Volume 70, Issue 9

In recent years, plant extracts have become the focus of corrosion inhibitor research due to their low toxicity, easy availability and economical preparation. This review presents most of the recent contributions made to the application of plant extracts as corrosion inhibitors for steel in sulphuric acid, as well as in both hydrochloric acid and sulphuric acid. The constituents, properties, adsorption modes and inhibition mechanisms of these natural products are discussed. Evaluation methods and the factors that influence the corrosion-inhibition efficiency of plant extracts are also summarised.

This study details the use of two permanently positively charged mono-substituted β -cyclodextrin derivatives, 6 I -deoxy-6 I -( N ′, N ′, N ′, N ′, N ′-pentamethyl-ethylene-l,2-diammonio)-cyclomaltoheptose dichloride (PEMEDA- β -CD) and the newly synthesised 6 I -deoxy-6 I -( N , N , N ′, N ′, N ′-pentamethyl-propylene-1,3-diammonio)-cyclomaltoheptose (PEMPDA- β -CD) as chiral selectors in capillary electrophoresis. Cyclodextrin (CD) derivatives were tested as additives in various buffers at various pH values with the optional addition of an organic modifier. Fourteen anionogenic analytes were tested, including native amino acids, N-blocked amino acids and profens, which were detected using a UV-VIS detector at optimal wavelengths of 214 nm, 254 nm or 280 nm. A borate buffer (15 mmol L –1 ) at pH 9.5 without the addition of an organic modifier was chosen as a suitable background electrolyte. In addition, the effect of the concentration of the chiral selector on the separation and enantioseparation of selected analytes was monitored. The additions of cyclodextrin derivatives varied within the concentration range of 0.0-5.0 mmol L –1 . Both chiral selectors were suitable for the enantioseparation of N -Boc- d,l -tryptophan, which was already separated on the baseline at 0.5 mmol L –1 concentration of the chiral selector.

A suitable analytical method making possible the determination of Gd and other rare-earth elements in samples related to hospital waste water treatment was sought with regard to various aspects of the experiment aimed at monitoring the fate of Gd-based contrast agents in the aquatic environment. The discrepancies and pitfalls of the proposed methodology were considered, resulting in a functional experimental plan. The inductively coupled plasma mass spectrometry (ICP-MS) method was used for the determination of Gd and other rare earth elements in river and hospital waste water and algae Parachlorella kessleri cultured in laboratory experiments. The sample preparation of algae prior to analysis was optimised. The ICP-MS method was validated using a recovery study, sample blanks, reference materials, and comparison with the inductively coupled plasma optical emission spectrometry (ICP-OES) method. The ICP-MS method was confirmed as suitable for monitoring the biosorption/bioaccumulation of Gd in algae and for evaluating the Gd anomaly in hospital waste water and rivers of Eastern Bohemia. In the laboratory experiments, the bioconcentration factors were calculated (all in L kg −1 ) for algae cultured in inorganic Gd salt (about 1100), in waste water from a magnetic resonance workplace (2300) and in waste water from a hospital waste water treatment plant (4400). A positive Gd anomaly in waters from the river Elbe in the Eastern Bohemia region was found less pronounced in the areas unaffected than in the areas affected by waste waters from hospital.

Candida infections are becoming increasingly prevalent and many clinical isolates are resistant to common azole derivatives treatment. Accordingly, the capacity of a series of 19 alkyl glycosides, mainly mannosides and glucosides but also a cellobioside with aglycone chain-length from C-6 to C-20, to inhibit the growth of laboratory and clinically isolated strains of Candida albicans , was investigated. The study showed that only glycosides with the C-10 and C-12 aglycones were effective growth inhibitors of both types of Candida strains, whose metabolic activity was also significantly reduced as revealed by an XTT assay.

