RU2288175C1 - Method of enhancing bactericidal properties of hydrogen peroxide used to disinfect drinking water - Google Patents

Abstract

FIELD: water treatment processes.

SUBSTANCE: invention relates to drinking water treatment processes and can be used to disinfect drinking water in water supply systems of residential sites and food industry enterprises. Bactericidal activity of hydrogen peroxide is enhanced by bringing hydrogen peroxide-treated water into contact with heterogeneous catalyst containing mixture of pyrolusite and rutile powders used in weight proportion (2-4):1. Catalyst may further contain flotation cinder - sulfuric acid production waste - in such amount that weight ratio pyrolusite/rutile/flotation cinder is (2-4):1:(1-2). Advantageously, flotation cinder contains, wt %: iron 47-55, copper 1.4-0.6, zinc 0.7-0.8, and, g/t: silver 25-35, cobalt 70-250, selenium 10-20. In a specific case, powder mixture of pyrolusite and rutile and, optionally, flotation cinder fraction 0.1-0.2 cm is moistened to achieve pasty state, dried for 1-2 h at 110-120°C, and molded in the form of pellets or granules. Further merits of invention reside in that above-indicated powder mixture, prior to be moistened, may be mixed with binding substance.

EFFECT: reduced expenses and provision of high efficiency in disinfection and resistance of treated water to repeated bacterial contamination.

6 cl, 5 ex

Description

The invention relates to methods for preparing drinking water by treating it with hydrogen peroxide in the presence of a heterogeneous catalyst. It can be used for disinfection of drinking water in the water supply systems of settlements, as well as food industry enterprises.

A known method of disinfecting water, which consists in the combined action of hydrogen peroxide and 0.05-1.0 mg / l of copper ions Cu ²⁺ . At the same time, copper not only enhances the bactericidal properties of hydrogen peroxide Н ₂ O ₂ , but also serves as a catalyst for its decomposition with the formation of water and molecular oxygen (Savluk IP et al. Antimicrobial properties of copper. Chemistry and technology of water, 1986, v. 8 , No. 6, p. 65-67). However, the bactericidal efficacy of this method is not high enough. In addition, the upper limit of copper concentration (1 mg / l) corresponds to the value of its MAC in drinking water and is two orders of magnitude higher than the value of its MAC in fishery reservoirs.

More effective is the method of chemical treatment and disinfection of water and water systems known from EP 0059978 C 02 F 1/50, which consists in the simultaneous use of quaternary ammonium compounds, water-soluble salts of copper and / or silver and a peroxide compound that liberates oxygen during decomposition. However, the implementation of this method requires the use of sufficiently scarce compounds.

The closest analogue of the claimed invention for its intended purpose, combination of essential features and the achieved result is a disinfection method, including its two-stage treatment with hydrogen peroxide and the subsequent introduction of a heterogeneous catalyst, which is obtained by mixing powdered pyrolusite with particles of finely divided metallic silver with a mass ratio of pyrolusite: silver, equal (800-1500): 1 (RU 2213707, 2003). This method is of relative complexity, requires the use of expensive silver and its preliminary crushing.

The technical problem to which the present invention is directed was to exclude the use of metallic silver, thereby reducing material costs while maintaining high efficiency of the water disinfection process and the resistance of the treated water to repeated (external) bacterial contamination.

The problem is solved in that the method of increasing the bactericidal activity of hydrogen peroxide, used to disinfect drinking water, by contacting the water treated with hydrogen peroxide with a heterogeneous catalyst containing pyrolusite, is characterized in that a mixture of pyrolusite and rutile powders is used as a catalyst in a mass ratio, respectively equal to (2 ÷ 4): 1.

Also, the differences are that the catalyst may additionally contain a flotation cinder, which is a waste of the sulfuric acid industry, with a mass ratio of pyrolusite: rutile: flotation cinder equal to (2 ÷ 4): 1: (1 ÷ 2).

Preferably, the flotation cinder contains in wt.% Iron - 47 ÷ 55, copper - 1.4 ÷ 0.6, zinc - 0.7 ÷ 0.8 and in g / t silver - 25 ÷ 35, cobalt - 70 ÷ 250 selenium - 10-20.

In a particular case, a mixture of powders of pyrolusite, rutile, and possibly a flotation cinder of a fraction of 0.1-0.2 cm is moistened to a pasty state, dried for 1-2 hours at a temperature of 110-120 ° C and formed into tablets or granules.

