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Batch electrodialytic treatment of copper smelter wastewater
Minerals Engineering 74 (2015) 60–63
Contents lists available at ScienceDirect
Minerals Engineering journal homepage: www.elsevier.com/locate/mineng
Technical note
Batch electrodialytic treatment of copper smelter wastewater Henrik K. Hansen ⇑, Claudia Gutiérrez, Jorge Ferreiro, Adrián Rojo Departamento de Ingeniería Química y Ambiental, Universidad Técnica Federico Santa María, Avenida España 1680, Valparaíso, Chile
a r t i c l e
i n f o
Article history: Received 21 October 2014 Accepted 15 January 2015
Keywords: Arsenic Copper Electrodialytic separation
a b s t r a c t In this paper, the electrodialysis technique is tested as a possible treatment of smelter wastewater containing mainly copper and arsenic. The results show that it is not feasible to treat the raw wastewater, because the highly acidic pH favours the proton electro migration compared to copper. However, when adjusting the pH of the wastewater to 2 and 3, the copper could be removed entirely into a copper concentration section. Less than 2.5% of the total arsenic migrated into the copper concentration section, indicating the possibility to separate copper from arsenic. At higher pH values and current density, copper is removed faster but at pH values greater than 3 precipitates start to form. Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction
2. Experimental
During the smelting of copper sulphides and the subsequent gas treatment, considerable volumes of wastewater are generated containing mainly copper, arsenic and other inorganic species (such as heavy metals, H+ and SO24 ) in concentrations that exceed the local legal threshold values (Chilean Republic, 2000). Actually, arsenic and heavy metals are removed by chemical precipitation with lime but this treatment results in large amounts of sludge, where important amounts of copper are lost. This paper presents the electrodialysis (ED) technique as an alternative to the previous treatment, allowing separating (and recovering) copper from arsenic. Fig. 1 illustrates the principle in the suggested method. Cu2+ is transported to Section 2, and arsenic species (either negatively charge or with no electrical charge at low pH) remain in Section 3 or are transported into Section 4. Earlier work has proven this separation but only from synthetic aqueous solutions and with high Cu-to-As ratios (Cifuentes et al., 2002). Other attempts have been done to separate As from Cu in earlier steps such as flotation (Long et al., 2014) or during the smelting process (Mihajlovic et al., 2007). In general it was concluded that it was difficult to separate Cu from As before or during smelting. The objectives of this work were to study the feasibility of separating the copper present in an arsenic-rich mineral processing wastewater using ED, evaluate and quantify the separation of copper from arsenic by electrodialysis, to study the influence of current density and pH of the wastewater, and to analyse the current efficiency with respect to copper.
The wastewater was sampled at the División Fundición Chagres copper smelter in V Region of Chile. Calcium hydroxide was added to adjust the pH of the wastewater to 1, 2 or 3. Total As and Cu contents were determined by AAS according to the Official Chilean Standard NCh 2313/10 Of. 96. As(III) concentration was determined by quantitative Vogel analysis. As(V) concentration was determined by the difference between the total As and As(III). Fig. 1 shows the cylindrical acrylic ED cell divided into 5 sections, separated by cation and anion exchange membranes. Sections 1, 2, 4 and 5 were filled initially with 0.1 M sulphuric acid. Section 3 was filled with wastewater. Stainless steel electrodes were placed in Section 1 (cathode) and Section 5 (anode). Ion exchange membranes were CMI-7000 and AMI-7001 from Membrane International Inc. Table 1 illustrates the operating conditions and results for the experiments carried out. Each experiment was performed as a batch ED experiment at fixed times (1, 2, 3, 4 or 5 h). Preliminary studies were conducted (tests a to c) on raw wastewater to investigate the copper removal without pH adjustment. In experiment series (1)–(9) pH was adjusted before ED treatment. Experiment series (10) were performed to evaluated the separation of Cu from As.
⇑ Corresponding author. E-mail address: [email protected] (H.K. Hansen). http://dx.doi.org/10.1016/j.mineng.2015.01.007 0892-6875/Ó 2015 Elsevier Ltd. All rights reserved.
3. Results and discussion Table 1 illustrates the result that only a small amount of copper moved into Section 2. These results illustrate that electromigration depends mainly on specie concentration and specie ionic mobility. The molar ratio hydronium/copper is approximately 3.8 at pH 1. In the raw wastewater pH is lower than 1, which
61
H.K. Hansen et al. / Minerals Engineering 74 (2015) 60–63
Cathode
Anode
+ +
6.0 cm
-
+
+
3.0 cm
-
-
+
Section 1
-
+
-
+
Section 2
Section 3
Section 4
Section 5
3.0 cm
3.0 cm
3.0 cm
3.0 cm
Anion exchange membrane
Cation exchange membrane Fig. 1. Electrodialytic cell.
