Effect of solution pH on the stability of mixed silica -alumina suspension in the presence of polyacrylic acid (PAA) with different molecular weights

The influence of solution pH (in the range 3–9) on mixed silica-alumina suspension in the absence and presence of polyacrylic acid (PAA) was studied. The composition of the adsorbent was SiO₂ (97%) and Al₂O₃ (3%). The turbidimetry method was applied to record changes in the stability of the investigated systems as a function of time. It was shown that the suspension without the polymer is less stable at pH 3, whereas at pH 6 and 9, the systems were stable. PAA with molecular weights 100 000 and 240 000 at pH 3 (improvement of system stability conditions) and PAA 2 000 at pH 6 (deterioration of suspension stability) have a great effect on the silica-alumina suspension stability. The stabilization-flocculation properties of polyacrylic acid are a result of a specific conformation of its chains on the solid surface where it depends on the solution pH and the polymer molecular weight.     

An elementary proof of the Loomis–Whitney theorem

Loomis and Whitney proved an inequality between volume and areas of projections of an open set in n-dimensional space related to the isoperimetric inequality. They reduced the problem to a combinatorial theorem proved by a repeated use of Hölder inequality. In this paper we prove a general inequality between real numbers which easily implies the combinatorial theorem of Loomis and Whitney.

     

Chromatographic separation of prebiotic oligosaccharides. Case study: separation of galacto-oligosaccharides on a cation exchanger

Chromatographic separation of prebiotic oligosaccharides, galacto-oligosaccharides from a typical post-reaction mixture containing unreacted substrate lactose and by-products glucose and galactose was investigated. A commercial cation-exchange resin Dowex 50WX4 was chosen as a prospective preparative-scale adsorbent and separation performance of its four ionic forms, H⁺, Na⁺, K⁺ and Ca²⁺, was tested. Since adsorption equilibrium isotherms were linear within the entire investigated range of concentrations, they were determined by pulse experiments for all saccharides present in a typical post reaction mixture including tri- and tetragalacto-oligosaccharides. From the four counter ions listed above, hydrogen offered the best selectivity and column performance. The selected H⁺-form of the cation exchanger was further investigated by means of frontal analysis where high ionic strength and elevated viscosity appear and can play a substantial role. Breakthrough curves were measured for monosaccharides, lactose, glucose–lactose mixture and a multicomponent commercial mixture of galacto-oligosaccharides, Vivinal^® GOS. The breakthrough curves were successfully described by the dispersive plug flow model with linear driving force approximation.     

Paramagnetic centres in exinite, vitrinite and inertinite

Exinite, vitrinite and inertinite from durain, vitrain and clarain of Polish medium-rank coal with 85.6% C were investigated by X-band (9.3 GHz) electron paramagnetic resonance spectroscopy. Multicomponent structure of the EPR spectra of these macérais was analysed. The number of component lines, their lineshapes and parameters: linewidths andg factors, were determined. Total concentrations and concentrations of paramagnetic centres responsible for the component lines were measured. The broad Gaussian, broad Lorentzian and narrow Lorentzian lines were observed in the experimental spectra of exinite and vitrinite. The EPR spectra of inertinite are superposition of two narrow Lorentzian lines with different linewidths. The evolution of paramagnetic centres during heating of the macerais at 300–650°C was studied. Paramagnetic centres with broad Lorentzian lines are the most active ones in the thermal decomposition. The EPR results indicate reactions between individual macerais during thermal decomposition of coal. Thermally excited multiplet states were found in exinite and vitrinite.     

Calculation of kinetic parameters from TG curve on the base of dehydration process of hydrous titanium dioxide

A direct method of evaluating of kinetic equation parameters based on TG curve is proposed. The method was applied to calculate kinetic parameters of the process of dehydration of hydrous titanium dioxide.

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Zusammenfassung Es wird ein direktes Verfahren zur Bestimmung der Parameter der kinetischen Gleichung auf der Basis von TG-Kurven gegeben. Das Verfahren wurde zur Berechnung der kinetischen Parameter des Dehydratationsprozesses von wasserhaltigem Titandioxid benutzt.

