New or Improved Process for Obtaining Thorium Oxide and for Enriching Monazite Sands.
Year: 1897

page_text: Date of Application, 21st Apr., 1897-Accepted, 14th Aug., 1897
New or Improved Process for Obtaining Thorium Oxide and for
Enriching Monazite Sands.
I, Dr. WILHELM BUDDEUS, of Paulstrasse 36, Berlin, in the Empire of Germany,
Chemist, do hereby declare the nature of this invention and in what manner the same
is to be performed to be particularly described and ascertained in and by the following
statement:-
The present invention relates to the art of obtaining thorium-oxide or thoria (Tho₂)
and more particularly to the method of treating monazite-sands, for such purpose, its
object being to concentrate such monazite-sands with a view of enriching them with
thorium oxide.
Monazite-sands contain an amount of monazite varying from a few per cent.
to about 90 per cent., contain also a corresponding amount of thorium-oxide,
that is to say, from about to 4 %. It is due to this fact that only the
high grade sands which contain from 3 to 4 % of the oxide have been put upon the
market.
The purpose of this invention is to render the low-grade monazite-sands, which
contain an average of 1% of thorium-oxide, marketable, and the said invention with
this object in view, consists of a method whereby these low-grade sands are enriched in
thorium-oxide, i.e. converted into a product containing from about 10% to about 20%
thorium-oxide according to the average percentage of monazite in the raw
material.
The costs of carrying out the process embodying my invention are covered by the
utilization of the waste-products formed in the course of the process, so that the
preparation of the high grade product, from the hitherto worthless low-grade
sand results in an additional advantage whereby the high-grade product under
my invention may be obtained more economically than similar products hitherto
employed.
My invention also involves such additional features, steps and methods as will be
hereinafter set forth and pointed out in the claims.
The following is a detailed description of what I consider the best way of carrying
out my invention :
Monazite-sand generally consists of a mixture of monazite proper, ferrous titanate
(titaniferrous iron) and zircon. Since the monazite contains the thoriumn-oxide it
follows that the proportional amount of the latter increases with that of the former.
A poor or low grain sand, containing e.g. 15 % of, monazite contains about 0,5 %
thorium-oxide. Now, under my invention, the zircon and titaniferrous sand, amounting
to about 85% in this grade of monazite-sand, are almost completely separated out in
an unchanged condition. Moreover, the phosphoric acid combined with the oxides of
cerium, lanthanum, didymium and thorium, amounting in this case to about 4% is
concurrently thrown out. From 1,000 kilograms of the raw material containing 15 %

page_text: inonazite, a resulting product of practically 130 kilograms containing about 4 %
thorium-oxide is obtained.
The process is conducted as follows:
The sand is crushed between crushing rollers or otherwise, to the fineness of the
Brazilians and i.e. so that the grains are from to millimeters in diameter. It should
not be ground fine, since the decomposition of its ingredients depends in a measure
upon the size of the grains. The sand so comminuted is then introduced into melted
caustic soda or caustic potash having a temperature of about 400° to 500°, Centigrade.
This results in completely depriving the monazite of its phosphoric acid and the
generation of steam. The caustic alkali readily attacks the grains of monazite-sand
having the size above specified, leaving the ferrous titanate and zircon almost entirely
unchanged.
Hot water is now added to this mass, whereby the alkali-phosphate and hydrate
are brought into solution.
The tribasic alkali-phosphate readily crystallizes out of this solution in a condition
ready for the market. Or the phosphoric acid radical may be separated out of the
mother liquor by precipitating it with lime water, barium, strontium or other suitable
hydrate, whereby the corresponding phosphate, i.e. the phosphate of calcium, barium,
strontium &c., is formed and precipitated and the entire amount of caustic alkali or
alkali-hydrate is recovered, by separating the mother-liquor from the precipitate by
filtering, decanting or other suitable methods. The mother-liquor, after separation
from the crystals of alkali-phosphate, or from the precipitate, the phosphate of calcium,
barium or other alkaline earth or equivalent is evaporated and the residue after
melting is again employed for the decomposing process.
