Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~6~
This is a divisional application of Canadian
Application No. 417,354 filed December 16, 1982 which re-
lates to a process for selectively stripping iron ions from
an organic solvent.
Various raw materials containing zinc are dis-
charged in the iron and steel industry and non-ferrous metal
industry. However, most of them are discarded because of
their low contents of zinc and higher contents of iron in
comparison of the zinc contents and consequently many prob-
lems in public circumstance protection have been brought out.
In the iron and steel industry, these materialsare produced mainly in dust collectors treating exhaust
gas from hiyh temperature portions of blast furnaces, con-
verters and electric furnaces, etc. While, in process
industries, these materials are produced mainly in portions
when scums formed in upper and under parts of fused zinc
galvanizing tanks and fine dusts generated from the total
surface thereof are treated and further dust collectors
which exhaust gas from scrap-treating shops typically pre-
sented by junked car scrapping shops. In the non-ferrous
metal industry, these materials are produced from processing
of leached residues in hydrometallurgical refining pro-
cesses, sludges in solution purifying processes slags, and
exhaust gas in pyrometallurgical processes. However, as
described above, valuable metals such as zinc, etc. cannot
be recovered from these materials due to high contents of
iron and these materials have long been wasted and discarded.
When the iron and zinc ions are contained in an
aqueous solution, it has been known for separation of their
ions that iron hydroxide is produced and removed by con-
trolling pH values but this method has a disadvantage that
zinc recovery is decreased due to a large amount of zinc
which coprecipitates with iron hydroxide. Although the
raw materials containing iron and zinc as mentioned above
can be dissolved by acids, economical zinc recovery is
very difficult due to coprecipitation of zinc with iron
and consequently these materials have been discarded.
Norwegian Institute of Technology proposed a
zinc recovery process for effective separation of zinc and
iron from raw materials containing them without using acid.
According to this process, ZnO in the raw materials is
selectively leached in contact with an organic solvent
containing Versatic acid without leaching.
ZnO( Solid) + 2RH(Org) ~ R2Zn(Org) + H20(Aq)
Furthermore, a process for recovering organic
solvents remaining in large amounts in leached residues
has been proposed in which the residues are washed with
an aqueous solution containing NaOH and Na2CO3 and then
with hot water. In this process, however, the residues
containing the organic solvent become massive and con-
sequently it is very difficult to recover the adheringorganic solvents from the residues.
Typical samples of zinc containing raw materials
discharged from the iron and steel industry are shown below~
FeZn Pb Ca Na A12O3 SiO2 C
Electric
furnace dust: 31.8 18.4 3.1 2.5 1.9 0.83 4.8 11.5
Blast
furnace dust: 35.2 1.6 0.3 3.7 - 2.3 5.~ 33.4
(in %)
--2--
~2~
As understood from the above, leaching process
with an organic solvent containing versatic acid mentioned
above is not economical for treating the materials, because
of their low contents of zinc, large c~mounts of ZnO-Fe203,
particularly in electric furnace dusts, and an increased
loss of organic solvent adhered in the leached residues.
The present inventors proposed a process for recovery of
organic solvents adhering in residues, in which the residues
is washed with isopropyl alcohol and acetone and then the
organic solvent is recovered by fractional distillation
of them. However, this process could not be industrially
used owing to its complexity and high recovery cost.
Also a process is known in which iron making raw
materials and raw materials containing large amounts of
zinc are recovered from raw materials of low zinc content,
such as blast furnace dust, by heating at 400 - 1600C in
a reducing atmosphere and volatilizing zinc and has been
commercially adopted but the economical advantage of this
process has been decreased by extraordinary enhancement
in price of heating fuels.
For these and other reasons, raw materials con-
taining less than 50% of zinc are not accepted by nonferrous
smelters due to the economical disadvantages and are at
present discarded.
~his invention proposes a resource cycle system
for treating economically liquid or solid raw materials
which contain relatively higher contents of iron in com-
parison with zinc contents and cannot be economically
treated by the conventional methods.
