Extraction of Non-Ferrous Metals as Inorganic Chlorides from Waste Lead Slags in the Presence of Chlorine-Containing Components of a Distilled Liquid

Introduction

The ammoniac way prevailing in the world soda production gives a considerable quantity of a liquid waste product – distilled liquid. Its composition, g/m³: СаСl₂– 118-125; NaCl – 58.6-80; CaCO₃– 6-15; CaSO₄– 2-2.7; Mg(OH)₂ – 3-10; CaO – 2-4; Fe₂O₃ +Al₂O₃ – 1-3; SiO₂–1-4.¹ There are some directions of partial recycling of the distilled liquid that allows obtaining: waterless calcium peroxide used for production of bleachers and disinfectants and for treatment of waste water and gas emissions²; phosphorus-containing fertilizers applied in agriculture³; ammonium chloride, which can be used in the textile industry, pharmaceutics, at soldering of metals, tinning, for filling of galvanic cells, as a nitric fertilizer⁴; high-quality chemically-precipitated calcium carbonate widely used in many industries for manufacturing various composite materials.⁵ After special preparation the distilled liquid can be applied for pumping in oil wells for the purpose of maintenance of strata pressure.⁶ But such the way of its recycling is possible only if soda ash manufacture is situated in the oil recovery area. There is a method of electrochemical processing of the distilled liquid with obtaining Са(OH)₂, NaОН and НСl.⁷ Also the distilled liquid is used at soda ash manufacturing by means of processing of a salt solution for desulfation of a brine and production of gypsum.⁸ We suggest to use the distilled  liquid for extraction of nonferrous metals as inorganic chlorides fromfuming slags.

Experimental Section

Materials and Methods

At implementation of the research we applied the fuming slags of JSC «Yuzhpolimetal» containing (%): ZnSiO₃‒6.4; ZnS ‒1.5;Cu₂O‒ 1.5; PbS‒0.2; PbSO₄‒ 0.2;SiO₂‒22.7; Fe₂O₃‒40.1; CaO‒13.9; MgO‒3.1; Al₂O₃‒5.4; MnO‒ 0.7; Na₂O‒2.91; others – 1.4. A mixture of calcium and sodium chlorides with a mass ratio of CaCl₂/NaCl=2(such the chloride ratio is typical of the distilled liquid. Its composition, g/m³: СаСl₂– 118-125; NaCl – 58.6-80; CaCO₃– 6-15; CaSO₄– 2-2.7; Mg(OH)₂ – 3-10; CaO – 2-4; Fe₂O₃ +Al₂O₃ – 1-3; SiO₂– 1-4) was used as a chlorinating agent. The chlorides content was constant and equal 6.8% of CaCl₂ and 3.4% of NaCl of the slag weight. The oxygen mass also was constant and made 100% of the theoretically necessary weight for oxidation of lead and zinc sulphides to their oxides.

The research was implemented by a thermodynamic modelling technique using a software package HSC-5.11 Chemistry, based on a Gibbs energy minimum principle,⁹ and also a rototable second-degree method of planning an experiment (Box-Hunter method).¹⁰ First of all, we studied the pressure and temperature effect on the quantitative distribution of substances in a system under study, and then on the basis of the obtained data–the equilibrium chloride sublimation  degree (α_chl) of lead, zinc and copper. The metals’ chloride sublimation degree was calculated according to the expression:

whereG_{met (chl)} ‒ weight of a metal turned into chloride, kg; G_{met (in)}‒ weight of a metal in slag, kg.

Results and Discussion

Temperature and Pressure Effect on the Quantitative Distribution of the Substances Containing Lead, Zinc and Copper in a System Slag – (CaCl₂ + NaCl) ‒ О₂

Fig. 1 contains the information obtained by means of the software packageHSC-5.11 about the quantitative distribution of the substances containing lead, zinc and copper at pressure of 1 and 0,1 bar. As follows from the figure, lead in the studied system is as PbCl₂, PbCl_2(g), PbCl_(g), PbSO₄; zinc as ZnSiO₃, ZnCl_2(g), ZnCl₂ and copper as Cu₂O, CuCl, CuCl_2(g), CuCl_(g). Decrease in the pressure promotes increase in α_chl(Me) and reduction of the process temperature.

