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Selective separation of copper(II) and nickel(II) from aqueous systems by polymer assisted ultrafiltration
Desalination 200 (2006) 728–730
Selective separation of copper(II) and nickel(II) from aqueous systems by polymer assisted ultrafiltration Raffaele Molinari*, Pietro Argurio, Teresa Poerio, Gianluigi Gullone Department of Chemical Engineering and Materials, University of Calabria, Via P. Bucci, Cubo 45/A, I-87030 Rende (CS), Italy Tel. +39 0984 496699; Fax +39 0984 496655; email: [email protected] Received 25 October 2005; accepted 6 March 2006
1. Introduction Various types of industrial wastewaters, such as that ones coming from mining, mineral processing, metal finishing and battery industries, contain metals as multicomponent mixtures [1]. Generally metal ions, especially heavy metals, are toxic and create a significant environmental hazard. Therefore, there is an urgent need for efficient separation techniques which may reduce the concentration of heavy metals to low values. To achieve recovery and processing of single or groups of metals the separation process should be selective. Polymer assisted ultrafiltration (PAUF) has been shown to be a promising process for removal of heavy metal ions from industrial effluents [2]. This process combines two operations: binding of metal ions to a water soluble polymer and separation of the metal–polymer complex by means of an ultrafiltration membrane [3,4]. An advantage of the PAUF technique is the high specificity of the separation achieved when a selective bonding agent is employed. Selectivity *Corresponding author.
can be due to the chemical properties of the bonding agent or to the operating conditions (e.g. pH, temperature, polymer/metal ratio, etc.). Indeed, the pH is one of the most important factors in the interaction of a metal ion with a binding polymer. In this work the selective separation of nickel(II) from copper(II) ion, both contained in a same solution, has been studied in a batch ultrafiltration system using polyethylenimine as the water soluble polymer and two UF membranes with different cut-off as the separation medium. Tests for determining the binding and release conditions between the metal ions and the polymer are reported. The methodology for separating both ions is described.
2. Results and discussion The optimal chemical conditions for the formation of PEI–Cu2+ complex were determined in our previous works [2–4] obtaining a pH value ³6. At pH = 6 the bonding capacity was 0.333 mg Cu2+/mg PEI, meaning a ratio PEI/Cu2+ = 3 (w/w).
Presented at EUROMEMBRANE 2006, 24–28 September 2006, Giardini Naxos, Italy. 0011-9164/06/$– See front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2006.03.503
R. Molinari et al. / Desalination 200 (2006) 728–730
729
Table 1 Copper and nickel recoveries (Rec%), volume and flux of permeate for Iris 10 and Iris 30 membranes at 150 min at different TMP ([Cu2+]IN = 50 mg/L; [Ni2+]IN = 50 mg/L; [PEI]IN = 450 mg/L; pH = 6.022) Membrane P [bar]
Iris 10
Iris 30
2
3
4
2
3
4
Rec% Cu Rec% Ni Vperm [mL] Jperm [L/h m2]
96.72 97.82 135.00 50.22
95.91 92.47 186.00 66.96
95.12 92.74 222.00 83.70
94.39 100.00 177.00 66.96
93.16 100.00 261.00 94.86
92.07 98.83 316.00 117.18
uncomplexed nickel should be progressively ‘washed’ passing in the permeate. Obtained results are reported in Table 1 for Iris 10 and Iris 30 membranes after a diafiltration time of 150 min, while in Figs. 1 and 2 the
Rec % Cu2+
100 98 96 94
4 bar 3 bar 2 bar
92 90 0
30
60
90
120
150
Time [min]
Fig. 1. Copper recovery versus the time in the selective ultrafiltration test with Iris 30 membrane at three TMP (conditions: see Table 1).
100 Rec % Ni2+
PEI–Ni2+ complexation was studied performing ultrafiltration runs because the complex did not give a significant spectrophotometric reading. Thus, nickel concentration was measured in the permeate by using an Iris 10 kDa membrane, initial concentrations [Ni2+] = 50 mg/L and [PEI] =150 mg/L, transmembrane pressure (TMP) of 2 bar, and changing the operative pH. The results showed an optimal complexation pH ³ 8. Operating at pH = 8 the binding capacity of PEI was found by performing UF tests with initial [Ni2+] = 50 mg/L and changing the polymer amount. The highest metal rejection was obtained operating with a PEI/Ni2+ ratio (w/w) equal to 6 (R% = 98.25), while lower rejection was obtained with a ratio of 3 (R% = 90.65). On the basis of the previous study, ultrafiltration tests were performed by using the following chemical conditions: [Cu2+]FEED = 50 mg/L; [Ni2+]FEED = 50 mg/L; [PEI]FEED = 150 mg/L; pH = 6.022. Both operating pH and polymer amount were chosen in order to optimise metals ions separation. Indeed, it is important to choose (i) a pH value for obtaining a preferential copper complexation, and (ii) polymer amount needed to bound only copper ion. These ultrafiltration tests were carried out in diafiltration mode by continuously feeding with ultrapure water at pH 6.022 the two batch cells of the UF set-up, previously filled with the feed phase (72 mL). With this method copper, complexed by the polymer, should be retained in the retentate, while
75 50 4 bar 3 bar 2 bar
25 0 0
30
60
90
120
150
Time [min]
Fig. 2. Nickel recovery versus the time in the selective ultrafiltration test with Iris 30 membrane at three TMP (conditions: see Table 1).
