Ferrous Chloride (FeCl2) Structure, Uses, Properties

The ferrous chloride is an inorganic solid formed by the union of an Fe cation^two+ and two chloride anions Cl^-. Its chemical formula is FeCl_two. It tends to absorb water from the environment. One of its hydrates is FeCl tetrahydrate_two•4H_twoOr which is a greenish solid.

It should be noted that it is very soluble in water and tends to oxidize easily in the presence of air, forming ferric chloride FeCl.₃. Because it is easily oxidizable and therefore capable of acting as a reducing agent, it is widely used in chemical and biological research laboratories..

Ferrous chloride has several uses, among which it stands out to help other agents in the oxidation of sludge derived from sewage or sewage treatment. It is also used in the iron coating process of metals and has some uses in the pharmaceutical industry..

The use of FeCl has also been experimented_two in the recovery of valuable metals from spent catalysts found in the exhaust pipes of vehicles that run on gasoline or diesel.

It is used in the textile industry to fix the colors in some types of fabric.

Article index

• 1 Structure
• 2 Nomenclature
• 3 Properties
  • 3.1 Physical state
  • 3.2 Molecular weight
  • 3.3 Melting point
  • 3.4 Boiling point
  • 3.5 Specific weight
  • 3.6 Solubility
  • 3.7 Other properties
• 4 Obtaining
• 5 Uses
  • 5.1 In the coloring of fabrics
  • 5.2 In wastewater treatment
  • 5.3 In chemical studies
  • 5.4 In biochemical studies
• 6 References

Structure

Ferrous chloride is made up of a ferrous ion Fe^two+ and two chloride ions Cl^- joined by ionic bonds.

Ferrous ion Fe^two+ has the following electronic structure:

1s^two, 2s^two 2 P⁶, 3s^two 3p⁶ 3d⁶, 4s⁰

where it can be seen that he lost two electrons from the 4s shell.

This configuration is not very stable, and for this reason it tends to oxidize, that is, to lose another electron, this time from the 3d layer, forming the Fe ion.³⁺.

For its part, the chloride ion Cl^- has the following electronic structure:

1s^two, 2s^two 2 P⁶, 3s^two 3p⁶

where you can see that it acquired an extra electron in the 3p shell, completing it. This configuration is very stable because all the electronic layers are complete.

Nomenclature

- Ferrous chloride

- Iron (II) chloride

- Iron dichloride

- Ferrous Chloride Tetrahydrate: FeCl_two•4H_twoOR

Properties

Physical state

Colorless to pale green solid, crystals.

Molecular weight

126.75 g / mol

Melting point

674 ºC

Boiling point

1023 ºC

Specific weight

3.16 at 25 ºC / 4 ºC

Solubility

Very soluble in water: 62.5 g / 100 mL at 20 ºC. Soluble in alcohol, acetone. Slightly soluble in benzene. Practically insoluble in ether.

Other properties

FeCl_two anhydrous is very hygroscopic. It absorbs water easily from the environment, forming a variety of hydrates, especially the tetrahydrate, in which for each FeCl molecule_two there are 4 molecules of H_twoOr attached to this (FeCl_two•4H_twoOR).

In the presence of air, it slowly oxidizes to FeCl₃. This means that the Fe ion^two+ easily oxidized to Fe ion³⁺.

If heated in the presence of air quickly forms ferric chloride FeCl₃ and ferric oxide Fe_twoOR₃.

FeCl_two it is corrosive to metals and fabrics.

Obtaining

It is obtained by treating an excess of iron metal Fe with an aqueous solution of hydrochloric acid HCl at high temperatures..

Faith⁰ + 2 HCl → FeCl_two + 2 h⁺

However, due to the presence of water by this method, the ferrous chloride tetrahydrate FeCl is obtained._two•4H_twoOR.

To obtain it anhydrous (without water incorporated in the crystals), some researchers have chosen to carry out the reaction of iron powder with anhydrous HCl (without water) in the solvent tetrahydrofuran (THF) at a temperature of 5 ºC..

The compound FeCl is obtained in this way_two•1,5THF, which when heated to 80-85 ºC under vacuum or in a nitrogen atmosphere (to avoid the presence of water) produces FeCl_two anhydrous.

Applications

Ferrous chloride has various uses, generally based on its reducing capacity, that is, it can be easily oxidized. It is used for example in paints and coatings, as it helps to fix them to the surface.

Iron is an essential micronutrient for human and some animal health. It is involved in the synthesis of proteins, in respiration and in the multiplication of cells.

Hence the FeCl_two it is used in pharmaceutical preparations. The Fe ion^two+ as such it is better absorbed than the Fe ion³⁺ in the intestine.