Table 1 Experimental plan and results from treatment of raw and pH adjusted copper smelter wastewater, for different pH, time and current densities. Analysed element
Experiment series
Current density (A m 1
Raw wastewater, pH < 1.0, initial concentration of Cu: 1652 mg L Cu a 150
Wastewater pH [ ]
b
225
c
300
Experiment series
Current density (A m2)
)
Time (h)
(analysed element: Cu) 4 5 4 5 3 4
1
) Section 3
1549 1608 1589 1604 1556 1549
) Section 2
2.4 7.4 10.1 <1 15.6 18.5
Cu (mg L
1
) Section 4
2.4 6.8 2.2 5.0 1.1 2.0
Time 5 h Cu (mg L 1)
pH adjusted wastewater, initial concentration of Cu, Section 3: 639 mg L 1 (analysed element: Cu) 1 1 300 3 552 492 2 89 136 2 225 3 575 536 2 69 96 3 150 3 582 549 2 56 79
442 287 454 196 504 144
358 323 456 251 515 200
212 345 319 276 423 188
pH adjusted wastewater, initial concentration of Cu, Section 3: 489 mg L 1 (analysed element: Cu) 2 4 300 3 295 156 2 124 357 5 225 3 358 282 2 96 249 6 150 3 407 334 2 93 184
13 461 157 357 246 233
0 510 32 449 162 305
– – 0 463 126 382
pH adjusted wastewater, initial concentration of Cu, Section 3: 498 mg L 1 (analysed element: Cu) 3 7 300 3 222 81 2 289 500 8 225 3 298 165 2 231 337 9 150 3 313 245 2 128 248
0 444 107 437 201 310
– – 0 467 145 378
– – – – 92 461
Arsenic (mg L Section 2
1
Time 2 h Cu (mg L 1)
1
Cu (mg L
Time 4 h Cu (mg L 1)
t (h)
Time 1 h Cu (mg L 1)
Cu (mg L
Time 3 h Cu (mg L 1)
Experiment series
Section
2
)
Copper (mg L Section 3
1
)
Section 4
Section 2
Section 3
Section 4
0 6.3 18.1 78.3 486
0 – 620 – 837
897 – 275 – 3
0 – 0.1 – 0.3
2
pH adjusted wastewater, current density 225 A m , pH: 2 (analysed elements: As and Cu) 10 0 0 2154* 1 6.5 1814 2 27.7 1890 3 42.9 1609 4 54.8 1327
* In the initial sample both total As, As(III) and As(V) were analysed. The results showed that the sample had 2154 mg L Therefore in the rest of the samples only total arsenic was measured – assuming presence of As(III) only.
1
of As(III) and less than 1 mg L
1
of As(V).
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H.K. Hansen et al. / Minerals Engineering 74 (2015) 60–63
100
Copper Removal from de middle section %
90 80 70 60 50 40 30 20 10 0
150 A m-2 225 A m-2 300 A m-2 150 A m-2 225 A m-2 300 A m-2 150 A m-2 225 A m-2 300 A m-2 pH 1
pH 2
1h
3h
pH 3
5h
Fig. 2. Copper removal from Section 3 for different pH and current densities used.
