastly, reusability study further confirmed the applicability of PA-PSC as a promising adsorbent for removing Cu(II) from aqueous solution.

Aromatic Ester-Functionalized Ionic Liquid for Highly Efficient CO2 Electrochemical Reduction to Oxalic Acid.

Electrochemical reduction of CO2 into valuable chemicals is a significant route to utilize CO2 resources. Among various electroreduction products, oxalic acid (H2 C2 O4 ) is an important chemical for pharmaceuticals, rare earth extraction, and metal processing. Here, an aprotic aromatic ester-functionalized ionic liquid (IL), 4-(methoxycarbonyl) phenol tetraethylammonium ([TEA][4-MF-PhO]), was designed as an electrolyte for CO2 electroreduction into oxalic acid. It exhibited a large oxalic acid partial current density of 9.03 mA cm-2 with a faradaic efficiency (FE) of 86 % at -2.6 V (vs. Ag/Ag+ ), and the oxalic acid formation rate was as high as 168.4 µmol cm-2 h-1 , which is the highest reported value to date. Moreover, the results of density functional theory calculations demonstrated that CO2 was efficiently activated to a -COOH intermediate by bis-active sites of the aromatic ester anion via the formation of a [4-MF-PhO-COOH]- adduct, which finally dimerized into oxalic acid.

Effects of Bacillus thuringiensis HC-2 Combined with Biochar on the Growth and Cd and Pb Accumulation of Radish in a Heavy Metal-Contaminated Farmland under Field Conditions.

The objective of this study was to explore the effect of heavy metal-resistant bacteria and biochar (BC) on reducing heavy metal accumulation in vegetables and the underlying mechanism. We tested Bacillus thuringiensis HC-2, BC, and BC+HC-2 for their ability to immobilize Cd and Pb in culture solution. We also studied the effects of these treatments on the dry weight and Cd and Pb uptake of radish in metal-contaminated soils under field conditions and the underlying mechanism. Treatment with HC-2, BC, and BC+HC-2 significantly reduced the water-soluble Cd (34-56%) and Pb (31-54%) concentrations and increased the pH and NH4+ concentration in solution compared with their vales in a control. These treatments significantly increased the dry weight of radish roots (18.4-22.8%) and leaves (37.8-39.9%) and decreased Cd (28-94%) and Pb (22-63%) content in the radish roots compared with the control. Treatment with HC-2, BC, and BC+HC-2 also significantly increased the pH, organic matter content, NH4+ content, and NH4+/NO3- ratio of rhizosphere soils, and decreased the DTPA-extractable Cd (37-58%) and Pb (26-42%) contents in rhizosphere soils of radish. Furthermore, BC+HC-2 had higher ability than the other two treatments to protect radish against Cd and Pb toxicity and increased radish biomass. Therefore, Bacillus thuringiensis HC-2 combined with biochar can ensure vegetable safety in situ for the bioremediation of heavy metal-polluted farmland.

Insights into the structures and electronic properties of Cun+1µ and CunS µ (n = 1-12; µ = 0, ±1) clusters.

ABSTARCT: The stability and reactivity of clusters are closely related to their valence electronic configuration. Doping is a most efficient method to modify the electronic configuration and properties of a cluster. Considering that Cu and S posses one and six valence electrons, respectively, the S doped Cu clusters with even number of valence electrons are expected to be more stable than those with odd number of electrons. By using the swarm intelligence based CALYPSO method on crystal structural prediction, we have explored the structures of neutral and charged Cun+1 and CunS (n = 1-12) clusters. The electronic properties of the lowest energy structures have been investigated systemically by first-principles calculations with density functional theory. The results showed that the clusters with a valence count of 2, 8 and 12 appear to be magic numbers with enhanced stability. In addition, several geometry-related-properties have been discussed and compared with those results available in the literature.

First-principle study of structural, electronic and magnetic properties of (FeC)n (n = 1-8) and (FeC)8TM (TM = V, Cr, Mn and Co) clusters.

The structural, electronic and magnetic properties of the (FeC)n (n = 1-8) clusters are studied using the unbiased CALYPSO structure search method and density functional theory. A combination of the PBE functional and 6-311 + G* basis set is used for determining global minima on potential energy surfaces of (FeC)n clusters. Relatively stabilities are analyzed via computing their binding energies, second order difference and HOMO-LUMO gaps. In addition, the origin of magnetic properties, spin density and density of states are discussed in detail, respectively. At last, based on the same computational method, the structures, magnetic properties and density of states are systemically investigated for the 3d (V, Cr, Mn and Co) atom doped (FeC)8 cluster.

Efficient conversion of wheat straw wastes into biohydrogen gas by cow dung compost.

Efficient conversion of wheat straw wastes into biohydrogen gas by cow dung compost was reported for the first time. Batch tests were carried out to analyze influences of several environmental factors on biohydrogen production from wheat straw wastes. The performance of biohydrogen production using the raw wheat straw and HCl pretreated wheat straw was then compared in batch fermentation tests. The maximum cumulative hydrogen yield of 68.1 ml H2/g TVS was observed at 126.5 h, the value is about 136-fold as compared with that of raw wheat straw wastes. The maximum hydrogen production rate of 10.14 ml H2/g TVS h was obtained by a modified Gompertz equation. The hydrogen content in the biogas was 52.0% and there was no significant methane observed in this study. In addition, biodegradation characteristics of the substrate were also discussed. The experimental results showed that the pretreatment of the substrate plays a key role in the conversion of the wheat straw wastes into biohydrogen by the composts generating hydrogen.

Copper-mediated direct aryloxylation of benzamides assisted by an N,O-bidentate directing group.

Copper-mediated selective mono- or diaryloxylation of benzamides has been achieved by using 2-aminopyridine 1-oxide as a new and removable N,O-bidentate directing group. The reaction system shows a broad substrate scope and provides a straightforward way for the synthesis of mono- and diaryloxylated benzoic acids.