PROCESS FOR RECOVERING METALS OF HIGH COMMERCIAL VALUE CONTAINED IN A MUD

METHODE DE SEPARATION DES METAUX A VALEUR COMMERCIALE ELEVEE PRESENTS DANS UNE BOUE

English Abstract

"PROCESS FOR RECOVERING METALS OF HIGH COMMERCIAL VALUE CONTAINED
IN A MUD."

Abstract of the disclosure:
A process for recovering metals of high commercial value from a
mud containing lead, antimony, silver, arsenic, bismuth and copper
by a wet method, by attacking with hydrochloric acid in aqueous
solution accompanied by air injection.

Claims

The embodiments of the invention in which an
exclusive property or privilege is claimed are defined as
follows:
1. A process for recovering metals of high
commercial value from a mud, characterised in that said anode
mud contains silver, arsenic, bismuth, copper, lead and
antimony in the form of elements or compounds thereof and
in that said process comprises the following operations;
a) attacking the mud with hydrochloric acid in aqueous
solution accompanied by air or oxygen injection;
b) decanting, syphoning and, if desired, filtering the attacked
mud of point a) to separate a thickened fraction rich in
silver from a solution depleted thereof;
c) attacking the thickened fraction of point by with hydro-
chloric acid in aqueous solution, if desired, accompanied
by air or oxygen injection;
d) decanting, syphoning and,if desired,filtering the attacked
thickened fraction of point c) to separate an argentiferous
residue from an aqueous solution rich in hydrochloric acid
and lead chloride;
e) washing and filtering the argentiferous residue of point
d) to separate a purified argentiferous residue rich in
silver chloride from an aqueous solution which is recycled
to stage c);
f) cooling and filtering the solution of point b) to separate
a residue rich in lead chloride from a solution containing
antimony, bismuth, silver, arsenic, copper and lead
chlorides;
g) cooling and filtering the aqueous solution rich in hydro-
chloric acid and lead chloride of point d) to separate a

residue rich in lead chloride from a solution rich in


11

hydrochloric acid which is recycled to stage a).

2. A process as claimed in claim 1, wherein the
solution containing antimony, bismuth, silver, arsenic, copper
and lead chlorides of point f) is subjected to the following
operations:
i) hydrolysing said solution;
ii) cooling and filtering the hydrolysed solution to
separate a residue containing antimony from a solution
depleted of said antimony,
iii) washing the antimony-containing residue with hydrochloric
acid in aqueous solution and then filtering to separate
a residue containing antimony oxychloride from an
aqueous solution which is recycled to stage i);
iiii) neutralising the depleted solution of point ii) with
Na2CO3 or another neutralising agent and then filtering
to separate a residue, which is recycled to stage i),
from an antimony-depleted solution containing bismuth,
arsenic, silver, copper, lead and antimony chlorides.

3. A process as claimed in claim 2, wherein the
antimony-depleted solution containing bismuth, arsenic,
silver, copper, lead and antimony chlorides of point iiii) is
subjected to the following operations:
j) neutralising said solution with Na2CO3 or another
neutralising agent and then filtering to separate a
residue containing bismuth from a bismuth-depleted solu-
tion which is rich in copper and arsenic chlorides;
jj) washing the bismuth-containing residue with hydrochloric
acid and then filtering to separate a residue consisting
of bismuth oxychloride from an aqueous solution which is
recycled to the hydrolysis stage i).


12

4. A process as claimed in claim 1, wherein the
purified argentiferous residue of stage e) rich in silver
chloride is converted to silver by reacting it with zinc
dust, ammonium hydroxide and water.
5. A process as claimed in claim 1, wherein the
purified argentiferous residue of stage e) rich in silver
chloride is converted to silver by direct reduction.

6. A process as claimed in claim 1, wherein the
residue rich in lead chloride of points f) and g) is fed to
a main lead treatment cycle.
7. A process as claimed in claim 1, wherein the
residue rich in lead chloride of points f) and g) is fed for
recovery of the lead in the form of the pure salt.


8. A process as claimed in claim 1, wherein the
anode mud is attacked in stage a) at a temperature of between
50° and 80°C for a period of between 0.5 and 3.0 hours.

