Colloidal ChemistryKapillarchemie, eine Darstellung der Chemie der Kolloide und Verwandter Gebiete. Herbert Freundlich
TL;DR: The chapter concludes with a classification of oxidases and special reference to the sources, preparation, and characteristics of laccase, tyrosinase, aldehydase, and the purin oxidases.
Abstract: and the fermentable substances. To BERTRAND we owe the introduction into science of the term oxidase. The adoption of this general term was based upon the discovery and characteristics of laccase and tyrosinase. The chapter concludes with a classification of oxidases and special reference to the sources, preparation, and characteristics of laccase, tyrosinase, aldehydase, and the purin oxidases. The third chapter is devoted to the peroxidases and catalases. The weight of opinion is inclined to the conception that peroxidases are substances capable of forming unstable peroxids from hydrogen peroxid, by double decomposition or by combining directly with the hydrogen peroxid to form unstable holoxid
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23 Apr 2019
TL;DR: In this paper, the authors studied the dynamic processes that lead to the chloride-induced breakdown of passive films and found that the depassivation process initiates by local acidification of the electrolyte near the film surface, followed by iron dissolution into the electrolytes, and iron vacancy formation in the passive film.
Abstract: The passivity of iron in alkaline media enables the use of carbon steel as reinforcement in concrete, which makes up the majority of modern infrastructure. However, chlorides, mainly from deicing chemicals or marine salts, can break down the iron passive film and cause active corrosion. Despite recent advances in nanoscale characterization of iron passivity, significant gaps exist in our understanding of the dynamic processes that lead to the chloride-induced breakdown of passive films. In this study, chloride-induced depassivation of iron in pH 13.5 NaOH solution is studied using reactive force field molecular dynamics. The depassivation process initiates by local acidification of the electrolyte near the film surface, followed by iron dissolution into the electrolyte, and iron vacancy formation in the passive film. Chlorides do not penetrate the passive film, but mainly act as a catalyst for the formation of iron vacancies, which diffuse toward the metal/oxide interface, suggesting a depassivation mechanism consistent with the point-defect model.
43 citations
TL;DR: In this paper, a facile synthesis of magnetite/coir pith supported sodium alginate beads from naturally available waste materials was further employed for removal of malachite green dye from synthetic aqueous solution underaparametric optimized condition of the adsorption process.
Abstract: The present study deals with facile synthesis of magnetite/coir pith supported sodium alginate beads from naturally available waste materials which was further employed for removal of malachite green dye from synthetic aqueous solution underaparametric optimized condition of the adsorption process. Several operating parameters such as stirring speed (50–250 rpm), adsorbent weight (0.5–7 g/L), pH (2–9), temperature (35–55 °C), and initial malachite green dye concentration (50–250 mg/L) were used to study the adsorption in a batch operation. The central composite design approach of response surface methodology in design-expert software revealed maximum removal efficiency of malachite green at pH of 7; initial malachite green dye concentration of 150 mg/L; adsorbent weight of 3g and temperature of 35 °C which showed adsorption efficiency (>98%). Analysis of Variance (ANOVA) suggested the equation to be significant for the process with a greater impact of adsorbent weight and malachite green concentration rather than the other three contributing parameters. Extensive kinetic, isotherm, thermodynamic, and eco-toxicological studies were performed to understand the behavior and sustainability of the developed materials. Final observation assured the reusability of the processed beads and hence showed gigantic potential for implementation on industrial-scale evaluation for the treatment of wastewater.
13 citations
TL;DR: Clay mineral studies in the U.S.R., mainly since 1960, are summarized in this article, where electron diffrac- tion techniques especially have been developed and used extensively for simultaneous recording of DTA curves and other properties.
Abstract: Clay mineral studies in the U.S.S.R., mainly since 1960, are summarized. Electron diffrac- tion techniques especially have been developed and used extensively. Methods have been developed for simultaneous recording of DTA curves and other properties. Polytypism of phyllosilicates has been studied intensively by Zvyagin and others. Mucfi new information on the structure and morphol- ogy of halloysites has been obtained by electron-optical methods. Other clay minerals extensively studied include allophanes, kaolinites, chlorites ("donbassite" is preferred to "sudoite" for diocta- hedral varieties), alushtite (or tosudite), monothermite, and various zinc-bearing clays. Much attention has been given to physico-chemical and colloid-chemical properties. The natural occurrence and alteration of clays and clay minerals are described in weathering and oxidation zones, in soils, and in Recent and Ancient sediments. Primary clay minerals of hydrothermal origin are described.
12 citations
TL;DR: In this paper, the authors investigate the growth of calcium sulfate crystal systems across a non-miscible aqueous-organic (hexane or dodecane) interface.
Abstract: The calcium sulfate crystal system is of considerable fundamental and practical interest, consisting of the three hydrates, gypsum (CaSO4·2H2O), bassanite (CaSO4·0.5H2O), and anhydrite (CaSO4). Each has significant applications; however, synthesis of anhydrite via conventional aqueous methods requires elevated temperatures and therefore high energy costs. Herein, we investigate calcium sulfate crystal growth across a nonmiscible aqueous–organic (hexane or dodecane) interface. This process is visualized via in situ optical microscopy, which produces high magnification videos of the crystal growth process. The use of interferometry, Raman spectroscopy, and X-ray diffraction allows the full range of calcium sulfate morphologies and hydrates to be analyzed subsequently in considerable detail. In the case of dodecane, gypsum is the final product, but the use of hexane in an open (evaporating) system results in anhydrite crystals, via gypsum, at room temperature. A dissolution–precipitation mechanism between ne...
10 citations
TL;DR: In this paper, a two-scale model of ion transport through a layered membrane, with flows being driven by a pressure gradient and an external electrical field, is presented, and the cross-coupling kinetic coefficient is obtained in a form which does involves the ζ -potential among the data provided the surface current is negligible.
Abstract: By the two-scale homogenization approach we justify a two-scale model of ion transport through a layered membrane, with flows being driven by a pressure gradient and an external electrical field. By up-scaling, the electroosmotic flow equations in horizontal thin slits separated by thin solid layers are approximated by a homogenized system of macroscale equations in the form of the Poisson equation for induced vertical electrical field and Onsager's reciprocity relations between global fluxes (hydrodynamic and electric) and forces (horizontal pressure gradient and external electrical field). In addition, the two-scale approach provides macroscopic mobility coefficients in the Onsager relations. On this way, the cross-coupling kinetic coefficient is obtained in a form which does involves the ζ -potential among the data provided the surface current is negligible.
7 citations
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...We perform calculation assuming that, as in [31], the applied potential difference results in the water level difference ....
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