Determination of chemical activity of organic substances in reference to iron compounds in aqueous solutions

FIELD: chemistry, water quality control, method for quantitative estimation of organic substance properties in aqueous solutions.

SUBSTANCE: indicator plate is immersed in aqueous solution and according to alteration of aqueous solution composition chemical activity of organic substances in this solution is determined. In clamed method tree vessels are used. Two vessels contain aqueous solution to be tested and the third vessel contains control aqueous solution free from organic contamination. In aqueous solutions containing in the second and third vessels indicator plates are immersed, then aqueous solutions in all vessels are heated up to 95-105°C, held at this temperature for 55-65 min, cooled to 15-25°C, filtered though membrane filter with pore size of 0.46 mum, then iron content is measured in all vessels and chemical activity of organic substances in aqueous solutions is calculated according to equation ka=ΔFe/Fe1, wherein ΔFe = Fe2- Fe1- Fe3; Fe1 is iron content in the aqueous solution of the first vessel; Fe2 is iron content in the tested aqueous solution of the second vessel; and Fe3 is iron content in the aqueous solution of the third vessel.

EFFECT: simplified method with enhanced functionality.

3 ex, 4 tbl

 

The invention relates to chemistry, in particular to the quality control of water containing organic impurities, and may find application in quantifying properties of organic compounds with respect to iron compounds in aqueous solutions, in particular when determining the chemical activity of organic compounds capable of forming complex compounds with iron, which may be formed on the surface of iron or in solution.

There is a method of determining the chemical activity of organic compounds in aqueous solutions, in which the aqueous solution is placed flat plate and change the appearance of the coating, weight, size, structure and other physical properties of the indicator plate, the depth of the foci of corrosion or changes in the composition of the medium determine the chemical activity of the aqueous solution [1].

The above-described method is characterized by limited functionality. In particular, in order to evaluate the chemical activity (corrosive properties) aqueous medium at pH 7-8 by the change in mass of the sample, it is necessary to carry out the experiment in a long time (several weeks). In these conditions it is possible only to estimate the influence of natural organic compounds on the chemical activity of aqueous solutions with significant concentrations of substances. koncentrirovannaya is provided by different means: by evaporation source solution by freezing it, but it modifies the physico-chemical properties of the solution and the ratio of components of its impurities.

To assess the chemical activity (corrosivity) of the aquatic environment by a known method, based on the change of the potential of the indicator plate in an aqueous solution, with the help of special instruments - potentiometers - shoot polarization curves and perform complex calculations.

The invention solves the problem of creating a method for determining the chemical activity of organic compounds in relation to the iron compounds in aqueous solutions, characterized by greater functionality while simplifying the experiment.

To solve the problem in the method of determining the chemical activity of organic compounds in relation to the iron compounds in aqueous solutions, in which is placed flat plate in an aqueous solution and by changing the composition of an aqueous solution determine the chemical activity of organic compounds in aqueous solution proposed according to the present invention to use three tanks, two of which put the investigated aqueous solution, and the third has the capacity to place the control aqueous solution containing no organic impurities in aqueous solutions contained in the second and third containers, place indicatorname plate, then aqueous solutions in each of the three tanks is heated to temperature [95÷105]°C, maintained at this temperature for [55÷65] minutes, cooled to a temperature of [15÷25]°C, filtered through a membrane filter with pore size and 0.46 μm, measure the iron content in water solutions of all three tanks, and chemical activity of organic compounds in aqueous solutions is determined by the ratio of activity:

ka=ΔFe/Fe1,

where ΔFe=Fe2-Fe1-Fe3

Fe1the content of iron in aqueous solution the first capacity;

Fe2the iron content in the investigated aqueous solution of the second capacitance;

Fe3the content of iron in aqueous solution in the third tank.

The invention is illustrated by examples of implementation, the results of which are shown in three tables and are the experimental data on the content of soluble iron and definition of the activity coefficient for aqueous solutions containing various additives.

In particular, table 1 presents experimental data on the content of soluble iron and definition of the activity coefficient of kafor aqueous solutions of various organic substances. As a control aqueous solution in example 1 (and, hence, in table 1) distilled water is used.

