Iron is present in water in the form of divalent and trivalent ions. How to clean drinking and technical liquids from these contaminants? An urgent problem for an ordinary family and a large enterprise. Consider the reasons on which the solubility of iron in water depends, the forms of pollutants, methods for removing ferrocompounds.
Why is tap water yellow and brown?
Iron compounds give the water a yellowish color, often there is an unpleasant aftertaste, you can notice pollution in the form of brown flakes. These phenomena are the deterioration of the organoleptic properties of drinking water. Color change is what water consumers pay attention to first of all. In addition, there are implications for human he alth. The consumption of poor-quality tap water, which contains iron, negatively affects the condition of the liver, teeth, the entire gastrointestinal tract, skin and hair.
Solubility in water is explained not only by the interaction of ferrocompounds from the composition of rocks with other substances in nature. risesthe concentration of Fe2+ and Fe3+ ions due to the corrosion process that constantly occurs in water supply devices and pipes made of iron alloys. Pipelines are gradually becoming unusable, the properties of products, in the production of which water with an admixture of iron was used, are changing.
What is the solubility of iron in water?
The chemical element, which was given the Latin name Ferrum, is the second most abundant in the earth's crust after aluminum. In large quantities on the planet there are deposits of iron pyrite or pyrite (its formula is FeS2). Ferro compounds are found in rocks of volcanic and sedimentary origin in the form of hematite, magnesite, brown iron ore.
The simple substance iron is a silver-gray ductile metal, insoluble in water. Oxides and hydroxides, many iron s alts also do not interact with water. The solubility of FeO in water is discussed in connection with its ability to oxidize to ferric oxide. When talking about an aqueous solution of FeO, they mean the content of ferrous ions. In some water sources, this figure reaches 50 or more milligrams per 1 liter. This is a high concentration, such drinking water should be purified.
How does iron get into natural waters?
Physical and chemical erosion leads to crushing, dissolution and destruction of rocks containing iron compounds. As a result of the reactions taking place innature, the ions Fe2+ and Fe3+ are released. They are actively involved in redox processes. The divalent ion is oxidized, donates an electron, and becomes triply charged. The solubility of iron in water is the presence of the cation Fe2+. As a result of the reactions taking place in the solution, different s alts are obtained. Among them are soluble, such as sulfates, and insoluble (sulfides, carbonates). When such water is iron-free, the soluble form becomes insoluble, flakes are formed that precipitate. Ferrous iron is oxidized to trivalent in the presence of oxygen or other oxidizing agents (ozone, chlorine).
Transformations of ions eventually lead to the appearance of brown rust resistant to further oxidation, its conditional composition can be represented as follows: Fe2O3• nH2O. Particle Fe3+ are part of the complex inorganic and organic substances found in surface waters.
Is the content of ferrocompounds in natural waters the same?
Concentrations of a chemical element and types of iron in water depend on the rock composition of the earth's crust and the state of various sources. Divalent and trivalent iron compounds, organic forms such as iron bacteria and colloidal substances (soluble and insoluble) may be present at the same time.
If there are deposits of sulfate ores, it is more likely that ferrous iron will be present in high concentrations. Solubility in waterferrocompounds increases with temperature near areas of volcanism. The iron content in rivers and lakes is higher if there is a discharge of wastewater from metallurgical and chemical plants.
How to purify water from iron?
Reagent and non-reagent methods are used to remove ferrocompounds. The basis of most processes is the oxidation of a divalent ion to a trivalent cation. They do the same with other impurities in water - they are converted into insoluble compounds and removed with a filter. The operation of most industrial installations is based on this principle.
What is the solubility of iron in water, determined using instruments. Then iron removal is carried out with chemical reagents: oxygen, chlorine, ozone, potassium permanganate, hydrogen peroxide. Chemical oxidation reactions take place and an insoluble precipitate is obtained. It can not only be filtered, but also removed after settling by decantation (drain clean water from the sediment). During ozonation and chlorination, disinfection (disinfection) occurs simultaneously. It is believed that the use of ozone is a more promising method, because chlorine is dangerous to human he alth.
What are the ways to remove iron from small volumes of water?
At home, hydrogen peroxide and potassium permanganate can be used from the above reagents. How to purify water from iron, if you want to get a small amount in a short time? When peroxide is added to water,sediment flakes. It is necessary to wait for it to settle to the bottom of the container and drain the water, or pass it through a regular jug filter. This purified water is suitable for drinking and cooking.
In relation to organic forms of iron, the above methods are ineffective. Those reagents mentioned above do not settle colloidal particles fast enough.
Ion exchange and catalysis - water iron removal methods
There are autonomous installations operating on the principles of catalysis, ion exchange. The devices are used to purify water in small industrial enterprises and cottages.
Iron in the catalytic method is removed using a special backfill produced from natural and synthetic raw materials. The filter for deferrization of water is a metal container. Backfill is placed inside and water is passed through. The substance is a catalyst for the oxidation of ferrous iron, converting it into an insoluble state from various forms.
In ion-exchange iron removal, cation exchangers are used, obtained from ion-exchange resins, such as zeolite (mineral). In recent years, the production of synthetic products for water iron removal by ion exchange has been launched.
Why do we need an alternative to reagents?
Chemicals are used for a long time if there is this harmful impurity - iron in water. Types of iron are different, so you need to look for the best solution, a method suitable for water purificationfrom a specific source for which forms and concentrations of iron have been established.
Chlorination is a thing of the past, this method has a negative impact on water quality and public he alth. Aeration or enrichment of water with air is a method practically devoid of disadvantages. Oxygen is passed through the water, iron is oxidized, and insoluble precipitate flakes can be removed by filtration or settling.
Iron removal is carried out without chemical reagents - using the electrochemical method. Two electrodes are immersed in a container of water to be cleaned. The negative electrode - the cathode - attracts and holds positively charged iron ions, in whatever form they are. Another non-reagent method is the use of special membranes.
Each of the above methods has not only advantages, but also disadvantages. The choice of method depends on the form in which the iron is present in the water.
