RU2732691C1 - Method of obtaining potassium iodate from iodine - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to chemical engineering of inorganic substances, specifically to a method of producing potassium iodate used in pharmaceutical and chemical industry. Described is a method of producing potassium iodate from iodine, involving oxidation of iodine in a burner flame, in which a rich iodine solution is fed into the burner in a propane-butane mixture, oxidiser is pure oxygen or air in tenfold excess of oxygen relative to combustible, combustion products are trapped by saturated solution of potassium hydroxide or carbonate, after saturation of the absorption solution, it is cooled to 5 °C and precipitated crystals of potassium iodate are separated by filtration.

EFFECT: simple technique of producing potassium iodate in refusing electrochemical methods of producing iodates and expensive and toxic oxidants.

1 cl, 1 tbl, 6 ex

Description

The invention relates to the field of chemical technology of inorganic substances, namely to a method for producing potassium iodate used in the pharmaceutical and chemical industries.

Known methods for producing potassium iodate based on the oxidation of iodine or potassium iodide with oxidizing agents such as Berthollet's salt, chlorine, bromine in an acidic or neutral medium [V.I. Ksenzenko, D.S. Stasinevich. Chemistry and technology of bromine, iodine and their compounds. - M .: Chemistry, 1995, 432 p., G. Remy. Inorganic chemistry course. T. 1. - M .: Mir, 1972, p. 777]. The disadvantage of these methods is the use of high concentrations of highly hazardous oxidants, high consumption of reagents, the need to dispose of reaction by-products, special corrosion-resistant equipment and safety equipment for the storage and use of oxidants.

Known methods of electrochemical oxidation of potassium iodide to potassium iodate in an aqueous solution on graphite anodes at a current density of 100-300 A / m ² and a temperature of 60-95 ° C [SU 865983, SU 1096307] in the presence of potassium dichromate. Their advantage is the absence of particularly hazardous reagents for oxidation, high current efficiency of potassium iodate, and simple control of the oxidation process.

The closest method for producing potassium iodate is the method proposed by the authors of patent RU 2210533 C1. The method is based on the interaction of iodine with potassium hydroxide, with the formation of iodide and potassium iodate in the reaction mass at an alkalinity of up to 8 kg / m ³ , the content of iodide ions up to 160 kg / m ³ and iodate ions up to 50 kg / m ³ . The mass is subjected to electrolysis, followed by evaporation at a temperature of at least 80 ° C for preliminary crystallization and crystallization upon cooling.

The similarity of the proposed method and the prototype lies in the use of an elevated temperature and the need for oxidation of iodide ions and iodine to iodate ions.

The disadvantages of the prototype are the high costs of time for filling the electrolyzer and draining the solution from the electrolyzer, high energy consumption during the evaporation of the solution before the crystallization of potassium iodate begins. And also during the intensive crystallization of potassium iodate to prevent coprecipitation of potassium iodide, it is necessary to maintain a low concentration of potassium iodide in the mother liquor. Oxidation of potassium iodide to a concentration close to zero leads to a decrease in the current strength and current efficiency of potassium iodate, and increases the electrolysis time. Maintaining the current strength requires an increase in the applied voltage, but at low iodide concentrations in the solution, the wear of the anodes increases and their operating time decreases.

The technical objective of the invention is to simplify the technology for producing potassium iodate, eliminate electrolysis processes accompanied by high energy consumption and increase the yield of the target product - potassium iodate.

The result of the invention is the simplification of the technology for producing potassium iodate while rejecting electrochemical methods for producing iodates, as well as expensive and toxic oxidants.

This result is achieved by the fact that in the proposed method, molecular iodine dissolved in liquefied combustible gas is oxidized with pure oxygen or air oxygen in the burner flame. The combustible gas is a propane-butane mixture, the excess of oxygen is ten times that of the fuel required for combustion. The yield of potassium iodate reaches 99.9% of theoretical, based on the initial iodine.

The method is carried out as follows.

A saturated solution of iodine in a propane-butane mixture (iodine content 12 g / 100 g of the mixture) is fed into the oxygen burner at a rate of 0.25-0.5 g / min. Technical oxygen is additionally supplied to the burner in an amount of 0.9-1.8 g / min, which corresponds to a volumetric feed rate of 6.4-12.8 l / min. The consumption of combustible gas is determined gravimetrically, oxygen - gas-volumetric. When air is used as an oxidizer, its consumption is increased fivefold compared to the oxygen consumption.

The combustion products are drawn by a vacuum pump through a series of absorption vessels filled with a saturated solution of potassium hydroxide or a saturated solution of potassium carbonate. The absorption of combustion products is carried out until an acidic reaction medium (pH 2.5-3) is created in the absorbers. After saturation of the absorption solution, it is cooled to 5 ° C and the separated crystals of potassium iodate are separated by filtration.

The specific conditions for the implementation of the method may vary.

Examples confirming the possibility of obtaining potassium iodate by the proposed method are shown in table 1.

The content of potassium iodate was determined in the absorption solution by iodometry. In view of the possible leakage of iodine into the absorption solution, it was also tested for the presence of molecular iodine and iodide ion. The presence of molecular iodine and iodide ion in the absorption solution was not detected in the course of confirming experiments, iodine was completely oxidized to iodate ion.

From the above examples, it can be seen that the proposed method can produce potassium iodate with a yield of up to 99.9%.

To implement the proposed method, standard equipment used in chemical technology can be used.

The inventive method is environmentally friendly, because the resulting product does not contain organic solvents, and the process does not generate toxic or difficult to dispose of waste or by-products. The heat released during the combustion of fuel can be used to heat the heat carriers.

The inventive method can be used to obtain potassium iodate both in laboratory practice and in industry and is suitable for both batch and continuous technological methods.

Table 1. Examples confirming the possibility of implementing the method of obtaining potassium iodate from iodine

Sample # / # Feed rate of iodine solution in propane-butane mixture, g / min Oxidizer type Oxidizer feed rate, gO ₂ / min, l Air / min. Excess oxidant, times Potassium iodate yield,% of theoretical 1 0.25 Air 6.4 ten 99.9 2 0,4 Air 10.3 ten 99.9 3 0.5 Air 12.8 ten 99.9 4 0.25 Oxygen 0.9 ten 99.9 five 0.3 Oxygen 1.1 ten 99.9 6 0.5 Oxygen 1.8 ten 99.9

Claims (1)

A method for producing potassium iodate from iodine, including the oxidation of iodine in a burner flame, characterized in that a saturated solution of iodine in a propane-butane mixture is supplied to the burner, pure oxygen or air in a tenfold excess of oxygen in relation to the fuel is the oxidizer, the combustion products are captured by a saturated solution potassium hydroxide or carbonate, after saturation of the absorption solution, it is cooled to 5 ° C and the separated crystals of potassium iodate are separated by filtration.