Volume 66, Issue 7

Solidified cryolite melts containing a known amount of Na2SO4 (0–713 mg kg−1 SO42−), Na2S, FeS, and CdS (0–400 mg kg−1 S2−) together with industrial electrolyte samples were tested for the content of sulphate and sulphide ions by ion chromatography. Added and analytically determined contents of sulphate and sulphide were compared and processed by means of linear regression analysis. It was found that the method of ion chromatography yields satisfying results (uncertainty below 1.1 %) and that it is especially suitable for the determination of low content of soluble sulphate or sulphide in solidified cryolite electrolytes. The method can be used for the estimation of insoluble sulphide content in cryolite melts as well. Results of industrial samples analysis showed that the content of sulphate and sulphide in the samples is influenced by their treatment before the analysis.

An interpretation of specific electron-donor-acceptor interactions between the adsorbent coating the walls of a capillary column and adsorbates from the groups of alicyclic and aromatic hydrocarbons is proposed. The adsorbent was based on silica the surface of which was modified with silane containing 3-benzylketoimine groups to improve its adsorption properties. The columns studied had walls coated with 3-benzylketoimine groups, and Cu(II) chloride complexes or with Ni(II) chloride complexes. The adsorbate-adsorbent interactions were interpreted on the basis of the Kovats retention index, specific retention volume, molecular retention index, and ΔM e values. The influence of particular elements of spatial structure and the positions of double bonds in the adsorbate molecule was evaluated on the modelling calculations based on the quantitative structure-retention relationships. The introduction of transition metal ions in the form of complexes into the adsorbents studied increased the strength of the interactions between the adsorption layer of the capillary column and the adsorbate molecules. The increased strength of the interactions was accompanied by increased selectivity of the columns with regard to a group of alicyclic and aromatic hydrocarbons. The analytical performance of the columns thus obtained was compared with that of a commercial column coated with the 100 % dimethyl polysiloxane phase.

Pepsin is widely used for the extraction of pepsin-solubilized collagens (PSC) from many resources. PSC-A and PSC-P were prepared from carp skin using 0.1 mol L−1 acetic acid and 0.02 mol L−1 Na2HPO4 (pH 7.2) as the dialysis solution, respectively. SDS-PAGE patterns showed PSC-A and PSC-P as type I collagens, as well as acid soluble collagen (ASC). When incubated at 40°C, no degradation was observed for ASC, but PSC-A and PSC-P were degraded into short peptides, showing lower stability than ASC. The results indicate that pepsin remaining in the PSCs resulted in their degradation, which was confirmed by the inhibition using pepstatin. This research revealed the behavior of the remaining pepsin in pepsin-solubilized collagens and an approach to the PSC stability improvement was proposed. Chromatography profiles showed that new PSC prepared by the improved method had almost the same stability as ASC.

In this work, the effects of elicitor concentration and elicitation day on the growth and asiaticoside production of centella cells were investigated. The results showed that 2-hydroxybenzoic acid from 50–200 μM and yeast extract from 2–5 g L−1 had different eliciting influences. The addition of 2-hydroxybenzoic acid and yeast extract to the cultures strongly enhanced asiaticoside production in centella cells. The increase in asiaticoside content induced by the addition of 100 μM of 2-hydroxybenzoic acid and 4 g L−1 of yeast extract at day 10 of inoculation was about 5- and 3.5-fold, respectively, as compared with that of the reference cells. In general, 2-hydroxybenzoic acid (abiotic elicitor) was more effective in enhancing asiaticoside biosynthesis than yeast extract (biotic elicitor).

Wood-decaying mushrooms can be applied for the pretreatment of lignocellulosic substrates such as leaves, hay and straw. The use of wood-decaying fungus Auricularia auricula-judae for the decomposition of sweet chestnut (Castanea sativa) leaves and hay is discussed in the proposed paper. Such pretreated substrate was employed in the anaerobic processes for biogas production. Comparison of pretreated and non-pretreated substrate revealed that an increase of 15 % in the biogas production can be achieved using the pretreated substrate. Composition of organic compounds in the sludge during the anaerobic process was identified by HPLC. The obtained results show that the utilization of pretreated leaves and hay leads to a gradual increase of the concentration of formic, acetic, and volatile fatty acids as well as to the formation of some aldehydes, ketones, and alcohols.

