Volume 69, Issue 10

Biogas upgrading is a widely studied and discussed topic. Many different technologies have been employed to obtain biomethane from biogas. Methods like water scrubbing or pressure swing adsorption are commonly used and can be declared as well established. Membrane gas permeation found its place among the biogas upgrading methods some years ago. Here, we try to summarize the progress in the implementation of gas permeation in biogas upgrading. Gas permeation has been already accepted as a commercially feasible method for CO 2 removal. Many different membranes and membrane modules have been tested and also some commercial devices are available. On the other hand, utilization of gas permeation in other steps of biogas upgrading like desulfurization, drying, or VOC removal is still rather rare. This review shows that membrane gas permeation is able to compete with classical biogas upgrading methods and tries to point out the main challenges of the research.

The analytical resolution of ketoconazole (KTZ) enantiomers was performed by high-performance liquid chromatography with sulphobutylether-β-cyclodextrin (SBE-β-CD) as a chiral mobile phase additive (chiral selector). Some important factors affecting the resolution of KTZ enantiomers were investigated. In addition, the molecular interaction between KTZ and SBE-β-CD was studied using the UV absorption spectrum and HPLC for an understanding of the resolution process. The results show that the type and concentration of the chiral mobile phase additive, the pH of the mobile phase and the volume fraction of methanol (φMeOH) in the mobile phase all have a clear influence on the resolution of KTZ enantiomers. Under optimal conditions, namely the use of 0.5 mmol L −1 SBE-β-CD as the chiral mobile phase additive, pH of 4.0 and φ MeOH in the mobile phase of 0.6, KTZ enantiomers are resolved with a resolution of 3.74. SBE-β-CD can bind to KTZ with a stability constant of 1157. The chromatographic method can provide the complexation stability constants of (+)-KTZ with SBE-β-CD (K (+) ) and (-)-KTZ with SBE-β-CD (K(−)). The intrinsic enantioselectivity was calculated from the K (+) to K (−) ratio as 1.34.

Organophosphorus (OP) compounds are extensively used in agricultural practice for pest management. However, their residues have a long half-life in the ecosystem as well as in the agro-products, posing a serious threat to human and animal health. Aryldialkylphosphatase (EC 3.1.8.1) is widely used in detoxification procedures. In the present study, aryldialkylphosphatase was immobilised on synthesised cross-linked nano-sized gel particles, also known as nanogels, in order to enhance the enzyme’s physicochemical properties. Accordingly, a new nanogel consisting of chitosan and myristic acid (CMA nanogel) was synthesised and characterised by way of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The aryldialkylphosphatase-CMA nanogel conjugate was then assayed by FTIR, and its physicochemical characteristics were also investigated. The data obtained from SEM and TEM showed the nanogels to be homogenous spherical particles less than 50 nm in diameter. The proper formation of the nanogel and nanobioconjugate was also confirmed by FTIR spectra. In comparison with the free enzyme, the pH and thermal stability of the aryldialkylphosphatase were enhanced by the covalent immobilisation. Moreover, the immobilised enzyme could maintain approximately half of its activity over more than one month. The kinetic parameters of the aryldialkylphosphatase- CMA nanogel conjugate were also shown to undergo remarkable improvements, hence the synthesised CMA-nanogel could act as a promising support for aryldialkylphosphatase immobilisation. It is suggested that the aryldialkylphosphatase-CMA nanogel could be used for detoxifying paraoxon; a nerve agent. Further clinical experiments are underway.

In this paper, Fe 3 O 4 nanoparticles coated with mesoporous silica were prepared successfully, noted as Fe 3 O 4 at the mobile composition of matter No. 41 (MCM-41). Also, Fe 3 O 4 at MCM-41 was grafted by both 3-aminopropyltriethoxysilane (APTS) and 3-chloropropyltriethoxysilane (CPS), noted as Fe 3 O 4 at MCM-41/APTS and Fe 3 O 4 at MCM-41/CPS. The compounds were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, vibrating sample magnetometry, thermogravimetry and N 2 adsorption/desorption. Then, the enzyme, porcine pancreas lipase (PPL), was immobilized onto these modified nanoparticles by covalent attachment, physical adsorption and cross-linking, noted as Fe 3 O 4 at MCM-41/CPS-PPL, Fe 3 O 4 at MCM-41-PPL and Fe 3 O 4 at MCM-41/APTS-PPL, respectively. The results showed that Fe 3 O 4 at MCM-41/CPS was the best nanomaterial for PPL immobilization, exhibiting enhanced immobilization efficiency (maximum 96 %), maximum relative activity (up to 96 %), high stability and reusability (83 % 56 days and 86.7 % ten cycles). Additionally, it offered some other advantages, such as easy recycling and reuse, complying with the trend of green chemistry. Therefore, Fe 3 O 4 at MCM-41/CPS in combination with a relevant method can be proposed for commercial applications.

