Volume 70, Issue 4

The mitigation of oxidative degradation under γ -irradiation promoted by eight commercial antioxidants: Ethanox 330, Hostanox O3, Irganox 1010, Topanol OC, Ionox 220, Santonox R, Santowhite, Cyanox 2246 loaded onto ethylene–propylene terpolymer at the concentration of 0.5 phr in respect of a pristine polymer was studied. The polymer samples were exposed to various doses up to 500 kGy. The kinetic parameters of oxidations: oxidation induction times, onset oxidation temperature, oxidation rates were evaluated by CL measurements. They validated the differences in the stabilisation activities by limitation of the oxidation gradient. The high efficiency of some of the antioxidants studied, such as Ionox 220 and Santowhite, ensured the delay in degradation even at a high irradiation dose (500 kGy). For the environments with γ -radiation exposure, a relevant sequence in the increasing protection efficiency could be established: Topanol OC; Hostanox 03; Irganox 1010; Cyanox 2246; Santonox R; Ionox 220; Santowhite. The FT-IR spectra were recorded for the calculation of the radiochemical yields resulting from the modifications occuring in the concentrations of oxygenated structures. The accumulations of hydroxyl- and carbonyl-containing products were calculated to evaluate the irradiation effects in EPDM-based products during a severe accident. The options for EPDM stabilisation are discussed based on chemiluminescence and FTIR analyses.

In the present paper, multi-element characterisation of 26 bagged teas was carried out using inductively-coupled plasma atomic emission spectrometry. Na, K, Ca and Mg were the metals with major contents. Among the essential elements, Fe and Zn were the most abundant, followed by Se, Cu, Mo and Cr. The tea bag samples also contained significant contents of Mn and Al. The chemometric techniques of linear correlation analysis, principal component analysis (PCA) and cluster analysis (CA) were used for differentiation of the tea bag samples according to their metal content. The samples analysed were classified into four groups by PCA and CA. The first group includes hibiscus, nettle, mint, rtanj tea, thyme, bearberry and sage. Green and black teas are in the second group. The third group contains strawberry, lime, pineapple, pomegranate, elder, blueberry, milfoil, apricot and chamomile. Exotic fruits, sweet cherry, forest fruits, apple, St John’s wort, rose hips, cherry and raspberry are in the fourth group.

Constant increase of carbon dioxide emissions from anthropogenic activities leads to the search of options for its recycling and utilization. Although recycled CO 2 utilization as a raw material for the production of chemicals and propellants can be challenging, it is the most sustainable way to mitigate its emissions. Among the most promising applications of CO 2 is its catalytic fixation with hydrogen via the methanation reaction to methane. CO 2 methanation, depending on the used catalyst and overall reaction conditions, can proceed through different mechanism or pathways. A literature review on the methanation reaction mechanism shows that CO 2 can be converted to methane either by direct methanation or through the formation of a CO intermediate. This article analyses the proposed reaction mechanisms of CO 2 methanation.

In this work vertical dual-array tubular coil baffles arranged in groups of four, six or eight were investigated and the results compared with those from four planar baffles. The baffle coefficients for a single phase, along with the power consumption and gas hold-up in the gas–liquid phase of a system with the various baffle configurations for single and triple Rushton turbines are presented. Measurements were carried out using a dish-bottom vessel with an inner diameter of 0.29 m. Two ambient-temperature media were used as the liquid phase, namely, tap water and a 0.5 M Na 2 SO 4 aqueous solution, representing coalescent and non-coalescent liquids, respectively. The results of the single-phase experiment revealed the coil baffles to have lower power numbers; when the baffle coefficient is ≥ 0.12, the mixing efficiency is the same as that for four planar baffles. The power consumption experiment using the gas–liquid phase showed that installing coil baffles prevented a large power draw in all types of media. In addition, the power draw characteristics are affected by the media. It was found that, because of the low K B number, flooding occurred more readily with coil baffles than with planar baffles. Gas–liquid dispersion experiments in an air–water system indicated that, at a low gas flow-rate, the gas hold-up values of the coil baffles were almost 60 % higher than those of the conventional four baffles. However, this phenomenon was not observed in the Na 2 SO 4 aqueous solution because of the existence of dead zones in viscous liquids. Finally, all the data from the power consumption and gas hold-up experiments on the gas–liquid phase were correlated.

The matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF) and micellar electrokinetic chromatography (MEKC) methods were used to identify and quantify five tannins, (+)-catechin, (–)-epigallocatechin, (–)-epigallocatechin gallate, (–)-epicatechin gallate and (–)-epicatechin, from aqueous, ethanolic and acetonic extracts of Calendula officinalis, Hypericum, perforatum, Galium verum and Origanum vulgare . The MALDI-TOF technique was used for screening tannins monomers and oligomers in plant extracts. The sandwich method and matrix 2,5-dihydroxybenzoic acid with a concentration of 10 mg mL –1 in acetonitrile/ultrapure water/trifluoroacetic acid (20 : 80 : 0.1, vol.) were used. The electrophoretic method developed for the separation and quantification of 5 catechins in 15 min exhibited good efficiency and precision, low limits of detection (0.0032–0.0153 μg mL –1 ) and quantification (0.0096–0.0466 μg mL –1 ). The correlation coefficients ( R 2 ) exceeded 0.9986 and the recovery values ranged between 94.25 % and 102.50 %. The present work provides new information on some of the less studied compounds present in plants frequently used in traditional medicine.

Ruthenium, rhodium and platinum are the most expensive of noble metals. As their natural sources are limited, it is important to develop an effective process for recovering Rh, Ru and Pt from waste sources. Their main suppliers are the following industries: chemical (spent catalysts), automotive, jewellery, dental and petrochemical. This paper presents studies on the extraction of Rh(III), Ru(III) and Pt(IV) from model aqueous chloride solutions using trihexyl(tetradecyl)phosphonium bromide (Cyphos IL 102). The effects of different parameters such as the influence of shaking time, HCl and NaCl concentrations in the feed solutions and also Cyphos IL 102 concentration in the organic phase, on the extraction of these metal ions were investigated. Additionally, the effect of the ageing of Rh(III) and Ru(III) chloride solutions on the extraction of these metal ions was studied.

To achieve highly sensitive nonenzymatic detection of H 2 O 2 , a novel electrochemical sensor based on Fe 3 O 4 –Ag nanocomposites was developed. Nanocomposites were synthesized by reducing [Ag(NH 3 ) 2 ] + at the gas/liquid interface in the presence of silver seeds and confirmed by transmission electron microscopy and X-ray diffractometry. Electrochemical investigations indicate that the sensor is able to detect H 2 O 2 within a wide linear range of 0.5 μM to 4.0 mM, sensitivity of 135.4 μA mM −1 cm −2 and low detection limit of 0.2 μM ( S / N = 3). Additionally, the sensor exhibits good anti–interference ability, stability and repeatability. These results show that the Fe 3 O 4 –Ag nanocomposite is a promising electrocatalytic material for sensors construction.

This comparative study focused on the different methods used for the treatment of model waste water polluted with the chlorinated acid dye Mordant Blue 9. Low-cost and commercially available ionic liquids – benzalkonium chloride and Aliquat 336 – were applied as liquid ion-exchangers to precipitate the Mordant Blue 9 by way of ion pair formation between the bulky ammonium cations of ionic liquids and anions of the above dye. The decolorisation efficiency of the ionic liquid application and the effect on reduction of the absorbance, adsorbable organic halogens, chemical oxygen demand and biological oxygen demand were compared with the conventional coagulation, sorption and Fenton oxidation techniques.

A series of novel cross-linkers, N -hydroxysuccinimide (NHS)-activated end-bit binary acid (NHS- C 4 , C 5 , C 6 , C 8 , C 10 , C 14 ), were synthesised to modify gelatin films and the crosslinking effects were compared. Homogeneous films with the exception of the film crosslinked by NHS-C 14 were observed and the thickness was measured using a scanning electron microscope. The section feature influenced by different film-treatment conditions was also recorded. The differential scanning calorimetry results indicated higher thermal stability. The water contact angles confirmed enhanced hydrophobicity. NHS-C 6 , which was used as a probe crosslinker, exhibited the best crosslinking effect that the content of the free -NH 2 achieved was the lowest out of all the crosslinkers. The biodegradation results of gelatin films modified by NHS-C 6 exhibited better degradation-resistance and excellent stability. In addition, the optimal experimental conditions were 45°C for 12 h when [NHS-C 6 ]/[-NH2] = 2.5.