Figure 1: Temperature and pressure effect on the quantitative distribution of the substances containing lead, zinc and copper in a system slag – (CaCl2 + NaCl) ‒ О2. Click here to view figure

 

Temperature Effect on the Chloride Sublimation Degree of Lead, Zinc and Copper from the Slag in the Presence of CaCl₂ and NaCl

Influence of temperature and  pressure on α_chl(Me)is represented in fig. 2.

Figure 2: Temperature effect on the chloride sublimation degree of lead, zinc and copper from the slag in the presence of CaCl2 and NaCl. Click here to view figure

 

Judging from the fig. 2 the decrease in pressure and increase in temperature leads to increase in α_chl(Me). We accept  α_chl(Pb) >α_chl(Zn) >α_chl(Cu).

The Research Matrix and Results

The research matrix (according to the second-degree rototableplanning) and results are represented in tables 1-3. On the basis of the results the regression equations of temperature (Т,°С) and pressure (lgP, bar) influence on the chloride sublimation degree of lead (α_chl(Pb), %), zinc (α_chl(Zn), %) and copper (α_chl(Cu), %) were obtained:

α_chl(Pb) = – 114.491–60 T,°C +0.2772 · T–5 · (lgP)² T,°C 10^-5 · T² 0.0367 · lgP T,°C

α_chl(Zn) = – 622.1–101.8 · lgP +0.823 · T–7.72 · (lgP)² – 2.44 · 10-⁴  · T² +0.045 · lgP · T;

α_chl(Cu) = – 1635.89 – 164.44 · lgP + 2.103 · T – 7.76 · (lgP)² – 6.62 · 10^-4 · T²+ 0.0735 · lgP · T.

Using these equations according to the technique¹¹ solid surfaces of temperature and pressure effect on α_chl(Pb),α_chl(Zn) and α_chl(Cu)and their horizontal sections were constructed (fig.3). As follows from fig. 3, α_chl(Pb) from 95 to 100% is observed in the area abcd, α_chl(Zn) from 90 to 100% ‒ in the area xyzf  and α_chl(Cu)‒ in the area nmet. Values of temperature and pressure in boundary points of these technological areas are represented in table 4.

Table 1: The planning matrix and the research results of the lead chloride sublimation from the fuming slag.

№	Variable parameter				Lead chloride sublimation  degree,%
	Code kind		Natural kind		αchl (initial)	αchl (calcul.)
	х1	х2	lgP, bar	T,°C
1	+1	+1	-0.3 (0.50)	1241.8	95.01	93.63
2	+1	-1	-0.3 (0.50)	958.2	76.52	74.79
3	-1	+1	-1.7 (0.02)	1241.8	99.92	99.82
4	-1	-1	-1.7 (0.02)	958.2	96.03	95.58
5	+1.414	0	-0.0 (0.00)	1100	79.04	80.80
6	-1.414	0	-2.0 (0.01)	1100	99.91	99.87
7	0	+1.414	-1.0 (0.1)	1300	99.12	99.74
8	0	-1.414	-1.0 (0.1)	900	123.03	83.42
9	0	0	-1.0 (0.1)	1100	95.03	95.24
10	0	0	-1.0 (0.1)	1100	95.32	95.24
11	0	0	-1.0 (0.1)	1100	94.71	95.24
12	0	0	-1.0 (0.1)	1100	94.83	95.24
13	0	0	-1.0 (0.1)	1100	96.44	95.24

 

Table 2: The planning matrix and the research results ofthe zinc chloride sublimation from the fuming slag.