According to -the invention of the parent appli-
cation, there is provided a process for selectively strip-
ping iron ions into an aqueous phase from an organic
solvent (A) containing iron and zinc ions and one or more
compounds selected from the group consisting of alkyl phos-
phoric acid, alky].-aryl phosphoric acid, alkyl thio phos-
phoric acid, and alkyl-aryl thio phosphoric acid together
with a petroleum hydrocarbon as a diluent for the organic
solvent. This process comprises contacting the organic
solvent (A) with an aqueous solution containing NH4 and F
ions to selectively strip the iron ions into the aqueous
solution~
The present divisional application is directed to
a process for recovery of zinc ammonium fluoride, zinc
chloride, zinc sulfate and zinc nitrate from solid raw
materials containing zinc and iron, which comprises the
steps of:
a) leaching a solid raw material containing zinc and
iron in contact with a first organic solvent which comprises
one or more compounds selected from the group consisting
of carboxylic acids together with a petroleum hydrocarbon
as a diluent for the organic solvent;
b) recoverng the first organic solvent adhering in
the leached residue discharged from step (a) by dissolution
with an aqueous solution containing one or more acids
selected from the group consisting of HCl, H2SO4 and HN03;
c) selectively extracting Fe ions from the resultant
aqueous solution containing mainly iron and zinc ions from
step (b) by contact with a second organic solvent;
d) regenerating the first organic solvent containing
zinc from step (a) by contacting it with an aqueous solu-
tion containing an acid selected from the group consisting
of HCl, H2SO4, and HN03 in addition to NH4 and F ions;
and
-- 4 --
~Z~i7~;7
e) recovering the corresponding zinc ammonium fluoride,
zlnc chloride, zinc sulfate or zinc nitrate from the aqueous
solution.
Thus, according to the invention, the organic
solvent (A) coextracts both iron and zinc ions or most of
iron ions and a small amount of zinc ions Erom an aqueous
solution containing iron and zinc ions. The iron ions
extracted therein are selectively stripped from the re-
sultant organic solvent in contact with an aqueous solution
containing NH4 and F ions. The zinc ions in the resultant
organic solvent are not stripped irrespective of the contact
time with the aqueous solution containing NH4 and F ions,
the concentrations of NH4 and F ions and pH values. Con-
sequently, the zinc ions can be separated from the iron ions.
The resultant organic solvent containing only zinc ions is
recycled to the extraction process for extraction of only
iron ions from the aqueous solution containing iron and zinc
ions.
Since zinc ions have a low extraction distribution
ratio, they are not transferred to the aqueous phase. Thus,
loss of zinc ions can be avoided and only iron ions can be
-- 5
~6~S~
extracted by and recovered from the aqueous phase. Therefore,
this process provides a process useful for removal of only
Fe3 ions without the loss of zinc ions and other valuable
metallic ions from metal plating sclutions, such as, zinc
galvanizing solutions.
Where zinc is to be recovered from solid raw
materials containi~g zinc and iron, an aqueous solution
containing mainly iron and zinc ions is obtained by dissolu-
tion of solid raw materials containing zinc and iron with
acid, the iron ions therein are converted to Fe3+ ions
by oxygen aeration, oxidation with chemicals such as H202,
etc. or electro~oxidation, and then Fe3+ ions are extracted
and removed from a strong acid region by contact with the
organic solvent (A) containing one or more compounds selected
from the group comprising alkyl phosphoric acid, alkyl-aryl
phosphoric acid, alkyl thio phosphoric acid and alkyl-aryl
thio phosphoric acid together with a petroleum hydrocarbon
as a diluent. In this way, the acid consumed for dissolving
the iron contained in the solid raw materials can be re-
covered and recycled to the dissolution process of rawmaterials~
This fact indicates that only iron can be sepa-
rated and recovered from other metals without consumption
of acid or alkali so that low iron contents do not cause
economical disadvantages. Therefore, metal values can
be economically recovered from various industrial wastes.
~03 or aqueous solution containing I~03 + H2S04 or HN03 +
HCl can be used for dissolution of raw materials in order
to omit the oxidation process of iron ions in the aqueous
solution after dissolution process of raw materials.
