Iron is the main enemy water pipes and heating elements household appliances. The presence of ferrocontaining components can be determined using the usual pharmaceutical drugs or an aquarist's kit.
First, let's remember the dangers of high iron content in water.
Iron is in fourth place in terms of abundance in the earth's lithosphere. The source of one of the most important elements of the circulatory system is rocks and compounds of underground wastewater from metallurgical, textile and paint factories.
IN drinking water increased content gland may indicate:
- Corrosion of “black” (cast iron or steel water pipes);
- Use of iron-containing coagulants at municipal water treatment plants.
According to the Sanitary and Epidemiological Rules and Standards SanPin 2.1.1074-01, the total content of the fourth most common chemical element in drinking water should not exceed 03 mg/l.
How to determine iron in water at home?
From school course chemistry knows that iron in liquids occurs in divalent (dissolved) and trivalent (chemically bound) forms (Table 1). In addition, there are organic compounds of one of the most common elements - iron bacteria.
Table 1.
|
Indicator |
Sulfosalicylic acid |
Potassium permanganate (potassium permanganate) |
Aquarist kit |
|
Ferrous iron |
|||
|
Ferric iron |
|||
|
Iron bacteria |
Determination of total iron content
The simplest method for determining iron in water is based on the interaction of cations of the fourth most abundant element with sulfosalicylic acid. A bright yellow compound formed in an alkaline environment is the first “symptom” of corrosion of water pipes
Progress of the experiment:
K 25 ml. add 1 ml of water. ammonia, 1 ml of sulfosalicylic acid (sold in a pharmacy) and 1 ml of ammonia. After 15 minutes, conclusions can be drawn about the presence (or absence) of iron cations in the sample.
How determine iron in water using potassium permanganate (potassium permanganate)?
Potassium permanganate is one of the most “universal” home indicators. To determine the presence of iron, a light pink solution of potassium permanganate is mixed with the sample samples. In case of a positive reaction, the color of the medium changes to yellowish-brown.
Using the “aquarist kit”
The aquarist's kit consists of an indicator, medium and reagents. To identify ferrous iron cations, tap water is poured into a vial containing the solution and reagents using a syringe. Based on the intensity of changes in the color of the medium, one can draw approximate conclusions about the amount of the dissolved element.
Determination of ferric iron
The simplest way to detect the presence of ferric iron is to settle the sample. Residents of large cities are well aware that tap water clean and transparent only on the first day of settling. The appearance of a characteristic red-brown precipitate is the first sign of the presence of ferric iron, which, when oxidized, turns into a reddish hydroxide.
Iron is an element difficult to absorb by the body. Drinking water with a characteristic “brown” tint can contribute to the development allergic reactions or diseases of the hematopoietic organs. In addition, even two milligrams of dissolved iron (MPC according to WHO) will be very difficult to hide in water with a very “unappetizing” appearance and an easily recognizable smell.
Guidelines MU 31-17/06 establish a methodology for measuring the mass concentration of total iron in drinking, natural, waste water and technological aqueous solutions using cathodic voltammetry.
The technique is included in the Federal Register of Measurement Methods under the number: FR.1.31.2007.03300.
Measuring ranges for iron content in water and process solutions
Guidelines MU 31-17/06 establish a method for determining iron in the concentration range from 0.03 to 5.0 mg/dm 3.
Measurement method
Total iron content is measured using cathodic voltammetry. During oxidative sample preparation various shapes iron turns into iron (3+). With a linear change in potential from plus 0.7 V to plus 0.2 V, iron (3+) ions in a weakly acidic solution of hydrochloric acid are reduced to iron (2+) on the gold-carbon-containing electrode. The iron signal during differentiation (dI/dE-E) in the form of a peak at a potential of 0.5 V is directly proportional to the concentration of iron (3+) in the solution.
The mass concentration of total iron in a water sample is determined by adding a certified mixture of iron (3+) to a solution of a previously prepared water sample.
Electrodes used
When determining iron, a three-electrode cell is used. A gold-coated electrode (gold-carbon-containing electrode) is used as a working electrode; as a reference electrode and auxiliary electrode - . Electrodes are included
The service life of the electrodes is at least 1 year.
To implement the technique, you must purchase
- or - for sample preparation.
The use of the following equipment improves the accuracy of measurement results according toGOST 31866-2012
- - for adding solutions at the stage of preparing samples for measurements.
- - for introducing the sample into glasses and diluting the processed sample.
