Technological scheme for copper slag processing

    Technological scheme for copper slag processing Stoyko Gyurov, Nikolay Marinkov, Yoanna Kostova, Diana Rabadjieva, Daniela Kovacheva, Christina Tzvetkova, Galia Gentscheva, Ivan Penkov PII: DOI: Reference:

S0301-7516(16)30242-3 doi:10.1016/j.minpro.2016.11.008 MINPRO 2980

To appear in:

International Journal of Mineral Processing

Received date: Revised date: Accepted date:

18 April 2016 4 November 2016 10 November 2016

Please cite this article as: Gyurov, Stoyko, Marinkov, Nikolay, Kostova, Yoanna, Rabadjieva, Diana, Kovacheva, Daniela, Tzvetkova, Christina, Gentscheva, Galia, Penkov, Ivan, Technological scheme for copper slag processing, International Journal of Mineral Processing (2016), doi:10.1016/j.minpro.2016.11.008

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT TECHNOLOGICAL SCHEME FOR COPPER SLAG PROCESSING Stoyko Gyurov1, Nikolay Marinkov2, Yoanna Kostova1, Diana Rabadjieva2, Daniela Kovacheva2, Christina Tzvetkova2, Galia Gentscheva2, Ivan Penkov1 1

Academician Angel Balevski Institute of Metal Science, Equipment and Technologies with Center

T

for Hydro and Aerodynamics, Bulgarian Academy of Sciences, 67 "Shipchenski prohod" str., 1574

Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, "Acad. Georgi

SC R

2

IP

Sofia, BULGARIA

Bonchev" str. bld.11, 1113 Sofia, BULGARIA

Corresponding author:

NU

Diana Rabadjieva

Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences

MA

"Acad. Georgi Bonchev" str. bld.11 1113 Sofia, BULGARIA

D

e-mail: [email protected]

TE

Abstract

A technological scheme for copper slag processing is proposed. It comprises 5 stages, namely: (i)

CE P

air oxidation of the copper slag at a temperature above 800oC for 2 h; (ii) hydrothermal treatment of the oxidized slag with sodium hydroxide solution (140 g/l) at 190oC for 3 h; (iii) separation of the solid from the liquid phase by hot filtration; (iv) gel formation through hydrolysis of the liquid

AC

silicate phase by changing pH; (v) obtaining of amorphous SiO2 (silica gel) by drying at 80oC. The processes used for slag manipulation were elucidated and optimized for silicon extraction. It was established that the increase in the oxygen partial pressure in the oxidizing gas does not change the mechanism nor significantly intensifies the oxidizing process. A decisive factor for the extraction of SiO2 during hydrothermal treatment was the concentration of NaOH. Its increase from 60 to 140 g/l reduced the amount of residual SiO2 more than half and significantly decreased the formation of analcime (NaAlSi2O6.H2O) in the solid phase. Hydrolysis of the liquid silicate phase by changing pH is an appropriate process for gel formation.

Key words: copper slag processing, silica gel, iron rich residue, thermal oxidizing, hydrothermal treatment

ACCEPTED MANUSCRIPT 1. Introduction Copper is derived mainly from copper–iron–sulphur minerals such as chalcopyrite (CuFeS2) and bornite (Cu5FeS4), as well as chalcocite (Cu2S) and enargite (Cu3AsS4) (Ayres et al., 2002). They usually are not found in pure form, but combined with each other and with different impurities

T

(especially FeS). Since copper ores typically contain no less than 95% of silicate compounds, the

IP

raw materials are subjected to comminution and flotation to produce copper concentrate, which is

SC R

then sent to a smelter. The purpose of the smelting is to eliminate as much of the unwanted iron, sulphur and gangue minerals as possible, while minimizing the loss of copper (Davenport et al., 2002). This is achieved by: (i) adding appropriate amount of silica, so that a separate fayalite (2FeO.SiO2) phase is formed that captures the iron (Hayes, 1993); and (ii) blowing air to remove

NU

the sulphur at high temperature as sulphur dioxide. The latter is captured and used for production of sulphuric acid, thus copper smelters have become integrated with acid plants that utilize offgas

