Volume 67, Issue 11

Direct production of ethyl levulinate (EL) from glucose catalysed by a liquid acid catalyst (sulfuric acid) and a solid acid zeolite catalyst USY NKF-7 (USY) in ethanol media was investigated in this study. Effects of the initial glucose concentration (C G0), reaction temperature (T), amount of acid catalyst, and water addition on the yields of EL were compared, respectively. The results show that higher yield of EL can be obtained at lower C G0. Higher temperature and acid concentration can accelerate the reaction rate, but the formation rate of the by-products increases more quickly than that of EL. Water addition also can result in the decrease of the yield of EL. Although sulfuric acid is efficient in the production of EL, the USY is more efficient in converting glucose to 5-ethoxymethyl-2-furaldehyde. Moreover, the use of USY can limit the diethyl ether production, and it can be reused for multiple times.

A model-based sensitivity analysis was performed in order to evaluate the importance of the individual operating parameters of a three-phase fluidised-bed biological reactor used for removing mercury ions from wastewater. The parameters analysed involve the immobilised biomass load (bacteria P. putida) on alginate beads, particle size, inlet flow-rate, mercury ion loads in the fed wastewater, and the solid fraction in the reactor. Predictions were generated by using pseudo-first-order, Michaelis-Menten, or pseudo-Haldane kinetic models. The results highlight the major influence of the biomass/solid load and of the liquid residence time on the reactor efficiency. Also, the resultant significant differences in the model predictions underline the importance of using a more accurate kinetic model for process design and control purposes.

Seven samples of the ash derived from biomass, representing both fly and bottom ash, were analysed for a wide spectrum of total and mobile contents of nutrient and potentially risk elements. Several techniques, X-ray fluorescence (XRF) spectrometry, instrumental neutron activation analysis (INAA), proton-induced gamma-ray emission (PIGE) and proton induced X-ray emission (PIXE), inductively coupled plasma-atomic emission spectrometry (ICP-OES), and flame atomic absorption spectrometry (F-AAS) were compared. The results showed fairly good agreement between the XRF and INAA results, where the correlation coefficients (r) varied between 0.96 and 0.98. Lower contents documenting insufficient dissolution of the ash samples in the applied acid mixture were observed for both ICP-OES and AAS. In this case, weaker correlation with the INAA results not exceeding r = 0.7 were obtained. Therefore, the sample decomposition step is a bottleneck of the accurate analysis of this type of materials. For the assessment of plant-available portions of the elements in the ash samples, the Mehlich III extraction procedure and the extraction with a 0.11 mol L−1 solution of CH3COOH were applied. The results showed relatively low mobility of the elements (especially micronutrients) in the ash samples regardless of their source and composition, suggesting limited immediate effect of direct ash application as a fertilizer.

The influence of different modifiers, phosphorus, potassium, aluminium, and cerium on the pigmentary properties of TiO2 was studied. The phase composition and distribution of modifiers in prepared TiO2 products was investigated using XRD analysis, the selective leaching method, and ICP-AES technique. The optical properties, photoactivity, morphology, and surface area of modified TiO2 were determined by spectrophotometric, fluorescent, SEM, and BET measurements. The research was directed towards obtaining a pigmentary TiO2 with the highest possible photostability. It was found that the final calcination temperature, at which the anatase-rutile transformation rate was > 97 %, depended on the kind and amount of the modifiers introduced into hydrated titanium dioxide. In comparing the colour of TiO2 products modified with Ce, it was found that the addition of K to the TiO2 series caused an increase in all the optical properties examined. The presence of K and Al in TiO2 modified with Ce resulted in decreased photocatalytic activity. The photostability of TiO2 modified with Ce and K improved with an increase in P2O5 content. The highest photostability was measured for the TiO2-CePKAl series. It was concluded that the differences in both the optical properties and photoactivity of TiO2 depended on its phase composition and the distribution of modifiers in the products obtained.