- or - for preparing plugs for measurements while controlling temperature and time.
Reagents used
| Name | Application information | Cost of analyzing one sample* |
|---|---|---|
| Standard sample (RM) of the composition of an aqueous solution of iron (3+) ions with an error of no more than 1% rel. at P=0.95 |
Included in Used for the preparation of certified mixtures |
Less than 0.001 ml (no more than 0.1 ml of CO diluted 100 times) |
| A solution of gold (III) ions with a mass concentration of 10 g/dm 3 (a solution of chloroauric acid with a concentration of 0.051 M) |
Included in the electrode kit. |
Less than 0.05 µl |
| Concentrated nitric acid, special purity. according to GOST 11125-84 | Used for sample preparation | 1 ml |
| Hydrochloric acid, special purity. according to GOST 14261-77 | Used for sample preparation and as a background electrolyte | 1.5 ml |
| Potassium chloride according to GOST 4234-77 special grade. or reagent grade | Used to prepare a solution of 1 M potassium chloride (for filling silver-silver chloride electrodes) | No more than 10 mcg |
|
Double-distilled water |
Used when taking measurements and washing dishes. |
(60-100) ml |
| Sodium bicarbonate (baking soda) according to GOST 2156-76 | Used for washing dishes | No more than 1 g |
*Reagent consumption is given to obtain three results of single measurements.
To supply water to private houses and cottages, they connect to the central water supply or drill wells. It is believed that water from a deep well is cleaner and healthier than tap water. This is not always the case. Yes, it does not contain chemicals, which are added at treatment plants, but there may be impurities of other elements, and in quantities exceeding the norm. Often water contains too much iron. It is not suitable for drinking and household needs. Is it possible to independently determine the causes of water problems? How to remove iron from well water?
Diagram of an autonomous water supply system in a private house
Iron concentration in water: when there is cause for concern
Iron is one of the most common elements in nature, so it is not surprising that well water contains large amounts of this metal. By sanitary standards its content should not exceed 0.3 mg/l, but sometimes the levels reach 20 mg/l.
- Taste qualities
If your well water has a metallic taste, it's definitely time to get tested to find out how contaminated it is. A change in taste may indicate that the norm is exceeded, because with an iron content of up to 0.1 mg/l, a person does not feel “metal in the mouth” at all. The higher the concentration, the more unpleasant the water tastes. This can be felt even in tea, coffee, and cooked dishes.
One of the signs of a high concentration of iron is the appearance of rusty streaks on plumbing fixtures and a brownish coating in kettles and pans. When washed in contaminated water, colored laundry may become discolored.
- Transparency
Depending on the form in which iron is dissolved in water, the liquid may appear cloudy. But this sign cannot be considered 100% reliable, because Sometimes impurities have little effect on the appearance of water.
This is what water with a high concentration of iron looks like
In what forms is iron found in water?
The following iron compounds are important for the well owner:
- Bivalent. It dissolves in water and does not change its color in any way or affect its transparency. The presence of an element can be determined as follows: water is poured into a white bowl and left for several hours. If sediment appears on the walls, it means there are impurities.
- Trivalent. Can change the color and transparency of water, because... does not dissolve. Usually has a brownish or yellow color. If you let the water sit, the iron will precipitate.
- Organic compounds. The metal in these forms does not produce sediment, but can change the color of the liquid to yellowish.
- Bacterial iron. Forms an iridescent film on the surface of the liquid, contaminating water supply elements with jelly-like deposits.
Difference between clean water from a well and oversaturated with iron
Maximum permissible concentration: bias in the calculation of WHO standards
Iron is necessary for the human body. In the blood, its content reaches 4-5 g, and the daily intake is 6-18 mg/day, depending on gender and age. But with an excess of a microelement, problems arise: it is poorly excreted from the body; the intestinal walls can remove up to 10 mg/day.
According to WHO standards, the maximum iron content in water is 0.3 mg/l. Moreover, such standards are established not according to objective criteria, but according to taste. The problem is that it is impossible to determine how much iron a person consumes. The microelement enters the body with various foods - liver, legumes, apples, fish, etc.
The maximum tolerated amount of iron for the body is 0.8 mg/kg body weight. This is also an approximate figure, because, as we have already found out, WHO focuses not only on medical criteria. In addition, there is too little confirmed data on specific disorders of the body when iron standards are exceeded.