In Alice 2 shows experimental data on the content of soluble iron and definition of the activity coefficient of k afor aqueous solutions containing the inhibitor ions (Inhibitor deposition of mineral salts). As a control aqueous solution in example 2, experiments 1÷3 (and, hence, in table 2)used an aqueous solution of sulphate (80 mg/DM3) and chloride (20 mg/DM3), brought to pH 8.8, and in experiments 4÷6 - source water samples.

And, finally, table 3 presents experimental data on the content of soluble iron and definition of the activity coefficient of kafor a 4%aqueous solution of sulfuric acid in the presence of various organic substances, in particular corrosion inhibitors. As a control solution of example 3 (and, hence, in table 3) used 4%solution of sulphuric acid.

The essence of the proposed method of determining the chemical activity of organic compounds in aqueous solutions is as follows.

To implement the method using three tanks, two of which are placed the test solution, containing organic impurities, and the third is the capacity of the control aqueous solution containing no organic impurities, which may be distilled water, solutions of inorganic compounds or natural aqueous solutions.

In aqueous solutions contained in the second and third containers, put the indicator plate. The choice of material and size of indicatores plate, as well as the volume of the solution intended for its premises, based on the experimental data, providing reproducible results.

Then aqueous solutions in each of the three tanks is heated to temperature [95÷105]°C, maintained at this temperature for [55÷65] minutes, cooled to a temperature of [15÷25]°C, filtered through a membrane filter with pore size and 0.46 μm, measure the iron content in water solutions of all three tanks, and chemical activity of organic compounds in aqueous solutions is determined by the ratio of activity:

ka=ΔFe/Fe1,

where ΔFe=Fe2-Fe1-Fe3;

Fe1the content of iron in aqueous solution the first capacity;

Fe2the iron content in the investigated aqueous solution of the second capacitance;

Fe3the content of iron in aqueous solution in the third tank.

It is known that to assess the ability of organic compounds in aqueous solutions to interact with cations of iron (II, III) can, in theory, the value of the constant instability (kn), however, these values can only be obtained for some pure substances under certain conditions. While the chemical activity of the aqueous solution is determined by several factors and the composition of organic reagents, typically includes n is as connections.

The basis of the proposed method of determining the chemical activity of organic compounds in aqueous solutions based on the evaluation of the properties of individual organic compounds or several compounds present in aqueous solution, with respect to compounds of iron. As a criterion for assessing chemical activity of organic compounds is proposed to use the activity coefficient of ka. The value of kachanges in a wide range from-n to +n. You can conclude the following:

- ceteris paribus experiment in the interval of values of kain the range from 0 to +n: the larger the value of n, the more the organic compound will increase the chemical activity of the aqueous solution in relation to iron compounds due to the formation of soluble complex compounds of iron;

- ceteris paribus experiment in the interval of values of kain the range from-n to 0; the smaller the value of n, the less chemical activity of organic compounds to the formation of soluble compounds in aqueous solution due to the fact that on the surface or in solution form insoluble organoiron compounds.

Example 1.

The essence of this example was to determine the chemical activity of the soluble iron in the-breaking solutions of different organic substances.

In two containers placed the test solution, which used a variety of aqueous solutions: salicylic acid with different organic matter content, Trilon B with different organic matter content and Aminat DS.

Trilon B - disubstituted sodium salt of ethylenediaminetetraacetic acid.

Aminat DS is a mixture of salts of phosphonic acids.

The third tank was placed control solution containing no organic impurities (distilled water). In addition, during the second and third containers were placed flat plate.

Then aqueous solutions in each of the three containers were heated to temperature [95÷105]°C, kept at this temperature for [55÷65] minutes, cooled to the temperature [15÷25]°C, filtered through a membrane filter with pore size and 0.46 μm and measured the iron content in water solutions of all three tanks, after which the chemical activity of organic compounds in aqueous solutions is determined by the activity coefficient in the above dependencies.

The research results of example 1 are summarized in table 1.