The synthesis of well-aggregated carbon nanotubes in the form of bundles was achieved by the catalytic reduction of 1,2-dichlorobenzene by a solvothermal approach. The use of 1,2-dichlorobenzene as a carbon source yielded a comparably good percentage of carbon nanotubes in the range of 60–70 %, at a low reaction temperature of 200°C. The products obtained were analysed by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy techniques. The X-ray diffraction studies implied the presence of pure, crystalline, and well-ordered carbon nanotubes. The scanning electron and transmission electron microscopic images revealed the surface morphology, dimensions and the bundled form of the tubes. These micrographs showed the presence of multi-walled carbon nanotubes with an outer diameter of 30–55 nm, inner diameter of 15–30 nm, and lengths of several hundreds of nanometers. Brunauer-Emmett-Teller-based N2 gas adsorption studies were performed to determine the surface area and pore volume of the carbon nanotubes. These carbon nanotubes exhibit a better surface area of 385.30 m2 g−1. In addition, the effects of heating temperature, heating time, amount of catalyst and amount of carbon source on the product yield were investigated.

In this paper, amphiphilic chitosan derivatives (N-octyl-N-mPEG-chitosan, mPEG = poly(ethylene glycol) monomethyl ether; OPEGC) were successfully synthesised via the Schiff base reduction reaction of chitosan and mPEG-aldehyde, or octanal, with chitosan acting as the backbone of the grafted copolymers, and mPEG-aldehyde providing the hydrophilic chain or octanal providing the hydrophobic alkyl chain. The synthesis was confirmed by characterisation employing Fourier transform infrared spectroscopy (FTIR) and 1H NMR. In the subsequent procedure, water-soluble quantum dots (QDs) and iron(II,III) oxide (IO) nanoparticles, widely used as nanoprobes in medical applications, were produced by the incorporation of QDs or IO inside the polymeric micelle core. Finally, the optical properties of QDs incorporated into OPEGC (OPEGC@QDs) were characterised by UV-VIS spectroscopy, fluorescence spectroscopy, cell viability was obtained through MTT, and the morphology of their assembly formed in water were observed by atomic force microscope (AFM) and transmission electron microscope (TEM) and the QDs content of OPEGC@QDs was calculated following thermo gravimetric analysis (TGA). In addition, the properties of IO incorporated into OPEGC (OPEGC@IO) were characterised by vibrating sample magnetometry (VSM), FT-IR, MTT, TGA, AFM, and TEM. The results indicated that the OPEGC composite nanoparticles with size narrowly distributed, good water solubility, and low cytotoxicity were prepared here, which represented a high quantum yield or good super-paramagnetism.

The purpose of this work was to compare hydroxyapatite (HAP) and composites of HAP, HAP with chitosan (CS), and HAP with poly(vinyl pyrrolidone) (PVP), in terms of their particle size and morphology, using different methods, such as Coulter counter analysis, X-ray diffraction (XRD), and transmission electron microscopy (TEM). Although many researchers have studied HAP and CS/HAP and PVP/HAP composites extensively, there is no evidence of a comparative study of their particle sizes. For this reason, different complementary methods have been used so as to provide a more complete image of final product properties — particle size — from the perspective of possible applications. The syntheses of HAP and HAP with polymer nanoparticles were carried out employing a precipitation method. Variation in particle size with synthesis time and influence of the reactants’ concentration on the materials’ preparation were systematically explored. Crystallite size calculated from XRD data revealed nanosized particles of HAP, CS/HAP, and PVP/HAP materials in the range of 2.5–9.2 nm. Coulter counter analysis revealed mean particle sizes of one thousand orders of magnitude larger, confirming that this technique measures agglomerates, not individual particles. In addition, the particles’ morphology and an assessment of their binding mode were completed by TEM measurements.

A range of cinnamic units containing 4,5-dihydrooxazoles was prepared using two different synthetic routes. The first method was based on the transformation of substituted cinnamic or benzoic acids to 2-styryl-4,5-dihydrooxazoles. Several derivatives containing phenolic groups were prepared in this manner. The second approach consisted of a reaction between the 4,5-dihydrooxazole moiety and double bond-containing compounds. These compounds contain two or more reactive centres capable of providing polymerisations and also organic reactions.

Thermodynamic properties (densities and viscosities) of binary mixtures of diethyl phthalate (DEP) + bromocyclohexane, dibutyl phthalate (DBP) + 1,2-dichlorobenzene, and vinyl acetate (1) + dimethyl phthalate (DMP) (2), + diethyl phthalate (2), or + dibutyl phthalate (2) were measured over the whole range of mole fractions at atmospheric pressure and different temperatures (T = 298.15 K to 308.15 K). For these mixtures, their excess molar volumes (V E) and viscosity deviations (Δη) were calculated from the experimental data. These results were correlated with the Redlich-Kister polynomial equation to derive the coefficients and standard errors.

