Lead recovery from PbO, PbCl2, PbS, PbSO4, and their mixtures in carbonate melts

Article abstract of DOI:10.1023/A:1021363102585

The reduction (with and without carbon) of PbO, PbCl₂, PbS, PbSO₄, and their mixtures in Na₂CO₃ and K ₂CO₃ melts was studied by thermodynamic modeling and experimentally.

Full text of DOI:10.1023/A:1021363102585

Inorganic Materials, Vol. 38, No. 12, 2002, pp. 1216–1223. Translated from Neorganicheskie Materialy, Vol. 38, No. 12, 2002, pp. 1436–1443.
Original Russian Text Copyright © 2002 by Barbin, Kazantsev, Moiseev, Vatolin.
Lead Recovery from PbO, PbCl2, PbS, PbSO4,
and Their Mixtures in Carbonate Melts
N. M. Barbin*, G. F. Kazantsev**, G. K. Moiseev**, and N. A. Vatolin**
* Institute of High-Temperature Electrochemistry, Ural Division, Russian Academy of Sciences,
ul. S. Kovalevskoi 20, Yekaterinburg, 620219 Russia
** Institute of Metallurgy, Ural Division, Russian Academy of Sciences,
ul. Amundsena 101, Yekaterinburg, 620016 Russia
Received October 10, 2001
Abstract—The reduction (with and without carbon) of PbO, PbCl2, PbS, PbSO4, and their mixtures in Na2CO3
and K2CO3 melts was studied by thermodynamic modeling and experimentally.
INTRODUCTION
which are known to be thermally stable and contain
only cations and CO23– anions.
The processing of lead battery scrap is accompanied
by the formation of fine lead-containing dust [1] in
amounts of 16–22% (relative to the material being pro-
cessed) in the course of blast smelting, 8–12% in rotary
furnaces, 14–18% in reverberatory furnaces, and 5–6%
during arc melting. The dust particles (up to 83%) are
less than 5 µm in size and consist, according to Dyuse-
baev et al. [2], of PbO, PbS, and PbCl2. All pyrometal-
lurgical techniques for processing such dust involve a
preparation stage (agglomeration, pelletizing, briquet-
31.65K2CO3 + 33.52Na2CO3 + 13.04PbO +
21.78Ar mixture. (Hereafter, compositions are given
in wt %.) The melt was assumed to contain PbO, PbO2,
Pb2O3, Pb3O4, Na2O, NaO2, Na2O2, Na2CO3, KO2,
K2O, K2O2, K2CO3, and PbCO3. The results indicate
that the weight fractions of PbO2, Pb2O3, Pb3O4, and
PbCO3 are no greater than 10–5. Lead is present in the
solution mainly in the form of PbO. The Na2CO3 :
ting, drying, and firing) and melting in the presence of K2CO3 weight ratio in the melt is 1.03 to 1.06 and is
fluxes (return slag, limestone, sand, iron ore or turn-
ings, and coke ash), which are dumped in the form of a
slag–matte phase. Together with black lead, slag and
dust are formed again and should be recycled back to
the process.
close to that in the parent Na2CO3–K2CO3 melt.
Thus, the introduction of PbO into the carbonate
melt results in the presence of additional ions (Pb2+ and
O2–), without changing the ionic composition.
31.45K2CO3 + 33.31Na2CO3 + 12.95PbO +
0.648C + 21.64Ar mixture. The reduction process in
this system leads to the formation of a metallic melt
containing 98–100 wt % Pb and 2.0–0.1 wt % C in the
range 1000–1500 K. The weight fraction of the metallic
solution relative to all the condensed phases is
0.16−0.2.
In this paper, we examine the processing of lead-
containing dust in molten alkali carbonates.
THERMODYNAMIC MODELING
OF LEAD RECOVERY FROM LEAD
COMPOUNDS IN MOLTEN CARBONATES
The species taken into account were Pb, Na, K, C,
and Na2C2 in the metallic melt and the same as above in
the carbonate melt.