     

Die optimale Anordnung von Gütern in Vorratslägern mit Hilfe der Mehrdimensionalen Skalierung

Zusammenfassung In dem Beitrag wird ein Verfahren zur Lösung innerbetrieblicher Standortprobleme vorgestellt, das sich sowohl methodisch als auch hinsichtlich seiner universellen Anwendbarkeit von bisher bekannten Verfahren abhebt. Die Platzzuweisung erfolgt auf das Basis empirisch ermittelter Verbundintensitäten, die mit Hilfe eines Verfahrens der nichtmetrischen mehrdimensionalen Skalierung (NMDS) auf ihre strukturellen Beziehungen hin untersucht werden. Es wird gezeigt, wie sich die NMDS-Lösung an räumliche Gegebenheiten anpassen läßt und wie das Verfahren zur Lösung eines konkreten Problems eingesetzt werden kann. Abschließend wird die Leistungsfähigkeit des Verfahrens im Vergleich zu einigen bekannten Heuristiken für verschiedene Problemgrößen überprüft.

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Summary The article presents an approach for solving plant-layout problems which differs from previously proposed heuristic techniques both with regard to the underlying methodology as well as its broad applicability. In the example chosen for demonstration the assignment of goods to locations in a warehouse is based on an operational definition of joint demand which allows the goods in question to be placed in a two- or three-dimensional space by a nonmetric multidimensional scaling procedure. It is shown how the resulting configuration can be modified in order to meet space restrictions. The article concludes with an experimental comparison of frequently cited heuristic techniques for solving analogous problems with up to 20 facilities to cope with.

     

Applications of uniform asymptotic regularity to fixed point theorems

In this paper, we show that there are no nontrivial surjective uniformly asymptotically regular mappings acting on a metric space, and we derive some consequences of this fact. In particular, we prove that a jointly continuous left amenable or left reversible semigroup generated by firmly nonexpansive mappings on a bounded \({\tau}\)-compact subset of a Banach space has a common fixed point, and we give a qualitative complement to the Markov–Kakutani theorem.     

Production of activated carbons from biodegradable waste materials as an alternative way of their utilisation

New carbonaceous adsorbents were prepared by means of direct, physical and chemical activation of corn cobs and cherry stones as well as coffee and tobacco industry waste materials. The effect of activation method on the textural parameters, acid-base character of the surface and sorption properties toward toxic gases of the materials obtained was tested. Depending on the precursor as well as method of preparation, the final products were micro/mesoporous activated carbons of surface area reaching to 1426 m²/g, showing largely different acid-base properties of the surface. The results obtained in our study have proved that a suitable choice of the activation procedure for industrial and agricultural biodegradable waste materials permits production of cheap carbonaceous adsorbents with very high sorption capacity towards nitrogen dioxide and hydrogen sulphide reaching to 83 mg NO₂/g_ads and 215 mg H₂S/g_ads, respectively.     

Phosphonium ionic liquids as extractants for recovery of ruthenium(III) from acidic aqueous solutions

The aim of this work is to investigate extraction of ruthenium(III) from acidic aqueous solutions with phosphonium ionic liquids such as trihexyl(tetradecyl)phosphonium chloride (Cyphos IL 101), trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate (Cyphos IL 104) and tributyl(tetradecyl)phosphonium chloride (Cyphos IL 167) as extractants. The influence of HCl content in the feed solutions on extraction of Ru(III) was investigated. The research was performed for model solutions containing Ru(III) and a mixture of waste solutions containing Ru(III) and Rh(III). In addition, investigation of the type of extractant and its concentration in the organic phase on extraction of Ru(III) was carried out. Co-extraction of protons to the organic phase was determined. To the best of our knowledge, the extraction of Ru(III) with Cyphos IL 167 (tributyl(tetradecyl)phosphonium chloride) as an extractant has not yet been described in the scientific literature.