means that electromigration of H3O+ is clearly favored over copper ions, and this explains why only low amounts of copper ions migrated. Furthermore, ionic mobility of H3O+ is about 12 times higher than Cu+2 (Vanysek, 2002). Consequently, when applying an electric field across the cell, the hydronium ion will move across the cation exchange membrane to Section 2 at a much faster rate than Cu+2. Therefore, ED is not suitable for separation of copper from arsenic in raw copper smelter wastewater with very low pH (<1), and pH had to be raised to 1, 2 and 3, respectively. Fig. 2 illustrates the removal of copper from Section 3 of the cell, for each pH and current density used. It can be noted that the copper removal increases with the pH of the wastewater and the current density. In addition, it can be seen that for pH 2 and 3 after 5 h, 100% of the copper has been removed with the current densities of 225 and 300 A m 2. This is in contrast to experiments at pH 1 for the same time, where only 67% of the copper was removed with the highest current density used. For pH 1, one can estimate the treatment time to reach 100% copper removal to be approximately 9–10 h at 300 A m 2. The effect of current density is evident in the results, and not surprisingly it is more favourable to use a higher current density for the separation process. The results also indicate that removal of copper from Section 3 is favored with increasing pH of the solution. With increasing pH, fewer protons would compete with Cu2+ in order to cross the cation exchange membrane. Furthermore, linear trends can be noticed in the removal of copper from the central section with time. Copper removal trends are more pronounced at pH 1 and 2. The linear trend is not so clear at pH 3, and the explanation for this may be because in this wastewater some precipitates were formed, which also make the handling of this wastewater difficult. Despite this, the total treatment time is less at pH 3 than at the other pH levels studied. Anyway, it is recommended that an adequate pH for this wastewater is around 2. The current efficiencies with respect to copper removal during ED were approximately 1.1% at pH 1, 2.1% at pH 2 and 2.5% at pH 3. In all cases the current efficiency was less than 5% but there is a tendency that when increasing the pH, the current efficiency increases also. The low current efficiencies obtained is due to the
presence of mainly H3O+ and secondly other dissolved species in the wastewater such as arsenic, cadmium, lead, iron, sulphate, chloride – explaining why not all current is used to transport copper. In addition, there are other factors contributing to the loss of power, such as short circuits between anode and cathode, as well from section to section, or current leakage through the electrodialytic cell or eddy current. To study the possibility of separating copper from arsenic, experiments were conducted using various treatment times with pH 2 adjusted wastewater at a current density of 225 A m 2. In these experiments, the arsenic and copper contents were measured in Sections 2, 3 and 4. As presented in Table 1 (last part), copper moves towards the cathode just as it should and is concentrated in Section 2. It is concluded that after 4 h of treatment only 0.3 mg L 1 of copper was observed in Section 3, which is where arsenic remains. Furthermore, some arsenic migrates into Section 2 since the membranes are not completely ion selective but the concentration of arsenic that is obtained here is only about 2.5% of the total arsenic in the wastewater. Therefore, one can obtain a copper rich solution with a very low arsenic content. In the original wastewater, the As:Cu ratio is 2.4, whereas in Section 2 after 4 h treatment at pH 2 and 225 A m 2 the ratio is around 0.065. Arsenic transport towards the anode (Section 4) is important (around 22% of the initial arsenic) – indicating presence of negatively charged species. Considerable arsenic remains in Section 3, indicating that the arsenic species at pH 2 are mainly of neutral charge. Copper moves in practice only towards the cathode. Based on these results it can be concluded that it is possible to separate Cu from As in copper smelter wastewater.
4. Conclusions It was found that it was not feasible to separate the copper from arsenic present in raw copper smelter wastewater by ED due to the high concentration of H3O+. The separation of Cu and As by ED is possible when adjusting the pH of the wastewater to 2. Copper could be removed entirely
H.K. Hansen et al. / Minerals Engineering 74 (2015) 60–63
by migration to the cathode; some arsenic did migrate to the anode section; however most of the arsenic stayed in the middle section. For the experiments conducted at pH 1, the copper removal/arsenic separation was relatively poor. The current density has a direct influence on the removal of copper, since at higher current density, copper is removed faster.
Acknowledgements Financial support of the FONDECYT Project No 1120111 is acknowledged. Ana González is acknowledged for experimental help.
63
References Chilean Republic, 2000. Supreme Decree 90: Emissions Standard for the Regulation of Pollutants Associated with Discharges of Liquid Waste to Surface Marine Waters and Continents. Chilean Republic/Ministry General Secretariat of the Presidency of the Republic. Cifuentes, L., Crisóstomo, G., Ibáñez, J.P., Casas, J.M., Alvarez, F., Cifuentes, G., 2002. On the electrodialysis of aqueous H2SO4–CuSO4 electrolytes with metallic impurities. J. Membr. Sci. 207, 1–16. Long, G., Peng, Y., Bradshaw, D., 2014. Flotation separation of copper sulphides from arsenic minerals at Rosebery copper concentrator. Miner. Eng. 66–68, 207–214. Mihajlovic, I., Strbac, N., Zivkovic, Z., Kovacevic, R., Stehernik, M., 2007. A potential method for arsenic removal from copper concentrates. Miner. Eng. 20, 26–33. Vanysek, P., 2002. Ionic conductivity and diffusion at infinite dilution. In: Lide, D.R. (Ed.), CRC Handbook of Chemistry and Physics, eighty third ed. CRC Press, Boca Raton, USA.