A novel silica-bonded propyl- N -sulfamic acid nanocatalyst (NHSO 3 H-KIT-5) supported on modified silica mesopore KIT-5 as an organic-inorganic hybrid with high specific surface area was successfully prepared. The 3-aminopropyltriethoxysilane (APTES) on KIT-5 was reacted with chlorosulfonic acid and accurately characterized by the FT-IR, XRD, SEM, EDAXS, and TGA techniques. This heterogeneous and recyclable catalyst catalyzed one pot, multicomponent condensation of benzil, aromatic aldehydes, and ammonium acetate in the presences of 0.05 g of nanocatalyst under solvent-free conditions to afford triaryl-imidazoles in excellent yields. This catalyst showed high catalytic activity under green conditions. This reaction was performed under open air conditions and required no special reaction conditions or chromatographic separation for purification.

Transport characteristics such as volumetric mass transfer coefficients, k L a , power input, P , gas hold-up, φ , and mixing time, t m , are the key parameters in the design of mechanically agitated gas– liquid contactors. For their successful design, values of the key parameters can be estimated using empirical correlations. Power input in this case is very often used as the scale of energy dissipation for other characteristics. Our goal was to propose reliable power input correlations for viscous batch processes, which are widely used in industry. The measurements were carried out in a pilot-plant vessel and also results from a laboratory vessel were used to develop the correlations. Different types of impellers and their combinations were used, including radial, axial, and combined liquid flow impellers. The power input was measured in a multiple-impeller vessel at different impeller frequencies and several gas flow rates. Correlation equations describing the behavior of particular impellers were evaluated. In addition, separate correlations for the bottom and upper sections in the multiple-impeller vessel were presented. These correlations can be used for impeller power prediction in industrial scale vessels under a wide range of operational conditions.

Chiral products play an important role particularly in the field of medicinal chemistry, where it is known that enantiomers often have very different biological properties and effects. One of the most powerful tool to obtain a product as a single enantiomer is asymmetric catalysis. Recently, organocatalysis, i.e. the use of small organic molecules to catalyze enantioselective transformations, has emerged as a prominent field in asymmetric synthesis. In this work, the use of hydrogels as a support for a chiral imidazolidinone organocatalyst (MacMillan catalyst) and its application in the reduction of activated olefins mediated by the Hantzsch ester is reported for the first time. Results showed a good activity of hydrogels in respect to both yield and enantioselection.

A series of Cu-based catalysts were prepared and employed in the N -ethylation of ethylenediamine with ethanol in a fixed-bed reactor. Satisfying results were obtained using Cu–Zn–La/Al 2 O 3 as a catalyst. In addition, Cu–Zn–La/SiO 2 , Cu–Zn–La/Al 2 O 3 and Cu–Zn–La/HZSM-5 were characterized by the Brunauer–Emmett–Teller method (BET), H 2 - temperature program reduction (H 2 -TPR), X-ray diffraction (XRD), transmission electron microscopic measurements (TEM) and NH 3 -temperature programmed desorption (NH 3 -TPD) in order to investigate the influence of supports on their catalytic performance. It was found that both the BET surface area and the acidity of the support are key factors in the catalytic performance. Moreover, reaction parameters including temperature, hydrogen pressure and liquid hourly space velocity were optimized. Under optimal conditions, a 73.3 % conversion of ethylenediamine and a 71.2 % selectivity of N -ethylethylenediamine were achieved. Finally, the lifetime of the catalysts was evaluated and the reaction proceeded continuously for over 200 h.

Citrus peels are underutilized in the processing industry and are commonly considered as waste as their chemical composition varies. However, it is possible to recover some value-added products, one of them being essential oil, which is widely used in the food industry. Due to the current increase in global demand for citrus essential oils, it is necessary to implement processes directed to the maximum recovery of oil from waste peels. Numerous efforts have been made without achieving significant improvements in yields. In this work, enzymatic pretreatments of orange, lemon, and grapefruit peels were applied to achieve increased yields of essential oil extracted by hydro-distillation. In two of the sources it was possible to increase the essential oil yield from two to six times. Moreover, a significant amount of fermentable sugars which can be used in the production of certain other compounds of interest through fermentation was obtained.

Liquid flow in a tubular reactor with flat internal baffles of various widths was investigated. On the basis of the laser Doppler anemometry (LDA) measurements, the main flow parameters, i.e. the mean and fluctuating velocity components and turbulent kinetic energy (TKE) were determined. The investigations demonstrated that the insertion of baffles into a pipe and a change in their width caused a generation of liquid stream whirls, induced liquid recirculation loops and intensified the flow considerably. The results can be useful in describing turbulent flow in tubular reactors with baffles and in optimising their design.