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Патент USA US2131313

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Patented Sept. 27, 1938
. , -
I No Drawing. Application May 24, 1937,
Serial No. 144,562
10 Claims. (01. 23-435)
This invention relates to making zinc pigments; with precipitation of the zinc as oxy-carbonate
and it comprises an improvement in processes by boiling the liquor, it is vfound in practice that
of recovering zinc in pigmentary form from sal the oxy-carbonatecarries enough chloride to be
skimmings and crude impure zinciferous mate-
objectionable. vAnd the presence of manganese, 7 h
5 rials generally by extraction withammoniacalcarbonate solutions wherein the ammoniacal
solution at one stage in the operation is‘ treated
which often occurs, is also harmful.
In a prior and copending application Serial
No. 92,235, I have described and claimed a cyclic
with a phosphate to precipitate manganese as
ammonium manganese phosphate insoluble in
process of recovering Zine Values on Which, in
some aspects, the present invention is an im
10 the ammoniacal liquid; and more speci?cally it
prevement. In the proeess'of the'priorgapplica- 10‘
relates to a process of recovering zinc sul?de in
a state of suf?cient purity for pigmentary purposes wherein the sal skimmings are ?rst ex-
tion Waste skimmings containing chlorides are
extracted with ammoniacal ammonium carbonate
solution in the presence of suflicient lime to react
tracted by ammoniacal ammonium carbonate
with the chlorides and form calcium chloride.
15 solution including recycled liquor, in the presence
of some lime, the liquid is separated from the
insoluble bodies, is boiled to precipitate zinc
oXy-carbonate with recovery of ammonia and ex-
After separation ‘0f insoluble impurities‘, the eX- 15;
tract liquor is boiled to drive off CO2 and am
mo‘iiia, Which are recovered, With seperatieh 0f 7
Zinev oXy-oarbonate- The oXy-oarbonate is sep
cess CO2, the precipitate is separated from a
arated. the mother liquor carrying considerable
2o mother liquor containing chlorides and other impurities, is redissolved in ammoniacal ammonium
carbonate solution, alittle phosphate added to the
solution to precipitate manganese and zinc is recovered as a substantially chlorine-free and man;
soluble impurity being discarded. The preeipi-. 20 ‘
tete is redissolved in ammoniacal ammonium car
honate solution, giving a further separation of '
inseiilbies which go out Of the system- The new
Solution is boiled to re-pi‘ecipitete vZine OXY-CBJ
25 ganese-free zinc sul?de by addition of a soluble
sul?de, best ammonium sul?de or hydrogen sul?de, the mother liquid being recycled for use in
the ?rst stated operation; all as more fully here-
bonate Which is ?ltered Off or. otherwise sepa- 25
rated, the mother liquor being recycled; being
added to the ammoniacal solution used in ex
tracting further quantities 0f the sal skimmings
inafter set forth and as claimed
This cyclic process represents certain economies
In the recovery of zinc from waste material,
such as the waste materials produced in the gal-
in heat and materials, and has the further out- 30;
Standing advantage in that the exit-Carbonate
vanizing industry and known as‘ galvanizer’s,‘
waste, sal skimmings, dry skimmingi's, zinc ashes,
recovered in the second precipitation issubstan
tially pure, being in particular practically free of
chioi‘ine- It is useful in making Zine pigments
etc., and from crude zinciferous ‘materials genera
35 ally, one of the many methods thatrhave been
and other Zihepreperatiehs, It is how my discovery that in such a process
ammoniacal solution of ammonium carbonate;
the operation is facilitated and purer products
Such a solution is advantageous as an extraction
agent because of its power of dissolvingfzinc oxide
Obtained by adding a small quantity of a Soluble
phosphate, such as ammonium phosphate 01‘ so
40 while leaving undissolved various impurities, such
as alumina and iron oxide, Silica and compounds
of the various heavy metals (Fe, 'Ni, Cu, Mn, etc.) .‘
dium phosphate, t0 the ammoniacai Zinc. Solu- 40‘
tion, advantageously the second solution: that
resulting from the Solution of the ?rst oXy-car
There is often somelittle dii?culty in Securing a . bonate precipitate.
wholly complete separation of the heavy metals
'45 in this operation.
