RU2288178C1 - Method for enhancing bactericidal activity of hydrogen peroxide - Google Patents

Abstract

FIELD: water treatment processes.

SUBSTANCE: invention relates to treatment of water with hydrogen peroxide in presence of heterogeneous catalyst and can be used to disinfect water in drinking and reuse water supply systems as well as when treating water in food processing industry. Method of industry comprises introducing hydrogen peroxide into water and bringing the latter into contact with heterogeneous catalyst, in particular magnetite, red iron ore, or brown iron ore, which is reduced into particles 0.5-2 cm in size, the latter being then subjected to oxidative firing in air atmosphere at 150-250°C during 1-2 h and brought into contact with hydrogen peroxide-containing water for residence time of disinfected hydrogen peroxide-containing water in heterogeneous catalyst bed equal to 0.5-1 h. Catalyst may further contain rutile preliminarily reduced into fragments 0.3-0.5 cm and then subjected to oxidative firing at 800-900°C conducted for 1-2 h, while supplying air in bottom-up direction to create fluidized rutile powder bed. Magnetite (or red, or brown iron ore)/rutile weight ratio is (5-10):1.

EFFECT: enhanced water disinfection process efficiency and reduced loss of catalyst.

3 cl, 1 tbl, 13 ex

Description

The invention relates to methods for treating water by exposure to hydrogen peroxide in the presence of a heterogeneous catalyst. It can be used for disinfecting water in drinking and recycling water supply systems, as well as water treatment in the food industry.

It is known that hydrogen peroxide is a promising, relatively inexpensive bactericidal drug for the disinfection of drinking and circulating water, which does not change its physico-chemical characteristics.

It was found that the introduction of certain substances into hydrogen peroxide significantly enhances the bactericidal properties of H ₂ O ₂ . Thus, a method of disinfecting water is known, which consists in the combined action of hydrogen peroxide and 0.05-1.0 mg / l of copper ions. In this case, copper not only enhances the antimicrobial properties of hydrogen peroxide, but also is a homogeneous catalyst for its decomposition (Savluk I.P. et al. Antimicrobial properties of copper // Chemistry and Water Technology, 1986, v. 8, No. 6, p. 65- 67). The disadvantages of the method are: 1) the difficulty of maintaining in water the indicated concentrations of copper ions; 2) the upper limit of the concentration of copper ions corresponds to the maximum permissible concentration in drinking water (1 mg / l) established for this substance (GOST 2874-82 "Drinking water").

It is known to use heterogeneous (in the form of solid particles) catalysts that enhance the bactericidal properties of hydrogen peroxide: powdered hopcalite mixed with finely divided metallic silver (RU 2213705, 2003), powdered natural mineral - pyrolusite based on manganese oxide β- MnO ₂ mixed with silver particles (RU 2213707, 2003). The disadvantages of these methods are: 1) the need for crushing of raw materials, which leads to high energy intensity of the process; 2) the need to use scarce and expensive metallic silver, which is also subjected to crushing; 3) subsequent molding of the catalyst from the mechanical mixture into granules or tablets.

The known ability of iron oxide (II) FeO and mixed iron oxide Fe ₃ O _{4 to} decompose hydrogen peroxide according to the scheme 2H ₂ O ₂ → 2H ₂ O + O ₂ ↑

(Shamb U., Seterfield Ch., Ventvers R. Hydrogen peroxide. - M.: Publishing house of foreign literature, 1958. - 409 p.). This property of iron oxides can be used, for example, to accelerate the release of oxygen from an aqueous solution of hydrogen peroxide, which will increase its bactericidal activity. This method is the closest analogue of the proposed method to increase the bactericidal activity of hydrogen peroxide. However, the indicated source of information does not indicate ways to optimize this process from the point of view of increasing its efficiency and manufacturability.

The technical problem to which the present invention is directed was to increase the efficiency of the water disinfection process by using a heterogeneous catalyst easy to prepare from available and relatively inexpensive raw materials, as well as reducing catalyst losses.

The problem is solved in that the method of increasing the bactericidal activity of hydrogen peroxide, including introducing hydrogen peroxide into water and contacting with a heterogeneous catalyst based on iron oxides, differs from the closest analogue in that magnetic, red or brown iron ore is used as a catalyst, which is ground to particles with a size of 0.5-2 cm, they are subjected to oxidative firing in an atmosphere of air at 150-250 ° C for 1-2 hours and brought into contact with water containing hydrogen peroxide, while The volume of stay of disinfected water containing hydrogen peroxide in a layer of a heterogeneous catalyst is 0.5-1 hours.