MA

(Biswas and Davenport, 2013). But, for every ton copper produced, roughly two tons of iron silicate slags are generated (Byung-Su Kim, et al. 2013). They are considered as wastes irrespectively of their significant content of valuable components including FeO (35-49 %), SiO2

D

(28-40%), CaO (1-10%), MgO (1-3%), Al2O3 (2-15%), Cu (about 1%), as well as Mn, Ni, Zn, Co

TE

below 1 % (Gorai et al. 2003). Deposition of this slag causes loss of valuable metals and creates environmental issues, owing to the occupation of large quantities of land (Gonzalez et al. 2005) and

CE P

the acidification of surrounding waters and soils (Rabadjieva et al. 2009). A more sustainable approach would be to reduce the amount of copper slag and to recycle it into useful products. With minimal treatment, the slag is often used in the production of cement and concrete (Toshiki et

AC

al. 2000; Moura et al. 1999; Shi and Qian 2000), glass (Dongping et al. 1997), abrasive materials (Wozniak and Herman 1988), bricks, tiles and roof tiles (Marghussian and Maghsoodipoor 1999). Various methods have also been developed to treat the slag for the recovery of the residual Cu and valuable metals such as Fe, Zn, Ni and Co, by ammonium chloride treatment (Nadirov et al. 2013), by oxidative acid leaching (Zhang Yang et al. 2010, Yunjiao Li et al. 2008), by hydrometallurgical methods (Chen et al. 2012, Rudnik et al. 2009), etc. However, no significant reduction in the slag volume was achieved by these methods, as the silicate components remain untapped. If the fayalite slag were to be decomposed into two phases, silica and mixture of iron oxides, the silica itself could be utilized. A new approach has been proposed for recycling the copper slag into iron oxide concentrate, alkali metal silicate or a solution of silicon in alkali metal hydroxide, which can be used to produce water glass and silica gel (Gyurov et al. 2012 EU patent No. 2 331 717 B1,). The proposed method consists of thermal decomposition of the main mineral component of the copper slag - fayalite (2FeO.SiO2) through oxidation in air atmosphere and subsequent hydrothermal treatment with alkali

ACCEPTED MANUSCRIPT hydroxides or carbonates. The hydrothermal process is carried out at 160oC for 6 h resulting in roughly 30% extraction of silicon. Silica gel is a hydrophilic absorbent, with a wide range of applications in the chemical and construction industries. We believe that a more in-depth study of the utilization of silicon

T

containing slag is needed to achieve better extraction of silicon in the form of silica gel. Thus,

IP

integrated production of sulfuric acid, silica gel and iron concentrates could be developed

SC R

eventually leading to the full utilization of all waste products and the minimization of environmental pollution.

The present study is an extension of the method proposed by Gyurov et al. (2012) for utilization of the copper slag for the preparation of silica gel and iron rich residue. The processes used for slag

NU

manipulation have been elucidated and optimized for silica extraction. As a result, a technological scheme for copper slag processing is proposed, which comprises: (i) oxidation of the copper slag;

MA

(ii) hydrothermal treatment of the oxidized slag with sodium hydroxide or carbonate; (iii) separation of the solid from the liquid phase; (iv) gel formation through hydrolysis of the liquid silicate phase;

D

(v) obtaining of amorphous SiO2 (silica gel).

TE

2. Experiments and methods of characterization 2.1 Oxidation of the copper slag

CE P

Two types of experiments were performed. 2.1.1. Non-isothermal oxidation

The non-isothermal oxidation of copper slag was carried out using the computerized combined

AC

thermal analysis apparatus LABSYSEvo (SETARAM Company, France) in the temperature range 25 – 1000oC. Gas mixtures of nitrogen and oxygen with an oxygen content of 18, 42, 63 and 100 vol % were used as the oxidant. Alumina crucibles with diameter of 4 mm and height of 10 mm were used. The sample weight in all tests was 80±1 mg. The experiments were carried out under dynamic conditions, with a heating rate of 10 oC min-1 and an oxidizing gas flow rate of 30 ml min1

.