Water with a maximum iron concentration of 0.3 mg/l already tastes unpleasant. Therefore, it is better for the well owner to focus not only on the standards, but also on his own taste buds. If there is a metallic taste, the water should be checked and purified, because even with normal, from the WHO point of view, iron concentration, the water is often impossible to drink without disgust.
How to properly collect a water sample for analysis at a sanitation station
If the well was drilled recently, water analysis is done immediately. Also, the need for analysis arises when there is a sharp change in taste or appearance liquids. There is a specific sampling algorithm. It must not be violated, otherwise the results will be biased. Basic rules for the fence:
- Glass or plastic containers with a volume of no more than 1.5 liters are used as containers. You cannot use beverage bottles with dyes and flavors, but you can collect the sample in a mineral water container.
- The bottle or jar is washed several times hot water, then cold - the same one that will be taken for analysis. Household chemicals cannot be used.
- Before drawing, open the tap for 15-20 minutes and allow the water to drain so that impurities deposited on the pipes do not affect the analysis results.
- Water is drawn by opening the tap to minimum. It should not be oversaturated with oxygen to prevent possible chemical reactions.
- When the container is filled to the brim, close it tightly. This will help block the air supply. After this, the bottle is placed in an opaque bag or bag to avoid exposure sun rays.
- The sample is delivered to the health station within the next three hours. If this is not possible, then at least on the same day.
It is not advisable to store water, but if you have to, wrap it in a dark, opaque bag and put it in the refrigerator. Water that has stood in the refrigerator for more than 2 days is unsuitable for analysis; the sampling must be repeated.
Attention! If there are industrial enterprises or other facilities whose activities may affect water quality, analysis should be done at least once a year.
Water analysis is carried out using special tests and chemical reagents
The most common methods of purifying iron from well water
The choice of cleaning method depends on the form in which the element is in the water. Most often this is divalent iron. It gives the water a metallic taste, but does not change color. The following methods are used for cleaning:
- ion exchange;
- reverse osmosis;
- traditional methods.
Iron removal filters and cartridges
Ion exchange method of iron removal. To clean, you will have to install a filter with an ion exchange cartridge. Experts recommend giving preference to Fe-10sl, Fe-20BB cartridges from Geyser; BA, which works on a different principle but is quite effective, is also suitable.
Reverse osmosis. More reliable way decrease in iron concentration. Reverse osmosis filter membranes are good at purifying water from many impurities, but problems can arise if the liquid contains too much ferric iron - it clogs the pores of the filter.
Iron removal mechanical filter
Effective “folk recipes” from home-grown kulibins
Our compatriots are accustomed to solving all problems on their own, without relying on high technology, and without extra costs. Their advice is very relevant and really useful. Experienced summer residents recommend simply settling the water and enriching it with oxygen, waiting until the iron precipitates, and carefully collecting clean, transparent liquid. This can be done like this:
- In a bucket. The simplest way: leave the water for several hours and carefully draw it from above.
- Open tank. The principle is the same, but the water is placed in a trough. To speed up chemical reactions, a regular aquarium compressor is lowered into the container.
- Storing water in a special tank. Water from the well is stored in a tank, collected as needed, and when the layer of sediment becomes too noticeable, the tank is simply cleaned.
Although the advice from the “nuggets” looks too simple, it is quite applicable and is based on objective chemical processes. If the iron is trivalent, then it will precipitate, and the collected water will be much cleaner. Bivalent iron becomes trivalent under the influence of oxygen, so an open tank and compressor - good options DIY cleaning.
It is better to give preference to filters from well-known manufacturers and purify the water as much as possible from all unnecessary impurities. But until you acquire the necessary equipment, “folk methods” will come in handy as a temporary measure. They are simple and do not require major expenses. For a summer house where there is not a lot of water consumption, it is enough to buy a large tank and a compressor. But for a home with permanent residence, a filter is a vital thing.
Video: determining heavy metals at home
If you have decided (like me) to independently assemble and run a budget-friendly water treatment plant in your dacha that is not afraid of frost, then you will not be able to do without the skill of independently testing the resulting water.
Water quality indicator
Organoleptic characteristics
1. Smell at 20 degrees.
2. Smell when heated to 60 degrees.
3. Taste and taste at 20 degrees.
4. Color
Generalized indicators
5. Hydrogen. show / pH / conc. hydrogen ions
6. General hardness
7. Carbonate hardness
8. Permanganate oxidation
9. Total mineralization / dry residue /
10. Alkalinity
Chemical indicators
11. Iron Fe Fe2+
12. Iron Fe total.
13. Manganese
14. Sodium + potassium
15. Calcium
16. Magnesium
17. Sulfates /SO 4 "/
18. Chlorides /Cl" /
19. Nitrates / by NO 3 "/
20. Nitrite /ion/
21. Silicates
22. Fluorides /F/
23. Bicarbonates
24. Ammonium nitrogen
26. Hydrogen sulfide / sulfides
I won’t be original if I say that the very first analysis should be done in the laboratory and for the maximum possible amount of contaminants.