The product from which the phosphoric acid and alkali has thus been separated,
after being thoroughly washed, is now stirred with water, made somewhat alkaline,
whereby the lighter oxides free from phosphoric acid are suspended and are thus
readily washed or separated from the heavier undecomposed grains of ferrous titanate
and zircon by elutriation or decanting the water containing the lighter oxides in
suspension. This is effected with extreme ease and thoroughly.
The oxides thus decanted or washed off are allowed to settle and the resulting sedi-
ment is then dried. It is readily decomposed and by reason of its fineness it does not
require to be ground.
This sediment or magma which contains all of the thorium oxide of the raw material
is now treated with aqueous sulphurous acid or other aqueous inorganic or organic
acids for the purpose of further concentrating the percentage of the thorium-oxide
contained therein. As a consequence of this treatment the greater portion of the
cerium-bases are brought into solution, leaving a residue which contains all of
the thorium-oxide. This is due to the previous treatment with caustic alkali,
whereby the thorium-oxide has been brought into a condition, wherein it is not
soluble in dilute acids, while the cerium-bases are completely and readily
dissolved.
The most suitable acid for this purpose is sulphurous acid by virtue of its
cheapness and its ready manufacture at the places where the monazite-sand is
found.
This operation may be carried out by putting the above described sediment or
magma of oxides mixed with water into a wooden vat or receptacle, which may be
lined with lead on its interior, and then introducing the sulphurous acid into the
mass. Since the gases generated in the calcining-furnaces in which the sulphurous
acid is prepared by calcining or roasting pyrites or other minerals yielding sulphurous
acid, leave the same in a hot condition the heat required for solution in the vats is
furnished by the gases from the furnace themselves. It should be observed, however,
that such solution takes place also in the cold or with moderate heat, though by no
means so rapidly.
After the contents of the vats have been saturated with sulphurous acid, the
mass is allowed to stand for some time during which the precipitate containing
all of the thorium oxide readily settles to the bottom. This precipitate is readily

page_text: obtained as a sediment or magma by drawing off the acid-liquor which contains
the cerium-bases, i.e. the cerium, lanthanum and didyınum compounds and washing
with water.
This sediment or magma either dried or moist is now ready for the market as a
commercial product, or it may be further treated with a view to obtaining pure
thorium-preparations or compounds.
This product is very readily worked into pure thorium-compounds. Its percentage
of thorium-oxide varies between 10 and 20% according to the original composition
of the monazite-sand.
By this process I am hence enabled to separate the useless ferrous titanate and
zircon-sand; to obtain all of the phosphoric acid in a marketable condition; to con-
tinually recover all or that portion of the decomposing agent (the alkali-bydrate) which
has not been combined with the phosphoric acid, and finally, as the most important
result, to obtain a marketable raw-material rich in thorium oxide which is very readily
manufactured into pure thorium-oxide.
The process is manifestly suitable for the treatment of Brazilian monazite-sand
whether the same be rich or poor in thorium-oxide and in general for the separation
of thorium-oxide from cerium-bases, ferrous titanate, zircon, phosphoric acid and other
impurities.
From the above description it is manifest that the process embodying my invention
may be considerably varied without departing from my invention. Thus other alkalis
may be used instead of the sodium hydrate or caustic soda for the separation of the
phosphoric acid, and any suitable acids may be employed for extracting the cerium
bases.
I do not, therefore, desire to be limited to the exact details herein before set forth,
but―
Having now particularly described and ascertained the nature of this
invention and in what manner the same is to be performed I declare that what I
claim is
1. In the art of concentrating raw material containing thorium and phosphoric
acid, the step which consists in treating such raw materials with alkali, whereby
the phosphoric acid is separated and thorium-oxide produced..
