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Extraction of cobalt(II) from aqueous solution by N,N′-carbonyl difatty amides
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Chinese Chemical Letters 22 (2011) 469–472 www.elsevier.com/locate/cclet
Extraction of cobalt(II) from aqueous solution by N,N0 -carbonyl difatty amides Emad A. Jaffar Al-Mulla a,*, Khalid Waleed S. Al-Janabi b a
b
Department of Chemistry, College of Science, University of Kufa, AnNajaf, Iraq Department of Chemistry, College of Education, Baghdad University, Baghdad, Iraq Received 20 July 2010 Available online 15 January 2011
Abstract The development of economic and environmentally friendly extractants to recover cobalt metal is required due to the increasing demand for this metal. In this study, solvent extraction of Co(II) from aqueous solution using a mixture of N,N0 -carbonyl difatty amides (CDFAs) synthesised from palm oil as the extractant was carried out. The effects of various parameters such as acid, contact time, extractant concentration, metal ion concentration and stripping agent and the separation of Co(II) from other metal ions such as Fe(II), Ni(II), Zn(III) and Cd(II) were investigated. It was found that the extraction of Co(II) into the organic phase involved the formation of 1:1 complexes. Co(II) was successfully separated from commonly associated metal ions such as Fe(II), Ni(II), Zn(III) and Cd(II). Co(II) stripping from the loaded organic phase was studied in aqueous solution. These results are useful to recover Co(II) from aqueous solution utilising (CDFAs) as an extractant. # 2010 Jaffar Al-Mulla. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: N,N0 -Carbonyl difatty amides; Solvent extraction; Co(II)
Cobalt is an essential trace element for all multicellular organisms. It is at the core of a vitamin-B12 [1]. On the other hand, some of cobalt compounds are carcinogenic [2]. Therefore, the determination of cobalt at trace level, in water and environmental samples is a great importance of environmental and public health. In addition, industrial use of cobalt has recently become extensive [3]. Pure cobalt finds important applications as a catalyst in a variety of petrochemical processes. The increase in industrial demand for cobalt will increase the need for cobalt recycling. Therefore, this metal should be recovered not only from primary sources such as its natural ores but also from secondary resources. In order to recover cobalt from various matrices, an effective separation process must be developed that allows efficient metal extraction. Solvent extraction method was widely applied in separation of metal ions from aqueous phase by contacting with an organic phase which contains a metal selective organic reagent dissolved in a diluent [4]. Organic reagents play an eminent role in the extraction because they can react with metal ions to give complexes. The solvent extraction by high-molecular-weight organic bases has recently become increasingly popular in the study of metal complexes [5]. High-molecular-weight amines and amides are common extractants for the extraction of
* Corresponding author. E-mail address: [email protected] (E.A.J. Al-Mulla). 1001-8417/$ – see front matter # 2010 Jaffar Al-Mulla. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2010.10.037
[()TD$FIG] 470
E.A.J. Al-Mulla, K.W.S. Al-Janabi / Chinese Chemical Letters 22 (2011) 469–472
Scheme 1. CDFA synthesis from palm oil.