Based on this analysis, select indicators that exceed the norms and assemble a system capable of purifying precisely those contaminants that go beyond the scope of SNIP (maximum guidelines). And also buy kits for testing water only for these contaminants.So. My water tested by the laboratory, at the time of construction of the well:
Having analyzed this piece of paper, we come to the conclusion that a system is needed to remove iron (15.58 units), manganese (1.7 units), hydrogen sulfide and hardness. Tests are also needed to analyze these contaminants.Having purchased and assembled the necessary components into the system (for now, purification is only for iron, manganese, hydrogen sulfide), we begin to analyze the water at home.
Water analysis kits that I use.
The photo numbers correspond to the items.
1. A very good (accurate) imported kit for determining iron in water. The kit was purchased at a pet store and is intended for determining iron in a freshwater aquarium (presumably with fish). Next come domestic kits, which are less accurate, but also cope with their tasks adequately.
2. Water pH determination kit. (Necessary when using Ph-dependent dehydrator loads, for example BIRM)
3. Test for Fe2, iron dissolved in water does not color the water, but gives it a characteristic taste and smell.
4. Test for Fe3, undissolved iron. Colors the water yellow. In common parlance - rust
5. Manganese test. At high concentrations it colors water from gray to black.
Let's start water analysis
6. We begin testing water by determining Fe2. We collect water directly from the well, from a depth of 4 meters. The water has a strong iron smell and is cloudy. We read the instructions on the piece of paper attached to the test and pour the required amount of test water into the bottle from the syringe. Then add the reagents.
7. The water turns an intense red color. This indicates that there is more iron Fe2 in the water than this test can show (definitely more than 5, we already know this from analysis from the laboratory)
8. We use the same test to check the water after the filters. Fe2 = 0, this means that all the iron after the filters has been oxidized into Fe3 and retained by the purification system.
9. The same water, after the purification system, but tested for Fe3. According to the test, the water contains undissolved iron Fe3 in an amount of up to 0.3 units, giving it a slightly yellowish tint.
10. We start the test with an imported kit that determines the total iron in water. There are 2 bubbles, for accuracy.
11. Reagents are poured into one bottle
12. The stand with bubbles is placed on a colored ruler and by looking inside we ensure that both bubbles have the same color. In the window we see the result - 0.1 units, which in principle does not contradict the test just carried out on domestic components.
13. If you take the bubbles out of the holder, the water with the reagents has a pinkish tint, indicating that there is iron in the water (though it’s not clear Fe2 or Fe3, like general, but we already know from previous tests that it’s Fe3)
Based on the tests performed, I had a question for the water treatment specialists.
Tests say what's in the water Fe2 missing- there is NO dissolved iron, but the test Fe3 claims that in the water is NOT dissolved iron in amounts up to 0.3 units. This iron is not filtered by a 1 micron cartridge and is not completely selected by activated carbon (this year some kind of wrong carbon was caught, or something, before everything was selected by carbon). The water has a barely noticeable yellowish tint.
But if you add hypochloride (“whiteness”) to this water with Fe3, then after a few minutes the water darkens, and after a few hours Fe3 flakes precipitate and the water becomes completely colorless.
Adding hydrogen peroxide or AquaAurat to this water does not cause such an effect, the water remains the same as it was - slightly yellowish.
WHAT IS THIS? Why does hypochloride oxidize already oxidized Fe3?
Purpose of the work. Learn to determine the content of iron compounds in water and carry out initial processing of the results.
Reagents and solutions.
1. Basic standard solution of ferroammonium alum. 0.8636 g FeHH 4 (SO 4) 2 12H 2 O on an analytical balance, dissolved in a volumetric flask to 1 dm 3 in small quantity distilled water, add 2.00 cm 3 HCl (ρ = 1.19 g/cm 3) and bring to the mark with distilled water. 1 cm 3 of solution contains 0.1 mg Fe 3+.