~%~
Since Fe3~ ions can be extracted and removed by
the organic solvent (A) from the region of strong acid
such as a nitric acid solution and a mixed solution con-
taining HN03 ~ H2S04 or ~03 + HCl, the acid after removal
of the Fe3+ ions can be recycled to dissolve the raw
materials.
Where the amount of metallic ions, such as zinc
ions (except for the iron ions) increases, at least stoichio-
metric amount of H2S04 or HCl with respect to the metallic
ions are added to dissolve the raw materials. This is a
well known recovery process for HN03 and HN03 wherein the
aqueous solution is extracted by an organic solvent contain-
ing phosphoric acid ester and the contained metal salts
are converted to the corresponding metal sulpha-te or metal
chloride as shown in the following equations.
Zn(N03)2 + 2HCl + 2TBP ~ 2TBP-~03 ~ ZnC12 . . . . (1)
(Aq) (Aq) (Org) (Org) (Aq)
Zn(N03)2 + H2S04 + 2TBP ~ 2TBP HN03 + ZnS04 . . . . (2)
(Aq) (Aq) (Org) (Org) (Aq)
Nitric acid extracted into the organic phase is
stripped and xecovered to an aqueous phase in contact with
water and can be used to dissolve the raw materials.
In the case of treating solid raw materials con-
taining ZnO, the zinc oxide in the solid raw materials
is extracted to an organic phase in contact with an organic
solvent (~) comprising one or more compounds selected ~rom
the group of carboxylic acids together with a petroleum
hydrocarbon as a diluent at the first stage as shown in
the following equation.
ZnO + 2RH ~ R2Zn + H20 . . . , . (3)
(solid)(Org) (Org) tAq)
As a large amount of the organic solvent (B) is
~dhering on the leached residue discharged from the first
stage, this process does not become an economical one unless
the adhering organic solvent can be recovered and the raw
materials contain large amounts of ZnO.
In the second stage, the organic solvent (B) is
recovered by dissolution of the residue with an aqueous
solution con-taining one or more acids selected from HCl,
H2S04 and HN03. Since the residue undissolved by the acid
is generally under 15% of the raw materials prior to the
leaching process in the first stage, loss of the oryanic
solvent (B) by adhesion is very small.
As the dissolution solution in the second stage
contains mainly iron and zinc ions and the iron ions in
the above aqueous solution can be selectively extracted
in contact with the organic solvent (A), HCl, H2S04 and
HN03 used for dissolution of iron can be recovered in the
third stage as shown in the following equations.
FeC13 + 3RH ~ R3Fe + 3HCl . . . . (4)
(Aq) (Org) (Org) (Aq)
Fe(~o3)3 + 3RH ~ R3Fe + 3HN03 . . (5)
(Aq) (Org) (Org) (Aq)
1/2 Fe2(S04)3 + 3RH f_ R3Fe + 3/2 H2S04 . . . (6)
(Aq) (Org) (Org) (Aq)
where RH indicates an extractant having H type-exchange
radical~
The iron ions extracted in the organic solvent
(A) are stripped by an aqueous solution containing NH4+
and F ions as disclosed by the present inven-tors and
the organic solvent (A) is regenerated as shown in the
following equation.
- 8 -
3 4HF2 ~ 3RH + (NH4)3FeF6 1 ' ' (7)
(Org) (Aq) (Org) (Solid)
The acids (HCl, H2SO4 and HNO3) regenerated
through the removal of iron ions in the third stage are
recycled to the dissolution process of residues in the
second stage.
The organic solvent (B) containing zinc ions
used lor leaching ZnO in the first stage is regenerated by
contact with an aqueous solution containing HCl, H2SO4,
HNO3 or NH4+ and F ions as shown in the following equations
and zinc can be recovered in the fourth stage.
R2Zn + 2HCl ~_ 2RH + ZnC12 . . . . (8)
(Org) (Aq) (Org) (Aq)
R2Zn ~ H2S04 ~_ 2RH + ZnS04 . . , , (9)
(Org) (Aq) (Org) (Aq)
R2Zn + 2HNO3 ~ 2R~I + Zn(N03)2 . . ~ (10)
(Org) (Aq~ ;(Org) (Aq)
R2Zn + 2NH4HF2 ~ 2RH + (NH4)2 4
~Org) (Aq) (Org) (Aq)
The process for producing metallic zinc and zinc
oxide from (~H4)2ZnF4 formed in the equation (11) has been
already proposed by the present inventors.