730
R. Molinari et al. / Desalination 200 (2006) 728–730
recoveries in the time using the Iris 30 membrane are reported. Best results in terms of nickel and copper recoveries were obtained by using the Iris 30 membrane at TMP of 2 bar. Besides at this pressure a lower water amount was needed to obtain total nickel recovery (see Table 1).
to obtain selective separations by means metal bonding to water soluble polymers. References [1]
3. Conclusion Complexation-ultrafiltration technique was efficiently used to achieve selective separation of nickel(II) and copper(II) ions from an aqueous solution operating in diafiltration mode. Nickel recovery in the permeate of 100% and copper recovery in the retentate of 94.39% were obtained by using the Iris 30 membrane at TMP of 2 bar. Obtained results show that formation of the metal–polymer complex is pH dependent and this is a key-point for the separation. The described methodology can be efficiently used
[2]
[3]
[4]
J. Muslehiddinoglu, Y. Uludag, H. Onder Ozbelge and L. Yilmaz, Effect of operating parameters on selective separation of heavy metals from binary mixtures via polymer enhanced ultrafiltration, J. Membr. Sci., 140 (1998) 251–266. R. Molinari, S. Gallo and P. Argurio, Metal ions removal from wastewater or washing water from contaminated soil by ultrafiltration–complexation, Water Res., 38 (2004) 593–600. R. Molinari, P. Argurio and T. Poerio, Comparison of polyethylenimine, polyacrylic acid and poly (dimethylamine–co–epichlorohydrin–co– ethylenediamine) in Cu2+ removal from wastewaters by polymer–assisted ultrafiltration, Desalination, 162 (2004) 217–228. R. Molinari, T. Poerio and P. Argurio, Polymer assisted ultrafiltration for copper-citric acid chelate removal from wash solutions of contaminated soil, J. Appl. Electrochem., 35 (2005) 375–380.
Selective separation of copper(II) and nickel(II) from aqueous systems by polymer assisted ultrafiltration Raffaele Molinari*, Pietro Argurio, Teresa Poerio, Gianluigi Gullone Department of Chemical Engineering and Materials, University of Calabria, Via P. Bucci, Cubo 45/A, I-87030 Rende (CS), Italy Tel. +39 0984 496699; Fax +39 0984 496655; email: [email protected] Received 25 October 2005; accepted 6 March 2006
1. Introduction Various types of industrial wastewaters, such as that ones coming from mining, mineral processing, metal finishing and battery industries, contain metals as multicomponent mixtures [1]. Generally metal ions, especially heavy metals, are toxic and create a significant environmental hazard. Therefore, there is an urgent need for efficient separation techniques which may reduce the concentration of heavy metals to low values. To achieve recovery and processing of single or groups of metals the separation process should be selective. Polymer assisted ultrafiltration (PAUF) has been shown to be a promising process for removal of heavy metal ions from industrial effluents [2]. This process combines two operations: binding of metal ions to a water soluble polymer and separation of the metal–polymer complex by means of an ultrafiltration membrane [3,4]. An advantage of the PAUF technique is the high specificity of the separation achieved when a selective bonding agent is employed. Selectivity *Corresponding author.
can be due to the chemical properties of the bonding agent or to the operating conditions (e.g. pH, temperature, polymer/metal ratio, etc.). Indeed, the pH is one of the most important factors in the interaction of a metal ion with a binding polymer. In this work the selective separation of nickel(II) from copper(II) ion, both contained in a same solution, has been studied in a batch ultrafiltration system using polyethylenimine as the water soluble polymer and two UF membranes with different cut-off as the separation medium. Tests for determining the binding and release conditions between the metal ions and the polymer are reported. The methodology for separating both ions is described.
2. Results and discussion The optimal chemical conditions for the formation of PEI–Cu2+ complex were determined in our previous works [2–4] obtaining a pH value ³6. At pH = 6 the bonding capacity was 0.333 mg Cu2+/mg PEI, meaning a ratio PEI/Cu2+ = 3 (w/w).
