The Experts below are selected from a list of 636 Experts worldwide ranked by ideXlab platform

Władysław Migdał - One of the best experts on this subject based on the ideXlab platform.

  • Separation technologies for metals recovery from industrial wastes
    Hydrometallurgy, 1997
    Co-Authors: Andrzej G. Chmielewski, T.s. Urbański, Władysław Migdał
    Abstract:

    Three hydrometallurgical processes for industrial wastes treatment are presented. The main separation techniques are: solvent extraction, leaching-precipitation, electro-oxidation, and ion exchange. Recovery of gold from solid wastes generated in the electronic and jewellery industries consists of thermal degradation, two-stage leaching with nitric Acid Solution to remove silver and other metals and then with aqua regia to dissolve gold, selective solvent extraction of gold with diethyl malonate, and reduction of gold from the organic phase. Vanadium recovery from residue ashes after burning heavy oil fractions consists of alkaline leaching of vanadium, filtration, neutralization of sodium vanadate Solution, precipitation of ammonium metavanadate, drying of the precipitate, and adsorption of the remaining vanadium from the filtrate on an anionite. From the remaining ashes nickel is recovered using Acidic leaching, filtration, precipitation of ammonium-nickelous sulphate, filtration, and drying. The third process concerns processing of electroplating sludges and waste waters containing chromium and copper. The waste waters are electro-oxidized to transform C&II> into chromate. Then metal cations are separated on a cationite. The purified electroplating baths are recycled directly to electroplating; other Solutions are first concentrated using anionite, followed by sodium chromate eluate conversion into concentrated Chromic Acid Solution. The sludges accumulated from waste water processing by hydroxide precipitation are re-dissolved in Chromic Acid Solution generated progressively by circulation between the dissolving and electro-oxidation steps. The concentrated Chromic Acid Solution obtained is purified on the cationite and recycled.

Pouria Payrow - One of the best experts on this subject based on the ideXlab platform.

  • Effect of surface treatment on the post-peak residual strength and toughness of polypropylene/polyethylene-blended fiber-reinforced concrete
    Journal of Composite Materials, 2011
    Co-Authors: Pouria Payrow, Michelle Nokken, D. Banu, Dorel Feldman
    Abstract:

    This study involved an experimental investigation into the improvement of mechanical properties of fiber-reinforced concrete (FRC) utilizing chemically treated polypropylene/polyethylene fibers. Four types of chemical surface treatments were examined: two types of Chromic Acid (Types B and C), potassium permanganate (PP), and hydrogen peroxide Solutions. Untreated and treated fibers were added at 0.32% by volume of concrete and also at 0.50% for the best treatment technique. Compressive and flexural strength were measured to quantify improvement. It was found that there were no significant differences in compressive strength. Type B Chromic Acid Solution was found to be the most effective technique in improving the flexural strength of FRC resulting in average increases of 8.9% and 17.6% for peak and residual strengths, respectively, compared to nontreated fibers. While not as effective as plasma treatments, further research may be warranted for chemical treatments. Surface wettability of the treated fibe...

  • Effect of Synthetic Fiber Surface Treatment on the Post-Crack Residual Strength and Toughness of Fiber Reinforced Concrete
    2008
    Co-Authors: Pouria Payrow
    Abstract:

    This research involves an experimental investigation into the improvement of bonding characteristics between a mixture of polyethylene/polypropylene fibers and concrete comparing various chemical and physical surface treatments and their effect on the mechanical properties of the fiber reinforced concrete (FRC). For the chemical surface treatment, several techniques of chemical etching of the fiber's surface were used, such as two types of Chromic Acid Solutions, potassium permanganate, and hydrogen peroxide Solutions. For the physical surface treatment, UV treatment and a combination of UV and Ozone treatment were used. Non-treated and treated fibers were added at 0.32% by volume and 0.50% for the best treatment method. Compressive, flexural strength and contact angle were measured to quantify bond improvement. Among the chemical treatment techniques, Chromic Acid Solution type B was found to be the most efficient technique versus potassium permanganate which had negative effect on the bonding strength between fibers and concrete. Investigations of physical treatment techniques showed using UV does not have a significant change on the bonding strength, but 10 minute exposure of fibers to the UV lamp in presence of ozone gave the best result in bonding of fibers. As a cumulative result, using the chemical treatment was found to be a more efficient technique rather than the physical treatment in surface modification of fibers. The contact angle was found to have no correlation to the toughness. The higher volume of fibers gave better properties than the surface treatment techniques indicating surface treatment may not be an economical alternative.

Andrzej G. Chmielewski - One of the best experts on this subject based on the ideXlab platform.