Additional differences are that the catalyst may also contain rutile mineral, pre-crushed to particles with a size of 0.3-0.5 cm and then subjected to oxidative roasting at a temperature of 800-900 ° C, carried out for 1-2 hours when applied air from bottom to top to create a fluidized bed of rutile powder. The optimal mass ratio of magnetic, red or brown iron and rutile is (5-10): 1.

As is known (Chemical Encyclopedia :, v.2, M .: Sov. Encyclopedia, 1990, p.139), magnetite ores or magnetic iron ore (the main mineral is magnetite Fe ₃ O ₄ ) most often contain up to 45-60% Fe; hematite ores or red iron ore (the main mineral is hematite Fe ₂ O ₃ ) usually contain 50-65% Fe; brown iron ore - Fe (III) hydroxide ores (the main mineral is goethite) contain up to 66.1% Fe. The advantage of these ores used to solve the problem lies in their wide distribution (Russia occupies one of the first places in the world in explored reserves of these ores).

As a result of our studies, it was found that these ore materials are quite active catalysts for the decomposition of peroxide, this process is accelerated by the impurities Mn, Ni, Ti, and Co included in their composition. The result is the formation of intermediate decomposition products of hydrogen peroxide - OH free radicals, characterized by increased bactericidal activity, and after a short time converted into H ₂ O molecules. In addition, it was found that the grinding of the initial ore (magnetite, hematite or brown ores) to the optimal particle size - 0.5-2 cm and their oxidative (in an atmosphere of air) firing in optimal mode - at 150-250 ° C for 1-2 hours - contributes to the burning out of some adverse impurities, strengthens these particles, increases the content of mixed iron oxide, which ultimately leads to an increase in the catalytic and bactericidal activity of the catalyst, and also reduces the consumption of the catalyst due to the almost complete elimination of its losses.

The use of catalysts in the form of relatively large particles (0.5-2 cm) prevents them from entering drinking water. In addition, such particles are conveniently stored until use in the disinfection process.

An even greater effect is observed with the combined use of catalysts based on iron oxides and titanium dioxide (rutile), while the optimal scheme for the preparation (roasting) of rutile is proposed. The proposed oxidative roasting of rutile increases the content of titanium dioxide in the powder (by 15 ÷ 20%), which increases its catalytic activity in relation to the process of water disinfection. Preferably the mass ratio of magnetic, red or brown iron and rutile is (5-10): 1.

Namely, the above set of essential features of the proposed invention provides the intended technical result.

The combined treatment of water with hydrogen peroxide and the proposed heterogeneous catalysts an order of magnitude or more (compared to using only peroxide or only a catalyst) increases the depth of water disinfection.

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

Example 1

Sanitary-indicative microorganisms of E. coli were introduced into natural water in an amount of 10 ³ individuals / l, then 0.5 g / l of hydrogen peroxide was introduced. After exposure for 1 hour, an analysis was performed to determine the number of surviving microorganisms.

Measurements were performed after 1 hour, 1, 3, 5, and 7 days. The results of the analysis are presented in the table.

Example 2

The content of microorganisms in the water is similar to example 1. Hydrogen peroxide was not introduced. Water containing microorganisms was passed through a column (reactor) with a catalyst — particles of magnetic iron ore ~ 0.5 cm in size so that the residence time of water in the catalyst layer was 1 hour. The results of bacteriological analysis are presented in the table.

Example 3

The content of microorganisms in the water is similar to example 1. Hydrogen peroxide was not introduced. As a catalyst, particles of red iron ore with sizes of ~ 1 cm were used, the contact time was 1 hour. The results of bacteriological analysis are presented in the table.

Example 4

The content of microorganisms in the water is similar to example 1. Hydrogen peroxide was not introduced. Particles of brown iron ore with sizes of ~ 1.5-2 cm, contact time - 1 hour were used as a catalyst. The results of bacteriological analysis are presented in the table.

Example 5

The content of microorganisms and the concentration of hydrogen peroxide in water are similar to example 1. The catalyst and the conditions for its use are in accordance with example 2. The results of the analysis are presented in the table.

Example 6

The conditions of the experiments are according to example 5. Difference: the catalyst is particles of magnetic iron ore, which was preliminarily fired in an atmosphere of air at 200 ° C for 1.5 hours. The results of bacteriological analysis are presented in the table.

Example 7

The experimental conditions and the content of hydrogen peroxide in water are according to Example 1. As a catalyst, particles of red iron were taken with a particle size of ~ 0.5 cm, the contact time was 1 hour. The results of bacteriological analysis are presented in the table.

Example 8

The experimental conditions are according to Example 7. Difference: the catalyst is 1 cm red iron particles, which were preliminarily fired in an atmosphere of air at 150 ° C for 2 hours. The results of bacteriological analysis are presented in the table.