2.1.2. Isothermal oxidation The isothermal oxidation was carried out at temperatures of 250, 400, 600, 800 and 1000°C for 2 h in an air atmosphere. Approximately 1 gram of slag was placed in an alumina crucible and was heated in a laboratory furnace at each temperature. 2.2. Hydrothermal treatment of the copper slag The oxidized slag was treated with a solution of sodium hydroxide or a mixture of sodium hydroxide and sodium carbonate in an autoclave installation under continuous stirring. The system was set to operate at temperatures up to 250oC and corresponding autogenous pressure of water

ACCEPTED MANUSCRIPT vapor. Both temperature and pressure were controlled. The optimum parameters of the process of extracting the silicon phase were obtained by varying the temperature, duration of the process and concentration of the alkaline solutions (Table 1). The resulting mixture of solid iron rich residue and liquid silicate was separated by hot filtration.

T

Then the solid residue was treated again with water in the autoclave in order to achieve additional

IP

extraction of the silicon.

SC R

2.3. Gel formation through hydrolysis of the liquid silicate phase

Two methods were used for carrying out the gelation of the silicate phase: • Natural formation of gel from the hydrosol extracted from the alkaline filtrate at room temperature for ten days;

NU

• Changing the pH of the liquid phase by acidification with hypo chloric acid down to pH 7-

MA

9 or pH 2-3.

2.4. Characterization of the solid and liquid phases 2.4.1. XRD analysis

D

The phase composition of the solid phases was determined by XRD analyses using an automatic

TE

Bruker D8 Advance powder X-ray difractometer with CuKα radiation (Ni filter) and registration by LynxEye solid-state position-sensitive detector. The X-ray spectra were recorded in the range from

CE P

5.3 to 100о 2θ with a step of 0.02о 2θ. A rotating speed of 30 rpm was found to provide sufficiently accurate measurements. Qualitative phase analysis was performed using the PDF-2 (2014) database of the International Centre for Diffraction Data (ICDD) by means of the DiffracPlusEVA software

AC

package. Rietveld based quantitative phase analysis was performed with the use of the TOPAS 4.2 software (TOPAS V4). The total quantity of SiO2 was calculated by summation of its contents in the silicon-containing phases. 2.4.2 SEM analyses

SEM images were recorded and the distribution of the chemical elements was determined using a JEOL JSM 35 CF scanning electron microscope with a TRACOR NORTHERN TN – 2000 X-ray microanalyzer using JEOL standards. 2.4.3. IR analysis Infrared spectra of the samples were recorded in KBr tablets (13 mm) using Thermo Nicolet Scientific iS5 FTIR spectrometer at a spectral resolution of 2 cm-1. Processing and analysis of the spectrum were made using the OMNIC software. 2.4.4. Chemical analysis The silicon content in the liquid phases was determined spectrophotometrically in the form of soluble complex β-silicomolybdic heteropolyacid at λmax = 400 nm, using UV-VIS

ACCEPTED MANUSCRIPT spectrophotometer Evolution 160 of Thermo Scientific Company, USA.

3. Results and discusion The copper slag used in the experiments was a waste product from the pyrometallurgical production

T

of copper in Aurubis Bulgaria AD Company. Mineralogical analysis indicated the presence of

IP

fayalite Fe2SiO4; a cubic magnetic phase with a spinel type structure and an unit cell parameter of

SC R

8.37 Å; quartz SiO2; calcite (Ca, Mg)CO3; and calcium mono carboaluminate Ca4Al2O6CO3.11H2O. The value of the unit cell parameter at room temperature of the spinel iron oxide (8.37Å) was lower than the reported values for pure magnetite: 8.3958Å (Mihailova and Mehandjiev, 2010); 8.3965 Å (Wechsler et al. 1984); 8.3970Å (Haavik et al., 2000) showing that the magnetite phase was slightly

NU

oxidized. The average chemical composition is presented in Table 2.

The slag was sifted through a 100 mesh sieve, and the fraction with particle size below 100 mesh

MA

was used in the experiment.