Table 1

Experimental data on the content of soluble iron and definition of the activity coefficient of kafor water dissolve the s various organic substances
no experienceThe composition of the aqueous solutionThe content of organic substances (TOC), mg/DM3The iron content, mg/DM3ka
Fe1Fe2Fe3
1.Salicylic acid (distillers. water)50,050,310,093,4
2.Salicylic acid (distillers. water)150,050,870,0914,6
3.Trilon B (distil. water)50,052,620,0949,6
4.Trilon B (distil. water)150,1322,90,09of 174.5
5.AMINAT DS (0.02% of volume)a 12.70,244,780,0418,8

It is known that to assess the ability of organic compounds in aqueous solutions to interact with cations of iron (II, III) can not only experimentally in accordance with the method described in [1], but also on the value of the constant instability (kn), the calculated is Anna on the basis of experimental data. However, these values of the constants instability (kncan be obtained only for some pure substances under certain conditions.

It is known that to assess the ability of organic compounds in aqueous solutions to interact with cations of iron (II, III) can not only experimentally by the method described in [1], but, theoretically, the value of the constant instability (kn). However, these values can only be obtained for some pure substances under certain conditions: the smaller the value of the constant instability (kn), the greater reactivity of organic compounds when other conditions are equal.

The value of the constant instability for salicylic acid kn(Fe-Sal+)=3,5×10-12for trylon B - kn(FeSlta-)=8×10-26.

The value of knTrilon B will be much more to interact with cations of iron (III) to form a soluble complex compounds than salicylic acid.

From the results of the study are presented in table 1, it follows that:

- with the same content in an aqueous solution of salicylic acid and trylon B activity coefficient of kafor a solution of the trylon B much more, i.e. the value of kacorrelated with a value of kn;

- by increasing the concentration of these ve the EU ETS 3 times the activity coefficient increases in proportion.

Since the solutions of the trylon B and salicylic acid actively interact with the iron compounds with the formation of soluble compounds, they are used for washing equipment from deposits in which structure - compounds of iron.

Reagent "AMINAT DS" is a fairly complicated solution of several organic compounds. For comparative evaluation of the properties of organic compounds for values of knand kathe reference solutions were used solutions of salicylic acid and trylon B with concentrations of 5 and 15 mg/DM3. With comparable content of total organic carbon chemical activity AMINAT DS is comparable with the activity of salicylic acid (table 1, experiments 2, 5).

Thus, example 1 shows that the inventive method of determining the chemical activity of aqueous solutions allows you to compare physico-chemical properties of solutions containing various organic substances, while significantly reducing time and relative simplicity of the experiment.

Example 2.

The essence of this example was to determine the chemical activity of the soluble iron to the aqueous solutions containing ions - inhibitor deposition of mineral salts of various organic substances.

In two containers placed the test solution, as that is about used different aqueous solutions of IMSA - inhibitor deposition of mineral salts.

The third tank was placed control solution containing no organic impurities (water solution of sulphate 80 mg/DM3and chloride 20 mg/DM3brought to pH 8.8). In addition, during the second and third containers were placed flat plate.

Then aqueous solutions in each of the three containers were heated to temperature [95÷105]°C, kept at this temperature for [55÷65] minutes, cooled to the temperature [15÷25]°C, filtered through a membrane filter with pore size and 0.46 μm and measured the iron content in water solutions of all three tanks, after which the chemical activity of organic compounds in aqueous solutions is determined by the activity coefficient in the above dependencies.

The research results of example 2 are summarized in table 2.

In the above example 2 was determined by the chemical activity of ions in the different possible situations:

- when changing its concentration in the control solution (experiments 1, 2, 3);

- at the same concentration, but in different aqueous solutions (experiments 1, 4, 5, 6).

Inhibitor of deposits of mineral salts (ions) (see table 2) is a mixture of organic phosphate complexes. In practice, the application of the inhibitor at high doses leads to cleaning of equipment and pipelines from the product of the s corrosion.