As mentioned above, this invention relates to a
process in which metal values such as iron and zinc, etc.
can be separated by selective removal of iron ions from
various aqueous solutions.
The extractant of alkyl phosphoric acid group used
in this invention is selected from the compounds (A) to (F)
shown below:
_ g .
(A) (B) (C)
O O O
; 11 II
RO - P- OH RO - P - OH RO - P- OH
OR OH OR
(D) (E) (F)
O O O O
Il 11 11 11
R - O - OH R - P - OH RO - P - O - P -OR
R OH OH OH
where R is alkyl radical containing 4 to 14 carbon atoms.
D2EHPA (Di-2-ethyl hexyl phosphoric acid) shown in the
example set forth hereinafter belong to the (A) group
having alkyl radical of C8H17.
The extractant of alkyl-aryl phosphoric acid
group used in this invention includes the compounds shown
below:
RO - P - OH
A
where R is an alkyl radical having 4 to 14 carbon atoms
and A is an aryl radical (phenyl, triyl, xylyl, etc.).
OPPA (octyl phenyl phosphoric acid) shown in the example
set forth hereinafter has an alkyl radical of C8H17 and
an aryl radical of C6H5.
The extractant of al~syl thio phosphoric acid
~roup and alkyl-aryl thio phosphoric acid group used in
this invention are selected from -the compounds shown belowo
- 10 -- ~
5~
(A1 ~B~
'; S S
Il 11
RO - P - SH RO- P - OH
OR OR
where R is alkyl or aryl radical having 4 to 22 carbon atoms.
D2E~TPA (Di-2-ethyl hexyl dithio phosphoric acid) shown
in the example set forth hereinafter belongs to the (A~ group
having an alkyl radical of C8H17.
The extractant used as the organic solvent (B)
in this invention is shown below. Carboxylic acid group
used in this invention is selected from the following
compounds.
(A) (B)
R R R
R - C - COOH R ~ C(CH2)nCOOH
where R is an alkylradical having 4 to 18 carbon atoms.
Versatic acid 10 (V-10) (trademark, produced by Shell
Chemical Co.) shown in the example belongs to the (A)
group having an alkyl radical of 9 to 11 carbon atoms.
The extractant of hydroxime used in this invention
includes the compound shown below:
CgHl ~ C~ ~ OH
~ ~ OH
where R is H,CH3 ~ ~ or ~ CH2-
- 11
ans X is Cl or ~. Similar hydroximes can be naturally
used in this invention. SME-529 (trademark, produced by
Shell Chemical Co.) used in the example is a hydroxime
in which R =CH3.
The petroleum hydrocarbon used in this in-
vention is alphatic or aromatic hydrocarbon or mixture
of these compounds. The commercial mixture of various
hydrocarbons such as kerosene is often used.
The concentration of extractant in the organic
solvent lies in the range of 2 to 75 volume % and higher
alcohol including 6 to 34 carbon atoms as a modifier may
be added in response to need. The concentration of extractant
in the organic solvent is determined according to concen-
trations of iron and zinc ions and kind or concentration
of anion and other heavy metallic ions in the aqueous
solution. Moreover, the kind or concentration of the
extractant is determined according to the conditions under
which it is reused such as in zinc electrowinning and
galvanizing processes.
Raw materials to be used in this invention
which comprise iron ions extracted and a small amount
of zinc ions coextracted in the organic solvent are
obtained from the ~ollowing solutions.
1) surface treating solutions and metal
plating solutions in iron and steel works,
2) surface treating solutions of piping
materials, sheets or plates, etc.;
3) aqueous solution used for organic
reaction,
4) any optional nonferrous metallurgical
- 12 -
5~
solutions in which mainly iron and zinc are contained and
other heavy metallic ions may be involved.
Solid raw materials containing zinc are obtained
from the following ma-terials.