9. A process as claimed in claim 1, wherein the
thickened fraction is attacked in stage c) at a temperature of
between 50° and 80°C for a period of between 0.5 and 2 hours.

10. A process as claimed in claim 1, wherein the
silver-depleted solution is cooled in stage f) to a tempera-
ture of between 15 and 25°C.
11. A process as claimed in claim 1 t wherein the
solution rich in hydrochloric acid and lead chloride is cooled
in stage g) to a temperature of between 15 and 25°C.

13

12. A process as claimed in claim 1, wherein
the molar concentration of the hydrochloric acid in aqueous
solution in the anode mud attack stage a) is chosen between
3 and 8 M.
13. A process as claimed in claim 1, wherein the
molar concentration of the hydrochloric acid in aqueous
solution in the thickened fraction attack stage c) is chosen
between 4 and 8 M.
14. A process as claimed in claim 2, wherein the
solution containing antimony, bismuth, silver, arsenic,
copper and lead chlorides is hydrolysed in stage i) at a
temperature of between 65 and 75°C.
15. A process as claimed in claim 2, wherein the
hydrolysed solution is cooled in stage ii) to a temperature
of between 15 and 25°C.
16. A process as claimed in claim 2, wherein the
antimony-depleted solution is neutralised in stage iiii) with
Na2CO3 to a final pH of between 1.2 and 2.
17. A process as claimed in claim 2, wherein in
stage iii) involving the washing of the antimony-containing
residue, the molar concentration of the hydrochloric acid in
aqueous solution is chosen between 0.5 and 0.7 M in order to
attain a final pH of between 1 and 1.2.
18. A process as claimed in claim 3, wherein the
solution is neutralised in stage j) with Na2CO3 to a final
pH of between 2.0 and 2.8.



14

19. A process as claimed in claim 3, wherein in
stage jj) involving the washing of the bismuth-containing
residue, the molar concentration of the hydrochloric acid
in aqueous solution is chosen between 0.01 and 0.1 in order
to attain a final pH of between 2.2 and 2.5.

Description

~2~ 2



"PROCESS FQR RECOVERING METALS OF ~IIGH COMMERCIAL V9LUE CONTAINED
IN A MUD."
This inrention relates to a process for recovering metals of high
commercial value from a mud containing lead, antimony and
other metals~
Such a mud is treated in known processes by a dried method7 The
operations involved in the dry method are very complicated, and
lead to both economical and ecological problems.
It has no~r been surprisin~ly found that the dra~rbacks of the known
art can be overcome by a process m~inly involving a wet route.
This process has substantial economical advantages, giving higher
yields with lower costs, together ~ith substanti~l ecological
advantages as it no longer produces fumes.
The process according to the present invention for recovering
metals of hig}l commercial value from a mud containing lead~
antimony and possibly other metals, including silver~ arsenic~
bismuth and copper, consists o~ attacking said mud at least once
by ~ wet method ~nth hydrochloric acid in aqueous solutionS
possibly accompanied by air in~ection~
More particularly, where the mud besides containing lead and
antimon~ also contains silver, arsenicS bismuth and copper in such
quantities as to make their recovery also convenient, said process
comprises the following operations:
a) attacking the mud with hydrochloric acid in aqueous soIution
accompanied by air or oxygen injection;
b) decanting, syphon;ng and possibly filtering the attacked mud of
point a) to separate a thickened fraction rich in silver from a
solution depleted thereof;




