Ferrous(II) sulfate (British English: iron(II) sulphate) is a salt with the formula FeSO4. It is used medically to treat iron deficiency, and also for industrial applications. Known since ancient times as copperas and as green vitriol, the blue-green heptahydrate is the most common form of this material. All iron sulfates dissolve in water to give the same aquo complex [Fe(H2O)6]2+, which has octahedral molecular geometry and is paramagnetic.
Ferrous Sulfate, Green vitriol, Iron vitriol, Copperas, Melanterite, Szomolnokite
and Chemical Characteristics (Typical)
95% passing 60mesh
In pp bags with liner, 25kgs net each.
In jumbo bags, 1 ton or 1.25 tons net each.
Iron(II) sulfate can be found in various states of hydration, and several of these forms exist in nature.
FeSO4·H2O (mineral: Szomolnokite,relatively rare)
FeSO4·4H2O (mineral: Rozenite,white, relatively common, may be dehydratation product of melanterite)
FeSO4·5H2O (mineral: Siderotil, relatively rare)
FeSO4·6H2O (mineral: Ferrohexahydrite, relatively rare)
FeSO4·7H2O (mineral: Melanterite,blue-green, relatively common)
Iron(II) sulfate heptahydrate,Melanterite (FeSO4·7H2O) The heptahydrate in solution (water as solvent) transforms to both heptahydrate and tetrahydrate when the temperature reaches 56.6 °C (133.9 °F). Then at 64.8 °C (148.6 °F) they form both tetrahydrate and monohydrate.
All mentioned mineral forms are connected with oxidation zones of Fe-bearing ore beds (pyrite,marcasite, chalcopyrite, etc.) and related environments (like coal fire sites). Many undergo rapid dehydration and sometimes oxidation.
Iron(II) sulfate tetrahydrate,Rozenite (FeSO4·4H2O)
Production and reactions
In the finishing of steel prior to plating or coating, the steel sheet or rod is passed through pickling baths of sulfuric acid. This treatment produces large quantities of iron(II) sulfate as a by-product.
Fe + H2SO4 → FeSO4 + H2
Another source of large amounts results from the production of titanium dioxide from ilmenitevia the sulfate process.
Ferrous sulfate is also prepared commercially by oxidation of pyrite:
2 FeS2 + 7 O2 + 2 H2O → 2 FeSO4 + 2 H2SO4
On heating, iron(II) sulfate first loses its water of crystallization and the original green crystals are converted into a brown colored anhydrous solid. When further heated, the anhydrous material releases sulfur dioxide and white fumes of sulfur trioxide, leaving a reddish-brown iron(III) oxide. Decomposition of iron(II) sulfate begins at about 680 °C (1,256 °F).
2 FeSO4 → Fe2O3 + SO2+ SO3
Like all iron(II) salts, iron(II) sulfate is a reducing agent. For example, it reduces nitric acid to nitrogen oxide and chlorine to chloride:
6 FeSO4 + 3 H2SO4 + 2 HNO3 → 3 Fe2(SO4)3 + 4 H2O + 2 NO
6 FeSO4 + 3 Cl2 → 2 Fe2(SO4)3 + 2 FeCl3
Ferrous sulfate outside titanium dioxide factory in Kaanaa, Pori.
Upon exposure to air, it oxidizes to form a corrosive brown-yellow coating of basic ferric sulfate, which is an adduct of ferric oxide and ferric sulfate:
12 FeSO4 + 3 O2 → 4 Fe2(SO4)3 + 2 Fe2O3
Industrially, ferrous sulfate is mainly used as a precursor to other iron compounds. It is a reducing agent, mostly for the reduction of chromate(Cr3+) in cement. The main advantages of iron sulphate in cement application
are its easy availability and relatively low cost.
Chromium is an unavoidable trace element of raw materials used in the producing of ordinary Portland cement. Today there is an even greater need to reduce the contribution to chromium levels in the clinker, which are skin irritating and toxic! To protect people and the environment, chromate has first
to be rendered harmless through reduction. The addition of ferrous sulfate based agents is curently the most widely used available technology.
To reduce the amount of soluble chromium in cement, chromium is changed to form an insoluble salt which does not irritate the skin. For this, the most common solution is by adding ferrous sulphate to cement. When water is added to the dry cement, a redox reaction between the bivalent iron (Fe2+) and the hexavalent chromium (Cr6+) will result in trivalent iron (Fe3+) and trivalent chromium (Cr3+). Trivalent chromium salts are almost not water soluble, herewith avoiding contact dermatitis.