1) dust obtained in dust collectors of exhaust
gas from blast furnaces, converters or electric furnaces in
iron and steel works,
2) scum of upper and under parts of fused
zinc plating tanks,
3) dust obtained in dust collectors of exhaust
gas around the tank,
4) sludge and leached residues obtained in
solution purifying process in nonferrous metallurgy;
5~ slag discharged from pyro-furnaces such
as reverberatory furnaces, electric furnaces, flash smelting
furnaces, crucible furnaces, etc.'
6) oxide ore or silicate ore containing low
zinc contents' and
7) materials containing iron, manganese, copper,
nickel and cobalt, etc. such as manganese nodule.
Further features and advantages of the inventions
of both the parent and divisional applications will become
more readily apparent from the following description of pre-
ferred embodiments, with reference to the appended drawings,
in which:
Fig. 1 shows a flow-sheet of the process for
separation and recovery of only iron ions from the organic
solvent (A) containing extracted iron ions and coexisted
zinc ions according to the invention;
Fig. 2 shows a flow-sheet of the process for
selective recovery of iron ions from optional aqueous
- 13 -
s~
solutions which are originated from surface treating process,
metal plating process or leaching process and contain mainly
iron and zinc ions and other heavy metallic ions except
those and various anion ions may exist;
Fig. 3 is a flow-sheet for economical recovery
of zinc by treatment of solid raw materials containing mainly
iron and zinc;
Fig. 4 is a flow-sheet for effective recovery
of zinc by treatment of solid raw materials containing iron
and mainly zinc as ZnO;
Fig. 5 is a graph showing the relation between
stripping percentage of zinc and iron ions extracted in the
organic solvent (A) and concentration of aqueous solution
containing ~H4 and F ions;
Fig. 6 is a graph showing the relation between
stripping percentage of zinc and iron ions extracted in the
organic solvent (A) and pH of aqueous solution containing
NH4 and F ions;
Fig. 7 is a graph showing the relation between
amounts of ZnO leached by the organic solvent (B) and
leaching time;
Fig. 8 is a graph showing the relation between
leaching percentage of ZnO, PbO, CdO and PbO2 hy the organic
solvent (B) and leaching time;
Fig. 9 is a graph showing the relation between
amounts of Zn in the aqueous phase and those in the organic
phase in the case using the organic solvent (B); and
Fig. 10 is a graph showing the relation between
temperature of the aqueous solution containing NH~ and F
ions and solubility of (NH4)3FeF6 and (NH4)2ZnF4.
The organic solvent (A) from the extraction
stage l containing extracted iron ions is introduced to strip-
ping sta~e 2 in order to contact with an aqueous solution 3
containing NH~ and F ions and only iron ions are trans-
Eerred to the aqueous phase so as to separate the coextracted
zinc ions as shown in the following equa-tion.
3 4 F2 ~ 3RH + (~14)3FeF6 .... (l2
(Org) (Aq) (Org) (Aq)
The zinc ions contained in the organic phase
together with the iron ions do not transfer into the aqueous
phase irrelevant to contacting time with the aqueous solution
involving NH4 and F ions, pH values or temperature of
solution as shown in Figs. 5 and 6.
In Fig. 2, the optional solution 4 containing
mainly iron and zinc ions is transferred to the extraction
sta~e l in order to selectively extract the iron ions by
contact with the organic solvent (A) and then zinc ions are
coextracted according to pH value and concentration of those.
Scrubbing stage of only zinc ion from the
organic phase using dilute acid prior to the stripping
stage 2 of iron ion has been adopted in the conventional
process. However, there is a disadvantage requiring a
treatment of the scrubbing solution including zinc ions.
In this invention, the organic solvent (A)
containing iron and zinc ions is contacted with the aqueous
solution 3 involving N~I4 and F ions in the stripping
stage 2 in order to transfer the iron ions extracted
in the organic phase into the aqueous phase as shown in
equation (12). Then, only zinc ions remain in the organic
phase because the reaction shown in equation (13) does not
occur.
- 15 -
~Z1~75~
R2Zn + 2NH4HF2--~2R H + (NH4)2ZnF4 ' ' ' (13)
,(Org) (~q) (Org) (Aq)
The organic solvent (A) containing zinc ions
is recycled to the extraction stage 5 , the iron ions are
selectively extracted by exchange reaction from the optional
aqueous solution 4 as shown in equations (14) and (15)
and the separability of iron and zinc ions is enhanced.