  • Separation technologies for metals recovery from industrial wastes
    Hydrometallurgy, 1997
    Co-Authors: Andrzej G. Chmielewski, T.s. Urbański, Władysław Migdał
    Abstract:

    Three hydrometallurgical processes for industrial wastes treatment are presented. The main separation techniques are: solvent extraction, leaching-precipitation, electro-oxidation, and ion exchange. Recovery of gold from solid wastes generated in the electronic and jewellery industries consists of thermal degradation, two-stage leaching with nitric Acid Solution to remove silver and other metals and then with aqua regia to dissolve gold, selective solvent extraction of gold with diethyl malonate, and reduction of gold from the organic phase. Vanadium recovery from residue ashes after burning heavy oil fractions consists of alkaline leaching of vanadium, filtration, neutralization of sodium vanadate Solution, precipitation of ammonium metavanadate, drying of the precipitate, and adsorption of the remaining vanadium from the filtrate on an anionite. From the remaining ashes nickel is recovered using Acidic leaching, filtration, precipitation of ammonium-nickelous sulphate, filtration, and drying. The third process concerns processing of electroplating sludges and waste waters containing chromium and copper. The waste waters are electro-oxidized to transform C&II> into chromate. Then metal cations are separated on a cationite. The purified electroplating baths are recycled directly to electroplating; other Solutions are first concentrated using anionite, followed by sodium chromate eluate conversion into concentrated Chromic Acid Solution. The sludges accumulated from waste water processing by hydroxide precipitation are re-dissolved in Chromic Acid Solution generated progressively by circulation between the dissolving and electro-oxidation steps. The concentrated Chromic Acid Solution obtained is purified on the cationite and recycled.

L.j.j. Janssen - One of the best experts on this subject based on the ideXlab platform.

  • Electrochemical regeneration of chrome etching Solution
    Journal of Applied Electrochemistry, 2002
    Co-Authors: Y. Van Andel, L.j.j. Janssen
    Abstract:

    A metal surface is chromatized with a Chromic Acid Solution to obtain a good adherence of polymer coatings. In this process Cr(VI) is reduced to Cr(III). The oxidation strength of the Solution decreases during use. The chrome Solution needs to be regenerated and purified. A new anode material, namely boron-doped diamond, was used to investigate the oxidation of Cr(III) to Cr(VI). It was found that the current efficiency for Cr(III) oxidation decreases with increasing total current density. The current density of Cr(III) oxidation increases linearly with increasing Cr(III) concentration and is practically independent of the Cr(VI) concentration. It was concluded that the diffusion of Cr(III) is the rate-determining step for the Cr(III) oxidation at Cr(III) concentrations form 40 to 160 mol m^−3. The surface of the boron-doped diamond shows no signs of chemical corrosion or mechanical destruction. A filter-press type cell divided into two compartments by a cation exchange membrane was proposed. A cost calculation was carried out for the oxidation of 1.28 mmol s^−1 Cr(III) in a 40 mol m^−3 chrome(III) Solution. Factors affecting the feasibility of this process include the costs of chemical waste disposal, the costs of Chromic Acid, government legislation and to a great extent the costs of the new anode material.

Shyang-ming Tseng - One of the best experts on this subject based on the ideXlab platform.

  • Surface characterization and platelet adhesion studies on polyethylene surface with hirudin immobilization
    Journal of Materials Science: Materials in Medicine, 2001
    Co-Authors: Jui-che Lin, Shyang-ming Tseng
    Abstract:

    Hirudin, a protein composed of 65 or 66 amino Acid, is a newly risen anticoagulant agent and has been considered as the most potent thrombin inhibitor. Hirudin can block the active site of thrombin by means of its carboxylic Acid reaction with the active regime of thrombin, and becomes a tightly bound complex, and thus controls the formation of thrombus. Hirudin was covalently immobilized onto the water-soluble carbodiimide preactivated and Chromic Acid oxidized PE surface. Surface chemistry analysis indicated that a certain amount of carboxylic Acid groups was generated on the polyethylene surface after oxidation with Chromic Acid Solution. The amount of carboxylic Acid functional group increased with the oxidation time. In addition, polyethylene surface was etched by Chromic Acid Solution, and a rougher surface was created. The morphology of oxidized polyethylene surface was similar to each other among the samples with oxidation time from 1 to 8 min. ESCA results indicated the number of hirudin molecules immobilized was constant at the reaction time studied. In vitro platelet adhesion assay indicated the number of adhered platelets on the oxidized polyethylene surface increased significantly after oxidation. In contrast, surface with hirudin immobilization showed a reduction in adhered platelet density than the Chromic Acid oxidized counterpart due to the decrease of platelet-activating capability by the hirudin–thrombin complex and the differences in the adsorbed protein composition. © 2001 Kluwer Academic Publishers