Showing papers on "Sodium chlorate published in 2001"

The use of sodium formate for the recovery of precious metals from acidic base metal effluents

Abstract: Zinc was used for the reduction of the platinum group metals (PGMs) in acidic effluents. Due to the increasing cost of zinc, sodium formate was investigated as an alternative reductant. In a base metal-containing acidic effluent, called diethylenetriamine barren, sodium formate was used to precipitate the PGMs. This effluent was the filtrate obtained after a precipitation procedure had been used to remove rhodium and iridium. It was found that pH 1.5 was the optimum starting pH for sodium formate reduction. The pH increased to approximately 4.5 after the addition of sodium formate. The optimum concentration of sodium formate was found to be 30 g dm−3 at a temperature of 100 °C where the process time was 6 h. Platinum and palladium were the most effectively reduced PGMs, both exhibiting an average precipitation efficiency of greater than 99%. Difficulty was experienced with the precipitation of iridium (average precipitation efficiency of 76%). The precipitated PGMs readily dissolved in hydrochloric acid (6 M) and sodium chlorate (2%). A reduction in costs resulted from the discontinuation of the use of zinc for reduction purposes. An additional advantage was that zinc was no longer introduced into the PGM refinery circuits. © 2001 Society of Chemical Industry

Method for making anhydrous sodium perchlorate

Abstract: The invention concerns a method for making anhydrous sodium perchlorate whereby an aqueous sodium perchlorate solution, directly derived from electrolysis of an aqueous sodium chlorate solution, is subjected to vacuum evaporation. The invention also concerns anhydrous sodium perchlorate crystals which preserve good pourability and methods for making them.

Oxidation of Alcohols with Benzyltriphenylphosphonium Chlorate Under Non-Aqueous Conditions

Abstract: Oxidation of benzylic alcohols with benzyltriphenylphosphoniunt chlorate (PhCH2Ph3P+ClO3 −) 1 (BTPPC) in refluxing acetonitrle is reported. The oxidation in the presence of a catalytic amount of aluminum chloride enhances the rate.

Chlorate Transport through Ion-Exchange Membranes

Abstract: A laboratory scale chlor-alkali membrane cell was used to measure the chlorate concentration in the outlet NaOH as a function of current density, temperature, film thickness, brine strength and various membrane properties. The chlorate concentration in the NaOH increased with increasing anolyte chlorate spiking level and temperature and decreasing current density and carboxylate film thickness and was strongly dependent on the type of ion-exchange membrane used. In addition, the presence or absence of sacrificial fibers in the membrane did not measurably influence the resultant chlorate concentration. Chlorate ions were transported to the catholyte side by diffusion and electroosmotic convection and transported toward the anolyte side by migration. This balance between the three modes of transport dictates the chlorate concentration present in the NaOH product.

Electrochemical and Corrosion Behavior of Dimensionally Stable Anodes in Chlorate Electrolysis: Efficiency of the Sodium Chlorate Production at Elevated Temperatures

Abstract: The electrochemical and corrosion behavior of dimensionally stable anodes in chlorate electrolysis is analyzed. The current efficiency (CE) for active chlorine and sodium chlorate is studied at 90°C as a function of the electrolysis duration, dichromate concentration, and solution pH. Effect of interruptions and decrease in the current on CE for the target product is examined. On average, the interruptions can diminish CE by 10–15%.

Process for producing chlorine dioxide by the combined use of different reducing agents

Abstract: The invention relates to a process for continuous production of chlorine dioxide by allowing sodium chlorate, sulfuric acid and a reducing agent to react in a reactor (1) at atmospheric or nearly atmospheric pressure, by continuously feeding an inert gas into the reactor, the temperature being 30 - 100 °C, from which reactor (1) the gas mixture containing mainly chlorine dioxide and inert gas is directed via a scrubber (3) to an absorption tower (4), where the chlorine dioxide is absorbed, and by feeding the reaction solution containing unreacted sodium chlorate from reactor (1) into reactor (2), into which a reducing agent and an inert gas are added, from which reactor (2) the gas mixture containing mainly chlorine dioxide and inert gas is directed via the scrubber (3) to the absorption tower (4). The reducing agent used in reactor (1) is sulfur dioxide and methanol and the reducing agent used in reactor (2) is hydrogen peroxide.

Method for improving blocking-resistant property of sodium chlorate crystal

Abstract: The anionic surfactant or ampho-surfactang with anion is added in the sodium chlorate saturated aqueous solution, the content of the above-mentioned surfactant in the sodium chlorate saturated aqueous solution is 0001%-5%, they are fully mixed and stirred uniformly so as to make sodium chlorate crystal fully soak in the sodium chlorate saturated aqueous solution containing the above-mentioned surfactant, solid and liquid are separated and dried to obtain the finished product or the sodium chlorate solid is sprayed with surfactant whose concentratino is 001%-10%, then dried so as to obtain the finished product It features that after said finished product is sotred for a long period, it does not block

Kinetics of the Sodium Chlorate Formation in Electrolysis of Chloride Solutions with Use of Dimensionally Stable Anodes

Abstract: The kinetics of the formation of sodium chlorate during electrolysis of chloride solutions with use of dimensionally stable anodes is studied. An analysis and calculations suggest that the experimental results are well described by the proposed set of differential equations under the assumption that the homogeneous chemical reaction of chlorate formation has second, rather than third, order by active chlorine.