3R2Zn + 2Fe ~- 2R3Fe + 3Zn . . . (14)
(Org) (Aq) ~Org) (Aq)
3RH + Fe ~-~ R3Fe + 3H O . , , ~ . (15)
(Org) (Aq) (Org) (Aq)
As the result, only iron ions from the aqueous
solution 4 taken from the place originating raw rnaterials
get out of the system at 7 as a crystal of ~NH4)3FeF6.
Metallic iron or iron oxide is produced by
thermal decomposition of (NH~)3FeF6 in hydrogen gas stream
or gas stream containing oxygen or H2O as shown in equations
(16) to (18) and simultaneously NH4HF2~ NH4F and F gases
generated in the thermal decomposition are absorbed and
recovered.
4)3 6 ~ 1 2 H2 ~ Fe + 3NH4HF2~ ~ . (16)
4)3 eF6 + 1 2 H2O ~ ~ Fe2O3 + 3NH4HF2 ~ (17)
( 4)3 e 6 + 1 2 2 ~~ 2 Fe203 -~ 3NH4F ~ 3F 1 ..(18)
In Fig. 3, raw material 14 is introduced to
acid leaching stage 6 in order to leach iron and zinc,
etc. (of course, other valuable metals except zinc, such as
nickel, cobalt, etc. may be leached) by con-tact with an
aqueous solution containing one or rnore acids selected from
HCl, H2S04 and HNO3. After the iron is oxidized in order to
- 16 -
lZl'~7~7
convert to Fe3~ ion in response to need (if leached with an
aqueous solution containing HN03, oxidation stage is omitted),
the aqueous solution 4 containing mainly iron and zinc is
transferred to the extraction stage 5 in order to extract
iron ions into the organic phase by contact with the organic
solvent (A) and most of raffinate is recycled to the acid
leaching stage 6 .
The raffinate containing zinc ions (nickel,
cobalt, etc. besides zinc are contained) is introduced
to the extraction stage 11 of zinc according to increase
of zinc ion in the raffinate. If the raffinate contains
HN03, it is transferred to the extraction stage 9 of
HN03 in order to extract HN03 with contact of an organic
solvent containing neutral phosphoric acid ester. HN03
transferred to the organic phase is introduced to the
stripping stage 10 to strip into an aqueous phase from
the organic phase by contact with water and is recycled to
the acid leaching stage 6 .
Iron ions transferred to the organic solvent
(A) (zinc ion may be coextracted) is introduced to the
stripping stage 2 in order to strip from the organic phase
by contact with an aqueous solution 3 containing NH4+ and
F ions~ Zinc ions in the organic phase are not at all
stripped and recycled to the extraction stage 5 . Iron
ions stripped in the aqueous phase get out of the system
at 7 as a crystal of (NH4)3FeF6.
In Fig. 4, the solid raw material is intro-
duced to the ZnO leaching stage 16 in order to selec-
tively extract ZnO with contact of the organic solvent (B)
as shown in equation (3). Zinc ions transferred in the or-
ganic phase are stripped in the following stripping stage 17
~Z~L~75~
by contact with HCl, H2S04, HNO3 or an aqueous solution con-
taining ~H4 and F ions and recovered in form of ZnC12,
ZnS04, Zn(N03)2 or (NH4)2ZnF4, respectively and simultaneously
the organic solvent (B) is regenerated.
If the raw material involves CdO and PbO,
those are leached as well as zinc in the direct leaching
stage 16 by the organic solvent as shown in Fig. 8 and
transferred to the organic phase. These impurities can be
selectively transferred into the aqueous phase from the
organic phase by contact with an aqueous solution 18 below
pH 5 in the scrubbing stage 17 and consequently only zinc
ions exist in the organic phase and high purity zinc salts
13 are recovered in the following stripping stage 19 .
Since the leached residue discharged from the
ZnO leaching stage 16 contains large amounts of the organic
solvent (B), it is recovered by dissolution of the residue
with an aqueous solution 15 containing one or more acids
selected from HCl, H2S04 or HNO3 in the following acid
leaching stage 6 . Undissolved residue 8 is abandoned
after water washing.