Contents lists available at ScienceDirect
Minerals Engineering journal homepage: www.elsevier.com/locate/mineng
Technical note
Batch electrodialytic treatment of copper smelter wastewater Henrik K. Hansen ⇑, Claudia Gutiérrez, Jorge Ferreiro, Adrián Rojo Departamento de Ingeniería Química y Ambiental, Universidad Técnica Federico Santa María, Avenida España 1680, Valparaíso, Chile
a r t i c l e
i n f o
Article history: Received 21 October 2014 Accepted 15 January 2015
Keywords: Arsenic Copper Electrodialytic separation
a b s t r a c t In this paper, the electrodialysis technique is tested as a possible treatment of smelter wastewater containing mainly copper and arsenic. The results show that it is not feasible to treat the raw wastewater, because the highly acidic pH favours the proton electro migration compared to copper. However, when adjusting the pH of the wastewater to 2 and 3, the copper could be removed entirely into a copper concentration section. Less than 2.5% of the total arsenic migrated into the copper concentration section, indicating the possibility to separate copper from arsenic. At higher pH values and current density, copper is removed faster but at pH values greater than 3 precipitates start to form. Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction
2. Experimental
During the smelting of copper sulphides and the subsequent gas treatment, considerable volumes of wastewater are generated containing mainly copper, arsenic and other inorganic species (such as heavy metals, H+ and SO24 ) in concentrations that exceed the local legal threshold values (Chilean Republic, 2000). Actually, arsenic and heavy metals are removed by chemical precipitation with lime but this treatment results in large amounts of sludge, where important amounts of copper are lost. This paper presents the electrodialysis (ED) technique as an alternative to the previous treatment, allowing separating (and recovering) copper from arsenic. Fig. 1 illustrates the principle in the suggested method. Cu2+ is transported to Section 2, and arsenic species (either negatively charge or with no electrical charge at low pH) remain in Section 3 or are transported into Section 4. Earlier work has proven this separation but only from synthetic aqueous solutions and with high Cu-to-As ratios (Cifuentes et al., 2002). Other attempts have been done to separate As from Cu in earlier steps such as flotation (Long et al., 2014) or during the smelting process (Mihajlovic et al., 2007). In general it was concluded that it was difficult to separate Cu from As before or during smelting. The objectives of this work were to study the feasibility of separating the copper present in an arsenic-rich mineral processing wastewater using ED, evaluate and quantify the separation of copper from arsenic by electrodialysis, to study the influence of current density and pH of the wastewater, and to analyse the current efficiency with respect to copper.
The wastewater was sampled at the División Fundición Chagres copper smelter in V Region of Chile. Calcium hydroxide was added to adjust the pH of the wastewater to 1, 2 or 3. Total As and Cu contents were determined by AAS according to the Official Chilean Standard NCh 2313/10 Of. 96. As(III) concentration was determined by quantitative Vogel analysis. As(V) concentration was determined by the difference between the total As and As(III). Fig. 1 shows the cylindrical acrylic ED cell divided into 5 sections, separated by cation and anion exchange membranes. Sections 1, 2, 4 and 5 were filled initially with 0.1 M sulphuric acid. Section 3 was filled with wastewater. Stainless steel electrodes were placed in Section 1 (cathode) and Section 5 (anode). Ion exchange membranes were CMI-7000 and AMI-7001 from Membrane International Inc. Table 1 illustrates the operating conditions and results for the experiments carried out. Each experiment was performed as a batch ED experiment at fixed times (1, 2, 3, 4 or 5 h). Preliminary studies were conducted (tests a to c) on raw wastewater to investigate the copper removal without pH adjustment. In experiment series (1)–(9) pH was adjusted before ED treatment. Experiment series (10) were performed to evaluated the separation of Cu from As.
⇑ Corresponding author. E-mail address: [email protected] (H.K. Hansen). http://dx.doi.org/10.1016/j.mineng.2015.01.007 0892-6875/Ó 2015 Elsevier Ltd. All rights reserved.
3. Results and discussion Table 1 illustrates the result that only a small amount of copper moved into Section 2. These results illustrate that electromigration depends mainly on specie concentration and specie ionic mobility. The molar ratio hydronium/copper is approximately 3.8 at pH 1. In the raw wastewater pH is lower than 1, which
61
H.K. Hansen et al. / Minerals Engineering 74 (2015) 60–63
Cathode
Anode
+ +
6.0 cm
-
+
+
3.0 cm
-
-
+
Section 1
-
+
-
+
Section 2
Section 3
Section 4
Section 5
3.0 cm
3.0 cm
3.0 cm
3.0 cm
Anion exchange membrane
Cation exchange membrane Fig. 1. Electrodialytic cell.