anionic metals [6–10]. CDFAs are interesting azotic ligands with non-bonded lone pairs of electrons on the nitrogen of the amino group and the oxygen of the carbonyl group. The protonation of amine and amide nitrogen groups in acidic solutions gives these ligands a cationic behaviour and consequently the potential for attracting metal anions. Although the coordination of amide ligands with many metal ions has been reported, no work has been done on the application of difatty amides for the separation and extraction of cobalt in aqueous solution. In this paper we report the results of our investigations on N,N0 -carbonyl difatty amides synthesized from palm oil as an extractant for cobalt ions. The presence of long-chain hydrophobic fatty acids (mainly C16 and C18) in palm oil suggests that it should be useful for the extraction of metal ions from aqueous solution. The utilisation of vegetable oils as raw materials for reagent synthesis allows the development of an extractant which is both economic and environmentally friendly. In addition, the synthesis of the N,N0 -carbonyl difatty amides (CDFAs) extractant is a simple and environmentally friendly process and uses abundant raw materials. 1. Experimental Palm oil was supplied by local market from Ngo Chew Hong Oils and Fats (M) Sdn. Bhd., Malaysia. (the fatty acids composition: C12:0, C14:0, C16:0, C18:0, C18:1, C18:2, C18:3, C20:0) [11].Urea, ethanol, sodium metal, chloroform, toluene, xylene and octanol were from Merck, Germany. Nickel(II) acetate, cadmium(II) acetate, zinc(II) acetate and cobalt(II) nitrate were from Fluka, Switzerland. Iron(II) sulfate was from BDH Chemical, England). In a 250 mL round-bottomed flask fitted with a reflux condenser and a magnetic stirrer, finely cut sodium was dissolved in 100 mL of super-dried ethanol. After all the sodium has reacted, palm olein was then added into this solution followed by dried urea (which was obtained by drying at 60 8C for 4 h) dissolved in 50 mL of hot (70 8C) ethanol. After mixing by shaking, the mixture was refluxed for 8 h on an oil bath at 110 8C. The contents of the flask were cooled to room temperature, transferred into a separatory funnel and allowed to settle over night. The bottom layer comprised of glycerol was removed. The top layer, which contain the products, was poured into a beaker, and mixed with 100 mL of hot distilled water (60.0 8C) and 10 mL of concentrated hydrochloric acid, and stirred for 15 min. Difatty amide solution was separated from the white mass of ethyl fatty ester by filtering. The clear solution containing difatty amide was then cooled in an ice bath. The pale yellow product was collected on a Buchner funnel and washed with 50 mL of cold water and then dried in a vacuum desiccator over phosphorous pentoxide. The preparation reaction is shown in the Scheme 1. The proposed mechanism of conversion palm oil into CDFAs was reported in our previous paper [12]. The presence of amide in CDFAs was determined by FTIR spectra. FTIR spectra in the range 4000–280 cm1 were obtained using PerkinElmer 1650 infrared Fourier transform spectrometer by KBr pellet technique. Designated concentration of Co(II) solution was shaken with a chloroform solution containing CDFAs in a mechanical shaker (Schwabach, Germany) for 30 min. And then, the solutions were allowed to stand for 10 min. The aqueous phase concentration of Co(II) was determined by FAAS. Hydrochloric acid (HCl) of various concentrations was used as aqueous phase to determine the effect the different concentrations on the percentage extraction of Co(II). 2. Results and discussion FTIR spectrum of CDFAs shows bands at 3010, 2922, 2855 cm1 resulting from C–H stretching of CH CH, C–H asymmetric stretching of CH, C–H symmetric stretching of CH2. Additionally, bands at 3346, 1624 and 1046 cm1 attributed to N–H stretching, C O stretching and C–N stretching of amide, respectively, indicating that unsaturated fatty amides have been formed [13]. Fig. 1 shows the FTIR spectra of palm oil, urea and CDFAs.
[()TD$FIG]
E.A.J. Al-Mulla, K.W.S. Al-Janabi / Chinese Chemical Letters 22 (2011) 469–472
471
Fig. 1. FTIR spectra of samples: palm oil, urea and CDFAs.
