SU971784A1 - Method for detecting chlorine dioxide and chlorine in aqueous solutions - Google Patents

Description

(54) METHOD FOR DETERMINING CHLORIDE AND CHLORINE BIOXIDE IN WATER BOTTOMS

one

The invention relates to the analysis of liquid media and can be used to determine the composition of aqueous solutions containing mixtures of chlorine dioxide and chlorine in bleaching and technological solutions of the pulp and paper, textile and chemical industries, as well as in laboratory practice.

Methods are known for analyzing chlorine and chlorine dioxide solutions based on the redox properties of the substances to be determined 1.

The relative square error in determining the concentrations of chlorine dioxide and chlorine in their mixtures reaches 5%. This is due to the instability of mixtures of chlorine and chlorine dioxide over time and the complexity of the redox interactions of the analytes and reagents.

The closest to the proposed technical essence and the achieved result is the method of spectrophotometric determination of the concentrations of chlorine oxide in aqueous solutions mixed with chlorine and oxygen-containing chlorine compounds. The method consists in measuring the optical density of the directly analyzed solution or its samples diluted with distilled water at several wavelengths 2.

The process of determination of chlorine dioxide and chlorine dioxide concentrations using the prototype method also leads to significant imperfections (up to 4./o) due to the volatility of the components to be determined (for example, at 20 ° С the total vapor pressure C102 and at their concentration 5-7 g / l 65 GPA) and their loss in the process of analysis.

ten

The aim of the invention is to increase the accuracy of the analysis.

This goal is achieved in that according to the method for determining chlorine dioxide and chlorine in aqueous solutions, including measuring the optical density of the analyzed solution, the latter is pre-treated with an aqueous solution of sodium hydroxide with the addition of 0.065-0.262 mol / l isopropanol.

When the amounts of alkali, equivalent or large amounts of chlorine dioxide and chlorine in the interaction with the reagent, reactions occur according to schemes 1 and 2. С1О / 2ОН - and propanl 0,582, 418 ClOf

C1 | OH-Propanol SG + CU + H. (2) The reactions according to schemes (1) and (2) are carried out for 2-3 sec. Disproportionation products of chlorine dioxide are nonvolatile and time stable in alkaline solutions. The stoichiometric coefficients of reaction products in disproportionation schemes are reproduced under the proposed reaction conditions. Therefore, the number of reaction products can be judged on the content of the starting products. The method is carried out in the following manner. The analyzed solution of a mixture of chlorine dioxide is treated with a reagent of the intended composition and the optical density of the solution treated with the reagent is measured at 260 and 292 nm. In tab. Figure 1 shows the molar absorption (CI) of C 1 O 2 and C O, determined at 20t3 ° C with distilled water as a comparison solution at A 260 and 292 nm. The concentrations of chlorine dioxide and chlorine in the analyzed solution are determined using Equations 3 and 6, -.260. ,, 6 - (-seo, 00-,) I 7 p. 292, „, - 292 ..-- 292 .. D (C ceo-tcto-Qeoj Cheo, -) Cyo l.lSAMceo Cceo, Ccf2 AMse Sseo-, Ceo - 2-concentrations of chlorine dioxide and chlorine dioxide, g / l, in the original solution; and С de - concentration of chlorite and hypochlorite ions in mol / l in the measurement of 260292 solution; and D is the optical density value of the measured solution at 260 and 292 nm; with c-iw с2Ч2j. J. -ctoj ctoz ceo-fcceo — the molar absorption coefficients of chlorite and hypochlorite at 260 and 292 nm; Mseo and Mse are the molar masses of chlorine and chlorine dioxide; A is the dilution factor of the initial solution when mixed with reagent; 1.718 factor, which takes into account the stoichiometry of the reaction (1). The accuracy of the analysis by the proposed method compared to the method, the prototype increases by more than 2 times. Example 1. From industrial bleaching solutions of the Kotlas PPM containing 5 g / l and 0.8 g / l C12, 10 ml samples are taken and injected into a 100 ml volumetric flask filled with 2/3 of 0.1 mol / l sodium hydroxide solution with the additive 1 ml of isopropanol. After adjusting the volume in the flask to the mark with 0.1 mol / l sodium hydroxide solution and stirring, measure the optical density of the resulting solution at 260 and 292 nm in cuvettes with a thickness of 0.5 cm using distilled water as a comparison solution. The concentrations of chlorine dioxide and chlorine in the initial solution are calculated using the 3-b-Lnalysis equation at 20 ± 1 ° C. The results are shown in Table. 2 (experiments 1-8). It also conducts the analysis of mixtures of chlorine dioxide and chlorine dioxide solutions at other concentrations of determinable substances in model solutions (Table 2, experiments 9-15). The analysis by the proposed method is compared with the analysis of the same solutions by the prototype method (see Table 2). Comparison of the values of standard quadratic deviations 6 | Dvr, “relative standard quadratic deviations of 5% (Table 2) by the proposed method and the prototype method show that the accuracy of chlorine dioxide analysis by the proposed method increases 7 times and chlorine 2 times. The proposed method can also be used to analyze solutions in which there is only chlorine or only chlorine dioxide (Table 3). In addition, the analysis creates an additional effect, which consists in improving the sanitary and hygienic conditions of the analysis due to the transfer of odorous and harmful substances of chlorine and chlorine dioxide to non-volatile, odorless compounds. The prototype method underestimates the chlorine dioxide concentration in average by 3% (Table 2). The proposed method creates an additional economic effect by reducing the consumption of chemicals during the production of chlorine dioxide. In tab. Table 3 shows the results of the analysis, as well as the results of the calculation of the relative error of determination of%) at various concentrations of isopropanol. In the range of isopropanol concentrations of 0.5-2.0 vol. / O (0.065-0.262 mol / l), the stoichiometric coefficients D41 of the permissible proportions of ClO are reproduced c6 (L) 0.063; 6vn% 0,3%. Thus, it has been found that, at the indicated concentrations of isopropanol, the error in the determination of chlorine and chlorine dioxide is reduced compared to the determination by the method of the prototype.

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Claims (1)

Claim A method for determining chlorine dioxide and chlorine in aqueous solutions of mixtures thereof, including measurement. optical density of the analyzed solution, characterized in that, in order to improve the accuracy of determination, the analyzed solution is pre-treated with an aqueous solution of caustic soda with the addition of 0.065-0.262 mol / l of isopropanol.