Presented in the table 2 data, it follows that:

with increasing doses of inhibitor in the control solution, the value of the activity coefficient of kaincreases, i.e. with increasing doses of inhibitor ability to form a soluble complex compounds with cations of iron (III) increases;

- the activity of ions in natural waters of different sources in relation to the iron compounds can vary greatly: katakes the values of-0.7; -2,8; -10.

Thus, the chemical activity of ions significantly influenced by specific natural organic compounds that can strengthen or weaken the effect of ions.

In table 2 data indicate that the reagent ions capable of forming soluble organoiron complex compounds with increasing its concentration in solution, however, when its concentration is 2 mg/DM3this ability will greatly depend on the properties of aqueous solution, in which you want to add the reagent, since ka<0.

When determining these properties other way long it will take not less than one year.

Table 2

Experimental data on the content of soluble iron and definition of coefficie is the activity of k afor aqueous solutions containing inhibitor (IOS)
no experienceThe composition of the aqueous solutionThe content of ions on C, mg/DM3The iron content, mg/DM3ka
Fe1Fe2Fe3
1.Ions (distillers. water) pH 8.8; (SO4)2=80 mg/DM3; Cl-=20 mg/DM320,050,620,187,8
2.Ions (distillers. water)pH 8.8; (SO4)2=80 mg/DM3; Cl-=20 mg/DM340,050,760,1810,6
3.Ions (distillers. water) pH 8.8; (SO4)2=80 mg/DM3; Cl-=20 mg/DM360,050,920,1813,8
4.Ions (sample # 1) pH 8.8; (SO4)2=67,2 mg/DM3; Cl-=6.25 mg/DM320,050,170,62-10
5.Ions (sample # 2) pH 8.8; (SO4)2=to 36.8 mg/DM3; Cl-=11.3 mg/DM320,190,27 0,62-2,8
6.Ions (sample # 3) pH 8.8; (SO4)2=45,9 mg/DM3; Cl-=20 mg/DM320,470,740,62a-0.7

Example 3.

The essence of this example was to determine the chemical activity of the soluble iron to the aqueous solutions containing 4%solution of sulfuric acid in the presence of various organic substances, corrosion inhibitors.

In two containers placed the test solution, which was used in different experiments, different aqueous solutions: methenamine, captax, INDAKOR, ALTHOSAN.

Methenamine - hexamethylentetramine.

Captax - 2-mercaptobenzthiazole.

INDAKOR - modified triethanolamine salt aminocaproic acid.

ALTHOSAN - alkyldimethylbenzylammonium chloride.

The third tank was placed control solution containing no organic matter (4%solution of sulfuric acid). In addition, during the second and third containers were placed flat plate.

Then aqueous solutions in each of the three containers were heated to temperature [95÷105]°C, kept at this temperature for [55÷65] minutes, cooled to the temperature [15÷25]°C, filtered through a membrane filter with pore size and 0.46 μm and measured the content of the iron in aqueous solutions of all three tanks, then the chemical activity of organic compounds in aqueous solutions is determined by the activity coefficient in the above dependencies.

The research results of example 3 are summarized in table 3.

Inhibitory effect estimate on the rate of corrosion in aggressive environment before and after the addition of the corrosion inhibitor. Most corrosion inhibitors are organic compounds. According to preliminary data obtained by other methods using potentiometric measurements (ceteris paribus experiment), the degree of inhibition by katakam is 99%and methenamine - 81%.

In laboratory conditions the value of the activity coefficient of kacaptax, determined in accordance with the inventive method, is 44×103, protrotype - 31×103, i.e. the efficiency of captax higher value of the activity coefficient of kaand correlates with the previously obtained result.

Table 3 shows the results of the analyses inhibitors offered by the firm "Prolac-E": the activity of the reagent ALTHOSAN significantly higher than that of the reagent INDAKOR. Moreover, the reagent ALTHOSAN on the efficiency of inhibition is similar to the reagent captax.

With the comparable value of the activity coefficient of ka(in experiments 3 and 5) require significantly Myung is more reagent ALTHOSAN, as used volumetric concentration of 10% reagent. While the consumption of the reagent captax is 0.02% mass 100% dry matter.

Thus, the effectiveness of new inhibitors and their doses can be determined in the process of the proposed experiment on the value of ka.