Additional differences are that a mixture of pyrolusite, rutile and possibly flotation cinder powders can be mixed with a binder prior to wetting.

Thus, it is new that pyrolyusite and rutile in a certain ratio are used as a heterogeneous catalyst. Pyrolusite is a mineral based on manganese oxide β - MnO ₂ . Rutile is a mineral, one of the crystalline modifications of titanium dioxide, sometimes with an admixture of iron, tantalum, niobium. It was found that when pyrolyusite powder is used in a mixture with rutile powder, the efficiency of the water disinfection process is non-additive.

The catalyst, in addition, may contain a flotation cinder. The latter is a large-tonnage waste of the sulfuric acid industry, formed during the roasting of flotation pyrite, which, in turn, is obtained by flotation of copper and zinc ores.

According to literature data (A.G. Amelin. Technology of sulfuric acid. - M .: Chemistry, 1971, p. 47-49), the composition of the flotation cinder (average data on sulfuric acid plants) are in the form of oxides (in wt. %): iron - 47 ÷ 55, copper - 1.4 ÷ 0.6, zinc - 0.7 ÷ 0.8 and others. In addition, the cinder contains, in g / t: gold - 3-16, silver - 25 ÷ 35, cobalt - 70 ÷ 250, selenium - 10-20 and other elements.

As a result of our research, it was found that the flotation cinder has a favorable composition for its use in a mixture with pyrolusite and rutile as a catalyst for the decomposition of hydrogen peroxide, sharply increasing the bactericidal activity of the latter. The ingredients included in the catalyst are hardly soluble in water, and their concentration in disinfected water is much lower than the MPC.

The proposed catalyst is prepared as follows. Pyrolusite and rutile, as well as, if necessary, the flotation cinder are crushed to a powder state, mixed in the above optimal ratios and used in the process of water disinfection. Another option for the preparation of the catalyst is possible - after mixing the powders, they are moistened to the state of a paste, which is then dried for 1-2 hours at 110-120 ° C and molded in the form of tablets or granules. According to the following use case, the powder mixture is combined with a binder (cement, clay, water glass, bentonite, etc.), after which the above operations are carried out. In this case, the mass ratio between the mixture of powders of pyrolusite, rutile (and possibly flotation cinder) and the binder is taken to be 1: (2 ÷ 3). The resulting catalyst is loaded into the reactor, after which contaminated water containing hydrogen peroxide is passed through it. The residence time of water in the heterogeneous catalyst layer is 0.5-1.0 hours.

The use of a catalyst in the form of tablets almost completely prevents it from entering drinking water. In addition, they are conveniently stored until use.

The combined treatment of water containing pathogenic microorganisms with hydrogen peroxide and the proposed heterogeneous catalyst by an order of magnitude or more (compared to using only hydrogen peroxide or only individual catalyst components) increases the depth of water disinfection. The catalyst also helps to remove excess hydrogen peroxide after the end of the disinfection process.

The following are examples of the implementation of the proposed method.

Example 1

The source water had the following indicators: temperature 21 ° С, pH 7.3, suspended solids 0.72 mg / l, color 28 degrees, permanganate oxidation by oxygen 28 mg / l, coli index 120. Then, hydrogen peroxide was introduced into water in an amount of 100 mg / l. The resulting water was kept for 0.4 hours and brought into contact with a heterogeneous catalyst in an amount of 1 mg / L. The catalyst was prepared by mixing powders of pyrolusite and rutile (particle size less than 0.05 mm), while the mass ratio between pyrolusite and rutile was set equal to 2: 1. Then, with the help of moistening, a paste was prepared, dried at a temperature of 110-120 ° C and molded in the form of granules. The contact time of the catalyst with disinfected water is 0.5 hours. Indicators of water obtained: suspended solids content of 0.28 mg / l, color 10 degrees, permanganate oxidation 10 mg / l for oxygen, if index 1 (one microorganism per 1 liter of water).

Example 2

The source water had the same indicators as in example 1. The process of disinfecting water with hydrogen peroxide is similar to example 1. The catalyst was prepared analogously to example 1. The difference was in the mass ratio of pyrolusite and rutile, in this case it was 4: 1. The contact time of the catalyst with disinfected water was 1 hour. Indicators of water obtained: suspended solids content 0.32 mg / l, color 12 degrees, permanganate oxidation by oxygen 13 mg / l, coli index 2.