Effect of pH on various metal ion extraction by CDFAs: The effect of pH on extraction of various metal ions (5 105 mol L1) was examined with (5 103 mol L1) solutions of CDFAs in chloroform. At the maximum extraction, the selectivity order of various metal ions using CDFAs is as shown in Table 1. It can be seen that that extraction cobalt (II) by CDFAs gave highest distribution ratio value. Since complex CDFAs–cobalt (II) ion was stronger than those the other metal ions. Effect of solvent on the extraction of Co(II): Different organic solvent such as toluene, xylene, chloroform and octanol were tested to inert diluents for the reagents. The extractions were performed at a fixed concentration CDFAs (5 103 mol L1) and cobalt (II) ion (5 105 mol L1) at pH 6.2. The highest extraction is obtained when chloroform is used. Effect of pH on the extraction percentage of Co(II): The optimum pH for the extraction was determined by carrying out the extraction with fixed concentration of CDFAs and cobalt (II) ion. Extraction of cobalt (II) was studied within the initial pH range 3.5–6.5. The experimental results show that the percentage of the extraction of cobalt (II) ion increases sharply with the increase of pH from 3.5 to 5 and then almost level off when the pH is further increased. The maximum of percentage of the extraction is obtained (91%) when at pH 6.2. Effect of shaking time on the extraction of Co (II): The extraction of cobalt (II) with CDFAs occurs rapidly. It was observed that equilibrium was achieved within 5 min. However, to ensure complete equilibrium, all extractions were carried out for 30 min. Effect of CDFAs concentration on the extraction of Co(II): The extraction was carried out by taking a fixed amount of cobalt(II) with varying amount of CDFAs. The plot of log D against log concentration of CDFAs gave a straight line of a slope 1.2 indicating that the molar ratio of CDFAs to cobalt(II) is 1:1. Separation of Co (II) from Ni (II) Cd (II) Fe (II) and Zn (II): The method allows the separating of Co (II) from binary mixture containing Ni(II) Cd(II) Fe(II) or Zn(II) in HCl (Table 2).
Table 1 Effect of pH on various metal ion extraction by CDFAs. Metal ion
Distribution ratio
pH
Co (II) Ni (II) Cd (II) Fe (II) Zn (II)
18.5 7.3 5.8 2.5 1.2
6.2 8.5 7.6 9.1 4.2
472
E.A.J. Al-Mulla, K.W.S. Al-Janabi / Chinese Chemical Letters 22 (2011) 469–472
Table 2 Percentage extraction of Co(II) from binary mixture with Ni(II) Cd(II) Fe(II) and Zn(II). HCl (mol L1) 1
10 103
%ECo (%ENi)
%ECo (%ECd)
%ECo (%EFe)
%ECo (%EZn)
91 (0.5) 90 (1)
93 (0.4) 93 (2)
97 (0.2) 92 (2)
95 (0.9) 98 (1)
3. Conclusion The CDFAs mixture prepared from palm oil is a good extractant for ion extraction from aqueous solution. Using chloroform as the solvent, the extraction involves the formation of a 1:1 Co(II): CDFAs complex and is affected by the acid concentration. The extraction of Co(II) from other metal ions is quantitative owing to the high selectivity of the extractant for Co(II) over Ni(II), Cd(II), Mn(II) and Fe(II). Thus, CDFAs can be successfully applied to the extraction of Co(II) from aqueous solution not only owing to its fast rate of extraction but also because of its high selectivity towards Co(II). References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
M.S. Bidabadi, Dadfarnia, S.A.M.H. Shabani, J. Hazard. Mater. 166 (2009) 291. J.L. Manzoori, A. Bavali-Tabrizi, Microchim. Acta 141 (2003) 201. S.G. Bhagwan, B. Narendar, D. Poonam, et al. Trans. Met. Chem. 24 (1998) 463. G.H. Jeffery, J. Baset, J. Mendham, et al., Vogel’s Text Book of Quantitative Inorganic Analysis, 5th ed., Longmam green, London, 1979. T.N. Lokhande, M.A. Anuse, M.B. Chavan, Talanta 47 (1998) 823. N. Iatsenko Gerhardt, A.A. Palant, S.R. Dungan, Hydrometallurgy 55 (2000) 1. R. Shukla, G.N. Rao, Talanta 57 (2002) 633. T. Sato, K. Sato, Hydrometallurgy 25 (1990) 281. J. Coca, F.V. Diez, M. Moriz, Hydrometallurgy 25 (1990) 125. B. Saliha, E.S. Mohamed, Acta Chim. Slov. 50 (2003) 663. W.H. Hoidy, M.B. Ahmad, E.A.J. Al-Mulla, et al. J. Oleo Sci. 59 (2010) 229. E.A.J. Al-Mulla, W.M.Z. Yunus, N.A. Ibrahim, et al. J. Oleo Sci. 58 (2009) 467. W.R. James, P. Monoj, K.M. Sharathkumar, J. Am. Oil Chem. Soc. 85 (2008) 783.