In thermodynamic modeling, we used the ASTRA-4
software package [3–5]. Thermodynamic functions
were taken from the IVTANTERMO and ASTRA-
OWN Databases.
The modeling results for condensed phases are dis-
played in Fig. 1.
Reaction products were treated as ideal solutions
[5]. PbO, PbCl2, PbS, and PbSO4 were assumed to mix
with carbonate melts. Metallic melts could dissolve
carbon and the carbides present. The weight ratio of the
carbonate melt to the Pb-containing material was
1 : 0.02 to 1 : 0.2; the weight ratio of the Pb-containing
material to carbon was 1 : 0.05 to 1 : 0.1.
The Pb content of the metallic phase is close to
100% in the temperature range 1000–1100 K and drops
to ~70% between 1100 and 1500 K owing to partial
lead vaporization (Fig. 1b).
The carbonate melt is dominated by Na2CO3 and
K2CO3. Their weight ratio varies from 1.06 to 1.065 in
the range 1000–1500 K. The lowest weight fraction of
PbO (5.5 × 10–5) is observed at 1000 K (Fig. 1a). In the
We modeled the carbon reduction of PbO, PbCl2,
PbS, and PbSO4 to Pb metal in Na2CO3 + K2CO3 melts,
0020-1685/02/3812-1216$27.00 © 2002 MAIK “Nauka/Interperiodica”

LEAD RECOVERY FROM PbO, PbCl2, PbS, PbSO4, AND THEIR MIXTURES
1217
100
presence of a carbon excess, metallic Pb is formed by
the reaction
(a)
1
2
(PbO) + 0.5C = [Pb] + 0.5CO2,
(1)
~
~
10–3
where (PbO) designates the component (atomic group)
of the oxide–carbonate melt, and [Pb] designates the
component of the high-temperature metallic solution.
The analysis results for the gas phase indicate that,
above 1000 K, the partial pressure of CO exceeds that
of CO2 owing to the reaction of carbon with the melt
and CO2 in the gas phase, C + CO2 = 2CO. PbO-to-Pb
reduction in carbonate melts can be conducted with the
participation of CO.
31.75K2CO3 + 33.52Na2CO3 + 13.04PbCl2 +
21.78Ar mixture. The carbonate melt was assumed to
contain PbO, PbO2, PbCO3, Pb2O3, Pb3O4, PbCl2,
PbCl4, NaO2, Na2O, Na2O2, NaCl, NaClO3, Na2CO3,
KO2, K2O, K2O2, KCl, KClO3, KClO4, and K2CO3.
Between 1000 and 1500 K, the main components of the
solution were K2CO3 (weight fraction of 0.3391 to
0.35834), Na2CO3 (0.43362 to 0.42578), PbO (0.13668
to 0.1373), KCl (0.082 to 0.069), and NaCl (0.0072 to
0.0172). The weight fractions of the other components
were on the average no higher than 10–6.
The introduction of PbCl2 leads to the formation of
new dominant species in the carbonate melt, in particu-
lar (PbO), rather than (PbCl2). At the same time, the
sodium and potassium carbonates partially convert into
(NaCl) and (KCl), respectively. Treating the reaction
products as ideal solutions, we arrive at the conclusion
that the introduction of PbCl2 leads to the formation of
new species, but all of the Pb is present not as (PbCl2),
as might be expected, but as (PbO). The process can
then be represented by the reaction scheme
10–4
3
10–5
100
η, wt %
(b)
1
100
90
80
70
60
50
4
η
10–1
10–2
10–3
Z
0.2
0.1
3
2
Z
800
1000
1200
T, K
1400
Fig. 1. Temperature-dependent concentrations of compo-
nents in (a) the carbonate melt of a 31.45K CO
33.31Na CO + 12.95PbO + 0.648C + 21.64Ar mixture and
(b) metallic melt: (a) (1) (Na CO ), (2) (K CO ), (3) (PbO);
(b) (1) [Pb], (2) [C], (3) weight fraction Z of the metallic
melt in the condensed phase, (4) lead recovery η.
