RU2110485C1 - Method for purification of industrial water - Google Patents

Abstract

FIELD: purification of sewage against halogen-organic compounds, preferably against trihalogenomethanes, halogenoacetic acids or salts thereof; production of chloroform and cooling agents. SUBSTANCE: sewage is brought into contact with cast cuttings or with cast shot. The process is carried out in alkaline medium (pH 7.5-13.3 being preferred) and at 30-150 C (boiling being preferred) and within period which is sufficient for decomposition of impurities (1-3 hours being preferred). It is advisable to carry out the process in the presence of oxidizing agent. While purification takes place in the presence of hypochlorite secondary contamination of the medium does not take place. EFFECT: improved efficiency of the method. 4 cl, 3 tbl

Description

 The invention relates to the chemical industry and can be used in the purification of industrial waters contaminated with organohalogen compounds, mainly wastewater from the production of chloroform and chladones.

 A known method of purification of aqueous solutions of volatile organohalogen compounds by evaporation of the latter from an aqueous solution into a carrier gas, passed through the solution, followed by trapping from gas and decomposition using a sorbent-silica gel with ultraviolet irradiation of the sorbent and / or treatment with ozone (US patent N 4941957 Cl. C 01 B 7/00, 1990).

 According to other known methods, for the decomposition of the organochlorine solvent in water, hydrogen peroxide and / or ozone are added to the water and irradiated with ultraviolet rays in the presence of a water-insoluble ferroelectric material (European Patent No. 0537451, class C 02 F 1/32, 1993; ISM. 38, No. 8, 1994, p. 10) or the wastewater is treated with hydrogen peroxide in the presence of porous iron in 2 stages: first in a closed vessel and then in an open vessel with aeration (European patent N 0544924, class C 02 F 1 / 72, 1993; ISM.v. 38, N 10, 1994, p. 87).

 There is also a method of removing contaminants from water, for example, carbon tetrachloride, by adsorption with activated carbon. Then the contaminants are destroyed by mixing the spent activated carbon with metal granules, for example with iron filings (UK patent N 2255088, CL C 02 F 1/70, 1992; ISM. Century 38, N 8, 1994, p. 17).

 However, all the described methods are not easy to implement due to the multi-stage or because of the corrosion activity of the reagents used.

 Closest to the proposed combination of essential features is the method according to British patent N 2255087, cl. C 02 F 1/70, 1992; ISM. issue 38, N8, 1994, p. 17; Chemistry. 1993, 16 and 212 P). In this method, water contaminated with organohalogen compounds, including chloroform, trichloroethane, solvents, pesticides, and the like, is passed through a permeable mixture of activated carbon and iron filings. The mixture is brought to a negative value of the ionization potential, which requires the absence of oxygen. In this case, the metal causes chemical destruction of contaminants. Activated carbon delays pollution, providing a long time in contact with iron. The metal is taken in the form of granules, sawdust, shavings, pre-washed with acid to dissolve the oxide layer.

 The disadvantage of this method is the difficulty of its implementation due to the need for lack of oxygen in the cleaning system, special preparation of the metal surface, preparation of a mixture of metal with activated carbon.

 The purpose of the invention is to simplify the process of water purification.

The goal is achieved by a method of purifying industrial waters contaminated with organohalogen compounds, in particular trihalomethanes and / or haloacetic acids, as well as their salts, including contacting the waters with an iron-containing material with a developed surface, where cast iron is used as an iron-containing material with a developed surface (in the form of shavings, fractions, etc.). Contacting is carried out in an alkaline environment. For this, a pH in the range of 7.5 - 13.3 is created in the waters supplied for contacting. In addition, the contacting is carried out at an elevated temperature for a time sufficient to decompose the pollutant, preferably at a temperature of 30-150 ^° C. and a residence time of 1 to 3 hours, preferably at a boiling point. Contacting can be carried out in the presence of hypochlorite.

Example 1 (see table. 1). For cleaning, industrial waters are taken, which are formed in the production of HFC 22 by the method of liquid phase hydrofluorination of chloroform, from the stage of purification of raw HFC 22, namely
in experiments 1 to 5, water from a cube after azeotropic isolation of HFC 22;
in experiment 6 - water from the droplet eliminator after the first stage of compression of the raw freon 22;
in experiments 7 - 9 - spent alkaline solution from the stage of washing the raw freon 22;
in experiments 10 and 11, a scrubbing liquid from cleaning exhaust vents.