In particular, this addition
serves to precipitate themangenese in the form
Traces of other metals than
of a - Phosphate insoluble in the ‘ammoniacal 45;
zinc going forward may impair pigmentary values
considerably. This is particularly true’ as re-
liquid- Most manganous compounds are more Or - '
less soluble in an excess of ammonium carbonate
but ammonium manganese phosphate is an eX'
gards manganese compounds which tend to discoloration in air.
used is the extraction of the material "with an
Extreme purity, at least as regards certain for-
The fact is utilized in the present in
eign bodies, is required in a good and permanent
By ?ltering out the manganese precipitate,_
zinc pigment. For some reason, even the pres-ence of chlorides in such a pigment is harmful.
In the use of ammoniacal ammonium carbon;
the second zinc precipitation from the ammoni
acal carbonate solution gives a material which
is not only chlorine-free but also manganese free.
55: ate solution for extracting sal skimmings, etc.‘
This removal of manganese is useful in the proc-_ 55?
ess of the prior application where there is a
double precipitation of oxy-carbonate but it is
now also useful in modi?ed processes where the
redissolved oxy-carbonate of the ?rst precipita
tion is converted into pigmentary Zinc sul?de
by an addition of a soluble sul?de. In so doing,
any soluble sul?de may be employed as a precipi
tant. If barium sul?de be used, the zinc sul?de
then carries barium carbonate which has pig
10 mentary value.
In practice of the cyclic process, the ?rst stage
or extraction-digestion of the crude material in
ammoniacal ammonium carbonatesolution with
addition of lime e?ects a substantially complete
15 solution of the zinc oxide compounds in the ma
bonate or as sul?de, I have found that it is often
not necessary to ?lter o?' the ammonium man
ganese phosphate precipitate. This white sub
stance may be allowed to remain with the zinc
precipitate without adverse discoloration effect.
In practice however it is usually advantageous to
add phosphate during the second extraction step
and to separate insoluble phosphate precipitate
from the ammoniacal carbonate zinc solution.
The second; precipitation'step‘ of the cyclic'proc
as a pigment.
As amethod of making zinc sul?de from crude
zinc raw materials generally, the process of ex
terial treated. Filtration separates insoluble im
purities existing as heavy metal compounds to
gether with silica and alumina and excess lime.
The subsequent boiling of the ?ltrate with pre
20 cipitation of zinc oxy-carbonate and recovery of
tracting the-oxide in‘ an ammoniacal carbonate
solution and precipitating zinc sul?de from such
a solution has great economic advantage over
prior processes in which zinc salts of strong min
‘ the ammonia and excess CO2 leaves nearly all
tion with sul?des and quantities of by-product
salts formed in the’ reaction have to be disposed
of. By using ammonium sul?de or hydrogen sul
of the soluble chlorides and other soluble impuri
ties in solution which is discarded. The precipi
tated zinc oxy-carbonate has only a small con
25 tent of chloride. The re-solution of this precipi
tate in ammoniacal carbonate gives a further
separation of insoluble impuritiesqand any zinc
which remains insoluble in the re-solution step
is recovered by the return of the insoluble matter
to be extracted in the ?rst digestion step. As I
have found, manganese if present has a tendency
to accompany thezinc in the several extraction
and precipitation steps. But I ?nd that a selec
tive precipitation of manganese and separation
from the zinc is e?ected by the addition of a small
amount of ammonium or sodium phosphate to
the circulating liquid system. The complex am
monium manganese phosphate is, advanta
geously, precipitated by the’ phosphate addition
40 with the insoluble impurities remaining from. the
re~solution of the ?rst precipitate in ammoniacal
However, if desired, it may be pre
cipitated and‘ removed separately. The second
oxy~carbonate of zinc solution, upon addition
45 thereto of ammonium or sodium sul?de, yields a
pure white zinc sul?de precipitate substantially
chloride-free and also vfree of heavy metal com
pounds. The process is operated to insure a sub‘
stantially complete separation of iron in the fer
50 ric form as insoluble compounds; the phosphate
addition aiding in this separation. In the ?nal
precipitation of zinc sul?de from the puri?ed
?ltrate derived from the second extraction by
ammoniacal carbonate, it is unnecessary to ef
55 feet a wholly complete precipitation of the zinc
content of the solution. Any zinc remaining in
the mother liquor after precipitation is returned
to the ?rst digestion or extraction step of the
process and is recovered. The soluble impurities
60 in this mother liquor, including salts of metals
resulting from the sul?de precipitation, are also
returned to the digestion and are discarded with
the ?ltrate obtained after the ?rst precipitation
of zinc oxy-carbonate. In the process the insol
65 uble impurities are separated and discarded in
the ?rst extraction and the soluble. impurities,
particularly chlorides, arediscarded in‘the ?l
trate liquor remaining after the ?rst precipita
I ?nd that the addition to the cyclic system
of smal lamounts of soluble phosphate aids ma
terially in the puri?cationrof the zinc product.