2. In the art of concentrating raw-materials containing thorium, the process which
consists in introducing a mixture of thorium phosphate and cerium-bases combined
with phosphoric acid into molten alkali-hydrate, whereby the phosphoric acid is
separated out and the thorium-phosphate and the phosphates of the cerium-bases are
converted into the corresponding oxides.
3 In the art of concentrating raw-materials containing thorium, the process which
consists in introducing raw materials containing the phosphates of thorium and
cerium-bases, together with ferrous titanate and zircon, into molten alkali-hydrate,
whereby the phosphoric acid is separated and the ferrous titanate and zircon are
unaffected.
4. The process, which consists in comminuting monazite-sand and intro-
ducing the same into molten alkali-hydrate, whereby the phosphoric acid is
separated and the thorium and cerium-bases are converted into the oxides.
5. The process which consists in treating a raw material containing phosphate
of thorium, ferrous titanate and zircon with an alkali-hydrate, then dissolving
the resulting mass in water, then separating the phosphoric acid radical from the
solution.
6. The process which consists in treating a raw material containing phosphate of
thorium, ferrous titanate and zircon with an alkali-hydrate, then dissolving the
resulting mass in water, then separating the phosphoric acid radical from the solution,
then separating the mother-liquor from the solid phosphate and then evaporating the
mother-liquor.
7. The process which consists in treating a raw-material containing phosphate of
thorium, ferrous titanate and zircon with an alkali-hydrate, then dissolving the

page_text: resulting mass in water, then separating the phosphoric acid radical from the
solution, then separating the mother-liquor from the solid phosphate and then
evaporating the mother-liquor, and then separating the thorium oxide from the residue
by washing.
8. The process which consists in comminuting monazite-sand and immersing the
same into molten alkali-hydrate, then dissolving the resulting mass in hot water, then
crystallizing out the resultant alkali-phosphate then evaporating the mother-liquor
after removing the crystals, then adding water to the residue and stirring and decanting
or otherwise, removing the liquor containing the thorium-oxide from the heavy sedi-
ment of ferrous titanate and zircon.
9. The process which consists in treating a compound containing the oxides of
thorium and of cerium-bases with acid, whereby the cerium-bases are dissolved and
separated from the thorium-oxide.
10. The process which consists in treating raw-material containing the phosphates
of thorium and of cerium-bases, together with zircon and ferrous titanate with alkali-
hydrates, then dissolving the resulting mass in hot water, then separating the phos-
phoric acid radical from the solution then evaporating the mother liquor, then mixing
the residue with water and stirring and separating the resultant oxides of thorium
and of cerium-bases from the zircon and the ferrous titanate and then treating
the mixture containing the oxides of thorium and of the cerium-basses with
sulphurous acid, whereby the oxides of the cerium-bases are dissolved out from the
mixture.
11. The process which consists in treating raw-materials containing the phosphates
of thorium and of the cerium-bases, together with zircon and ferrous titanate, with
alkali hydrates then dissolving the resulting mass in hot water, then separating the
phosphoric acid radical from the solution, then evaporating the mother-liquor, then
mixing the residue with water and stirring and separating the resultant oxides
of thorium and of the cerium-bases from the zircon and the ferrous titanate and
then treating the mixture containing the oxides of thorium and of the cerium
bases with an acid, whereby the oxides of the cerium-bases are dissolved out from
the mixture.
12. The process which consists in comminuting monazite sand and then immersing
the saine
into molten alkali-hydrate, then dissolving the resulting mass in hot
water, then crystallizing out the resultant alkali-phosphate then evaporating the
nother liquor after removing the crystals, then adding water to the residue
and stirring and decanting or otherwise removing the liquor containing the
thorium-oxide from the heavy sediment of ferrous titanate and zircon, and then
treating the mixture containing the thorium-oxide with sulphurous acid whereby
the cerium-bases are dissolved out and a product containing only the thorium-oxide
is obtained.
HERBERT HADDAN & Co.,
18, Buckingham Street, Strand, London, Agent to Applicant.