The aqueous solution 4 containing mainly iron
and zinc ions is transferred to the iron extraction stage
in order to extract iron ions by contact with the organic
solvent (A) after oxidation, if necessary. The organic
solvent (A) containing iron ions is introduced to the
stripping stage 2 in order to transfer those into the
aqueous phase by contact with an aqueous solution containing
N~4+ and F ions and simultaneously regenerated.
The a~ueous solution containing zinc ions after
removal of iron ions is introduced to the zinc extraction
~ 18 -
stage 11 . ~f HNO3 solution 15 is used in the acid
leaching stage 6, the above aqueous solution is transferred
to the zinc extraction stage 11 after extraction and
recovery of ~O by contact with an organic solvent con-
taining neutral phosphoric acid ester in the ~O3 extrac-tion
stage 9 . Zinc ions extracted in the organic phase produce
various zinc salts 13 by contact with HCl, H2SO4, XNO3 or
an aqueous solution containing NH4+ and F ions as shown in
equations (8) to (11).
The aqueous solution 4 containing iron
and zinc ions in this invention is an optional solution
containing one or more acids selected from the group con-
sisting of sulphuric acid, hydrochloric acid, nitric
acid, acetic acid, gluconic acid, citric acid, oxalic acid,
salicylic acid, hydrofluoric acid, etc.
Heavy metallic ions coexisting with iron and
zinc ions in the raw materials are consisting of Mn, Al, Ni,
Co, Pb, Sn, Mg, Mo, W, As, Cu ions, etc.
The following non-limiting examples further
illustrate the invention.
Example 1
The organic solvent (A~ which comprises 30%
D2EHPA + 70% n-paraffine and contains 10.5 g/~ of iron and
1.1 g/~ of zinc was stripped with various aqueous solutions
containing NH4+ and F ions. The results are shown in
Table 1.
- 19 - .
~2~ 7
Table 1
_ _
Stripping Percentage (%)
__
Concentration of Aqueous Solution Containing
(NH4)2F2 & N~I4HF2
_
pH metal 20 g/~ 50 g/~ 100 g/~ 150 g/~200 g/~ 250 g/~
Fe 10.1 31.0 90.9 95.1100.0 100.0
Zn 0 0 0 0 0 0
7 Fe - 91.4 98.7 99~9100.0
Zn - 0 0 0 0
Fe 49.7 99.3 100.0 - - -
Zn _ _ _ _
Fe 67.2 100.0 100.0
Zn 0 0 0 - - _
The relationship between pH values of strip
solutions and stripping percentages of iron and zinc ions
in the organic phase ls shown in Fig. 6. The mole ratio of
contained arnmonium and fluorine linearly changes with pH
values. It is clear from these results that only iron ions
can be selectively transferred into the aqueous phase (strip
solution) from the organic solvent containing iron and zinc
ions and consequently zinc ions remain in the organic phase
and can be recycled to the extraction stage.
Example 2
The results of iron extraction from the
aqueous solution containing mainly iron and zinc ions are
shown in Table 2.
- 20 -
757
o ~
r~
o
h ,~
a ~, o
~-r~ ~ r~ ~D
J, U~ ~ N ,~ O
X ~ rd N O O O
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S~
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O ~ ~ ~
r~ ~ ~ O O
~ ~ _,_1 N O
ta ~Q ~
~ ~ ~ ~ r~ r~
C ~ ~ _~
~ ~ r~
O h U
O O ~ ~U~ ~ ~
~ X ~:o~ -I N~
_ ,_
.~: ~
0~ _~ O ~
~rl ~ r~r~ ~ O
~).a (~) ~r` N d'
,~ ~ ~ _, O O O
,4~ rd a~ O O O
~ ~ f IL~.