Chinese Chemical Letters 22 (2011) 469–472 www.elsevier.com/locate/cclet
Extraction of cobalt(II) from aqueous solution by N,N0 -carbonyl difatty amides Emad A. Jaffar Al-Mulla a,*, Khalid Waleed S. Al-Janabi b a
b
Department of Chemistry, College of Science, University of Kufa, AnNajaf, Iraq Department of Chemistry, College of Education, Baghdad University, Baghdad, Iraq Received 20 July 2010 Available online 15 January 2011
Abstract The development of economic and environmentally friendly extractants to recover cobalt metal is required due to the increasing demand for this metal. In this study, solvent extraction of Co(II) from aqueous solution using a mixture of N,N0 -carbonyl difatty amides (CDFAs) synthesised from palm oil as the extractant was carried out. The effects of various parameters such as acid, contact time, extractant concentration, metal ion concentration and stripping agent and the separation of Co(II) from other metal ions such as Fe(II), Ni(II), Zn(III) and Cd(II) were investigated. It was found that the extraction of Co(II) into the organic phase involved the formation of 1:1 complexes. Co(II) was successfully separated from commonly associated metal ions such as Fe(II), Ni(II), Zn(III) and Cd(II). Co(II) stripping from the loaded organic phase was studied in aqueous solution. These results are useful to recover Co(II) from aqueous solution utilising (CDFAs) as an extractant. # 2010 Jaffar Al-Mulla. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: N,N0 -Carbonyl difatty amides; Solvent extraction; Co(II)
Cobalt is an essential trace element for all multicellular organisms. It is at the core of a vitamin-B12 [1]. On the other hand, some of cobalt compounds are carcinogenic [2]. Therefore, the determination of cobalt at trace level, in water and environmental samples is a great importance of environmental and public health. In addition, industrial use of cobalt has recently become extensive [3]. Pure cobalt finds important applications as a catalyst in a variety of petrochemical processes. The increase in industrial demand for cobalt will increase the need for cobalt recycling. Therefore, this metal should be recovered not only from primary sources such as its natural ores but also from secondary resources. In order to recover cobalt from various matrices, an effective separation process must be developed that allows efficient metal extraction. Solvent extraction method was widely applied in separation of metal ions from aqueous phase by contacting with an organic phase which contains a metal selective organic reagent dissolved in a diluent [4]. Organic reagents play an eminent role in the extraction because they can react with metal ions to give complexes. The solvent extraction by high-molecular-weight organic bases has recently become increasingly popular in the study of metal complexes [5]. High-molecular-weight amines and amides are common extractants for the extraction of
* Corresponding author. E-mail address: [email protected] (E.A.J. Al-Mulla). 1001-8417/$ – see front matter # 2010 Jaffar Al-Mulla. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2010.10.037
[()TD$FIG] 470
E.A.J. Al-Mulla, K.W.S. Al-Janabi / Chinese Chemical Letters 22 (2011) 469–472
Scheme 1. CDFA synthesis from palm oil.