+
3
2
2
3
2
3
2
3
PbCl2 + 0.5(K2CO3) + 0.5(Na2CO3)
(2)
content of the metallic melt drops from 1.0 to 0.1 wt %
in the temperature range 1000–1300 K.
= (PbO) + (KCl) + (NaCl) + CO2.
The introduction of PbCl2 into the carbonate melt
favors the formation of (PbO), (KCl), and (NaCl), with-
out a drastic decrease in the content of (K2CO3) and
(Na2CO3), and CO2 release as a result of exchange reac-
tion between components. The addition of carbon to the
melt leads to the reduction of (PbO) to Pb by reaction (1).
31.65K2CO3 + 33.52Na2CO3 + 13.04PbS +
21.78Ar mixture. The species taken into account were
PbSO4, PbO, PbO2, Pb2O3, Pb3O4, PbS, NaO2, Na2O,
Na2O2, Na2S, Na2SO4, Na2CO3, KO2, K2O, K2O2, K2S,
K2SO4, K2CO3, and PbCO3 in the carbonate melt and
C, Pb, Na, Na2C2, and K in the metallic melt.
31.45K2CO3 + 33.3Na2CO3 + 12.95PbCl2
+
0.648C + 21.64Ar mixture. The composition of the
carbonate melt was taken the same as above. The calcu-
lation results for condensed phases are displayed in
Fig. 2.
As is seen in Fig. 2a, the weight ratio of (Na2CO3) to
(K2CO3) in the melt varies little with temperature, from
1.25 at 1000 K to 1.20 at 1500 K, and is close to that in
the melt containing no reductant. The (KCl) and (NaCl)
concentrations vary more significantly; with increasing
temperature, the former decreases, while the latter
rises. The weight fraction of Pb-containing groups is
below 10–5.
The composition of the metallic melt is similar to
that in the presence of PbO (Figs. 1b, 2b). With increas-
ing temperature, the weight fraction of the metallic
melt relative to all the condensed phases present
decreases from 0.133 to 0.08. The Pb recovery is close
The results for condensed phases are shown in
Fig. 3. The metallic melt in this system consists of
almost pure lead (Fig. 3b). In the temperature range
1200–1300 K, Pb recovery is close to 89%, and the Pb
content of the phase mixture is Ӎ13 wt %.
The carbonate melt has a complex composition
to 100% at 1000 K and is 59% at 1500 K. The carbon (Fig. 3a). The introduction of PbS leads to the appear-
INORGANIC MATERIALS Vol. 38 No. 12 2002

1218
BARBIN et al.
100
10–1
10–2
ance of metallic Pb and the formation of (Na2S), (K2S),
(a)
(PbS), (PbO), (Na2SO4), and (K2SO4), whose concen-
trations vary significantly in a number of cases. At
1000 K, the solution consists mainly of (Na2CO3),
(K2CO3), and (PbS). Increasing the temperature to
above 1000 K causes chemical reactions which reduce
the (PbS) content and substantially raise the (K2SO4)
content. The highest (K2S), (Na2S), (Na2SO4), and
(PbO) concentrations are observed at ~1200 K.
1
2
4
3
Consider the likely sequence of transformations,
using (Na2CO3) as an example.
10–3
100
The introduction of PbS into the carbonate melt
causes no significant chemical processes at low temper-
atures: only mixing and (PbS) formation occur. Subse-
quent heating may lead to the thermal decomposition of
(PbS),
η, wt %
(b)
1
100
η
90
80
70
60
50
2(PbS) = 2[Pb] + 2S,
(3)
10–1
10–2
10–3
4
Z
0.2
0.1
3
and reaction between the forming sulfur and the car-
bonate,
Z
2(Na2CO3) + 2S = (Na2S) + (Na2SO4) + 2CO. (4)
2
The overall reaction is
800
1000
T, K
1200
1400
2(PbS) + 2(Na2CO3)
(5)
= 2[Pb] + (Na2S) + (Na2SO4) + 2CO.