Table 3

Experimental data for the determination of the activity coefficient of kafor a 4%aqueous solution of sulfuric acid in the presence of various organic chemicals (corrosion inhibitors)
no experienceThe name of the additiveThe content of organic matter, mg/DM3The iron content, mg/DM3ka
Fe1Fe2Fe3
1.--0,0522320,0944,6×103
2.Methenamine0,5 (mass.)0,056352232-31,9×103
3.Captax0,02 (mass.)0,05232232-44×103
4. INDAKOR0,02 (volume)0,0512402232-19,9×103
5.ALTHOSAN0,02 (volume)0,052182232-40,3×103

As follows from tables 1-3, the value of kachanges in a wide range from-n to +n. You can conclude the following:

- ceteris paribus experiment in the interval of values of kain the range from 0 to +n: the larger the value of n, the more the organic compound will increase the chemical activity of the aqueous solution in relation to iron compounds due to the formation of soluble complex compounds of iron;

- ceteris paribus experiment in the interval of values of kain the range from-n to 0; the smaller the value of n, the less chemical activity of organic compounds to the formation of soluble compounds in aqueous solution due to the fact that on the surface or in solution form insoluble organoiron compounds.

Based on the above research results, we can conclude that the results of the experiment allow us not only to compare the proposed reagents for chemical activity, but also to choose the optimal dose of the reagent.

The selection of protected areas is normal dose of reagent ALTHOSAN 6% solution of hydrochloric acid (HCl) is illustrated in table 4.

Table 4

Experimental data on the optimum dose of the reagent ALTHOSAN 6% solution HCl
no experienceVolume % reagentThe iron content, mg/DM3ka
Fe1Fe2Fe3
10,010,053201155-16,6·103
20,020,05501155-22,1·103
30,030,05501155-22,1·103
40,040,05501155-22,1·103

As follows from table 4, the minimum value of the activity coefficient of kais achieved when the content of reagent equal to the volume of 0.02 percent. Therefore, when the content of such quantity of reagent activity coefficient of katakes the minimum value and does not change when increasing the concentration of reagent in solution. Therefore, the dose equal volume of 0.02 percent is optimal.

The inventive method ODA the division of chemical activity of organic compounds in relation to the iron compounds in aqueous solutions is characterized, as compared with known similar way, adopted for the prototype, the ability to determine the chemical activity of organic compounds capable of forming complex compounds with iron, which may be formed on the surface of iron, and in solution, so it can find wide practical application in solving various production problems associated with water treatment.

The inventive method of determining the chemical activity of organic compounds in relation to the iron compounds in aqueous solutions developed in the chemical laboratory of JSC "Sverdlovenergo" and is used to solve various problems associated with the evaluation of the properties of organic substances in the aquatic environment.

The results obtained confirm its efficiency and wide applicability in the future.

Literature:

1. GOST 9.905-82. Unified protection against corrosion and ageing. Methods of corrosion testing. General requirements. Publishing house of standards, 1983, p.1, 3÷4.

The method of determining the chemical activity of organic compounds in relation to the iron compounds in aqueous solutions, in which is placed flat plate in an aqueous solution and by changing the composition of an aqueous solution determine the chemical activity of organic compounds in aqueous solution, characterized in that use three the flask, in two of which placed the investigated aqueous solution, and in the third tank is placed a control aqueous solution containing no organic impurities in aqueous solutions contained in the second and third containers are placed flat plate, then aqueous solutions in each of the three tanks is heated to a temperature (95÷105)°C, maintained at this temperature for 55÷65 min, cooled to a temperature of 15÷25°C, filtered through a membrane filter with pore size and 0.46 μm to measure the iron content in water solutions of all three tanks, and chemical activity of organic compounds in aqueous solutions is determined by the activity coefficient

ka=ΔFe/Fe1,

where ΔFe=Fe2-Fe1-Fe3;

Fe1the content of iron in aqueous solution the first capacity;

Fe2the iron content in the investigated aqueous solution of the second capacitance;

Fe3the content of iron in aqueous solution in the third tank.



 

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