anionic metals [6–10]. CDFAs are interesting azotic ligands with non-bonded lone pairs of electrons on the nitrogen of the amino group and the oxygen of the carbonyl group. The protonation of amine and amide nitrogen groups in acidic solutions gives these ligands a cationic behaviour and consequently the potential for attracting metal anions. Although the coordination of amide ligands with many metal ions has been reported, no work has been done on the application of difatty amides for the separation and extraction of cobalt in aqueous solution. In this paper we report the results of our investigations on N,N0 -carbonyl difatty amides synthesized from palm oil as an extractant for cobalt ions. The presence of long-chain hydrophobic fatty acids (mainly C16 and C18) in palm oil suggests that it should be useful for the extraction of metal ions from aqueous solution. The utilisation of vegetable oils as raw materials for reagent synthesis allows the development of an extractant which is both economic and environmentally friendly. In addition, the synthesis of the N,N0 -carbonyl difatty amides (CDFAs) extractant is a simple and environmentally friendly process and uses abundant raw materials. 1. Experimental Palm oil was supplied by local market from Ngo Chew Hong Oils and Fats (M) Sdn. Bhd., Malaysia. (the fatty acids composition: C12:0, C14:0, C16:0, C18:0, C18:1, C18:2, C18:3, C20:0) [11].Urea, ethanol, sodium metal, chloroform, toluene, xylene and octanol were from Merck, Germany. Nickel(II) acetate, cadmium(II) acetate, zinc(II) acetate and cobalt(II) nitrate were from Fluka, Switzerland. Iron(II) sulfate was from BDH Chemical, England). In a 250 mL round-bottomed flask fitted with a reflux condenser and a magnetic stirrer, finely cut sodium was dissolved in 100 mL of super-dried ethanol. After all the sodium has reacted, palm olein was then added into this solution followed by dried urea (which was obtained by drying at 60 8C for 4 h) dissolved in 50 mL of hot (70 8C) ethanol. After mixing by shaking, the mixture was refluxed for 8 h on an oil bath at 110 8C. The contents of the flask were cooled to room temperature, transferred into a separatory funnel and allowed to settle over night. The bottom layer comprised of glycerol was removed. The top layer, which contain the products, was poured into a beaker, and mixed with 100 mL of hot distilled water (60.0 8C) and 10 mL of concentrated hydrochloric acid, and stirred for 15 min. Difatty amide solution was separated from the white mass of ethyl fatty ester by filtering. The clear solution containing difatty amide was then cooled in an ice bath. The pale yellow product was collected on a Buchner funnel and washed with 50 mL of cold water and then dried in a vacuum desiccator over phosphorous pentoxide. The preparation reaction is shown in the Scheme 1. The proposed mechanism of conversion palm oil into CDFAs was reported in our previous paper [12]. The presence of amide in CDFAs was determined by FTIR spectra. FTIR spectra in the range 4000–280 cm1 were obtained using PerkinElmer 1650 infrared Fourier transform spectrometer by KBr pellet technique. Designated concentration of Co(II) solution was shaken with a chloroform solution containing CDFAs in a mechanical shaker (Schwabach, Germany) for 30 min. And then, the solutions were allowed to stand for 10 min. The aqueous phase concentration of Co(II) was determined by FAAS. Hydrochloric acid (HCl) of various concentrations was used as aqueous phase to determine the effect the different concentrations on the percentage extraction of Co(II). 2. Results and discussion FTIR spectrum of CDFAs shows bands at 3010, 2922, 2855 cm1 resulting from C–H stretching of CH CH, C–H asymmetric stretching of CH, C–H symmetric stretching of CH2. Additionally, bands at 3346, 1624 and 1046 cm1 attributed to N–H stretching, C O stretching and C–N stretching of amide, respectively, indicating that unsaturated fatty amides have been formed [13]. Fig. 1 shows the FTIR spectra of palm oil, urea and CDFAs.
[()TD$FIG]
E.A.J. Al-Mulla, K.W.S. Al-Janabi / Chinese Chemical Letters 22 (2011) 469–472
471
Fig. 1. FTIR spectra of samples: palm oil, urea and CDFAs.