Table 1 Experimental plan and results from treatment of raw and pH adjusted copper smelter wastewater, for different pH, time and current densities. Analysed element
Experiment series
Current density (A m 1
Raw wastewater, pH < 1.0, initial concentration of Cu: 1652 mg L Cu a 150
Wastewater pH [ ]
b
225
c
300
Experiment series
Current density (A m2)
)
Time (h)
(analysed element: Cu) 4 5 4 5 3 4
1
) Section 3
1549 1608 1589 1604 1556 1549
) Section 2
2.4 7.4 10.1 <1 15.6 18.5
Cu (mg L
1
) Section 4
2.4 6.8 2.2 5.0 1.1 2.0
Time 5 h Cu (mg L 1)
pH adjusted wastewater, initial concentration of Cu, Section 3: 639 mg L 1 (analysed element: Cu) 1 1 300 3 552 492 2 89 136 2 225 3 575 536 2 69 96 3 150 3 582 549 2 56 79
442 287 454 196 504 144
358 323 456 251 515 200
212 345 319 276 423 188
pH adjusted wastewater, initial concentration of Cu, Section 3: 489 mg L 1 (analysed element: Cu) 2 4 300 3 295 156 2 124 357 5 225 3 358 282 2 96 249 6 150 3 407 334 2 93 184
13 461 157 357 246 233
0 510 32 449 162 305
– – 0 463 126 382
pH adjusted wastewater, initial concentration of Cu, Section 3: 498 mg L 1 (analysed element: Cu) 3 7 300 3 222 81 2 289 500 8 225 3 298 165 2 231 337 9 150 3 313 245 2 128 248
0 444 107 437 201 310
– – 0 467 145 378
– – – – 92 461
Arsenic (mg L Section 2
1
Time 2 h Cu (mg L 1)
1
Cu (mg L
Time 4 h Cu (mg L 1)
t (h)
Time 1 h Cu (mg L 1)
Cu (mg L
Time 3 h Cu (mg L 1)
Experiment series
Section
2
)
Copper (mg L Section 3
1
)
Section 4
Section 2
Section 3
Section 4
0 6.3 18.1 78.3 486
0 – 620 – 837
897 – 275 – 3
0 – 0.1 – 0.3
2
pH adjusted wastewater, current density 225 A m , pH: 2 (analysed elements: As and Cu) 10 0 0 2154* 1 6.5 1814 2 27.7 1890 3 42.9 1609 4 54.8 1327
* In the initial sample both total As, As(III) and As(V) were analysed. The results showed that the sample had 2154 mg L Therefore in the rest of the samples only total arsenic was measured – assuming presence of As(III) only.
1
of As(III) and less than 1 mg L
1
of As(V).
62
H.K. Hansen et al. / Minerals Engineering 74 (2015) 60–63
100
Copper Removal from de middle section %
90 80 70 60 50 40 30 20 10 0
150 A m-2 225 A m-2 300 A m-2 150 A m-2 225 A m-2 300 A m-2 150 A m-2 225 A m-2 300 A m-2 pH 1
pH 2
1h
3h
pH 3
5h
Fig. 2. Copper removal from Section 3 for different pH and current densities used.