3.1 Oxidation of the copper slag

D

In our previous works (Gyurov et al. 2014, Gyurov 2011) we had studied the process of copper slag

TE

oxidation by DTA-TG analysis in synthetic air by varying the heating rates and oxidizing gas flow rates. We established that the oxidation mechanism was not affected by either rate. In this study we

CE P

investigated the effect of increasing partial pressure of oxygen in the oxidizing gas at fixed heating rate (10°C.min-1) and flow gas rate (30 ml.min-1). The results (Fig. 1) show a similarity in the shapes of DTA and TG curves and also in the values of the registered temperature maxima and

AC

mass changes. The results revealed that, independent of the oxygen partial pressure, the slag oxidation passes through a four-stage mechanism (Gyurov et al. 2014, Gyurov et al. 2011) as follows: (i) oxidation of magnetite and formation of metastable spinel (γ-Fe2O3); (ii) transformation of γ-Fe2O3 into the stable -Fe2O3; (iii) oxidation and decomposition of fayalite (2FeO.SiO2); (iv) decomposition of the residual fayalite and polymorphic transformations in the silicate and iron phases. The separation of the individual stages was impossible for all studied heating rates. An intensification of the oxidation process was observed. It was manifested by the tendency of shifting the temperature maxima to lower values and increasing mass that resulted from a rising oxygen content. From a technological point of view these changes are minor, thus the oxidation in air was considered as the more appropriate route. XRD analysis of the slag oxidized in a furnace at different temperatures (Fig. 2) confirmed that the decomposition of fayalite begins at temperatures above 400°C. At 800°C the observed phases were hematite (Fe2O3) and magnetite (Fe3O4) with small crystallite sizes. The silica phase was amorphous. No peaks of fayalite were observed, indicating that the fayalite was completely

ACCEPTED MANUSCRIPT oxidized. The increase in crystallinity of magnetite after oxidation at 1000°C is an indication of degradation of the residual fayalite and simultaneous polymorphic transformations in the silicate and iron phases. The results of the experiments on the oxidation of the slag showed that the optimum conditions for

IP

T

carrying out the process of oxidation in air are: temperature above 800°C and duration of 2 h.

SC R

3.2 Hydrothermal treatment of the oxidized slag

Treatment of the oxidized slag with an alkaline solution (aqueous sodium hydroxide and/or carbonate) is a key stage in the recycling process. Its purpose is to divide the oxidized slag into two components: an iron-rich phase (iron concentrate) and a silicon-bearing solution.

NU

The SEM image of a cross section of a slag oxidized at 900оС (Fig. 3) shows that the oxidized slag grains are built of amorphous silicon-containing phase covered by layers of hematite and magnetite-

MA

like spinel. These surface layers hinder the interaction of the silicon phase with the alkaline solutions. Therefore, the influence of reaction time, temperature, and concentration of the alkaline solution on the silicon recovery was studied according to the conditions described in Table 1. The

D

evaluation of the effectiveness of the process was based on the amount of SiO2 that remained in the

TE

solid phase.

The results (Fig 4) indicate that the increase in the reaction time from 2 to 4 h and in the

CE P

temperature from 160 to 200°C did not significantly affect the rate of SiO2 extraction. A decisive factor for the extraction process was the concentration of NaOH: the increase from 60 to 140 g/l reduced the amount of residual SiO2 by more than half. The presence of Na2CO3 in the solution also

AC

promoted SiO2 extraction.

XRD analysis of the solid residue obtained after hydrothermal treatment showed that in addition to the silicon extraction in the solution as sodium silicate, synthesis of the silicon-containing crystalline phase NaAlSi2O6.(H2O) (analcime) was observed (Fig. 5a). When a mixture of sodium hydroxide and sodium carbonate was used as alkaline reagent, the formation of analcime was strongly suppressed, and a new silicon-containing crystalline phase Na7.26(CO3)0.93Al6Si6O24 (cancrinite) appeared instead (Fig. 5b). The amount of analcime mainly depends on the concentration of sodium hydroxide and decreases with the increase in NaOH concentration, Figure 6. Fig. 7a presents the electron microscope image of the grains of slag residue after hydrothermal treatment (190°C, NaOH 100 g/l, 3 h, washed with water for 2 h). Figures 7b-7h present the X-ray microanalysis of the distribution of elements in the sample. It can be seen that each grain is composed of areas with different chemical composition. For the hydrothermally treated sample, the individual layers may be broken down into smaller grains. Silicon containing areas coincide with

ACCEPTED MANUSCRIPT those of aluminum, calcium, potassium and sodium, revealing the presence of complex silicates, while iron containing areas are associated with those of titanium and magnesium, showing that the latter two elements are present as dopants in the iron oxide phases. Quantitative X-ray analysis of the solid residue after treatment of the oxidised slag with 140 g/l

T

NaOH solution at 190°C for 3 h revealed mass fractions of 79.8 % of iron oxides and 8.9% of SiO2,

SC R

IP

i.e., more than 70% silicon extraction was reached.