Fig. 2. Temperature-dependent concentrations of compo-
nents in (a) the carbonate melt of a 31.45K CO
33.3Na CO + 12.95PbCl + 0.648C + 21.64Ar mixture
+
3
2
Also possible are the reactions
2
3
2
and (b) metallic melt: (a) (1) (Na CO ), (2) (K CO ),
2
3
2
3
2(PbS) + 2(Na2CO3) = 2(PbCO3) + 2(Na2S), (6)
(3) (NaCl), (4) (KCl); (b) (1) [Pb], (2) [C], (3) weight frac-
tion Z of the metallic melt in the condensed phase, (4) lead
recovery η.
2(PbCO3) = 2(PbO) + 2CO2,
with the overall reaction
(7)
(a)
100
6
1
2(PbS) + 2(Na2CO3) = 2(Na2S) + 2(PbO) + 2CO2. (8)
10–1
2
4
This reaction accounts for the presence of (PbO) in the
melt. A part of the (PbO) may react with the CO result-
ing from reaction (5):
10–2
10–3
7
3
5
8
5
(PbO) + CO = [Pb] + CO2.
(9)
η, wt %
(b)
100
10–1
10–2
10–3
Under the assumption that all of the CO formed by
reaction (5) reacts by reaction (9) with the equivalent
amount of (PbO) resulting from reaction (8), we obtain
the approximate reaction scheme
Z
3
η
80
40
0
0.2
0.1
2
1
3
Z
--
(PbS) + 2(Na2CO3) = (Na2S)
4
800
1000
T, K
1200
1400
(10)
1
--
+ [Pb] + (Na2SO4) + CO2.
4
Fig. 3. Temperature-dependent concentrations of compo-
nents in (a) the carbonate melt of a 31.65K CO
+
3
2
The above assumptions are supported by the fol-
lowing:
(1) The total partial pressure of all sulfur-containing
vapor species (S, S2, S3, SO, SO2, SO3, and S2O) is
10−7 MPa; i.e., sulfur does not vaporize.
33.52Na CO + 13.04PbS + 21.78Ar mixture and (b) metal-
2
3
lic melt: (a) (1) (Na CO ), (2) (K CO ), (3) (Na S), (4) (K S),
2
3
2
3
2
2
(5) (Na SO ), (6) (K SO ), (7) (PbO), (8) (PbS); (b) (1) weight
fraction Z of the metallic melt in the condensed phase,
(2) lead recovery η, (3) [Pb].
2
4
2
4
INORGANIC MATERIALS Vol. 38 No. 12 2002

LEAD RECOVERY FROM PbO, PbCl2, PbS, PbSO4, AND THEIR MIXTURES
1219
(2) The main components of the gas phase are CO2
and CO; the CO2 partial pressure is higher than the CO
pressure by at least one order of magnitude.
(a)
100
10–1
10–2
10–3
1
2
4
(3) In scheme (10), the (Na2S) : (Na2SO4) molar
ratio is 3. According to our modeling results, this ratio
varies from 2.8 to 4.2 in the range 1100–1300 K, with
an average of 3.6.
3
6
5
η, wt %
(b)
100
10–1
10–2
10–3
The proposed reaction scheme may account for the
obtained results. One should keep in mind that only a
part of the CO is used to reduce (PbO) to Pb, and only
a part of the (PbO) is reduced to Pb. The relative impor-
tance of the reactions in question may vary with tem-
perature.
3
η
Z
2
1
80
0.2
0.1
Z
40
0
4
800
1000
T, K
1200
1400
The difference between (K2CO3) and (Na2CO3) is,
in our opinion, too small to radically change the reac-
tion scheme.
