Iron Oxide

Introduction

Iron Oxide is also known as Ferric Oxide. It is an essential component of haemoglobin, RBCs. It helps in carrying the oxygen from the lungs to all the parts of the body. The deficiency of haemoglobin causes anaemia that leads to fatigue. Iron oxide nanoparticles have various properties of magnetic properties, biocompatible nature, and moderated grain size. It can be synthesized in the laboratory by physical, chemical, and biological routes. It occurs naturally in the form of magnetite, and hematite. Iron oxide (Hematite) is the main component of the steel industry.

What is Iron Oxide?

Iron oxide is an inorganic compound formed by the combination of Iron (Fe) and Oxygen(O). The chemical formula of iron-oxide is (Fe₂ O₃). The three components of iron oxide found are Ferrous oxide(FeO), ferric(II)Oxide(Fe₂ O₃), and Ferroferric(III)Oxide(Fe₃ O₄). It occurs naturally in the metamorphic, Sedimentary, and igneous rocks.

Brief Explanation of Iron Oxide

Iron and oxygen are combined to form iron oxide. Rust, a kind of ferric oxide, is the most well-known of the 16 known iron oxides and oxyhydroxides. Oxyhydroxides and iron oxides are common and essential components of numerous geological and biological processes. They are found in haemoglobin and are employed in iron ore, pigments, catalysts, and thermites. In paints, varnishes, and coloured concrete, iron oxide is a reasonably priced and long-lasting pigment.

• Ferrous oxide(FeO) − It is greenish to black in colour powder compound. It occurs naturally in the form of a wustite and can also be prepared in the laboratory by passing hydrogen over ferric oxide or by heating ferrous compounds in absence of oxygen. It is used as a pigment in glass.

• Ferric Oxide(Fe₂ O₃) − It is commonly known as rust. The iron readily reacts with oxygen and water. The iron gets oxidized and forms red to brown colour ferric oxide. It is found naturally as the mineral Hematite. In the laboratory, it is heating ferrous compounds in the air. It is used by jewellers as rouge, and for polishing metals.

• Ferroferric Oxide(Fe₃ O₄) − It contains iron with II and III oxidation state. It is found naturally in the form of the mineral Magnetite. It is found in the form of red-black or black crystals. It can also be prepared in laboratories by passing steam over the red-hot iron. Ferroferric oxide has high electric resistivity and magnetic permeability. It is used in industries for manufacturing computer memories, magnetic tapes, etc. It is also used as a polishing agent.

Structure

Iron oxide exists in various polymorphic forms. In this, the two iron are connected with six atoms of oxygen. It acquires the Rhombohedral $\mathrm{\alpha}$ and cubic β, and orthorhombic ε forms.

Ferric Oxide

Physical Properties

Properties	Attribute
Colour	Red-brown solid
Odour	Odourless
Solubility	Insoluble in water but soluble in a sugar solution, and aqueous tartaric acid.
Molecular Weight	159.69 g/mol
Density	5.242 g/dm3
Melting Point	1475 to 1565o C
Boiling Point	3414o C

Chemical Properties of Iron Oxide Fe₂ O₃

• Reaction with water − When Iron oxide reacts with water and forms iron hydroxide.

  $$\mathrm{Fe_2 O_{3}+ H_2 O → Fe(OH)_3}$$

• Reaction with Sulphuric Acid − when iron oxide reacts with sulphuric acid it forms iron (III) sulphate and water.

  $$\mathrm{Fe_2 O_3+ H_2 SO_4 → Fe_2 (SO_4 )_3+ H_2 O}$$

• Reduction of Ferric Oxide − In blast furnaces, the iron oxide is reduced to iron metal by different forms of carbon.

  $$\mathrm{2Fe_2 O_3+ 3C → 4Fe+ 3CO_2}$$

• Redox Reaction with Aluminium − Iron oxide when reacts with aluminium produces exothermic thermite and oxide of aluminium. This thermite is used in the preparation of weapons, cast-iron utensils, railway tracks, etc.

  $$\mathrm{Fe_2 O_3+Al → Al_2 O_3+2Fe}$$

Preparation of Iron Oxide

The iron oxide in the laboratory is produced by heating the iron in the air, the iron in this preparation is oxidized to ferric oxide.

$$\mathrm{4Fe+ 3O_2+2H_2 O → 4FeO(OH)}$$

The product is electrolyzed by the sodium bicarbonate solution and dehydrated at 200^o C to get iron oxide.

$$\mathrm{2FeO(OH) → Fe_2 O_(3 )+H_2 O}$$

Uses of Iron Oxide Fe₂ O₃

• Super magnetic Iron Oxide is used for imaging, hyperthermia treatment, and drug delivery.

• Iron oxide nanoparticles are used for target drug delivery in cancer patients, target drug delivery, and MRI test as carriers.

• Ferric (III)oxide is used in the steel industry as feedstock for steel and iron production.

• Ferric oxide is used as pigments like pigment yellow, pigment brown, and pigment red. These pigments are used in cosmetics and dental blends with titanium oxides.

• It is used by jewellers as rouge for polishing metals.

• It is also used in paints as a pigment.

• Ferric oxide and chromium oxide are used in magnetic tapes and audiocassettes.

• It is also used in pharmaceutical industries as the nanoparticles of ferric oxide are non-toxic and biodegradable.

• Black Iron oxide or magnetite has resistance to corrosion hence used in anti-corrosion black paints. This paint is applied to iron bridges, and towers to protect them from rusting.

Conclusion

We have studied in the above tutorial that iron oxide is an inorganic compound that is insoluble in water. It exists in various forms like Ferrous oxide, Ferric oxide, and Ferro ferric oxide, with oxidation numbers (II, and III). It occurs naturally in the form of many minerals like Hematite, Magnetite, Maghemite, etc. We can prepare the different forms of iron oxide in the laboratory by different methods. The rust we usually found on iron utensils or iron plates is because of the ferric oxide. Its nanoparticles are biocompatible and used for the treatment of cancer patients, gastrointestinal imaging, etc. It is used in coating, nanofibers, textiles, paints, cosmetics, and steel industries.

FAQs

1. How to prepare Iron oxide nanoparticles?

The nanoparticles of iron oxides are prepared by precipitating iron oxide in isobutanol, ammonium hydroxide, and sodium hydroxide solution. It is treated at 300 to 600_o C for 5-6 hours.

2. What are Iron oxide nanoparticles?

Iron oxide nanoparticles are hydrophilic polymers covered by iron oxide crystals. These are categorized into super magnetic iron oxide nanoparticles (SPIONs) and Ultrasmall super magnetic iron oxides (USPIONs). These are used for various biomedical purposes like target drug delivery, as carriers in MRI testing, and bio-imaging.

3. What are the harms of iron oxide?

If you are exposed to the fumes of iron oxide for a long time, it can cause pneumoconiosis, aches, cough, shortness of breath, etc. If exposed to the eyes, it can cause iron staining and discolouring.

4. Which iron oxide pigments are approved by the Food Drug Administration for cosmetics?

Pigment brown-6 and pigment red-101 for use in cosmetics. The pink colour of calamine lotion is due to iron oxide.

5. Where can we find minerals of natural Iron oxide?

We can find the natural minerals of iron oxide in sedimentary rocks, Mafic and ultramafic rocks, in the form of hematite, and magnetite minerals.

6. What are the applications of Iron (III) oxide?

The Iron (III) oxides are thermally stable and insoluble in water, that why they are suitable for the manufacturing of ceramics like bowls, glass, and optics, in aerospace instruments, electrical fuel cells, etc.