When the soluble phosphate is added to the sec
ond ammoniacal carbonate extract prior to the
75 second precipitation ‘of zinc either as .oxy-caré
ess in which ‘the zinc is precipitated as zinc sul?de
yields a product of unusual purity and stability.
eral acids such as the sulfate are treated in solu
?de as the zinc precipitant in the present process,
ammonia and ammonium Vcarbonateare recov 2.5
ered and cyclically reused. Whensodium sul?de
is the precipitant, soda; is removed with the
solubles by return of the liquid for. cyclic use‘ in
extracting zinc crudes;
The separation effected between zinc and man 30
ganese in ammoniacal carbonate solution by addi
tion of phosphate isa valuable feature in the ex
traction of crude materials generally.
‘What I claim is},
l. A process of »making zinc sul?de for pig
ments .from crude zinc materials, which com
prises extracting the material with a solution of
ammonium carbonate and ammonia, boiling the
solution extract to precipitate zinc oxy-carbonate,
redissolving the precipitate in ammoniacal, am
monium carbonate" solution with vaddition of a
soluble phosphate and precipitating vzinc sul?de
from said solution by addition :of a soluble sul
2. A process of converting chloride-containing
zinc compoundsintoa (substantially chloride-free
zinc sul?de which comprises treating the chloride
compound with anammoniacal ammonium car
bonate solution withaddition oflime to dissolve
zinc compounds, discarding insoluble matter, boil
ing the solution to precipitate zinc oXy-carbonate
separatingfthe pre'cipitatewith-discard of soluble
matter and redissolving it in ammoniated am
monium carbonate solution with separation of
insoluble matter and precipitating zinc sul?de
from this solution by‘addition'thereto of a soluble 551
3. In a process ofrecovering ‘zinc compounds
from crude zincifer'ous' materials containing man
ganese compounds wherein zinc compounds are
?rst extracted by an ammoniacal solution, precip
itated by boiling the solution extract, re-extracted
in an ammoniacal solutioniand reprecipitated, the
improvement which comprises adding a soluble
phosphate to thesecondammoyniacal zinc solu
4. In obtaining 'from' impure chloride-contain
ing-‘zinciferous , material-substantially pure zinc
sul?de, a cyclic process which comprises extract
ing the material with ammoniacal ammonium
carbonate solution with an addition of lime con
verting chlorides of'the material to calcium chlo
ride and with discard ofinsoluble matter, boiling
the extract to recover ammonia ‘and to precipitate
zinc oxy-carbonatardiscarding chloride-contain
ing liquor, redissolving the precipitate in am
moniacal ammonium carbonate solution with
separation and recycling of insoluble matter,
adding to this second solution a soluble sul?de to
precipitate substantially pure zinc sul?de and re
cycling the liquor from the precipitation to the
?rst ammoniacal extraction of impure materials.
5. In the process of claim 4, adding a solublev
phosphate to the re-soluticn of zinc oxy
10 carbonate in ammoniacal ammonium carbonate
6. In the recovery of zinc from zinciferous
materials as commercial pigments the process of
obviating the effects of manganese compounds
15 when present which comprises adding a small
amount of phosphate to an ammoniacal solution
of zinc, the amount being about that sui?cient to
precipitate the manganese present.
7. In the process of claim 6, removing the man
20 ganese precipitate and converting the zinc into
zinc sul?de.
8. In a cyclic process of recovering zinc values
from impure materials by a double extraction in
ammoniacal carbonate solution and reprecipita
tion with discard of insoluble impurities at one
point in the‘ cycle and of dissolved impurities at
another point, the improvement which comprises
adding a soluble phosphate to one of said am
moniacal carbonate solution extracts to aid in
removal of the insoluble impurities and recover
ing pigment zinc sul?de by adding a soluble sul
?de for the reprecipitation from the second am
moniacal carbonate extract.
9. In processes of extracting zinc values from 10
crude manganiferous materials with extraction
by an aqueous ammoniacal carbonate solution,
the improvement in recovering a pure zinc prod
uct Which comprises adding a soluble phosphate
to said zinc solution in about the amount re
quired to precipitate the manganese and remov
ing the insoluble manganese ammonium phos
phate thereby formed.
10. In the process of claim 2, precipitating zinc
sul?de from the second ammoniacal ammonium
carbonate solution by addition thereto of am
monium sul?de.
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