Fig. 4. Temperature-dependent concentrations of compo-
nents in (a) the carbonate melt of a 31.45K CO
+
3
By modeling the thermal decomposition of PbS in
an argon atmosphere between 1000 and 2000 K at a
total pressure in the system of 105 Pa (16 components
taken into account), we found that crystalline PbS does
not decompose into Pb and S under these conditions.
Consequently, the decomposition
2
33.31Na CO + 12.95PbS + 0.648C + 21.64Ar mixture and
2
3
(b) metallic melt: (a) (1) (Na CO ), (2) (K CO ),
2
3
2
3
(3) (Na S), (4) (K S), (5) (PbS), (6) (PbO); (b) (1) weight
fraction Z of the metallic melt in the condensed phase,
(2) lead recovery η, (3) [Pb], (4) [C].
2
2
(PbS) = [Pb] + S,
(11)
1000–1100 K, the melt contains substantial amounts of
(Na2S) and (K2S) (Fig. 4a).
where sulfur is an active component, highly reactive
with the other melt components, is only possible in
molten carbonates.
The p(CO2)/p(CO) ratio (the main components of
the gas phase) decreases from 5.9 at 1000 K to 1.34 at
1500 K.
31.65K2CO3 + 33.52Na2CO3 + 13.04PbSO4 +
ensures the formation of metallic Pb without other 21.78Ar mixture. The addition of PbSO4 leads to the
Thus, the introduction of PbS into carbonate melts
reductants.
exchange reaction
31.45K2CO3 + 33.31Na2CO3 + 12.95PbS +
PbSO4 + (M2CO3) = (M2SO4) + (PbO) + CO2, (12)
0.648C + 21.64Ar mixture. The compositions of the
carbonate and metallic melts are the same as above. The
results for condensed phases are displayed in Fig. 4.
where M = Na or K.
In the temperature range 1000–1500 K, the main
components of the carbonate melt, containing PbSO4,
PbO, PbO2, Pb2O3, Pb3O4, PbS, NaO2, Na2O, Na2O2,
Na2S, Na2SO4, Na2CO3, KO2, K2O, K2O2, K2S,
K2SO4, K2CO3, and PbCO3, are (PbO) (weight fraction
of 0.1256 to 0.124), (Na2SO4) (2.77 × 10–3 to 2.24 ×
10−2), (Na2CO3) (0.437 to 0.423), (K2SO4) (9.48 × 10–2
to 7.09 × 10–2), and (K2CO3) (0.34 to 0.36).
The addition of carbon produces some changes in
comparison with the above system. In a wide tempera-
ture range (1000–1400 K), the weight fraction of Pb in
the metallic melt is unity, and the weight fraction of the
metallic melt in the phase mixture is Ӎ0.15. Lead
recovery attains Ӎ97.5% at 1100–1300 K. At the same
time, just as in the carbon-free system, the degree of
reduction is sufficiently high only in a limited tempera-
ture range (Fig. 4b), in contrast to the processes in the
presence of PbO or PbCl2 and carbon. This indicates
that (PbS) undergoes chemical transformations only
above 1000 K. According to Chizhikov [6], the vapor
pressure during PbS decomposition at 1270 K is
13.3 Pa. Thus, (PbS) in carbonate melts begins to
decompose at temperatures 250–300 K lower as com-
pared to PbS in air.
The main component of the gas phase (along with
Ar) is CO2, which confirms that reaction (12) does
occur.
31.45K2CO3 + 33.3Na2CO3 + 12.95PbSO4
+
0.647C + 21.64Ar mixture. We took into account the
same components of the carbonate melt as above. The
composition of the metallic melt was the same as in all
the systems considered.
The results for condensed phases are displayed in
Fig. 5. The highest fraction of the metallic melt (0.095)
The main components of the carbonate melt at
1000 K are (Na2CO3), (K2CO3), and (PbS); above
INORGANIC MATERIALS Vol. 38 No. 12 2002

1220
BARBIN et al.
100
10–1
10–2
10–3
lead is present in the form of (PbS). At higher tempera-
(a)
tures, lead is formed by reactions (3)–(10). Since reac-
tion (13) requires a substantial amount of carbon,
metallic Pb is formed largely by reactions (3)–(10).