Example 3

The initial water had the following indicators: temperature 18 ° С, pH 6.9, suspended solids 0.89 mg / l, color 30 degrees, permanganate oxidation by oxygen 29 mg / l, if index 250. Then hydrogen peroxide was introduced into water in an amount of 200 mg / l. The resulting water was kept for 0.5 hours and brought into contact with a heterogeneous catalyst in an amount of 1 mg / L. The catalyst was prepared by mixing powders of pyrolusite, rutile and flotation cinder (particle size 0.1-0.3 mm), while the mass ratio of pyrolusite: rutile: flotation cinder was 2: 1: 2. To the resulting mixture was added a binder - bentonite clay at a mass ratio of a mixture of powders pyrolusite-rutile-flotation cinder: clay equal to 1: 3. Then, with the help of moistening, a paste was prepared, dried at a temperature of 110 - 120 ° C and molded in the form of granules. The contact time of the catalyst with disinfected water is 0.5 hours. Indicators of water obtained: suspended solids 0.28 mg / l, color 10 degrees, permanganate oxidation 10 mg / l for oxygen, coli index 1.

Example 4

The method was carried out as in example 3, the difference was that the mass ratio of pyrolusite: rutile: flotation cinder was 4: 1: 1, cement was used as a binder with a mass ratio of a mixture of powders of pyrolusite-rutile-flotation cinder: cement equal to 1: 2, the contact time of the catalyst with disinfected water is 1 hour. Indicators of water obtained: suspended solids 0.23 mg / l, color 9 degrees, permanganate oxidation 9 mg / l for oxygen, pathogenic microorganisms were not detected.

Example 5 (comparative).

The source water had the same indicators as in Example 1. Only hydrogen peroxide was added to the water in an amount of 200 mg / L. After 1 hour, a chemical and bacteriological analysis of water was performed. Indicators of water obtained: suspended solids content 0.38 mg / l, color 16 degrees, oxygen permanganate oxidation 16 mg / l, coli index 6.

The water treated according to examples 1-4 was kept in a pre-sterilized container for 72 hours, then the coli index was determined; he was 1-2. After that, the water was subjected to bacteriological infection with a culture of E. coli 1257 in an amount of 100 individuals / l and after 24 hours a bacteriological analysis of water was carried out. If the index has not changed. There was no smell and unpleasant taste near the water. The effect lasted for a month.

For comparison, experiments were conducted on treating water only with hydrogen peroxide, only pyrolyusite, only rutile, and only flotation cinder in the form of granules. In none of these cases was it possible to obtain a stable disinfecting and preserving effect when storing water for a month.

Thus, the proposed method of disinfecting water is effective, relatively simple and affordable, allowing one stage to produce deep disinfection of water, achieved without the use of expensive silver. This became possible due to the fact that the most favorable qualities of each of the components appeared and intensified in the mixed catalyst.

Claims (6)

1. A method of increasing the bactericidal activity of hydrogen peroxide used to disinfect drinking water by contacting hydrogen peroxide-treated water with a heterogeneous catalyst containing pyrolusite, characterized in that a mixture of pyrolusite and rutile powders is used as a catalyst in a weight ratio of respectively (2 ÷ 4) :one. 2. The method according to claim 1, characterized in that the catalyst further comprises a flotation cinder, which is a waste of the sulfuric acid industry, with a mass ratio of pyrolusite: rutile: flotation cinder equal to (2 ÷ 4): 1: (1 ÷ 2). 3. The method according to claim 2, characterized in that the flotation cinder contains, wt.%: Iron - 47 ÷ 55, copper - 1.4 ÷ 0.6, zinc - 0.7 ÷ 0.8 and g / t: silver - 25 ÷ 35, cobalt - 70 ÷ 250, selenium - 10-20. 4. The method according to claim 1, characterized in that the mixture of powders of pyrolusite and rutile fractions of 0.1-0.2 cm is moistened to a pasty state, dried for 1-2 hours at a temperature of 110-120 ° C and molded in the form of tablets or granules. 5. The method according to claim 2, characterized in that the mixture of powders of pyrolusite, rutile and flotation cinder fractions of 0.1-0.2 cm are moistened to a pasty state, dried for 1-2 hours at a temperature of 110-120 ° C and formed in the form of tablets or granules. 6. The method according to claim 4 or 5, characterized in that the mixture of pyrolyusite, rutile powders and, if necessary, flotation cinder are mixed with a binder prior to wetting.