Effect of pH on various metal ion extraction by CDFAs: The effect of pH on extraction of various metal ions (5 105 mol L1) was examined with (5 103 mol L1) solutions of CDFAs in chloroform. At the maximum extraction, the selectivity order of various metal ions using CDFAs is as shown in Table 1. It can be seen that that extraction cobalt (II) by CDFAs gave highest distribution ratio value. Since complex CDFAs–cobalt (II) ion was stronger than those the other metal ions. Effect of solvent on the extraction of Co(II): Different organic solvent such as toluene, xylene, chloroform and octanol were tested to inert diluents for the reagents. The extractions were performed at a fixed concentration CDFAs (5 103 mol L1) and cobalt (II) ion (5 105 mol L1) at pH 6.2. The highest extraction is obtained when chloroform is used. Effect of pH on the extraction percentage of Co(II): The optimum pH for the extraction was determined by carrying out the extraction with fixed concentration of CDFAs and cobalt (II) ion. Extraction of cobalt (II) was studied within the initial pH range 3.5–6.5. The experimental results show that the percentage of the extraction of cobalt (II) ion increases sharply with the increase of pH from 3.5 to 5 and then almost level off when the pH is further increased. The maximum of percentage of the extraction is obtained (91%) when at pH 6.2. Effect of shaking time on the extraction of Co (II): The extraction of cobalt (II) with CDFAs occurs rapidly. It was observed that equilibrium was achieved within 5 min. However, to ensure complete equilibrium, all extractions were carried out for 30 min. Effect of CDFAs concentration on the extraction of Co(II): The extraction was carried out by taking a fixed amount of cobalt(II) with varying amount of CDFAs. The plot of log D against log concentration of CDFAs gave a straight line of a slope 1.2 indicating that the molar ratio of CDFAs to cobalt(II) is 1:1. Separation of Co (II) from Ni (II) Cd (II) Fe (II) and Zn (II): The method allows the separating of Co (II) from binary mixture containing Ni(II) Cd(II) Fe(II) or Zn(II) in HCl (Table 2).
Table 1 Effect of pH on various metal ion extraction by CDFAs. Metal ion
Distribution ratio
pH
Co (II) Ni (II) Cd (II) Fe (II) Zn (II)
18.5 7.3 5.8 2.5 1.2
6.2 8.5 7.6 9.1 4.2
472
E.A.J. Al-Mulla, K.W.S. Al-Janabi / Chinese Chemical Letters 22 (2011) 469–472
Table 2 Percentage extraction of Co(II) from binary mixture with Ni(II) Cd(II) Fe(II) and Zn(II). HCl (mol L1) 1
10 103
%ECo (%ENi)
%ECo (%ECd)
%ECo (%EFe)
%ECo (%EZn)
91 (0.5) 90 (1)
93 (0.4) 93 (2)
97 (0.2) 92 (2)
95 (0.9) 98 (1)
3. Conclusion The CDFAs mixture prepared from palm oil is a good extractant for ion extraction from aqueous solution. Using chloroform as the solvent, the extraction involves the formation of a 1:1 Co(II): CDFAs complex and is affected by the acid concentration. The extraction of Co(II) from other metal ions is quantitative owing to the high selectivity of the extractant for Co(II) over Ni(II), Cd(II), Mn(II) and Fe(II). Thus, CDFAs can be successfully applied to the extraction of Co(II) from aqueous solution not only owing to its fast rate of extraction but also because of its high selectivity towards Co(II). References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
M.S. Bidabadi, Dadfarnia, S.A.M.H. Shabani, J. Hazard. Mater. 166 (2009) 291. J.L. Manzoori, A. Bavali-Tabrizi, Microchim. Acta 141 (2003) 201. S.G. Bhagwan, B. Narendar, D. Poonam, et al. Trans. Met. Chem. 24 (1998) 463. G.H. Jeffery, J. Baset, J. Mendham, et al., Vogel’s Text Book of Quantitative Inorganic Analysis, 5th ed., Longmam green, London, 1979. T.N. Lokhande, M.A. Anuse, M.B. Chavan, Talanta 47 (1998) 823. N. Iatsenko Gerhardt, A.A. Palant, S.R. Dungan, Hydrometallurgy 55 (2000) 1. R. Shukla, G.N. Rao, Talanta 57 (2002) 633. T. Sato, K. Sato, Hydrometallurgy 25 (1990) 281. J. Coca, F.V. Diez, M. Moriz, Hydrometallurgy 25 (1990) 125. B. Saliha, E.S. Mohamed, Acta Chim. Slov. 50 (2003) 663. W.H. Hoidy, M.B. Ahmad, E.A.J. Al-Mulla, et al. J. Oleo Sci. 59 (2010) 229. E.A.J. Al-Mulla, W.M.Z. Yunus, N.A. Ibrahim, et al. J. Oleo Sci. 58 (2009) 467. W.R. James, P. Monoj, K.M. Sharathkumar, J. Am. Oil Chem. Soc. 85 (2008) 783.