The batch styrene polymerization process presents transient and nonlinear temperature behavior. In this work, manual control and open loop experiments were carried out in order to build a process knowledge database. Initially, a cascade feedback control loop was implemented by manipulating the thyristor unit of the electrical heater in the thermal fluid tank. Aiming at the MPC development, algebraic equations of a neural network and its adjusted parameters were implemented in an electronic worksheet. Every five seconds, the worksheet was updated with measurements (reactor temperature, thermal fluid temperature and thyristor position) by means of the OLE for the Process Control protocol (OPC). The one-step-ahead temperature prediction was then employed in the objective function of the worksheet solver which used Visual Basic Applications programming. The manipulated variable action was then calculated and sent to the process. A hybrid controller (cascade feedback and MPC) outperformed the pure strategies since the time-integral performance indexes, IAE and ITAE, were reduced by around 22 % and 32 %, respectively. Methodology for the Model Predictive Control presented in this study was considered feasible because the solver of Microsoft Office Excel (2007) is very friendly, easy to understand and ready to implement using VBA.

The effect of purine (concentration range of 1.00 × 10−6–1.00 × 10−2 M) on the behavior of copper in a 0.5 M Na2SO4 solution (pH 7 and pH 9) was studied using the open circuit potential measurement, potentiodynamic polarization, and chronoamperometry. Potentiodynamic polarization shows that purine acts as a copper corrosion inhibitor in both alkaline and neutral sulfate solutions. The efficiency of inhibition increases as the purine concentration increases. Chronoamperometric results follow the same trend as the results of potentiodynamic polarization. The inhibition effect can also be observed visually by microscopic examination of the electrode surface. Purine is adsorbed on copper surface according to the Langmuir adsorption isotherm.

In this parametric study, the effects of coal and oxidiser type, air-to-fuel ratio, steam-to-fuel ratio, reactor temperature, and pressure on H2 and CO amounts at the gasifier output, H2/CO, and higher heating value of the syngas produced have been calculated using a coal gasification model. Model simulations have been performed to identify the optimum values which are assumed to be 100 % for both cold gas efficiency and carbon conversion efficiency in the gasification process. From this study, it may be observed that the moisture content of the coal type is of crucial importance for the air gasification process; the O2 content of similar coals (taking into consideration the moisture and H2 content) is of significant importance for the air gasification process. When compared with air gasification, air-steam gasification becomes a more effective coal gasification method. The optimum working condition for air-steam gasification is to carry out the process at one atmosphere. High gasifier temperatures are not needed for the air-steam gasification of coal.

Tungstate sulfuric acid (TSA) was prepared, characterized, and applied for direct synthesis of novel and known benzimidazoles through a condensation reaction of o-phenylenediamines with orthoesters under solvent-free conditions. TSA was characterized by powdered X-ray diffraction (XRD), X-ray fluorescence (XRF), and FTIR spectroscopy. This novel and eco-friendly method is very cheap and has many advantages such as excellent yields, recyclable and eco-friendly catalyst, and simple work-up procedure.

Through exploration of the electrophilic substitution reaction of 3-((2E,4E)-5-phenylpenta-2,4-dienoyl)-2-hydroxy-2,4,6-cycloheptatrien-1-one (3-((2E,4E)-5-phenylpenta-2,4-dienoyl)tropolone) with halogen and diazonium salts as well as the nucleophilic cyclisation reaction with hydroxylamine hydrochloride and substituted phenylhydrazine hydrochlorides by employing our reliable methods, we have synthesised a series of new (E,E)-1,3-diene-bearing troponoid-based compounds. All the newly synthesised molecules represent an issue of great interest, since the presence of conjugated 1,3-diene moiety can be developed further via other reactions.

In this paper, the reaction of aniline with ammonium persulphate and concentrated HCl was studied. As a result of our experimental studies, 2,4,6-trichlorophenylamine was identified as the main product. This shows that a high concentration of HCl does not favour oxidative polymerisation of phenylamine, even though the ammonium persulphate/HCl system is widely used in polyaniline synthesis. On the basis of the experimental data and density functional theory for reaction path modelling, we proposed a mechanism for oxidative chlorination of aniline. We assumed that this reaction proceeded in three cyclically repeated steps; protonation of aniline, formation of singlet ground state phenylnitrenium cation, and nucleophilic substitution. In order to confirm this mechanism, kinetic, thermochemical, and natural bond orbital population analyses were performed.