№	Variable parameter				Zinc chloride sublimation  degree,%
	Code kind		Natural kind		αchl (initial)	αchl (calcul.)
	х1	х2	lgP(bar)	T,°C
1	+1	+1	-0.3 (0.50)	1441.8	70.02	68.48
2	+1	-1	-0.3 (0.50)	1158.2	22.21	18.72
3	-1	+1	-1.7 (0.02)	1441.8	65.33	66.51
4	-1	-1	-1.7 (0.02)	1158.2	33.33	36.68
5	+1.414	0.0	-0.0 (0.00)	1300.0	95.01	91.61
6	-1.414	0.0	-2.0 (0.01)	1300.0	92.02	90.75
7	0.0	+1.414	-1.0 (0.1)	1500.0	31.84	33.04
8	0.0	-1.414	-1.0 (0.1)	1100.0	71.01	71.72
9	0.0	0.0	-1.0 (0.1)	1300.0	71.02	71.72
10	0.0	0.0	-1.0 (0.1)	1300.0	72.33	71.72
11	0.0	0.0	-1.0 (0.1)	1300.0	73.12	71.72
12	0.0	0.0	-1.0 (0.1)	1300.0	71.63	71.72
13	0.0	0.0	-1.0 (0.1)	1300	71.71	71.72

 

Table 3: The planning matrix and the research results of the copper chloride sublimation from the fuming slag.

№	Variable parameter				Copper chloride sublimation  degree,%
	Code kind		Natural kind		αchl (initial)	αchl (calcul.)
	х1	х2	lgP(bar)	T,°C
1	+1	+1	-0.3 (0.50)	1370.7	36.42	41.10
2	+1	-1	-0.3 (0.50)	1329.3	12.21	8.93
3	-1	+1	-1.7 (0.02)	1370.7	97.21	98.13
4	-1	-1	-1.7 (0.02)	1329.3	88.02	80.57
5	+1.414	0.0	-0.0 (0.00)	1400.0	13.03	11.22
6	-1.414	0.0	-2.0 (0.01)	1400.0	98.11	102.0
7	0.0	+1.414	-1.0 (0.1)	1500.0	80.32	75.24
8	0.0	-1.414	-1.0 (0.1)	1300.0	33.13	40.07
9	0.0	0.0	-1.0 (0.1)	1400.0	64.52	64.32
10	0.0	0.0	-1.0 (0.1)	1400.0	63.04	64.32
11	0.0	0.0	-1.0 (0.1)	1400.0	62.92	64.32
12	0.0	0.0	-1.0 (0.1)	1400.0	65.23	64.32
13	0.0	0.0	-1.0 (0.1)	1400.0	63.91	64.32

 

Figure 3: Temperature and pressure effect on the chloride sublimation degree of lead, zinc and copper in a system slag – (CaCl2 + NaCl) ‒ О2. Click here to view figure

 

Table 4: Technological parameters of the optimal areas of the metals’ chloride sublimation  from the slags  by the use of the calcium and sodium chlorides mixture typical for the distilled liquid.

Metal (area, figure)	Parameter	Points
		а	b	c	d
Lead (abcd, fig.3, І)	T,°C	933.7	1130.1	1300	1300
	lgP(bar)	-1.75(0.0177)	-1.75(0.0177)	-1.195(0.06)	-0.48(0.33)
	αchl,%	95.0	100.0	100.0	95.0
Zinc (xyzf, fig.3, ІІ)	Parameter	Points
		x	y	z	f
	T,°C	1279.3	1417.1	1500	1500
	lgP(bar)	-2.0(0.01)	-2.0(0.01)	-1,695(0.02)	-0.972(0.1067)
	αchl,%	90.0	100.0	100.0	90.0
Copper (nmet, fig.3, ІІІ)	Parameter	Points
		n	m	e		t
	T,°C	1337.7	1382.9	1500		1500
	lgP(bar)	-2.0(0.01)	-2.0(0.01)	-1.75(0.0177)		-1.418(0,381)
	αchl,%	90.0	100.0	100.0		90.0

 

As follows from the data of table 4, to achieve the 95-100% lead chloride sublimation  degree the necessary temperature is 933.7‒1300°С and lgP should be from –0.48 to –1.75 (pressure of 0.33-0.0177 bar); for achievement of the 90.0-100% chloride sublimation  degree for zinc respective parameters are T=1279.3-1500°C and lgP from –0.972 to –2 (pressure of 0.107-0,01 bar), for copper ‒ temperature of 1337.7-1500°С and lgP from –1.418 to –2 (pressure of 0.038-0.01 bar). Judging by the table data, at pressure of 0.01 bar the high copper chloride sublimation degree is possible at high temperatures (1337.7°С); for zinc it can be lowered to 1279.3°С and for lead ‒ to 933.7°С. At implementation of the sinter-chlorinating roasting of the slags the process temperature should not exceed the slag’s melting temperature (1200°С,¹²) that is its maximal value may be 1100-1150°С. For achievement of high α_chl(Zn) and α_chl(Cu) values at these temperatures the process pressure should be reduced.