'~ ~

~Z(~7~

-- 2 -

c) attacking the thickened fraction of point b) with hydrochloric
aGid in aqueous solution, if desired, ~c~Y~ ;Pd by air or
oxygen injection;
d) decanting, syphoning and possibly filtering the attacked
thickened fraction of point c) to separate an argentiferous
residue from an aque~us solution rich in hydrochloric acid and
lead chloride;
e) washing and filtering the arg_ntiferous residue of point d) to
~eparate a puriied argen~iferous residue rich in silver
chloride from an aqueous solution ~;hich is recycled to sta~e c);
f) cooling and filterin~ the solution of point b) to separate a
residue rich in lead chloride from a solution cont~;n;n~
antimony, bismuth, silver~ arsenic~ copper and lead chlorides;
g) co~ling and fil~ering the aqueous solution rich in hydrochloric
acid and lead chloride of point d) to separate a residue rich
in lead chloride fro~ a solution rich in hydrochloric acid
which is recycled to stage a).
The puxified ar~entiferous residue ~:ithdr~wn from stage e) can
subsequently be converted to silver by reacting it with zinc dust,
2~ ammonium hydroxide and water, or alternatively by direct reduction.
The lead chloride residue withdrawn from stages f) and g) can be
fed for lead recovery as a pure salt~ or alterl~tively if the
attacked a mud origin~tes from industrial le~d electrorefini~g,
it can be fed tQ a main lead treatment cycle.
The process o~ the present invention also comprises the selectiYe
~eparation of the elements present ir the solution containing
antimony~ bismuth, sil~er, arsenic, coppe- and lead chlorides




.. ,.
:
....

1207~52

- 3 -

formed in stage f~ by the following operations:
i) hydrolysing the 601ution;
ii) cooling and filtering the hydrolysed solution to separate
a residue cont~;n;n~ antimony from a solution depleted of
6aid antimony;
iii) w~h;ng the antimony-cont~;n;ng residue with hydrochloric
acid in aqueous solution and then ~iltering to separate a
residue cont~;n;nz antimony oxychloride from an aqueous
solution wh.ich is recycled to stage i);
iiii) nsutrRl;~;n~ the depleted solution of point ii) with NA2CO3
or another neutr~l;s;ng agent and then filtering to separaie
a residue, which i5 recycled to stage i)7 from an antimony_
depleted solutinn cont~;n;ng bismuth~ ar6enic, sil~er~
copper, lead and antimony chlorides.
~he process of the present invention also comprises treating the
antimony~depleted solution cont~;n;ng bismuth~ arsenic~ 6ilver,
copper9 lead and antimony chlorides formed in stage iiii) by the
following operations:
j) neutr~ ;ng the solution with ~a~C03 or another neutralising
agent and then filtering to separate a residue containing
bismuth from a bismuth-depleted solution which is rich in
copper ~nd arsenic chlorides;
jj) ~h;n~ the bismuth-cont~;n;n~ residue with hydrochloric acid
and then filtering to separate a residue consisting of bismuth
ox~chloride from an aqueous 601ution which is recycled to the
hydrolysis stag~
The mud may be attacked in stage al at a temperature of between

` 12(~7~

- 4 -

50 and 80C for a time of between 0O5 and ~.0 hours~ while the
thickened fraction attack of stage c~ may be carried out at a
temperature again of between 50 and 80 C but for a time of
between 0O5 and 2.0 hours.
The molar concentration of the hydrochloric acid in aqueous solu-
tion may be chosen between 3 and 8 M in the anode mud attack stage
a)~ and between 4 and 8 H in the thickened fraction attack stage
c),
In sta~e f~ and stage g), both the silver-depleted solution and the
solution rich in hydrochloric acia and lead chloride may be cooled to
a temperature of between 15 and 25 C~
Tha solution cont~;n;n~ antimony, bismuth, silver, arsenic, copper
and lead chlorides may be hydrolysed in stage i~ at a temperature of
between 65 and 75 C~ and the hydrolysed solutio~ may be ~ooled to a
temperature o~ between 15 and 25 C.
Neutralisation with Na2C03 may be carried out in the case of the
antimony~depleted solution of 6tag~ iiii) to gi~e a final pH chosen
between 1.2 and 2, and in the case of the ~olution of stage j) to
give a fi~al pH chosen between 2.0 and 2.8.
Ths ~olar concentration of the hydrochloric acid in aqueous
~olution must be chosen in stage iii) involving ~.r~.sh;ng o~ the
antimony-cont~in;n~ residue at a value o~ between 0~5 and 0O7 M
~o as to ha~e a final pH of between 1 ana 1.2, and must be chosen
~ stage jj) invol~ing the ~ h;n~ of the bismuth-cont~;n;nE residue
at a value of between 0.01 and 0.1 M so as to have a final pH of
betwePn 2.2 and 2.5~
- The invention will be more apparent with reference to the diaO~rams