3.3. Gel formation through hydrolysis of the liquid silicate phase and obtaining of SiO2 The alkaline silicate solution obtained after filtration containing 17-21 g/l of silicon was used for the preparation of silica gel via two modes: 1) without changing the pH of the starting alkaline

NU

solution (hydrosol) at room temperature for ten days; and 2) by changing the pH of the starting alkaline solution (hydrosol) at room temperature down to two pH ranges: 7-9 and 2-3. The latter

MA

approach was chosen, as it is easy to implement and is well known (Brinker & Scherer, 2013). It was shown that the pH values affected the concentration of the negatively charged silicon species which build a highly cross-linked structure of the so-called colloidal sol and thus accelerated the

D

polymerization processes.

spectra are shown in Fig. 8.

TE

The gel resulting from each of the variants was dried at a temperature of 80oC. The characteristic IR

CE P

The IR spectra (Fig. 8) comprise characteristic bands of Si-OH groups, water, adsorbed OH groups etc., which correspond to the gel-forming condition and the related processes of hydrolysis and condensation. Three bands were observed around 1640 cm-1 (1667, 1639 and 1634) and at 3450 cm. They are characteristic of physically bound water in the gel material and depend on the conditions

AC

1

of preparation. A band about 1460 cm-1 was observed in all spectra, due to the presence of carbonate ions in the gel. Bands corresponding to the vibration of silanol Si-OH groups at 940 cm-1 with different intensities are shifted to the lower lengths (917 in Fig.8c and 901 in Fig.8a) indicating that complete hydrolysis and partial hydrolysis have taken place, respectively (the corresponding band is missing in Fig.8b). A condensation reaction realized by oxygen bridges Si-O-Si was observed in the three types of gel. In all three spectra, intensive bands characteristic for these bridges are observed in the range 1000 - 1100 cm-1. Their presence clearly points to the start of linking processes in the silicon structure.

4. Conclusions A technological scheme for copper slag processing was proposed and the process conditions were optimized. The scheme comprises 5 stages, namely:

ACCEPTED MANUSCRIPT (i)

Air oxidation of the copper slag at a temperature above 800oC for 2 h;

(ii)

Hydrothermal treatment of the oxidized slag at 190ºC with sodium hydroxide solution (140 g/l) for 3 h;

(iii) Separation of the solid from the liquid phase by hot filtration;

IP

Obtaining of amorphous SiO2 (silica gel) by drying at 80oC.

SC R

(v)

T

(iv) Gel formation through hydrolysis of the liquid silicate phase by changing the pH;

Acknowledgments:

The results were obtained with the financial support of the NSF of Bulgaria project № E 02/1/12.12.2014 entitled "Study of the interaction of complex composite-silicates of metallurgical

NU

slag with alkaline solutions" funded by the Fund "Scientific Research" of Bulgaria.

MA

The authors wish to thank “Aurubis Bulgaria” AD for supplied slag.

References

Andrzej, G., Miroslaw, U., Ryszard, D., 1992. Service properties of grinding wheels with copper

D

smelting slag as binder component. Mechanic 65(5-6), 167-169.

TE

Ayres, R. U., Ayres, L. W., Rаde, I., 2002. The Life Cycle of Copper, its Co-Products and ByProducts. Mining, Minerals and Sustainable Development, No 24, 1-200

266.