Volumetric and viscometric properties of glycine and methionine (amino acids) in a 0.2 vol. % amikacin sulphate (antibiotic drug) aqueous solution with the molality range of 0.025 mol kg−1–0.25 mol kg−1 were measured over the temperature range of 20°C–40°C at the interval of 5°C. Different parameters like apparent molar volume (ϕ V), apparent molar adiabatic compression (ϕ κ), isentropic compression (κ S) along with other acoustical parameters were calculated. Parameters like viscous relaxation time (τ), free volume (V F), internal pressure (Π I), and molar cohesive energy (MCE) were calculated from dynamic viscosity measurements. The ϕ V values are positive in both cases, but with higher magnitude observed in methionine. These positive values of ϕ V are indicative of strong solute-solvent interactions at all temperatures. In case of methionine there is a sharp initial increase in the ϕ V values which become almost constant with further additions of the amino acid. Structural differences in the two amino acids studied are clearly reflected in the different nature of the plots of different parameters. In case of an amino acid-drug system, dynamic viscosity increase has been attributed to the increase in the hydrophilic-ionic and hydrophilic-hydrophilic interactions with the increase in the amino acid concentration which in turn may cause more frictional resistance to the flow of the solution. All other parameters are discussed in terms of solute-solvent and solvent-solvent interactions.

Antioxidant activity of erodiol was examined at the M05-2X/6-311+G(d,p) level of theory in the gas and aqueous phases. The structure and energy of radicals and anions of the most stable erodiol rotamer were analyzed. To estimate antioxidant potential of erodiol, different molecular properties were examined: bond dissociation enthalpy, proton affinity together with electron transfer energy, and ionization potential followed by proton dissociation enthalpy. It was found that hydrogen atom transfer is the prevailing mechanism of erodiol behavior in gas; whereas single electron transfer followed by proton transfer and sequential proton loss electron transfer mechanisms represent the thermodynamically preferred reaction paths in water.

A data set of amidino bis-benzimidazoles, in particular 2′-arylsubstituted-1H,1′H-[2,5′]bisbenzimidazolyl-5-carboximidine derivatives with anti-malarial activity against Plasmodium falciparum was employed in investigating the quantitative structure-activity relationship (QSAR). Quantum chemical and molecular descriptors were obtained from B3LYP/6-31g(d) calculations and Dragon software, respectively. Significant variables, which included total energy (E T), highest occupied molecular orbital (HOMO), Moran autocorrelation-lag3/weighted by atomic masses (MATS3m), Geary autocorrelation-lag8/weighted by atomic masses (GATS8m), and 3D-MoRSEsignal 11/weighted by atomic Sanderson electronegativities (Mor11e), were used in the construction of QSAR models using multiple linear regression (MLR) and artificial neural network (ANN). The results indicated that the predictive models for both the MLR and ANN approaches using leave-one-out cross-validation afforded a good performance in modelling the anti-malarial activity against P. falciparum as observed by correlation coefficients of leave-one-out cross-validation (R LOO-CV) of 0.9760 and 0.9821, respectively, root mean squared error of leave-one-out cross-validation (RMSELOO-CV) of 0.1301 and 0.1102, respectively, and predictivity of leave-one-out cross-validation (Q LOO-CV2) of 0.9526 and 0.9645, respectively. Model validation was performed using an external testing set and the results suggested that the model provided good predictivity for both MLR and ANN models with correlation coefficient of the external set (R Ext) values of 0.9978 and 0.9844, respectively, root mean squared error of the external set (RMSEExt) of 0.0764 and 0.1302 respectively, and predictivity of the external set (Q Ext2) of 0.9956 and 0.9690, respectively. Furthermore, the robustness of the QSAR models is corroborated by a number of statistical parameters, comprising adjusted correlation coefficient (R Adj2), standard deviation (s), predicted residual sum of squares (PRESS), standard error of prediction (SDEP), total sum of squares deviation (SSY), and quality factor (Q). The QSAR models so constructed provide pertinent insights for the future design of anti-malarial agents.

A series of coumarins was synthesised via the silica tungstic acid-catalysed Pechmann reaction; some of these were employed for known three-component reactions with aromatic aldehydes and malononitrile in the presence of sodium hydrogen phosphate (Na2HPO4) as a basic catalyst, affording a variety of potentially anti-HIV active khellactone analogues.