Inhibiting effect of oxidized zirconium on parasitic cathodic reactions in the sodium chlorate process Part I: Hypochlorite reduction

Abstract: To clarify the effect of oxidized zirconium on parasitic cathodic reactions in the chlorate process, electrochemical studies were carried out at laboratory scale. The techniques used were cyclic voltammetry and recording of polarization curves. In this paper the reduction of hypochlorite ions to chloride ions was studied. It is shown that oxidized zirconium cathodes reduces the rate of hypochlorite reduction, although not entirely inhibiting it, which is mainly related to a lowered active area due to the porous layer of zirconium dioxide. Further, it has also been shown that the oxidized samples are partly passivated, giving high overvoltages for the hydrogen evolution reaction. These overvoltages gradually decrease during cathodic polarization due to the simultaneous reduction of the zirconium oxide. Studies of the selectivity indicate that hypochlorite reduction occurs on the oxidised zirconium cathodes to a high extent, the thermal oxide being somewhat better. This further proves that zirconium oxide is not a suitable cathode material for the sodium chlorate process.

System for controlling cupric chloride-sodium chlorate etching solution

Abstract: PROBLEM TO BE SOLVED: To provide a practical method for controlling a cupric chloride-sodium chlorate etching solution. SOLUTION: The cuprous chloride generated in copper etching by a cupric chloride-sodium chlorate etching solution is regenerated according to the equation: 6CuCl+NaClO3+6HCl→6CuCl2+NaCl+3H2O. In this case, the pH of the etching solution is set at 0.5 to 2.5, the ORP value at +500 to +1200 mV, the concentration of sodium chlorate at 0 to 1 mol and the specific gravity at 1.25 to 1.45 to control the solution. A sample measuring cell, a pH sensor, an ORP sensor, a specific gravity sensor and a temperature sensor are provided, and further, a device for processing the signal outputs from the respective sensors is furnished to perform this method.

Cupric chloride etching liquid composition

Abstract: PROBLEM TO BE SOLVED: To improve the etching rate and etching factor of an enchant used for copper etching. and to enable the regeneration of the liquid. SOLUTION: The cupric chloride enchant composition for oxidizing and etching copper by a cupric chloride solution contains 1 to 4 mol cupric chloride, 0.5 to 2 mol sodium chlorate, 0.5 to 5% perchloric acid and a suitable amount of hydrochloric acid for oxidizing the copper to copper (I). Accordingly, the etching rate and etching factor are improved by the combination of the sodium chlorate and the perchloric acid or the addition of ferric chloride and the regeneration is made possible.

Synthesis of sulfur-based water treatment agent from sulfur dioxide waste streams

Abstract: We propose a process that uses sulfur dioxide from coal combustion as a raw material to synthesize polymeric ferric sulfate (PFS), a water treatment agent. The process uses sodium chlorate as an oxidant and ferrous sulfate as an absorbent. The major chemical mechanisms in this reaction system include oxidation, hydrolysis, and polymerization. Oxidation determines sulfur conversion efficiency while hydrolysis and polymerization control the quality of product. Many factors, including SO{sub 2} inlet concentration, flow rate of simulated flue gas, reaction temperature, addition rate of oxidant and stirring rate, may affect the efficiencies of SO{sub 2} removal. Currently, the effects of SO{sub 2} inlet concentration, the flow rate of simulated flue gas and addition rate of flue gas on removal efficiencies of SO{sub 2}, are being investigated. Experiments shown in this report have demonstrated that the conversion efficiencies of sulfur dioxide with ferrous sulfate as an absorbent are in the range of 60-80% under the adopted process conditions. However, the conversion efficiency of sulfur dioxide may be improved by optimizing reaction conditions to be investigated. Partial quality indices of the synthesized products, including Fe{sup 2+} concentration and total iron concentration, have been evaluated.

Chemical preparation of chlorate salts

Abstract: A novel method of producing metal chlorates is described which involves the reaction of ammonium chlorate with metal carbonates and/or metal bicarbonates. The reaction yields extremely pure metal chlorate, as well as ammonia and carbon dioxide by-products. These by-products combine to produce ammonium bicarbonate. The ammonium bicarbonate may then be reacted with sodium chlorate to produce ammonium chlorate, which may be recycled for use in the production of metal chlorates.

Kinetics of Oxygen Evolution on Dimensionally Stable Anodes during Chlorate Electrolysis

Abstract: The kinetics of oxygen evolution on dimensionally stable anodes during chlorate electrolysis at markedly different concentrations of chloride and sodium chlorate is studied. The theoretical model developed for the process kinetics assumes that molecules of hypochlorous acid participate in the oxygen evolution. The process rate is characterized by first reaction order by active chlorine, provided molecules of hypochlorous acid can inhibit the process due to their reversible adsorption on the anode surface. Mathematical modeling methods are employed to demonstrate the model adequacy to experiment.