CE P

Biswas, A. K., Davenport, W.G., 2013. Extractive metallurgy of copper. Third Edition, Elsevier,

Brinker, C. J., Scherer, G.W., 2013. Sol-Gel Science: The Physics and Chemistry of Sol-Gel

AC

Processing. Academic Press Inc. London. Byung-Su Kim, Seul-Ki Jo, Doyun Shin, Jae-Chun Lee, Soo-Bock Jeong, 2013. A physicochemical separation process for upgrading iron from waste copper slag. International Journal of Mineral Processing. 124, 124–127 Chen, M., Han, Z., Wang, L., 2012. Recovery of valuable metals from copper slag by hydrometallurgy. Advanced Materials Research, 402, 35-40. Davenport, W. G., King, M., Schlesinger, M., Biswas, A. K., 2002. Extractive Metallurgy of Copper, Fourth Edition. Elsevier Science Limited: Kidlington, Oxford, England, 57–72. Dongping, T., Xianwan, Y., Zhong, Y.T., Jishu, Y., 1997. Study of manufacture of colored glasses from slags of copper smelting. Yelian Bufen 5, 41-43. Gonzalez, C., Parra, R., Klenovcanova, A., Imris, I., Sanchez, M., 2005. Reduction of Chilean copper slags: a case of waste management project. Scandinavian Journal of Metallurgy 35, 1-7. Gorai, B., Jana, R.K., Premchand, 2003. Characteristics and utilisation of copper slag—a review.

ACCEPTED MANUSCRIPT Resources, Conservation and Recycling. 39 (4), 299-313. Gyurov, S., Kostova, Y., Klitcheva, G., Ilinkina, A., 2011. Thermal decomposition of pyrometallurgical copper slag by oxidation in synthetic air. Waste Management Research. 29 (2), 157-164.

T

Gyurov, S., Rabadjieva, D., Kovacheva, D., Kostova, Y., 2014. Kinetics of copper slag oxidation

IP

under non isothermal conditions. Journal of Thermal Analysis and Calorimetry. 116(2),

SC R

945–953

Gyurov, G. A., Georgiev, Ch. G., Belomorski, M. H., Gyurov, S. A., 2012. Method for recycling of slag from copper production. EP 2 331 717 B1/ 15.08.2012 Bulletin 2012/33. Haavik, C., Stolen, S., Fjellvag, H., Hanfland, M., Hausermann, D., 2000. Equation of state of

NU

magnetite and its high-pressure modification: Thermodynamics of the Fe-O system at high pressure, Sample at P = 0 GPa. American Mineralogist. 85, 514-523.

Company: Brisbane, 173–179.

MA

Hayes, P. C., 1993. Process Principles in Minerals and Materials Production. Hayes Publishing

Marghussian, V. K., Maghsoodipoor, A., 1999. Fabrication of unglazed floor tiles containing

D

Iranian copper slags. Ceramics International. 25,617-622.

TE

Mihailova, I., Mehandjiev, D., 2010. Characterization of fayalite from copper slag. Journal of the University of Chemical Technology and Metallurgy. 45(3), 317-326

CE P

Moura, W., Masuero, A., Molin, D., Dal Vilela, A., 1999. Concrete performance with admixtures of electrical steel slag and copper slag concerning mechanical properties. American Concrete Institute. 186, 81 - 100.

AC

Nadirov, R.K., Syzdykova, L.I., Zhussupova, A.K., Usserbaev, M.T., 2013. Recovery of value metals from copper smelter slag by ammonium chloride treatment. International Journal of Mineral Processing. 124, 145–149. Rabadjieva, D., Tepavitcharova, S., Todorov, T., Dassenakis, M., Paraskevopoulou, V., Petrov, М., 2009. Chemical speciation in mining affected waters: the case study of Asarel-Medet mine. Environmental Monitoring and Assessment, 159, 353-366. Rudnik, E., Burzyńska, L., Gumowska, W., 2009. Hydrometallurgical recovery of copper and cobalt from reduction-roasted copper converter slag. Minerals Engineering 22 (1), 88-95 Shi, C., Qian, J., 2000. High performance cementing materials from industrial slags-a review. Resources, Conservation Recycling. 29, 195-207. TOPAS V4, 2008. General profile and structure analysis software for powder diffraction data, User's Manual, Bruker AXS, Karlsruhe, Germany Bruker AXS. Toshiki, A., Osamu, K., Kenji, S., 2000. Concrete with copper slag fine aggregate. J Soc Mater Sci Jpn. 49, 1097-2102.