Corn stalk-based adsorbents modified from corn stalk were prepared by Cu(0)-mediated reversible-deactivation radical polymerization (Cu(0)-mediated RDRP). They were applied to remove metal ions and they exhibited good adsorption capacity, especially for Hg(II). Adsorption properties of corn stalk can be enhanced by introducing cyano, amino, amidoxime, and carboxyl groups onto its surface, which results in efficient adsorbents for different metal ions. TGA, SEM, EA, and FTIR analyses were employed to characterize the structures of corn stalk- graft -polyacrylonitrile (CS- g -PAN), corn stalk- graft -polyacrylamide (CS- g -PAM), amidoxime corn stalk- graft -polyacrylonitrile (AO CS- g -PAN) and carboxyl corn stalk- graft -poly(methyl acrylate) (CO CS- g -PMA). The maximum adsorption capacity for Hg(II) was 8.06 mmol g −1 of AO CS- g -PAN. Kinetics of the Hg(II) adsorption on AO CS- g -PAN was found to follow the pseudo-second-order model and the adsorption isotherms were well fitted with the Freundlich isotherm model.

In this study, the treatability of metal-plating waste water by modified direct contact membrane distillation (DCMD) at different temperature differences (∆ T = 30°C, 40°C, 50°C, and 55°C was investigated. Two different hydrophobic membranes made of poly(tetrafluoroethylene) (PTFE) and poly(vinylidene fluoride) (PVDF) having different pore sizes (0.22 μm and 0.45 μm) were used. The results indicated that conductivity, COD, sulphate, copper, and nickel could be successfully removed by modified DCMD. The rejection efficiencies for conductivity, COD, and sulphate were 99 %, 86 %, and 99 %, respectively. Copper rejection was effective with both membranes while nickel concentration was below the limit of detection in the effluent. It was found that the pollutant rejection efficiency was affected by the raw water characteristics, membrane properties, and influent heating temperatures. In addition to the water quality parameters, the flux was measured to evaluate membrane performance. A high flux was obtained at 65°C (∆ T = 55°C) with 0.45 μm pore size PTFE membrane (24.1 L m −2 h −1 ) and with PVDF membrane (17.1 L m −2 h −1 ). The flux was mainly affected by temperature and membrane properties. As a result, modified DCMD and all the membranes used in this study were effective for the treatment of metal-plating waste water.

The influence of water pH and cationic surfactant content on the interfacial properties and stability of an Algerian bitumen aqueous emulsion were investigated. While the stability was quantified by both the test-bottle method and size distribution measurements, the interfacial properties of the water–bitumen interface were assessed using interfacial tension measurements. Optical microscopy was also used to visualise the dispersed water droplets in the oil phase. The results showed that addition of the cationic surfactant at a concentration of 25 mmol L −1 in acidic water (pH 2) improves the bitumen emulsion stability and effectively decreases the interfacial tension.

Two Schiff base derivatives, 4-(2-amino-3-pyridyliminomethyl)phenol ( I ) and 3-(2-amino-3- pyridyliminomethyl)nitrobenzene (II ), were synthesised and characterised by spectroscopy. The structure of I was determined by single crystal X-ray diffraction studies. The asymmetric Schiff base derived from 2,3-diaminopyridine selectively recognise transition and heavy metal cations, and some anion. Ligands I and II form stable complexes with Cu 2+ , Zn 2+ , Pb 2+ , Al 3+ whereas ligand I also binds F − ions. The stoichiometry for the host : cation is 1 : 1 and 2 : 1. The addition of F − ion in CH 3 CN to ligand I causes a colour change of the solution from colourless to yellow. The binding behaviour of ligand I towards several ions was investigated using density functional theory calculations.

Six quaternary ammonium salts were designed and synthesised with moderate to high yields in three steps, based on cardanol, a low-cost and abundant renewable resource. The new ammonium salts can act as reactive surfactants due to their having both a hydrophilic ammonium group and a hydrophobic unsaturated alkyl chain. The gemini surfactants with a linker of a linear saturated aliphatic hydrocarbon chain exhibited a relatively low CMC value(≤ 0.2 mmol L −1 ) and surface tension (≤ 27 mN m −1 ), signifying that this kind of amphiphile exhibited good surface active properties. The photo-active gemini surfactant with critical micelle concentration (CMC)of 0.05mmolL −1 was used successfully as the sole emulsifier in the emulsion polymerization of methyl methacrylate (MMA).In addition, abenzyl bromide-containing surfactant can act as both an atom transfer radical polymerization (ATRP) initiator and an emulsifier in an activator generated by the electron transfer atom transfer radical polymerization (AGET ATRP) of MMA in emulsion. The value of the number-average molecular mass of the resulting cardanol-endpoly (methyl methacrylate) (PMMA) is M n, GPC = 45.1 kDa, with polydispersity of 1.39.