. ~ ,

~2~7~i2
-- 5 ~


of the accompanying figures which are not however to be
considered as limitative of the invention itself;
Figure 1 represents a block flow diagram of a process
in accordance with the present invention.
Figures 2 and 3 represent block flow ~;Agr~ms
illustrating the selective separation of elements in accordance
with the present invention.
The mud 1 (Figure 1~, either in the wet state or
precalcined in order to eliminate organic residues, is
attacked at 2 with hydrochloric acid in a~eous solution 3,
accompanied by aix or oxygen injection 4.
The attacked mud undergoes decantation, syphoning
and possibly hot filtration at 5, by means of which a silver-
rich thickened fraction 6 is separated from a silver-depleted
solution 7.
The silver-rich thickened fraction 6 undergoes a
second attack at 8 with hydrochloric acid in aqueous solution
9, possibly accompanied by air or oxygen injection 10~
The attacked thickened fraction is itself subjected
to decantation, syphoning and possibly hot filtration at 11,
in order to separate an argentierous residue 12 from an
aqueous solution 13 rich in hydrochloric acid and lead
chloride.
The aqueous solution is cooled and filtered at 14 in
order to separate a residue rich in lead chloride 15 fxom an
aqueous solution rich in hydxochloric acid 3, which is
recycled to the 1st attack 2.
The argentiferous residue 12 is washed with water 16
at 17, and subsequently filtered at 18 to separate a purified

argentiferous residue 19 from an aqueous solution 20 which is
recycled to the 2nd attack 8.
The silver-depleted solution 7 is cooled at 21 and


~,,s

~2~ Si2


subsequently filtered at 22 to separate a residue rich in
lead chloride 23 from a solution 24 containing antimony,
bismuth, sil~er, arsenic, copper and lead chlorides.

3L5i2



If the mud originates from industrial lead electrore~i.ning,
the residue rich in lead chloride (streams 15 and 23) can be fed
to the main lead treatment cycle, or otherwise the lead can be
recovered as the pure salt.
The subsequent selective separation of the elements from solution
24 is shown aiagran~atisally in Figures 2 and 3~
The solution containin2 antimony, bismuth~ silver~ arsenic, copper
and lead chlorides is fed to a hydrolysis stage at 25, cooled at 26
and then filtered at 27 to thus separate a residue 28 containing a
high percentage o~ antimony from an antimony-depleted solution 29
~he residue 28 is washed at 30 with nydrochloric acid in aqueous
solutio~ 31, and ~iltered at 32 to thus separate a residue 33,
containing mainly antimony oxychloride~ ~rom an aqueous solution
34 ~Yhich is recycled to the hydrolysis stage 25.
- 15 The nntimony_depleted solution 29 is neutralised at 35 with Na2CO~
or another neutrAl;c;n~ agent 36, and ~iltered at 37 to separate
a residue 38, which is recycled to the hydrolysis sta~e 25, from
a solution 39 cont~;n;n~ bismuth~ arsenio, silver; copper~ lead
~ and antimony chlorides~in which the bismuth, arsenic and possibly
the copper are present in hi~h percentage.
The antimony-depleted solution 39 is neutralised at 40 with Na2C03
or another neutr~l;s;n~ a~ent 417 and ~iltered at 42 to separate
a residue 43 containing bismuth ~rom a bismuth-depleted solution
44 which is rich in copper and arsenic chloridesO
The bismuth-cont~;n;nr residue 43 is washed at 45 with hydrochloric
acid in aqueous solution 46~ and filtered at 47 to separate a
residue 48 containing mainly bisn~lth oxychloride, from an aqueous