2. A working standard solution of FeNH 4 (SO 4) 2 is prepared on the day of analysis by diluting the stock solution 20 times. 1 cm 3 of solution contains 0.005 mg Fe 3+.
3.Sulfosalicylic acid solution. 20 g of sulfosalicylic acid are dissolved in a 10 cm 3 volumetric flask in a small amount of distilled water and adjusted to the mark with this water.
4.2M NH 4 Cl solution. 107 g of NH 4 Cl are dissolved in a 1 dm 3 volumetric flask in a small amount of distilled water and adjusted to the mark with this water.
5 Ammonia solution (1:1) 100 cm 3 of 25% ammonia solution is added to 100 cm 3 of distilled water and stirred.
Utensils and equipment.
1 Photoelectric colorimeter KFK-2.
2.50 ml volumetric flasks.
3.Pipettes for 1 ml - 3 pcs.
4 50 ml graduated cylinder.
5. Heating device.
6. 300 ml conical flasks for the number of samples plus one.
General information. Iron is an essential element for life and is part of the hemoglobin in the blood. It is contained in water in the form of iron ions Fe 3+ and Fe 2+, the latter are easily oxidized to Fe 3+ ions. A large amount of oxygen is spent on oxidation, so it is necessary to especially strictly monitor the iron content, primarily Fe 2+, in wintering ponds, where an unfavorable gas regime may develop under the ice. When Fe 3+ ions combine with humic acids dissolved in water, a loose brown precipitate forms.
Despite the fact that iron is a biogenic element, its content in quantities exceeding optimal values can be harmful and lead to the death of fish. The harmful effects of excess iron are increased in an acidic environment. Significant amounts of iron can end up in water bodies from industrial wastewater.
Determination principle iron compounds is based on the interaction of Fe 3+ ions in an alkaline medium with sulfanilic acid to form a yellow-colored complex compound. The color intensity, proportional to the mass concentration of iron, is measured at a wavelength of 400-430 nm. The measurement range for the mass concentration of total iron without sample dilution is 0.10-2.00 mg/dm 3 .
Progress of determination. When the mass concentration of total iron is no more than 2 mol/l, 50 ml of the test water is measured using a measuring cylinder (at higher concentrations, the sample is diluted with distilled water), placed in a conical flask, heated to a boil and evaporated to a volume of 35-40 ml.
The solution is cooled to room temperature, transfer to a 50 ml volumetric flask. To the resulting solution add 1 ml of ammonium chloride solution, 1 ml of sulfosalicylic acid, 1 ml of ammonia solution, stirring thoroughly after adding each reagent. Using indicator paper, determine the pH of the solution, which should be greater than 9. If the pH< 9, го прибавляют 2-3 капли раствора аммиака (1:1) до рН>9. The volume of solution in the volumetric flask is adjusted to the mark with distilled water and left to stand for 5 minutes for color development.
The optical density of colored solutions is measured using a violet filter (λ = 400-430 nm) and cuvettes with a working layer thickness of 2.3 or 5 cm in relation to 50 ml of distilled water, to which the same reagents are added as in the test sample. The mass concentration of total iron is determined using a calibration curve.
Construction of a calibration graph. 0.0 is poured into a series of volumetric flasks with a capacity of 50 cm 3; 1.0; 2.0; 5.0; 10.0; 15.0; 20.0 cm 3 workers standard solution and dilute to the mark with distilled water, mix, and analyze as test water. A scale of solutions corresponding to a mass concentration of iron of 0.0 is obtained; 0.1; 0.2; 0.5; 1.0; 1.5; 2.0 mg/dm3. A calibration graph is constructed, plotting the mass concentration of iron on the abscissa axis, and the corresponding optical density values on the ordinate axis.
Processing of analysis results. If the sample volume taken for analysis is less than 50 ml, then the iron concentration is calculated using the formula:
X = (P. 50)/V,
where C is the mass concentration found from the calibration curve, mg/dm 3 Fe 3+ ; V - sample volume taken for analysis, ml; 50 - volume of standard solution, ml.
The final result of the analysis is taken as the arithmetic mean of the results of two parallel determinations, the permissible differences between which should not exceed 25% at the mass concentration of iron at the MPC level.
The convergence of analysis results (A) in percentage is calculated using the formula:
Report. The report on this laboratory work consists of an oral interview with the teacher. The measurement results are presented in the prescribed form.
TEST QUESTIONS
1. What are the forms of iron dissolved in water?
2. What is the principle for determining iron dissolved in natural waters?
LABORATORY WORK No. 14