This Invention relates to a process for the removal of iron from inorganic
chemicals
OBJECTS OF THE INVENTION
It is an object of this invention to propose a process for the removal of iron from
Inorganic chemicals, which Is economical
It Is a further object of this Invention to propose a process for the removal of Iron
from inorganic chemicals, which is simple and involves a few steps.
BRIEF DESCRIPTION OF THE INVENTON
Thus according to this invention is provided a process for the removal of iron
from inorganic chemicals, comprising in the steps of;
mixing an inorganic chemical solution containing iron with a solution of a
thiocyanate compound to form an iron thiocyanate complex, followed by
extraction or the complex with atleast one phosphate compound in an organic
solvent for the removal of the Iron complex from the inorganic chemical solution
In accordance with this Invention, the inorganic salt solution Is mixed with an
excess thiocyanate compound such as sodium, potassium or ammonium
thiocyanate. The pH of the solution is maintained at < 7 and the reaction is
conducted at ambient temperature. The iron present in the salt solution
complexes with the thiocyanate. The amount of thiocyanate will be added
depends on the amount of Fe3+, and an equimolar quantity is added. Normally
the amount varies from 10 ppm to 50,000 ppm depending on the total amount of
ferric ion. The complex is thereafter extracted with at least one phosphate
compound in an organic solvent. The organic phosphate compound is selected
from tri ortho/para cresyl phosphate, tri normal or isobutyl phosphate, tri normal
or isoamyl phosphate, tri normal or isohexyl phosphate, tri normal heptyl
phosphate, tri normal or iso octyl phosphate and any mixture of these
compounds In any proportion. The organic solvent Is selected from benzene,
toluene, xylene, kerosene, diesel or their mixtures
The ferric ions react with tributyl phosohate (TBP) and thiocyanate to lead to the
tributyl phosphate iron thiocyanate complex
Fs +3 + TBP+cns? (TBP) Fe(CNS) (TBP)2 Fe (CNS)3 (TBP)3 Fe (CNS)3.
These complexes are soluble in organic solvent which helps to extract Fe3 from
aqueous medium.
The solvent can be recovered after stripping the ferric ion by salt or acid solution
of oxalate acid EDTA acid fartaric acid phosphoric acid or its derivatives. If
oxalate is used, normally a 1% to a saturated solution is employed for the step of
stripping.
The invention will now be explained in greater detail with the help of the following
non-limiting example.
EXAMPLE
Ten ltrs. of saturated solution of zirconium oxy chloride containing 400 ppm ferric
Ion Is treated with ammonium thiocyanate so that concentration of thiocyanate
becomes 600 ppm The red colored solution is extracted with 5 ltrs 20% (w/w)
solution of tributyl phosphate in kerosene. This extraction is repeated six times so
that the colour of the zirconium salt becomes colorless or faint pink. Again
ammonium thiocyanate is added to zirconium salt solution so that concentration
of thiocyanate becomes 100 ppm. It is again extracted with 5 Itrs. 20% (w/w)
solution of tributyl phosphate In kerosene. The process is repealed so that final
color of the solution is free from any pink color.
The method according to the invention can be used for the removal of iron from
zirconium and aluminum salts to reduce the iron content the level less than 10
ppm. The principle is based on the higher solubility of ferric thiocyanate in
organic phosphate present in organic solvent.
WE CLAIM;
1. A process for the removal of iron from inorganic chemicals containing iron,
comprising in the. steps of:
mixing an inorganic chemical solution containing iron with a solution of a
thiocyanate compound such as herein described, to form an iron thiocyanate
complex, followed by extraction of the complex with atleast one phosphate
compound such as herein described, in an organic solvent for the removal of the
iron complex from the inorganic chemical solution.

2. The process as claimed in claim 1 wherein the iron is present as a ferric (Fe+3 )
salt.
3. The process as claimed in claim 1 wherein said inorganic chemical solution is a
solution of zirconium and aluminium salts.
4. The process as claimed in claim 1 wherein said thiocyanate compound is selected
from sodium, potassium,, ammonium thiocyanate.
5. The process as claimed in claim 1 wherein the phosphate compound is selected
from tri ortho/para cresyl phosphate, tri normal butyl or isobutyl phosphate, tri
normal amyl or isoamyl phosphate, tri normal hexyl or isohexyl phosphate, tri
normal heptyl phosphate, tri normal octyl or isooctyl phosphate and any mixture
of these compounds in any proportion.
6. The process as claimed in claim 1 wherein the organic solvent is selected from
benzene, toluene, xylene, kerosene, diesel or their mixtures.
7. The process as claimed in claim 1 wherein the extraction is carried out till the
solution is finally free from pink colour.
8. The process as claimed in claim 1 wherein the thiocyanate is added in a
proportion of 1:1 with respect to too amount of ferric ion.
9. The process as claimed in claim 1 wherein an acid selected from oxalic acid,
EDTA acid, tartaric acid, phosphoric acid or their derivatives used for
stripping the ferric ion and recovering the solvent
10. The process as claimed in claim 9 wherein the acid or its derivatrive is added to
the organic solvent contouring the ferric thiocyanate complex, followed by
washing the solvent with water to regenerate the solvent
11. The process as claimed in claim 10 wherein a 1% to a saturated solution of oxalic
acid or its derivative is used for the step of stripping the iron complex.
12. The process for the removal of iron from inorganic chemicals substantially as
herein described and illustrated

mixing an inorganic chemical solution containing iron with a solution of a thiocyanate
compound such as here in described to form an iron thiocyanate complex, followed by
extraction of the complex with at least one phosphate compound such as herein described
in an organic solvent for the removal of the iron complex from the inorganic chemical
solution.