Ferric Chloride or Iron (III) Chloride (FeCl3) is used as a flocculant in sewage treatment and drinking water production. When small quantities of ferric chloride are added to the raw water, iron(III) hydroxide precipitates and adsorbs finely divided solids and colloids.
It is usually produced and marketed as a concentrated solution with a minimum concentration of 40% w/w. Starting from this solution is also possible to produce a solid crystallized Ferric Chloride with 37°C melting point.
Consito developed know-how and technologies for ferric chloride 40% w/w solution production plants, both for waste water treatment and drinking water grades.
We can provide for some different processes to produce ferric chloride, according to the feedstock:
The raw materials are likewise cheap and easily available so that the manufacture of ferric chloride is frequently an attractive supplement for chlor-alkali producers.
Ferric chloride 40% w/w solution can be produced by different processes, according to the feedstock.
Ferrous chloride is obtained by contact of ferric chloride with iron into a dissolution vessel, according to the following reaction:
The ferrous chloride solution resulting from iron dissolution is then filtered and oxidized to ferric chloride in the chlorination section by chlorine gas, according to the following reaction:
Two third of the ferric chloride solution are recycled back to the dissolution vessel and one third is discharged as product.
This feedstock is a powder of soft iron obtained from rolling-mill process. Production process is analogue to the above description with iron scraps as raw material.
Starting from ferric oxide, by product of steel mills, or from hematite, it is possible to obtain ferric chloride by simple reaction with 32% HCl:
This feedstock is a mixture of ferric oxide and ferrous oxide obtained as scales from rolling-mill process. A previous treatment with 32% HCl followed by chlorination gives place to complete conversion to ferric chloride, according to the following reactions:
By a particular process it is possible also to use as feedstock the sludge from steel pickling with HCl. Reduction of chorine consumption is also obtained. Final concentration by evaporation is generally required to reach a 40% w/w solution.
| Typical final product quality | |
|---|---|
| Purity on dry basis | % 99 |
| Appearance | dark brown solution |
| Density | 1.43 g/ml at 20°C |
| Solubility in water | 1% |
| Melting point | -12 °C |
| Viscosity | 10 mPA at 20°C |
| Chemical properties | acidic and highly corrosive |
| Min concentration of active matter FeCl3 | % 40 +/- 3 |
| Min concentration of active matter Fe(III) | % 13,7 +/- 3 |
| Manganese | % max 2 |
| Iron (II) | % max 2.5 |
| Insoluble | % max 0.2 |
Typical main raw material consumptions for each process:
Referred to 1 metric ton of FeCl3 solution 40% w/w:
| Process | a | b | c | d | e | |
|---|---|---|---|---|---|---|
| Iron scraps | kg | 140 | 140 | |||
| Soft iron | kg | |||||
| Ferric oxide | kg | 200 | ||||
| Mixed oxides | kg | 200 | ||||
| Pickling liquors | kg | 1,400 | ||||
| Soft iron | kg | |||||
| Chlorine | kg | 270 | 220 | 20 | 50 | |
| HCl 32% | kg | 750 | 800 | 300 | ||
| Evaporated | kg | 720 |
Ferric Chloride or Iron (III) Chloride (FeCl3) is used as a flocculant in sewage treatment and drinking water production. When small quantities of ferric chloride are added to the raw water, iron(III) hydroxide precipitates and adsorbs finely divided solids and colloids.
In Europe, chemical using of ferric chloride for drinking water is well defined by the UNI EN 888:2005 Regulation.
Applies to iron (III) chloride (a), iron (III) chloride hexahydrate (b) and iron (III) chloride solution (c) for treating water intended for human consumption. It covers characteristics and defines requirements and corresponding test procedures for iron (III) chlorides (a), (b), and (c), together with information on its use in water treatment.
Impurity and main by-products: limit as mass fraction of Fe(III) content in %
Reference: Table 3 - Impurities
Fe (II) has a lower coagulant efficiency compared to Fe(III). Also hydrolysis of Fe(II) starts at pH8 and therefore Fe(II) can remain into the water at lower pH values.
An excess of insoluble matters indicates the presence of foreign matter Iron is a component of the product will usually be removed in the treatment process.
Chemical parameters: limit as mg / kg of Fe(III)
Reference: Table 4 - Chemical parameters
Cyanide (Cn-), pesticides and polycyclic aromatic hydrocarbons are not relevant since the raw materials used in the manufacturing process are free of them. For max impact of iron (III) chloride on trace metal content.