2
1
We performed calculations for reaction (13) with
consideration for the actual amount of added carbon. In
a mixture containing 0.043 mol of PbSO4 and
0.0996 mol of carbon, the amount of carbon is 92.7% of
the one required in reaction (13). For this reason, in the
system under consideration Pb is only formed by reac-
tions (3)–(10). There is no free carbon for reaction (1),
and the (PbO) groups survive.
3
5
7
4
8
5
6
Calculations show that, for reaction (13) to reach
completion and the resulting (PbO) to then be reduced
to Pb, the amount of carbon must be increased by a fac-
tor of 1.1287 (from 5 to 5.935 wt % relative to PbSO4).
The optimal composition of the starting mixture is then
31.41K2CO3 + 33.27Na2CO3 + 12.935PbSO4 + 0.768C +
21.62Ar.
η, wt %
(b)
100
10–1
10–2
10–3
100
90
1
Z
3
2
0.2
0.1
η
80
70
60
50
Z
31.65K2CO3 + 33.52Na2CO3 + 4.345PbO +
4.345PbCl2 + 4.345PbS + 21.78Ar mixture. The spe-
cies taken into account were PbO, PbO2, Pb3O4, PbCl2,
PbS, NaO2, Na2O, NaCl, NaClO3, Na2S, Na2SO4,
Na2CO3, KO2, K2O, KCl, KClO3, K2S, K2SO4, K2CO3,
and PbCO3 in the carbonate melt and C, Pb, K, Na, and
Na2C2 in the metallic melt.
800
1000
T, K
1200
1400
Fig. 5. Temperature-dependent concentrations of compo-
nents in (a) the carbonate melt of a 31.45K CO
+
3
2
33.3Na CO + 12.95PbSO + 0.647C + 21.64Ar mixture
2
3
4
and (b) metallic melt: (a) (1) (K CO ), (2) (Na CO ),
2
3
2
3
The results for condensed phases are shown in
Fig. 6. Since the possible processes with the participa-
tion of the reactants under consideration were dis-
cussed in detail above, we will restrict ourselves here to
general observations.
(3) (K SO ), (4) (Na SO ), (5) (K S), (6) (Na S), (7) (PbO),
2
4
2
4
2
2
(8) (PbS); (b) (1) [Pb] ([C] ≤ 1 ppm by weight), (2) weight
fraction Z of the metallic melt in the condensed phase,
(3) lead recovery η.
In the range 1100–1200 K, Pb recovery is up to
90%. In spite of the lower PbS content of the starting
mixture compared to the Na2CO3 + K2CO3 + PbS + Ar
mixture, 90% of the Pb present is reduced to the metal-
lic state.
and the highest Pb recovery are observed in the range
1200–1300 K. The recovery is relatively low, presum-
ably because of the reductant deficiency.
Consider the possible sequence of transformations.
At low temperatures, the reduction of Pb is insignifi-
cant. The main components of the melt result from the
following processes:
The temperature range in which Pb recovery is
~70% extends from 1100–1400 K in the Na2CO3–
K2CO3–PbS–Ar system to 1000–1400 K in the mixture
under consideration. Consequently, PbO and PbCl2
additions make PbS a more efficient reductant. By
adjusting the relative amounts of PbS, PbO, and PbCl2,
it is possible to effectively reduce such mixtures to Pb
metal in Na2CO3 + K2CO3 melts without carbon. Note
that the presence of free (PbO) in carbonate melts
makes it possible to recover an additional amount of Pb
on the addition of carbon (Fig. 6a).
(1) (K2SO4) and (PbO) may be formed by reaction (12).
(2) The other components are formed by the reac-
tion
2PbSO4 + 5C + (K2CO3)
(13)
= (PbS) + (PbO) + (K2S) + 5CO2.
After the completion of reaction (13), the residual car-
bon reacts with (PbO) by reaction (1) to form lead.