EU LEGISLATIVE MEASURES
The directive 2003/53/ES, which has come into force since the beginning of January 2005, is focused on reducing amounts of harmful hexavalent chromium (Cr6+) in cement binding agents and products based on them. This directive determines that producers of cement and cement containing products have to ensure a Cr6+ content in bag deliveries below 2 ppm.
That is why cements contain so called reducing agents which, when mixed with water, reduce content of Cr6+ below 0.0002 % and are efficient for the time of cement storage, i.e. for min. 90 days from the date given on the cover under conditions determined by the National Annex NA 1 to EN 197-1.
From the point of view of judging reducing properties of agents the European standard EN 196-10 Methods for testing cements – Part 10:
Determination of content of water soluble chromium (Cr6+) in cement (2007-01-01) is in force. This standard specifies a method for determining water soluble chromium in cement.
It also involves a reference method for determining Cr6+ content in cements and cement containing materials and two other methods which are recommended as alternative ones for internal checking tests in companies. A procedure for judging agreement of a cement with requests of the Directive 2003/53/EC and an instruction for photometric determination of chromium (Cr6+) reduction capacity are involved, as well.
DOSING AND EFFICIENCY OF REDUCING AGENTS
Ferrous sulphate from titanium dioxide manufactures (copperas) which contains divalent iron (Fe2+) acting as efficient element for reducing harmful hexavalent chromium (Cr6+) to trivalent one (Cr3+) is the most used raw material for decreasing hexavalent chromium in praxis. The efficient doses of the reducing agent related to amounts of cement being manufactured can differ (a range of 0.1 – 0.5 %) and depend on raw materials, fuel (for burning) and way of its adding to cement. The addition of a reducing agent in the phase of clinker milling can influence the agent efficiency. An increased temperature of clinker before and during the milling process is important thermal exposition which accelerates chemical reactions of the reducing agent, what can decrease its efficiency. A better homogeneity of particles and their higher fineness joined with increased specific surface area are other contributions of this procedure. The accurate adjustment of the level of dosing is based on laboratory and plant tests for each of technologies of processing and processed raw material basis.
Efficient reducing agent for reducing Cr6+ in cement industry. Suitable for dosing into clinker before milling (cement, dry plaster mixtures, etc.). Recommended agent for removing harmfull hexavalent Chromium from industrial wastes.
Together with other iron compounds, ferrous sulfate is used to fortify foods and to treatiron-deficiency anemia. Constipation is a frequent and uncomfortable side effect associated with the administration of oral iron supplements. Stool softeners often are prescribed to prevent constipation.
Ferrous sulfate was used in the manufacture of inks, most notably iron gall ink, which was used from the middle ages until the end of the eighteenth century. Chemical tests made on the Lachish letters [circa 588/6 BCE] showed the possible presence of iron (Torczyner, Lachish Letters, pp. 188–95). It is thought that oak galls and copperas may have been used in making the ink on those letters. It also finds use in wool dyeing as a mordant. Harewood, a material used in marquetry and parquetry since the 17th century, is also made using ferrous sulfate.
Two different methods for the direct application of indigo dye were developed in England in the eighteenth century and remained in use well into the nineteenth century. One of these, known as china blue, involved iron(II) sulfate. After printing an insoluble form of indigo onto the fabric, the indigo was reduced to leuco-indigo in a sequence of baths of ferrous sulfate (with reoxidation to indigo in air between immersions). The china blue process could make sharp designs, but it could not produce the dark hues of other methods. Sometimes, it is included in canned black olives as an artificial colorant.
Ferrous sulfate can also be used to stain concrete and some limestones and sandstones a yellowish rust color.
Woodworkers use ferrous sulfate solutions to color maple wood a silvery hue.
In horticulture Ferrous (II) Sulfate is used for treating iron chlorosis. Although not as rapid-acting as iron chelate, its effects are longer-lasting. It can be mixed with compost and dug into to the soil to create a store which can last for years. It is also used as a lawn conditioner, and moss killer.
In the second half of the 1850s ferrous sulfate was used as a photographic developer for collodion process images.
Ferrous sulfate is sometimes added to the cooling water flowing through the brass tubes of turbine condensers to form a corrosion-resistant protective coating.
It is used in gold refining to precipitate metallic gold from auric chloride solutions (gold dissolved in solution with aqua regia).
It has been used in the purification of water by flocculation and for phosphate removal in municipal and industrial sewagetreatment plants to prevent eutrophication of surface water bodies.
It is used as a traditional method of treating wood panelling on houses, either alone, dissolved in water, or as a component of water-based paint.
Green vitriol is also a useful reagent in the identification of mushrooms.