 These waters contain trihalogenomethanes as a pollutant: difluoromethane (HFC 22), fluorodichloromethane (HFC 21), chloroform.

 As contact material in experiments 1–4, 7, 8, and 11, cast iron shavings obtained by turning parts from gray cast iron of the SCh-20 grade are used, and in experiments 5, 6, 9, and 10, a cast-iron split shot of the DChK brand N 1 is used. , 4 in accordance with GOST 11964-81.

 Water purification is carried out in a round bottom flask equipped with a reverse water cooler, the outlet of which is connected to a gas meter. The flask is equipped with a tube for a thermometer, a fitting for supplying purified water from a calibrated funnel through a siphon reaching the bottom of the flask, and a drain pipe for discharging purified water.

 A known volume of cast-iron shavings or cast-iron shot is loaded into the flask and a certain volume of purified water is poured. In a series of experiments, sodium hydroxide is preliminarily added to water to create a certain pH value. The flask is installed on a hot plate, the contents are heated to a predetermined temperature at which they are held for a certain time. Then, a continuous supply of water for treatment begins at a predetermined speed via a siphon under a layer of contact material and the withdrawal of purified water from above this layer. The gas collected in the gas meter is analyzed.

 Specific cleaning conditions and the results are presented in table. 1. From the table. 1 it can be seen that a high degree of water purification from freons 22, 21 and chloroform has been achieved. Water purification is accompanied by the formation of the products of the hydrolysis of trihalomethanes - formate ion and carbon monoxide, as well as the products of chloroform reduction - methylene chloride, methyl chloride and methane.

 Example 2 (see table. 2). For cleaning, industrial water is taken, obtained in the production of chloroform during the washing of the product from chlorine, which is an aqueous alkaline solution of sodium hypochlorite mixed with chlorate contaminated with chloroform. Contact material - shavings of cast iron grade SCH-20. The equipment and the order of the experiments - as in example 1. The specific conditions and results of the experiments are in table. 2. Experiments show that during water purification in the presence of hypochlorite, secondary pollutants — formate and carbon monoxide — do not form, while water also differs from hypochlorite.

Example 3 (see table. 3). For cleaning, industrial chloroform production waters are taken according to the chlorine method, containing 11.7 g / l sodium dichloroacetate (DHAN) and having a pH of 12.4. In a glass apparatus equipped with a reflux condenser and mounted on an electric stove, 100 ml of cast iron particles with a particle size of 1-3 mm and 250 ml of the indicated water are loaded. The contents of the apparatus are maintained at a boiling point (approximately 103 ^o C) for 3 hours, taking water samples after an hour for analysis. The results of the experiment are in table. 3. Experience shows a high degree of water purification from sodium dichloroacetate. Water containing dichloroacetic acid is cleaned in the same way: the latter is previously converted into sodium dichloroacetate by the addition of alkali.

The implementation of the invention on industrial equipment, designed for pressure, will allow water purification at a higher temperature - up to 150 ^o C, which should accelerate the process of destruction of pollution.

The above examples demonstrate a high degree of water purification from organohalogen compounds, which is important due to the stringent requirements for the purity of water for such compounds. For example, the MPC of chloroform in fishery ponds is 0.005 mg / L, the MPC of chloroacetic acids and their salts is 0.028 mg / L. 5
Thus, the proposed method allows you to simply and efficiently clean industrial water (effluents, technological solutions) from organohalogen compounds. The implementation of the method in an industrial environment does not require large expenditures.

Claims (4)

 1. The method of purification of industrial waters contaminated with organohalogen compounds, in particular trihalomethanes and / or haloacetic acids, as well as their salts, comprising contacting the waters with an iron-containing material with a developed surface, including cast iron, characterized in that the contacting is carried out in an alkaline environment at elevated temperatures for a time sufficient to decompose the pollutant. 2. The method according to claim 1, characterized in that in the water supplied to the contacting water create a pH of 7.5 - 13.3 and contacting is carried out at a temperature of 30 - 150 ^o C and a residence time of 1 to 3 hours  3. The method according to claims 1 and 2, characterized in that the contacting is carried out at boiling water.  4. The method according to claims 1 to 3, characterized in that the contacting is carried out in the presence of hypochlorite.

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