1~C17~52



solution 49 which is recycled to the hydrolysis stage 25~
One example is given hereinafter with reference to the accompanying
figures.
EXAM~LE
The feed is an anode mud originating from lsad electrorefining,
having a weight in the wet state (w.w.) of 10000 g, and a soJids
content (s.w.) of 7936 g, of composition: -
S~ 4103~ % 3280.7 g
Bi 8~64 % 685.7 ~
Ag 7~86 sb 623.7 g
~s 6.18 % 490.4 g
Cu 2.49 % 197~6 g
Pb 8.10 ,~ 642~8 g
7~.61 ,' 5~20 9 g
The remainder of ~he solias content to 100% (i.e. 25~39~o) consist~
of combined o~ygen, combin~d sulphur, halogenæ~ silica and organic
substances.
The 1st attack is carried out nt Goc for 3 hours with a 6 M
aqueous solution of hydrochloric acid, accompanied by air inj~ction~
The 2nd attack is carried out again at 60 C but for 2 hours with a
7,5 M aqueous solution of hydrochloric acid.
The washed argentiferous residue 19, having a w.w. of 1793 g and
a s.w. of 1201 g is composed of:
Sb 0.19 % 2.3 g
Bi o.o4~,b o.5 g
Ag 48~61 ,~ 583.8 g

As 0~0~5~ 0.4 g

~2~ 52



cu . o.ol~sb 0~1 g
Pb 13.25 ~ 159.1 g
The remainder of the solids content to lOKP~ comprises combined
oxygen, combined sulphur, halogens, silica and organic substances.
The residue 23 containing essentially lead chloride and having a
w.w. of 721 g and a s.w. of 582.2 g is composed of:
Sb lr43 % 8~3 g
Bi 0~31 % 1~8 g
Ag 5.41 % 31~5

1~ ~s 0.24 ~ 104 g
cu o.og6% o.6 g
Pb 63.07 7~ 367.2 g
The chloride solution 24 to be fed to the stage for separating the
metals contained in i~ and having a volume of 43.400 litres is
composed of:
Sb 75.35 ~/1 3270.2 g
Bi 15.79 ~1 685~3 g
Ag 0.20 g/l 8.7 g .
~s 11.26 g/l 488~7 g
Cu 4054 ~/1 197.0 g
Pb 2.69 æ/l 116~7 g
The hydrolysis is carried out at a temperature of 70 C, followed
by cooling to 20Co
The neutralisation 35 is carried out with a M nal pH of 1.79
whereas the w~sh;n~ in 30 attains a final pH of 1~
The residue 33 having a w.w. of ~578~7 g and a s.w. of 4300.6 g
is composed of:

31 20~


Sb 66~62 % 2865.0 g
Bi 0.25 %10.7 g
Ag 0.092% 3.9 g
As 2.30 %98.9 g
Cu 0.02 % o.8 g
Pb . 0.28 %12.0 g
The antimony-depleted solution 39 of 235.59 litres is composed
of: .
Sb o.46 ~1108.4 æ
Bi 2.21 g/l520.6 g
Ag 0.0081~/11.9 g
As 1.35 g/l313.0 g
Cu 0.82 ~/1193.2 0
. Pb 0.26 ~/161.2 g
: ~ 15 The mud stream 38 which is recycled to the hydrolysis stage~ and
has a w.w. of 3179.6 g and a s.w. o~ 1012.47 g~ contains:
Sb 29.39 %297~5 g
Bi . 15.13 ~153~2 g
Ag ~0.277~ 2.8 g
As 7-5 % 71,4 g
Cu 0.~2 562.2 ~
Pb 4.27 ~43.2 g
The antimony~depleted solution 39 is neutralised at 40 to a fi~l
p~ ~ 2~3.
~he subsequent ~lash 44 is carried out to a final pH of 2.3.
The residue 48 having a w~w. of 2269 g and a s~w. of 926 g contains:

7~2

- 10 -

Sb 6~82 ~0 6301 g
Bi 55~89 % 517~5 g
Ag o.o630~' oO6 g
As 1~05 % 9~7 g
cu O~0g7% Oo9 g
Pb 6~27 % 5801 g
The bismuth_depleted solution 44 of 228.506 litres contains.
Sb 0.193g/1 44.1 g
Bi 0.0175g/1 4~0 g
A 0.0057g~1 1.3 g
As 1~35 ~1 308~5 g
Cu o.84 g/l 192.0 g
pb 0.015 g/l 3~4 g
.,