Example 9

The experimental conditions and the content of H ₂ O ₂ introduced into the water are similar to Example 1. As a catalyst, particles of brown iron ore with sizes of 0.5-0.7 cm were taken, the contact time was 0.5 hours. The results of bacteriological analysis are presented in the table.

Example 10

The conditions of the experiments - according to example 9. Difference: the catalyst was preliminarily fired in an atmosphere of air at 150 ° C for 1.5 hours. The results of bacteriological analysis are presented in the table.

Example 11

The experimental conditions are according to Example 6. Difference: rutile was additionally used as a catalyst. To prepare the catalyst, the natural rutile mineral with a TiO ₂ content _of about 93% was crushed to particles 0.3-0.5 cm in size, calcined at 800 ° C for 2 hours with air supply from the bottom up to create a fluidized bed of rutile powder. The content of TiO ₂ in the calcined rutile increased to 99.5%. Then, the calcined rutile was mixed with particles of magnetic iron ore in a mass ratio, respectively, equal to 1: 5. The results of bacteriological analysis are presented in the table.

Example 12

The experimental conditions are according to example 8. Difference: rutile was additionally used as a catalyst. To prepare the catalyst, the natural rutile mineral was ground to a particle size of 0.5 cm, burned at a temperature of 900 ° C for 1 hour with air supply from the bottom up to create a fluidized bed of rutile powder. Then, the calcined rutile was mixed with red iron particles in a mass ratio, respectively, equal to 1: 10. The results of bacteriological analysis are presented in the table.

Example 13

The experimental conditions are according to Example 10. Difference: rutile was additionally used as a catalyst. To prepare the catalyst, the natural rutile mineral was crushed to a particle size of 0.3 cm, burned at a temperature of 850 ° C for 1.5 hours with air supply from the bottom up to create a fluidized bed of rutile powder. Then, the calcined rutile was mixed with particles of brown iron ore in a mass ratio, respectively, equal to 1: 7. The results of bacteriological analysis are presented in the table.

The test results showed that the combination of hydrogen peroxide with the proposed heterogeneous catalysts not only dramatically increases the depth of disinfection, but also gives the treated water resistance to secondary bacterial contamination and prevents the reactivation of surviving microorganisms. In addition, it was found that the loss of the proposed catalysts (due to entrainment, dissolution, etc.) during the 3 months of operation was no more than 5%.

Table Example Disinfectant The number of surviving microorganisms (individuals / l) after 1 hour 1 day 3 days 5 days 7 days one Only H ₂ O ₂ one hundred 2 10 52 112 2 Only magnetic iron ore 800 620 410 320 120 3 Only red iron ore 720 630 390 220 80 four Only brown iron ore 690 480 240 210 72 5 N ₂ O ₂ + magnetic iron ore 8 2 one not found. not found. 6 N ₂ O ₂ + magnetic iron ore (firing) four 3 2 one not found. 7 H ₂ O ₂ + red iron ore 12 8 four four 2 8 N ₂ O ₂ + red iron ore (firing) 6 four 3 2 one 9 N ₂ O ₂ + brown iron ore 16 10 6 four 2 10 H ₂ O ₂ + brown iron ore (firing) 10 5 four 2 2 eleven N ₂ O ₂ + magnetic iron ore (firing) + rutile (firing) 3 one one not found. not found. 12 H ₂ O ₂ + red iron ore (firing) + rutile (firing) four 2 2 one not found. 13 H ₂ O ₂ + brown iron ore (calcination) + rutile (calcination) 6 four 2 one one

Claims (3)

1. A method of increasing the bactericidal activity of hydrogen peroxide, comprising introducing hydrogen peroxide into water and contacting with a heterogeneous catalyst based on iron oxides, characterized in that magnetic, red or brown iron ore is used as a catalyst, which is crushed to particles of size 0.5-2 cm, is subjected to oxidative firing in an atmosphere of air at 150-250 ° C for 1-2 hours and brought into contact with water containing hydrogen peroxide, while the residence time of the disinfected water containing hydrogen peroxide , in the layer of heterogeneous catalyst is 0.5-1 hours 2. The method according to claim 1, characterized in that the catalyst further comprises a rutile mineral, pre-crushed to particles with a size of 0.3-0.5 cm, which are subjected to oxidative firing at a temperature of 800-900 ° C, carried out for 1-2 h when supplying air from the bottom up to create a fluidized bed of rutile powder 3. The method according to claim 2, characterized in that the mass ratio of magnetic, red or brown iron ore and rutile is (5-10): 1.