means that electromigration of H3O+ is clearly favored over copper ions, and this explains why only low amounts of copper ions migrated. Furthermore, ionic mobility of H3O+ is about 12 times higher than Cu+2 (Vanysek, 2002). Consequently, when applying an electric field across the cell, the hydronium ion will move across the cation exchange membrane to Section 2 at a much faster rate than Cu+2. Therefore, ED is not suitable for separation of copper from arsenic in raw copper smelter wastewater with very low pH (<1), and pH had to be raised to 1, 2 and 3, respectively. Fig. 2 illustrates the removal of copper from Section 3 of the cell, for each pH and current density used. It can be noted that the copper removal increases with the pH of the wastewater and the current density. In addition, it can be seen that for pH 2 and 3 after 5 h, 100% of the copper has been removed with the current densities of 225 and 300 A m 2. This is in contrast to experiments at pH 1 for the same time, where only 67% of the copper was removed with the highest current density used. For pH 1, one can estimate the treatment time to reach 100% copper removal to be approximately 9–10 h at 300 A m 2. The effect of current density is evident in the results, and not surprisingly it is more favourable to use a higher current density for the separation process. The results also indicate that removal of copper from Section 3 is favored with increasing pH of the solution. With increasing pH, fewer protons would compete with Cu2+ in order to cross the cation exchange membrane. Furthermore, linear trends can be noticed in the removal of copper from the central section with time. Copper removal trends are more pronounced at pH 1 and 2. The linear trend is not so clear at pH 3, and the explanation for this may be because in this wastewater some precipitates were formed, which also make the handling of this wastewater difficult. Despite this, the total treatment time is less at pH 3 than at the other pH levels studied. Anyway, it is recommended that an adequate pH for this wastewater is around 2. The current efficiencies with respect to copper removal during ED were approximately 1.1% at pH 1, 2.1% at pH 2 and 2.5% at pH 3. In all cases the current efficiency was less than 5% but there is a tendency that when increasing the pH, the current efficiency increases also. The low current efficiencies obtained is due to the
presence of mainly H3O+ and secondly other dissolved species in the wastewater such as arsenic, cadmium, lead, iron, sulphate, chloride – explaining why not all current is used to transport copper. In addition, there are other factors contributing to the loss of power, such as short circuits between anode and cathode, as well from section to section, or current leakage through the electrodialytic cell or eddy current. To study the possibility of separating copper from arsenic, experiments were conducted using various treatment times with pH 2 adjusted wastewater at a current density of 225 A m 2. In these experiments, the arsenic and copper contents were measured in Sections 2, 3 and 4. As presented in Table 1 (last part), copper moves towards the cathode just as it should and is concentrated in Section 2. It is concluded that after 4 h of treatment only 0.3 mg L 1 of copper was observed in Section 3, which is where arsenic remains. Furthermore, some arsenic migrates into Section 2 since the membranes are not completely ion selective but the concentration of arsenic that is obtained here is only about 2.5% of the total arsenic in the wastewater. Therefore, one can obtain a copper rich solution with a very low arsenic content. In the original wastewater, the As:Cu ratio is 2.4, whereas in Section 2 after 4 h treatment at pH 2 and 225 A m 2 the ratio is around 0.065. Arsenic transport towards the anode (Section 4) is important (around 22% of the initial arsenic) – indicating presence of negatively charged species. Considerable arsenic remains in Section 3, indicating that the arsenic species at pH 2 are mainly of neutral charge. Copper moves in practice only towards the cathode. Based on these results it can be concluded that it is possible to separate Cu from As in copper smelter wastewater.
4. Conclusions It was found that it was not feasible to separate the copper from arsenic present in raw copper smelter wastewater by ED due to the high concentration of H3O+. The separation of Cu and As by ED is possible when adjusting the pH of the wastewater to 2. Copper could be removed entirely
H.K. Hansen et al. / Minerals Engineering 74 (2015) 60–63
by migration to the cathode; some arsenic did migrate to the anode section; however most of the arsenic stayed in the middle section. For the experiments conducted at pH 1, the copper removal/arsenic separation was relatively poor. The current density has a direct influence on the removal of copper, since at higher current density, copper is removed faster.
Acknowledgements Financial support of the FONDECYT Project No 1120111 is acknowledged. Ana González is acknowledged for experimental help.
63
References Chilean Republic, 2000. Supreme Decree 90: Emissions Standard for the Regulation of Pollutants Associated with Discharges of Liquid Waste to Surface Marine Waters and Continents. Chilean Republic/Ministry General Secretariat of the Presidency of the Republic. Cifuentes, L., Crisóstomo, G., Ibáñez, J.P., Casas, J.M., Alvarez, F., Cifuentes, G., 2002. On the electrodialysis of aqueous H2SO4–CuSO4 electrolytes with metallic impurities. J. Membr. Sci. 207, 1–16. Long, G., Peng, Y., Bradshaw, D., 2014. Flotation separation of copper sulphides from arsenic minerals at Rosebery copper concentrator. Miner. Eng. 66–68, 207–214. Mihajlovic, I., Strbac, N., Zivkovic, Z., Kovacevic, R., Stehernik, M., 2007. A potential method for arsenic removal from copper concentrates. Miner. Eng. 20, 26–33. Vanysek, P., 2002. Ionic conductivity and diffusion at infinite dilution. In: Lide, D.R. (Ed.), CRC Handbook of Chemistry and Physics, eighty third ed. CRC Press, Boca Raton, USA.