Presented at EUROMEMBRANE 2006, 24–28 September 2006, Giardini Naxos, Italy. 0011-9164/06/$– See front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2006.03.503
R. Molinari et al. / Desalination 200 (2006) 728–730
729
Table 1 Copper and nickel recoveries (Rec%), volume and flux of permeate for Iris 10 and Iris 30 membranes at 150 min at different TMP ([Cu2+]IN = 50 mg/L; [Ni2+]IN = 50 mg/L; [PEI]IN = 450 mg/L; pH = 6.022) Membrane P [bar]
Iris 10
Iris 30
2
3
4
2
3
4
Rec% Cu Rec% Ni Vperm [mL] Jperm [L/h m2]
96.72 97.82 135.00 50.22
95.91 92.47 186.00 66.96
95.12 92.74 222.00 83.70
94.39 100.00 177.00 66.96
93.16 100.00 261.00 94.86
92.07 98.83 316.00 117.18
uncomplexed nickel should be progressively ‘washed’ passing in the permeate. Obtained results are reported in Table 1 for Iris 10 and Iris 30 membranes after a diafiltration time of 150 min, while in Figs. 1 and 2 the
Rec % Cu2+
100 98 96 94
4 bar 3 bar 2 bar
92 90 0
30
60
90
120
150
Time [min]
Fig. 1. Copper recovery versus the time in the selective ultrafiltration test with Iris 30 membrane at three TMP (conditions: see Table 1).
100 Rec % Ni2+
PEI–Ni2+ complexation was studied performing ultrafiltration runs because the complex did not give a significant spectrophotometric reading. Thus, nickel concentration was measured in the permeate by using an Iris 10 kDa membrane, initial concentrations [Ni2+] = 50 mg/L and [PEI] =150 mg/L, transmembrane pressure (TMP) of 2 bar, and changing the operative pH. The results showed an optimal complexation pH ³ 8. Operating at pH = 8 the binding capacity of PEI was found by performing UF tests with initial [Ni2+] = 50 mg/L and changing the polymer amount. The highest metal rejection was obtained operating with a PEI/Ni2+ ratio (w/w) equal to 6 (R% = 98.25), while lower rejection was obtained with a ratio of 3 (R% = 90.65). On the basis of the previous study, ultrafiltration tests were performed by using the following chemical conditions: [Cu2+]FEED = 50 mg/L; [Ni2+]FEED = 50 mg/L; [PEI]FEED = 150 mg/L; pH = 6.022. Both operating pH and polymer amount were chosen in order to optimise metals ions separation. Indeed, it is important to choose (i) a pH value for obtaining a preferential copper complexation, and (ii) polymer amount needed to bound only copper ion. These ultrafiltration tests were carried out in diafiltration mode by continuously feeding with ultrapure water at pH 6.022 the two batch cells of the UF set-up, previously filled with the feed phase (72 mL). With this method copper, complexed by the polymer, should be retained in the retentate, while
75 50 4 bar 3 bar 2 bar
25 0 0
30
60
90
120
150
Time [min]
Fig. 2. Nickel recovery versus the time in the selective ultrafiltration test with Iris 30 membrane at three TMP (conditions: see Table 1).
730
R. Molinari et al. / Desalination 200 (2006) 728–730
recoveries in the time using the Iris 30 membrane are reported. Best results in terms of nickel and copper recoveries were obtained by using the Iris 30 membrane at TMP of 2 bar. Besides at this pressure a lower water amount was needed to obtain total nickel recovery (see Table 1).
to obtain selective separations by means metal bonding to water soluble polymers. References [1]
3. Conclusion Complexation-ultrafiltration technique was efficiently used to achieve selective separation of nickel(II) and copper(II) ions from an aqueous solution operating in diafiltration mode. Nickel recovery in the permeate of 100% and copper recovery in the retentate of 94.39% were obtained by using the Iris 30 membrane at TMP of 2 bar. Obtained results show that formation of the metal–polymer complex is pH dependent and this is a key-point for the separation. The described methodology can be efficiently used
[2]
[3]
[4]
J. Muslehiddinoglu, Y. Uludag, H. Onder Ozbelge and L. Yilmaz, Effect of operating parameters on selective separation of heavy metals from binary mixtures via polymer enhanced ultrafiltration, J. Membr. Sci., 140 (1998) 251–266. R. Molinari, S. Gallo and P. Argurio, Metal ions removal from wastewater or washing water from contaminated soil by ultrafiltration–complexation, Water Res., 38 (2004) 593–600. R. Molinari, P. Argurio and T. Poerio, Comparison of polyethylenimine, polyacrylic acid and poly (dimethylamine–co–epichlorohydrin–co– ethylenediamine) in Cu2+ removal from wastewaters by polymer–assisted ultrafiltration, Desalination, 162 (2004) 217–228. R. Molinari, T. Poerio and P. Argurio, Polymer assisted ultrafiltration for copper-citric acid chelate removal from wash solutions of contaminated soil, J. Appl. Electrochem., 35 (2005) 375–380.