It is used for the manufacture of FeCl₃. It is used in metallurgy, in iron coating baths, to provide a more ductile deposit.

Here are other featured uses.

In the coloring of fabrics

FeCl_two It is used as a mordant or dye fixative in some types of fabric. The mordant reacts chemically and binds simultaneously to the dye and the fabric, forming an insoluble compound on it..

In this way, the dye remains fixed to the fabric and its color intensifies..

In wastewater treatment

FeCl_two used in sewage or waste water treatment plants (sewage).

In this application, ferrous chloride participates in the oxidation of the sludge, through a process called Fenton oxidation. This oxidation causes the breakdown of the mud flocs and allows the release of the water that is strongly bound to it..

The sludge can then be dried and disposed of in an environmentally friendly way. The use of ferrous chloride helps to reduce the costs of the process.

It has also been recently proposed to use it to reduce the formation of hydrogen sulfide or hydrogen sulfide in these sewage waters..

In this way, the corrosion produced by this gas and also unpleasant odors would be reduced..

In chemical studies

Due to its reducing properties (the opposite of oxidant), FeCl_two It is widely used in various investigations in chemistry, physics and engineering laboratories.

Certain scientists used ferrous chloride vapors to extract valuable metals such as platinum, palladium, and rhodium from spent catalysts in gasoline or diesel-powered vehicles..

These catalysts are used to remove gases that are harmful to humans and the environment. They are located in the exhaust pipe of cars and trucks that run on gasoline or diesel.

After a certain time, the vehicle's catalytic converter wears out and loses its effectiveness and must be replaced. The spent catalyst is discarded and efforts are being made to recover the valuable metals it contains..

According to the researchers, these metals formed magnetic alloys with the iron in ferrous chloride..

The alloys could be extracted with magnets and then the valuable metals recovered by well-known methods..

In biochemical studies

For possessing the cation Fe^two+, which is an important micronutrient in humans and some animals, FeCl_two used in biochemistry and medicine studies.

Certain studies have shown that ferrous chloride improves the fungicidal efficacy of cold argon plasma..

Cold plasma is a technology used for the sterilization of medical surfaces and instruments. It is based on the formation of hydroxyl radicals OH · from the humidity of the environment. These radicals react with the cell wall of the microorganism and cause its death.

In this investigation the FeCl_two improved the effect of cold plasma and accelerated the elimination of a fungus resistant to other disinfection methods.

Some scientists found that the use of FeCl_two allows to increase the yield in the reactions to obtain glucose starting from sugarcane bagasse.

In this case, being the Fe^two+ an essential microelement for human health, its presence in traces in the product would not affect humans.

References

1. Fukuda, S. et al. (2019). Ferrous chloride and ferrous sulfate improve the fungicidal efficacy of cold atmospheric argon plasma on melanized Aureobasidium pullulans. J Biosci Bioeng, 2019, 128 (1): 28-32. Recovered from ncbi.clm.nih.gov.
2. Ismal, O.E. and Yildirim, L. (2019). Metal mordants and biomordants. In The Impact and Prospects of Green Chemistry for Textile Technology. Chapter 3, pp. 57-82. Recovered from sciencedirect.com.
3. Zhang, W. et al. (2019). Co-catalysis of magnesium chloride and ferrous chloride for xylo-oligosaccharides and glucose production from sugarcane bagasse. Bioresour Technol 2019, 291: 121839. Recovered from ncbi.nlm.nih.gov.
4. Zhou, X. et al. (2015). Role of indigenous iron in improving sludge dewaterability through peroxidation. Scientific Reports 5: 7516. Recovered from ncbi.nlm.nih.gov.
5. Rathnayake, D. et al. (2019). Hydrogen sulphide control in sewers by catalyzing the reaction with oxygen. Science of the Total Environment 689 (2019) 1192-1200. Recovered from ncbi.nlm.nih.gov.
6. Taninouchi, Y. and Okabe, T.H. (2018). Recovery of Platinum Group Metals from Spent Catalysts Using Iron Chloride Vapor Treatment. Metall and Materi Trans B (2018) 49: 1781. Recovered from link.springer.com.
7. U.S. National Library of Medicine. (2019). Ferrous Chloride. Recovered from: pubchem.ncbi.nlm.nih.gov.
8. Aresta, M. et al. (1977). Iron (0) Oxidation by Hydrogen Chloride in Tetrahydrofuran: a Simple Way to Anhydrous Iron (II) Chloride. Inorganic Chemistry, Vol. 16, No. 7, 1977. Recovered from pubs.acs.org.
9. Cotton, F. Albert and Wilkinson, Geoffrey. (1980). Advanced Inorganic Chemistry. Fourth Edition. John Wiley & Sons.