However, the amount of carbon is insufficient to reduce
27.11K2CO3 + 33.31Na2CO3 + 4.32PbO +
4.32PbCl2 + 4.32PbS + 0.648C + Ar mixture. The
melt compositions are the same as above. The results
all of the (PbO) to Pb; moreover, a large percentage of for condensed phases are displayed in Fig. 7.
INORGANIC MATERIALS Vol. 38 No. 12 2002

LEAD RECOVERY FROM PbO, PbCl2, PbS, PbSO4, AND THEIR MIXTURES
1221
The introduction of carbon markedly increases Pb
EXPERIMENTAL AND RESULTS
recovery (>95% in the range 1000–1200 K, Ӎ99% at
1100 K). At the same time, carbon seems to be present
in excess, as evident by the significant amount of unre-
acted carbon in the range 700–900 K (Fig. 7b).
The chemical composition of Pb-containing dust
was determined using a PE-405 atomic absorption
spectrophotometer:
Dust
component
Pb
Sn
Zn
S
Sb
Cl
As
SiO2
FeO
wt %
64.7–67.47 0.42–0.75 0.26–0.98 5.34–6.80 0.34–0.94 3.20–9.18 0.38–0.65 2.28–0.50 0.15–0.19
The phase composition of the dust was determined ture composition, reductant concentration, tempera-
on a DRON-UM-1 x-ray diffractometer with mono- ture, and holding time (table), we optimized the reduc-
chromatized Cu radiation. X-ray examination revealed
the presence of PbSO4 (dominant phase) and smaller
amounts of PbCl2, PbS, and PbO. In addition, a number
of reflections from Zn2SnO4 were detected.
tion conditions to achieve the highest possible Pb
recovery.
Our results demonstrate that molten alkali carbon-
ates are candidate media for recovering Pb from its
compounds. The process is influenced by the composi-
tion of Pb-containing waste, the amount of the reduc-
tant, temperature, and reduction time. In most of the
systems studied, the Pb recovery amounts to 90–100%,
which exceeds the level of the other known processing
methods [8]. In carbonate melts, no reductant is needed
to recover Pb from PbS (table, mixture 4) [9] or mix-
tures of PbS and other Pb compounds (mixtures 6, 8)
[10]. The introduction of a reductant into Pb-containing
carbonate melts increases Pb recovery (mixtures 5, 7, 9).
The density of the dust was determined as described
in [7]. The true density was 2.3–2.5 g/cm3, and the
apparent density was 1.60 ± 0.05 g/cm3.
Reactions were run in a resistance-heated furnace.
The temperature was maintained with an accuracy of
±2 K. After melting a 1 : 1 mixture of Na2CO3 and
K2CO3 in a BeO crucible, Pb compounds were added.
The weight ratio of the carbonate melt to the Pb-con-
taining material was 1 : 0.02 to 1 : 0.6. In a number of
experiments, carbon was added as a reductant. After
holding at temperature, the crucible was withdrawn
Thermodynamic modeling results agree quantita-
from the furnace and air-cooled. Next, the solidified tively with experimental data, to within the experimen-
melt was analyzed for metallic Pb. By varying the mix- tal uncertainty.
Experimental results on Pb recovery from Pb compounds (waste) in Na2CO3 + K2CO3 melts
Reduction
No.
Pb compound
T, K
wt % Pb*
time, h
1
2
3
4
5
6
7
8
9
PbO (litharge)
PbCl2
1020
1020
1200
1270
1270
1170
1170
1220
1220
2
2
4
3
3
3
3
4
4
99
99
80
85
95
90
99
95
99
PbSO4
PbS (galenite)
PbS (galenite)
PbO + PbCl2 + PbS (dust)
PbO + PbCl2 + PbS (dust)
PbO + PbCl2 + PbS + PbSO4 (Pb-containing waste)
PbO + PbCl2 + PbS + PbSO4 (Pb-containing waste)
Note: Mixtures 1–3, 5, 7, and 9 contain wood coal as a reductant; mixtures 4, 6, and 8 contain no reductant.