Thermodynamic activity of sodium oxide and oxidation potential in NaOH-Na 2 O-Na 2 O 2 -H 2 O- NaH melt at the temperature of 400°C was investigated. Galvanic cell for the potentiometric measurements consisted either of a sodium electrode formed by β and βʺ-alumina semi-closed tube filled with liquid sodium or a platinum wire and of an oxygen electrode made from ZrO 2 (Y 2 O 3 ) solid electrolyte with the Bi-Bi 2 O 3 reference mixture. The number of exchanged electrons determined from the electromotive force measurements was in good agreement with the assumed reactions. The activity coefficient of sodium oxide was lower than one. Voltammetric measurements were carried out with a sodium reference electrode and a nickel auxiliary electrode. Behaviour of platinum, gold, silver and nickel as working electrodes was studied. The experiments were carried out in nitrogen atmosphere. Several types of zirconia semi-closed tubes were tested for long-term measurements under the process conditions.

Quantitative changes of carnosine and free amino acids in high-fat (43-50 mass %) fermented sausages during ripening were analysed using a 600 MHz VNMRS NMR spectrometer. Seven free amino acids were identified in the samples and a relatively high content of carnosine was observed in the final stage of ripening. The NMR method for the determination of free amino acids and carnosine content applied in this work has been used for the first time and it has proven to be suitable for the analysis of fermented sausages.

Arabinoxylan (AX) microspheres were formulated by ionotropic gelation for extended drug delivery. AX from Plantago ovata was tested for gelation with aluminium, barium, calcium, magnesium, and iron(III) chloride. Only calcium was found to lead to weak gelation with AX. The conventional needle extrusion produced fragile AX beads with calcium and hence the spray drying process was adopted for the preparation of metronidazole hydrochloride (MH) loaded AX microspheres. MH loading in AX microspheres was 30.8 mass %, 31.9 mass %, and 29.3 mass % in formulations gelled with 0.05 g, 0.1 g, and 0.15 g of calcium chloride per 100 mL of solution, respectively. Scanning electron microscopy revealed the crystallinity reduction of MH in microspheres. The surface of drug loaded calcium gelled AX microsphere was rougher than that of an ungelled one. Interactions of calcium with AX and the amorphous nature of the drug in the microspheres were evidenced by infrared spectroscopy and X-ray diffraction studies. Calcium-induced gelation can extend the drug release to over 90 min in 0.1 M HCl despite the hydrophilic nature of AX and the high solubility of metronidazole.

This paper involves the preparation of polythiophene (PTP) and its composite by the oxidative polymerisation method by using ferric chloride as an oxidant and thiophene monomer. The gadolinium( III) complex obtained by the refluxing technique was used as dopant in the PTP matrix. On the basis of the spectroscopic characterisation, seven-coordinate geometry is proposed for the complex. Conductance measurement confirms the non-selectrolyte nature of complex. The PTP and its composite were subjected to FTIR, X-ray diffraction and scanning electron microscope techniques. The powder X-ray diffraction pattern showed the high crystalline nature of the complex which in turn developed a good degree of crystallinity in the PTP composite. The average particle size was calculated as 4.655 ˚A and 3.737 ˚A for the dopant and PTP composite, respectively, by using Debye Scherrer’s equation. Thermal analysis was performed by thermogravimetric (TG) analysis, differential thermal analysis (DTA) and differential scanning calorimetry (DSC) techniques. The TG, DTA and DSC results were well-correlated. The thermal analysis revealed the high thermal stability of the dopant which in turn improved the thermal stability of the PTP composite, revealing the potential of the composite for high temperature applications.

Polypyrrole nanotubes were prepared by the oxidation of pyrrole with iron(III) chloride in a reaction mixture containing methyl orange. They were subsequently coated with polyaniline or poly(p-phenylenediamine) in situ during the oxidation of respective monomers in their presence. A part of the coaxial nanotubes was deprotonated using ammonia solution. The conductivity of polypyrrole nanotubes of 60 S cm −1 , was reduced after the coating, and again after the deprotonation, but maintained at a level above 10 −4 S cm −1 . Infrared and Raman spectra reflect the presence of the polymer overlayer deposited on the polypyrrole template. Thermogravimetric analysis was used as a tool for the analytical carbonisation of samples in an inert nitrogen atmosphere. The conversion of conducting polymers to nitrogen-containing carbon nanotubes was confirmed using Raman spectra.