The information about influence of the pressure reduction on α_chl(Cu) at the lowered temperatures (1100-1150°С) is represented in table 5.

Table 5: Pressure effect on α_chl(Cu) at the lowered temperatures.

1100°С	3.6% (0.1 bar)	14.3% (0.01 bar)	54.8% ( 0.001  bar)	100% (0.00032 bar)
1150°С	7.4% (0.1 bar)	31,6% ( 0.01 bar)	86.4% (0.001   bar)	100% (0.00056 bar)

 

It is evident, that at temperature of 1150°С and pressure of 0.001 bar α_chl(Cu)  exceeds 85%. At the same time, zinc and lead completely pass in a gaseous condition.

The Experiments Connected with Determination of the Possibility of Application of the Distilled Liquid for Extraction of Lead, Zinc and Copper from the Fuming Slags

The experiments connected with determination of the possibility of application of the distilled liquid for extraction of lead, zinc and copper from the fuming slags were carried out on a sintering plant.¹³ The charge mass was 300-350 g. Before the sintering roasting the slag and coal (5% of the slag mass) are grinded to the fraction <0.1 mm and pelletized using a solution of the distilled liquid. The granules in diameter of 1-1.2 cm were dried at 200°С during 30 min. The dry granules were loaded on a fire grate of an agglomeration cylinder (on which we preliminary placed a burnt limestone layer). Ignition of the granules is realized by means of a blowtorch. After the ignition (in 5-8 min) the layer wise burning of the charge with the simultaneous chloride sublimation  of the metals occurred. Suction of the gases (including the chloride sublimation  gases) is realized with the help of a smoke sucker. Vacuum under the fire-grate was controlled by a manometre. Duringthe ignition periodit was 0.006-0.0065 bar, and during thechloride sublimation  period ‒ 0.01-0.015 bar. The process duration was 35-40 min. Temperature of the material in the layer was 1150-1180°С. The metals’ chloride sublimation  degree  was calculated  under the formula:

where G_Me(slag) И G_Me(sin) ‒mass of a metal in a slag and in a sinder after roasting, g. On the basis of the results of 3 experiments it was found, that the chloride sublimation degree of copper made 73-88%, zinc – 82-96% and lead ‒ 93-98%.

Conclusion

On the ground of the results of the experiments on application of the distilled liquid – the waste of soda manufacture – for extraction of lead, zinc and copper from the dump slags by chloride sublimation it is possible to draw the following conclusions:

At equilibrium conditions lead is extracted the most effectively from the slags by chloride sublimation , then zinc and copper: at pressure of 1 bar and temperature of 1500°С the chloride sublimation degree for lead makes 98.63%, for zinc – 64.45% and for copper – 21.91%;

To achieve the 95-100% lead chloride sublimation  degree the needed temperature is 933.7‒1300°С and lgP should be from –0.48 to –1.75 (pressure of 0.33-0.0177 bar); for achievement of the 90.0-100% chloride sublimation  degree for zinc respective parameters are T=1279.3-1500°C and lgP from –0.972 to –2 (pressure of 0.107-0,01 bar), for copper ‒ temperature of 1337.7-1500°С and lgP from –1.418 to –2 (pressure of 0.038-0.01 bar);

It was experimentally proved, that at the sinter-chlorinating roasting at temperature of 1150-1180⁰С and pressure of 0.006-0.001 bar the chloride sublimation degree for lead makes 93-98%, for zinc ‒ 82-96%, for copper – 73-88%.

Author Contributions

All authors contributed in equal parts to the search and analysis of literature data, writing the text and designing the graphs. D. Pazylova is responsible for the coordination of work and correspondence with the journal.

Acknowledgments

The work was supported by projects of the Ministry of Education and Sciences of the Republic of Kazakhstan.

Conflicts of Interest

There is no conflict of interest.

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