E~~ ~,,0~ O O O
O t~) ,~
r~ ~O ro ~ N
~ ) ~_ O
0,~ X ~ ~
NLr~ ~ ~)
1~ O
O ~ ~
r-l O O
tJ' h o o O
or~ ~-
orl r~ ~ o
~ ~oo o~ ~
~rl ~ o
o ~ - ~ ~ r~
rlrl ~ W ~ CD
) NL~ rl ~)
~ o n o
~ ~0 ~ Xr; O O
._.__
-- 21 --
It is shown from Table 2 that only iron ions
can be selectively extracted by maintaining an extremely
high H+ ion concentration in the initial aqueous phase,
but zinc cannot be prevented from coextraction, where it
is impossible to maintain a high H+ ion concentration or
an extraordinarily high zinc ion concentration in comparison
with the iron ion concentra-tion.
Example 3
Analysis of dust generated in a fused zinc plating
process is shown below.
Fe Zn Pb Mn F Cl
1 . 6% 65. 9% 3. 1% 0 . 32% 0. 15% 27 . 7%
1000 g of the above dust was used for the test.
The organic solvent (B) used comprises 30% V-10 and 70%
isoparaffine. The results of leaching tests are shown in
Fig. 7. 224 g of leached residue having the following com-
position was obtained.
Fe Zn Pb Mn F Cl
7.12% 23.33/o 15.~% 1.41% 0.82% 12.59%
0. 32 g of the organic solvent (B) was contained
in 1 g of residue.
The amount of undissolved residue was 18 g after
dissolution of the above one by 180 g/~ HN03 and all the
adhering organic solvent (B) could be recovered.
The composition of HN03 dissolving solution
is shown below.
Fe Zn Pb Mn
22. 7 g/,~ 74. 56 g/~ 8.4 g/e 4. 5 g/e
Iron concen-tration in the above solution could
be decreased under 0. 008 g/~? by twice contact with the
~2~L~i7~
organic solvent containing 30% D2EHPA and 70% n-paraffine.
Example 4
The organic solvent (B) which comprises 30%
V-10, 5% SME-529 and 65% isoparaffine and contains amounts
of Zn, Cd and Pb ions as shown in the following table was
used for the test.
Zn Cd Pb
62.08 g/~ 3.229 g/~ 3.689 g/~
An aqueous solution containing ZnC12, ZnS0~ or
Zn(N03)2 is selected as a scrubbing solution of Pb and Cd
coextracted and the scrubbing result based on the 0/A ratio
of 10/1 is shown in Table 3.
~ 23 -
~%~ 7
. ~ ' o o
`; ~ In LO U~
.
Q t~ ~D o 1`
~ Q ~ O
U P~ O O O
~1 ~ `1 0 0
f~ ~_ ~ ~ ~
O O O
~ ~ ~ oO I
~ ~ O ~
N ('1 ~ ~1
_
.~
~ ~ ~ O
~1 ~ o o o
ra ~ ~ Ln
E~ a) ~ o o Ln
f~ ~ O O O
C) O O O
~ ~ ~r) o 1~
O
`_
M ~ Lt~
'~ ~ O O O
.~ t~
ta ~ ~ o
N N N N
-- 24 --
~2~
It is found from Table 3 that almost Cd and
Pb in the organic solution (B) can be recovered. After Pb
~;ions in the organic phase are transferred to the aqueous
phase by scrubbing with ZnSO4, the amount of Pb in the
aqueous phase does not exceed 0.004 g/~ because it is
crystallized as PbSO4 crystal.
Example 5
The results of stripping zinc ions extracted
in the organic solvent (B) are shown in Fig. 9. In the
Figure, _ o o- and ~___ ~ indicate 30% V-10 + 70%
isoparaffine and 30% V-10 + 5% SME-529 + 65% isoparaffine,
respectively. 259.85 g/~ ~I2SO4 and 190.9 g/~ HCl were
used as a strip solution and similar stripping results were
obtained~
The results of stripping with aqueous solution
containing NH4+ and F ions are shown below.
Organic solvent Zn Concentration in Zn Concentration
the initial Org phase after stripping
30% V-10 + 70%
isoparaffine 63.00 g/~ 0.003 g/~
30% V-10 ~ 5%
SME-529 + 65% 41.33 g/,e 0.007 g/~
isoparaffine
It could be confirmed that zinc ions transferred
into the aqueous phase were crystallized as (NH4)2ZnF4 crystal.
- 25 - ~