* Lead recovery.
INORGANIC MATERIALS Vol. 38 No. 12 2002

1222
BARBIN et al.
100
10–1
10–2
10–3
100
10–1
10–2
10–3
(a)
(a)
2
1
1
2
10
4
4
3
3
5
6
5
7
9
6
6
8
7
8
η, wt %
(b)
100
10–1
10–2
10–3
η, wt %
(b)
3
100
10–1
10–2
10–3
100
3
Z
η
100
Z
0.2
0.1
η
90
80
70
60
50
2
2
0.2
0.1
90
80
70
60
50
Z
1
1
Z
4
800
1000
1200
1400
T, K
800
1000
T, K
1200
1400
Fig. 6. Temperature-dependent concentrations of compo-
nents in (a) the carbonate melt of a 31.65K CO
+
3
Fig. 7. Temperature-dependent concentrations of compo-
nents in (a) the carbonate melt of a 27.11K CO
2
33.52Na CO + 4.345PbO + 4.345PbCl + 4.345PbS +
+
3
2
3
2
2
21.78Ar mixture and (b) metallic melt: (a) (1) (K CO ),
33.31Na CO + 4.32PbO + 4.32PbCl + 4.32PbS +
2
3
2 3 2
(2) (Na CO ), (3) (KCl), (4) (K SO ), (5) (NaCl),
0.648C +Ar mixture and (b) metallic melt: (a) (1) (K CO ),
2 3
2
3
2
4
(6) (Na SO ), (7) (K S), (8) (Na S), (9) (PbS), (10) (PbO);
(2) (Na CO ), (3) (KCl), (4) (K S), (5) (NaCl), (6) (Na S),
2
4
2
2
2 3 2 2
(b) (1) weight fraction Z of the metallic melt in the con-
densed phase, (2) lead recovery η, (3) [Pb] ([C] ≤ 1 ppm by
weight).
(7) (PbS), (8) (PbO); (b) (1) weight fraction Z of the metal-
lic melt in the condensed phase, (2) lead recovery η,
(3) [Pb], (4) [C].
The main impurities in Pb-containing dust are anti- metal recovered in carbonate melts contains the follow-
mony, tin, zinc, and arsenic (0.3 to 0.9 wt %). The Pb ing impurities:
Dust
component
Sb
Sn
Zn
As
Cu
Bi
Fe
wt %
0.50–1.50
0.10–1.0
0.0004–0.009
0.01–0.04
0.03–0.10
0.001–0.03
0.001–0.010
Recovered Pb corresponds in purity to grade SSu3
(RF Standard GOST 1292-74) and requires no further
processing or remelting.
The proposed method involves no agglomeration,
blast smelting, or Pb refining steps. The raw materials
are easier to prepare, and the process includes a small
number of steps.
The method allows one to obviate the need for pyro-
metallurgical processing of blast furnace dust in the
lead industry, thereby notably reducing the cost of the
product.
CONCLUSIONS
Thermodynamic calculations suggest that carbonate
melts are suitable media for Pb recovery from PbO,
PbCl2, PbS, PbSO4, and their mixtures.
ACKNOWLEDGMENTS
In our experiments, a high Pb recovery from these
compounds and industrial waste was reached.
This work was supported by the Russian Foundation
for Basic Research (Ural), project no. 01-03-96498.
INORGANIC MATERIALS Vol. 38 No. 12 2002

LEAD RECOVERY FROM PbO, PbCl2, PbS, PbSO4, AND THEIR MIXTURES
1223
Models for Describing Reaction Products in Equilibrium
Metallic Melts, Vsesoyuznaya konferentsiya po osnovam
metallurgicheskikh protsessov (All-Union Conf. on the
Foundations of Metallurgical Processes), Moscow:
Chermetinformatsiya, 1991, part 1, p. 23.
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INORGANIC MATERIALS Vol. 38 No. 12 2002