New oxovanadium(IV) and cadmium(II) complexes with reduced Schiff bases derived from N,Nʹ- o-phenylenebis(salicylideneimine) have been synthesized and characterized using infrared and UVvisible spectra, ESR, and thermogravimetry. The complexes were identified as [ML] · (H 2 O) species, where deprotonated ligands are coordinated to metal through N 2 O 2 donor atoms. Antioxidant activity of the ligands and complexes was evaluated, revealing that the complexes exhibit a higher scavenging activity than the corresponding ligands. The prepared cadmium complexes showed slightly higher activity than the vanadium ones. Antifungal activity was tested against different human fungi including yeasts of the Candida genus (C. albicans and C. glabrata) and an opportunistic mould Aspergillus fumigatus. The oxovanadium complexes exhibited a very low activity toward C. albicans while the cadmium ones showed a significant growth inhibition of all the fungi tested; mainly of A. fumigatus though this mould is poorly susceptible to current antifungal agents like Itraconazole.

Several Lewis acid ionic liquids (LAILs) with different acidic scales were synthesised and used as catalysts for the synthesis of benzofuranol by condensation of pyrocatechol and 3-chloro-2- methylpropene in one pot. The catalytic activity of these ionic liquids was correlated with their Lewis acidity. Low to moderate conversion with excellent selectivity to benzofuranol was obtained in the presence of the appropriate LAILs. Compared to the two-step synthetic method currently used in industry, a higher yield plateau (81.1 %) of benzofuranol was achieved in the presence of [BMIm][AlCl 4 ] IL as catalyst at 418 K after 4 h. Furthermore, the catalyst is readily separated from the resultant products via decantation and could be reused after treatment in vacuum.

Swelling behaviour of poly(N-vinylcaprolactam) (PVC) and poly(N-vinylcaprolactam-co-itaconic acid) (P(VC-co-IA)) gels was investigated in different solvents (water, ethanol, methanol, isopropyl alcohol (IPA), chloroform, toluene, acetone) and in binary solvent mixtures (ethanol/chloroform, ethanol/methanol, IPA/chloroform, ethanol/water, IPA/water). Gels were synthesised in ethanol by the free radical cross-linking polymerisation method at 60°C for 24 h in the presence of azobis( isobutyronitrile) and allyl methacrylate as the initiator and cross-linker, respectively. And also, ethanol/distilled water mixture (φ r = 4 : 1) was used as the synthesis medium to determine its effect on the swelling of gels. It was found that the presence of water in the synthesis medium significantly affected the equilibrium swelling value (ESV) and the swelling tendency of gels both in solvents and in solvent mixtures. All gels synthesised in ethanol showed the highest swelling in chloroform. The gels synthesised in the ethanol/water mixture displayed different swelling behaviour. In this case, while chloroform was still valid for maximum swelling of PVC, P(VC-co-IA) had the highest swelling in methanol. Solubility parameters of gels were predicted by the van Krevelen-Hoftyzer (VKH) and Hoy methods (group contribution methods) and theoretical calculations verified the experimental swelling order.

Thermophysical properties, such as density (ρ), refractive index (n D ), and viscosity (η) of the binary systems of ionic liquids (ILs) [C n mim]Cl (C n mim = 1-alkyl-3-methylimidazolium; n = 2, 4) and three dipolar aprotic solvents (NMP (N-methyl-2-pyrrolidinone), DMI (1,3-dimethyl- 2-imidazolidinone), and DMPU (1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone)) were measured based on the solubility of ILs in the molecular solvents at temperatures from 288.15 K to 318.15 K and the pressure of p = 0.1 MPa. Moreover, intermolecular interactions, such as weak hydrogen bonding and Coulomb forces, were discussed based on the determined properties.

A case study of the robust model-based predictive control (MPC) of an exothermic continuous stirred tank reactor (CSTR) with uncertain parameters is presented. Three robust MPC approaches are considered and the simulation results are compared in terms of quality of control performance and total consumption of coolant. The results reveal the main benefits of the considered approaches and confirm that the robust MPC can bring about a reduction in consumption of the coolant.