The electrochemically mediated atom transfer radical polymerisation ( e ATRP) of n-butyl acrylate was investigated under a variety of catalyst concentrations. Poly( n -butyl acry late)- block- polyurethane-block-poly ( n -butyl acrylate) copolymers were prepared via electrochemically mediated atom transfer radical polymerisation ( e ATRP) using only 7 × 10 –6 mole % of Cu II complex. The successful chain extension and formation of penta-block copolymers confirmed the living nature of the poly(alkyl acrylates) prepared by e ATRP. In this work, the tri-block and penta-block urethane-acrylate copolymers were synthesised for the first time by using tertiary bromine-terminated polyurethane macro-initiators as transitional products reacting with n -butyl acrylate, and subsequently with tert -butyl acrylate in the presence of the Cu II Br 2 /TPMA catalyst complex. The results of 1 H NMR spectral studies support the formation of tri-block poly ( n -butyl acrylate)- block -polyurethane- block -poly( n -butyl acrylate) copolymers, and penta-block poly( tert -butyl acrylate)- block -poly ( n -butyl acry late)- block -polyurethane- block -poly ( n -butyl acrylate)- block- poly( tert -butyl acrylate) copolymers.

Diazene sulphonates are readily available compounds which are soluble in water and polar solvents. They strongly absorb the UV-VIS light and they decompose under UV irradiation via radical or ionic intermediates. These properties render them valuable, e.g. for analytical purposes and for photo-printing. In this presentation, it will be demonstrated that polymers with a pendant diazene sulphonate function as cross-linking agents and with pendant aromatic amines as hole-transporters can be considered as useful materials for organic light-emitting device (OLED) technology.

Kaolinite is a suitable material for fixing TiO 2 nanoparticles in a composite form. The kaolinite/TiO 2 composite has promising photoactive properties which are as important as is the possible impact of the composite on the environment. Accordingly, the stability of the kaolinite/TiO 2 composite dried at 105°C (KTI1) and calcined at 600°C (KTI6) and the stability of the original kaolinite treated at various temperatures (105–800°C) were studied by the leaching test in accordance with European standard BS EN 12457-2:2002 (British Standards Institution, 2002). The stability was evaluated on the basis of elements leached from the materials to extraction agents. Atomic emission spectrometry with inductively coupled plasma was used for determining the concentration of elements. In order to better understand the process of calcination and the structure changes in the kaolinite/TiO 2 composite and calcined kaolinite, the materials were evaluated using X-ray powder diffraction and infrared spectroscopy with Fourier transformation. The processes of kaolinite dehydroxylation and metakaolinite formation were observed. Kaolinite is an appropriate carrier for composite preparation due to its stability even after its treatment at high temperatures. The experiments confirmed the TiO 2 nanoparticles to be very strongly bound to the kaolinite surface. On the other hand, the experiments demonstrated that the presence of TiO 2 on the kaolinite surface caused the release of Al in high concentrations to the final extracts, especially after kaolinite/TiO 2 composite calcination.

Biocompatible polymer sponge materials based on biodegradable natural polymer chitosan, which can be loaded with clinician-selected drugs are still in the centre of interest for their wide use in clinical practice. This study shows possibilities of the technology which combines simple addition of β-cyclodextrin (β-CD), with dialdehyde starch (DAS) as a cross-linking agent of chitosan, to chitosan solutions for subsequent formation of sponge matrix. The advantage of such system is in avoiding chemical modifications and working only with natural substances. It is shown that, in matrix formation during lyophilisation, β-CD molecules tend to accumulate on the surface of the porous matrix structure. This was confirmed by a study of the known inclusion complex of β-CD and salicylic acid (SA) in heptane. The same study was applied to berberine (BER) which can also form an inclusion complex with β-CD in a water solution. Moreover, adsorption of drugs on the surface of the porous structure has to be also taken into account. This enables the production of sponge topical medical preparations useful for sustained release of BER.