ACCEPTED MANUSCRIPT Wechsler, B.A., Lindsey, D.H., Prewitte, C.T., 1984. Crystal structure and cation distribution in titanomagnetites (Fe3-xTixO4) MT 100-1350. American Mineralogist. 69, 754-770. Wozniak, K., Herman, D., 1988. Glass binder-bonded copper slag grains to form abrasive tools. Journal of Materials Science. 23(1), 223-228.

T

Yunjiao, Li, Perederiy, I., Papangelakis, V.G., 2008. Cleaning of waste smelter slags and recovery

IP

of valuable metals by pressure oxidative leaching. Journal of Hazardous Materials. 152,

SC R

607–615.

Zhang Yang, Man Rui-Lin, Ni Wang-Dong, Wang Hui, 2010. Selective leaching of base metals

AC

CE P

TE

D

MA

NU

from copper smelter slag. Hydrometallurgy. 103 (1-4), 25-29.

ACCEPTED MANUSCRIPT Figure Captions

Fig. 1 DTA (a) and TG (b) curves of the copper slag oxidized at different oxygen contents (1synthetic air (18 vol% O2); 2 - 42 vol% O2; 3 - 62 vol % O2; 4 - 100 vol % O2). process.

SC R

Fig. 3 SEM image of a cross section of a slag oxidized at 900оС.

IP

T

Fig. 2 X-ray powder diffraction analysis of the copper slag at the different stages of the oxidation

Fig.4 Influence of the different parameters on the silicon extraction.

Fig. 5 X-ray powder diffraction analysis of the residual solid after hydrothermal processing by treating with NaOH (a) and a mixture of NaOH and Na2CO3 (b).

NU

Fig. 6 Amount of analcime phase obtained at various concentrations of sodium hydroxide. Fig. 7 SEM (a) and X-ray microanalysis (b-h) of the distribution of elements present in the

MA

monitored area.

Fig. 8 IR spectrum of the gelling material: a) during natural aging of the gel; b) at high pH alkaline

AC

CE P

TE

D

conditions; c) at low pH of the liquid phase achieved by acidification.

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

AC

CE P

Fig. 1

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

AC

CE P

Fig. 2

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

AC

CE P

Fig. 3

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

AC

CE P

Fig. 4

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

AC

CE P

Fig. 5a

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

AC

CE P

Fig. 5b

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

AC

CE P

Fig. 6

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

AC

CE P

Fig. 7a

AC

Fig. 7b

CE P

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

AC

Fig. 7c

CE P

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

AC

Fig. 7d

CE P

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

AC

Fig. 7e

CE P

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

AC

Fig. 7f

CE P

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

AC

Fig. 7g

CE P

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

AC

Fig. 7h

CE P

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

AC

CE P

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

Fig. 8

ACCEPTED MANUSCRIPT Table 1. Conditions of the experiment for hydrometallurgical treatment of the copper slag T, oC

Concentration of alkali reagent, g/l NaOH Na2CO3 160 3 140 180 3 140 190 3 60 3 80 2 100 3 100 80 20 70 30 4 100 3 140 200 3 140 Note: The amount of the copper slag was 200 g and the solid to liquid ratio

NU

SC R

IP

T

t, h

AC

CE P

TE

D

MA

– 1:5 g/ml in all experiments

ACCEPTED MANUSCRIPT Table 2 Average chemical composition of the initial copper slag in mass %

SiO2

Al2O3

CaO,

MgO

Na2O

K2О

CuO

50.93

31.26

6.93

1.39

1.43

3.02

1.74

0.6

AC

CE P

TE

D

MA

NU

SC R

IP

T

Fe oxides

ACCEPTED MANUSCRIPT

MA

NU

SC R

IP

T

TECHNOLOGICAL SCHEME FOR COPPER SLAG PROCESSING

AC

CE P

TE

D

Graphical abstract

ACCEPTED MANUSCRIPT Highlights

T

IP SC R NU MA D TE CE P

 

Technological scheme for copper slag processing is proposed The scheme includes thermal oxidation, hydrothermal treatment, gelling of the liquid and drying Process optimization was done Extraction of the silicon was over 70%

AC

 