The paper is aimed on the investigation of natural ageing of plasticized poly(lactic acid)/poly( β- hydroxybutyrate) PLA/PHB blend films during their one-season application as mulches under real field conditions in the western part of Slovakia. Acetyl tributyl citrate (ATBC) was used as the plasticizer. The analysis was performed on three differently exposed parts of the foil: i) buried in soil, ii) exposed to sunlight, and iii) shadowed by plants. In parallel, UV irradiation of the blend under laboratory controlled conditions (constant temperature of 30°C and relative humidity of 55 %) was carried out. The degradation effect was followed by changes in the molar mass, chemical and crystalline structures, as well as in thermal and mechanical properties. The ternary PLA/PHB/ATBC blend lost its tensile properties faster when buried in soil than when exposed to sunlight. This result is in agreement with the data obtained for the UV-irradiated materials. Young’s modulus values showed a significant mechanical degradation under the UV irradiation as well as during natural ageing. The study was also focused on the influence of mulches on the yield and quality of sweet pepper production, characterized by carotenoids and vitamin C content.

A series of 2-amino-4 H -benzo[ h ]chromene and 2,7-diamino-4 H -benzo[ h ]chromene derivatives were prepared as potential cytotoxic agents. The structures of the synthesised compounds were established on the basis of spectral data. The in-vitro cytotoxic activity of the synthesised compounds against the cell lines MCF-7, HCT-116 and HepG-2 was investigated in comparison with vinblastine and colchicine, using an MTT colorimetric assay. The structure-activity relationship of 4 H -benzo[ h ]chromenes with modification at the 3-, 4- and 7-positions was explored. The results of the anti-tumour evaluation revealed that compounds VIIIc, VIId, VIIb, VIIe, VIIIg and VIIIc, VIId , VIIb, VIIe, VIIIg, VIIc, VIIIe, Vf, IIIa inhibited the growth of MCF-7 in comparison with vinblastine and colchicine, while VIIb, VIId, VIIe, IIIa, VIIa, VIIIc, VIIc, IIId, IIIg, IIIf, IIIb, IIIh, VIIIb , VIIIa, VIIIe, IIIc, Vg, IIIe, VIIIg, Vf, IIIf inhibited the growth of HCT-116 in comparison with colchicine. In addition, compounds VIIe, IIIg, IIIa, VIIc and VIIe, IIIg, IIIa, VIIc, VIIb, VIIa, VIIIf , VIIIe inhibited the growth of HepG-2 in comparison with vinblastine and colchicine, respectively.

Lactic acid is recognised as a biocompatible medium for the chemoselective synthesis of the 1,2-disubstituted benzimidazole scaffold via a direct one-pot cyclocondensation of o -phenylenediamine with aldehydes. Various 1,2-disubstituted benzimidazole derivatives were successfully synthesised with high selectivity with good to excellent yields without any additional catalyst or additive. Most products could be isolated by a simple filtration after completion of the reactions. Satisfactory results were also obtained from multi-gram scale reactions.

Electron beam (EB) irradiated wool was examined for sorption of chromic ions. Sorption increased with the adsorbed dose non-monotonously, which is a result of the generation of S-oxidized groups, secondary structure variation, and the breaking of the keratin backbone. For a dose of 400 kGy, an increase by 120 % was observed at the cystine dioxide and cysteine acid amounts. Examining sorption of unexposed wool and that irradiated with doses of 25 kGy and 40 kGy for basic, methylene blue (MB), or acidic, pyrogallol red (PR) dyes revealed that such low doses have no effect on the carboxylic or amino groups of keratin. Sorption of MB is independent of the EB treatment and is identical for both samples due to the interaction of MB amino groups with the carboxylic groups of wool; however, the sorption capacity for PR is a function of the EB treatment. The sample irradiated with the dose of 25 kGy showed higher PR sorption than that with the EB dose of 40 kGy, which was equal to that of unexposed wool. While the 25 kGy sample provided more active sites for PR interaction compared with the unexposed one, the 40 kGy sample contained already enough active sites to generate intra- and intermolecular interactions inside wool. Thus, PR adherence to the 40 kGy sample was restricted and comparable to the level of unexposed wool.