Separation and Micro amount Determination of Pb (II) and Cd (II) Via Solvent Extraction Method

 

Safa Majeed Hameed¹, Sahar Aqeel Hussain²

¹Department of Chemistry, Faculty of Education for Girls, University of Kufa, Al-Najaf, 54001, Iraq

²Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Kufa, Al-Najaf, 54001, Iraq

ABSTRACT:

In this paper, laboratory prepared azo derivative 2-[(4-Formyl phenyl) azo]-4,5-diphenyl imidazole (FPAPI) has been used as complexing agents for extraction Pb(II) and Cd(II) ions from aqueous solutions. Spectroscopy study was at λ_max=533nm for ion pair complex of Pb(II) and λ_max=543nm for ion pair complex of Cd(II) and all effective parameters on the extraction process were also studied. The optimum pH results for giving higher extraction efficiency of Pb(II) and Cd(II) were 8 and 9 respectively. In addition to other parameters such as shaking time, thermodynamics, an organic solvent, interferences, electrolytes, the paper has adopted different methods to determine the most feasible structural geometry of extracted ion-pair complex of [1:1]²⁺, anion, [Pb-FPAPI]²⁺, 2NO₃^-, [Cd-FPAPI]²⁺, 2NO₃^-.

 

 

 

INTRODUCTION:

The solvent extraction method was applied for the separation of Cd²⁺ ions from aqueous media by using the organic reagent 2-[Benzothiazolylazo]-4-benzylphenol ^[1]. Extraction of chloro anion complexes of Cd²⁺ and Hg²⁺ was by different extractants in relation to liquid ion exchange technique such as α-Naphthyl amine, 4-Aminobenzoic acid, 2-[(4-Carboxymethyl phenyl) azo]-4,5-diphenyl imidazole. Cryptand C222^[2]. 2-[Benzo thiazolyl azo]-4-Benzyl phenol was used as extractant to form complex with Pb (II) having λ_max=393 nm. All the optimum conditions were studied^[3]. Lead (II) has been extracted from Cl^-and Cl^-/NO₃^-media by using extractants: 1-(3-pyridyl) undecan-1-one oxime and (3-[1-(hydroxyimine) undecyl]-1-propyl pyridinium bromide in addition to 3-[1-(hydroxyimine) undecyl]-1-propylpyridinium chloride).

 

The study specified that Pb(II) has been extracted as anion complexes PbCl₃⁻ and PbCl₄^2−[4]. Separating Pb(II) and Zn (II) from a galena ore leachate was performed by means of combined tributylphosphate TBP and bis (2,4,4-trimethylpentyl) phosphinic acid Cyanex 272. The stoichiometry of the lead-extractable species has been HPbCl₃·TBP ^[5]. Cloud point extraction method used for preconcentration of Pb (II) and Cd(II)ions in various samples after complexation by 2-[(Benzothiazolyl)azo]-4-benzyl phenol with Pb(II) and 2-[(3-Bromophenyl) azo]-4,5-diphenylimidazole with Cd(II) ions was quantitatively extracted in Triton-x-100^[6]. The newfangled biological reagent 2-[Benzo thiazolyl azo]-4,5-diphenyl imidazole has organized as a complexing agent for separation of Cu²⁺ ion in several testers including plants, soil, water and human blood serum^[7]. Many studies included solvent extraction approaches for spectrophotometric determing of Pb(II) and Cd (II) as cation^[8-16] or anion^[17-20] in different samples.

 

In this study, azo derivative 2-[(4-Formyl phenyl) azo]-4,5-diphenyl imidazole (FPAPI) has been prepared as complexing agents for extraction Pb(II) and Cd(II) ions from aqueous solutions. The overshadowed application method totally accommodates for separation and determination of other metal cation with diverse organic reagents. All used foreign ions have interference with ions under study. Using electrolyte in aqueous solutions helps to increase extraction efficiency.

 

EXPERIMENT:

Materials:

All chemicals were imported from a distinguished commercial company and used as received without more purification. Stock solution of 1mg/ml Pb(II) has prepared by dissolving 0.1590g of Pb(NO₃)₂ (Fluka) in 100mL distilled water by volumetric flask, while stock solution of 1mg/ml Cd(II) was prepared by dissolving 0.0210g of Cd(NO₃)₂.4H₂O (Fluka) in 100mL purified water through volumetric flask. Organic reagent solution (1×10^-2M) 2-[(4-Formyl phenyl) azo]-4,5-diphenyl imidazole was prepared by dissolving 0.3523g in 10mL chloroform. Other employed solutions have been organized by dilution with purified water in a suitable volumetric flask, as well as all other solution need in this research prepared at the same procedure.

 

Instrumentation:

For UV-Vis spectrophotometric studies and absorbance, measurements were done by Biochrom spectrophotometer (Biochrom Libra S60) (UK) Cambridge CB40FJ. The pH was measured by pH-meter, WTW (Germany). For shaking, HY-4 vibrator was used with AD in the case of multiple speediness levels. Electrostatic water bath (WNB7-45 England) has been employed for maintaining the required temperature.

 

General extraction method:

An aliquot of 5mL solutions uses a known quantity of Pb(II) or Cd (II) ions each alone at optimum pH_ex for each ion. Add 5mL of (1×10^-4M) organic reagent (FPAPI) dissolved in chloroform. The two layers were shaken for optimum shaking time in an electrical shaker. Afterward, separate two layers and measure the absorbance of organic phase at a maximum wavelength in contradiction of the organic reagent as a blank. The remaining quantity of Pb (II) and Cd (II) in the aqueous phase were determined by dithizone method^[21] and by the return to calibration curves Fig.(1). Lastly, calculate distribution ratio (D) from metal ion quantity remain in aqueous phase and the transferred quantity to organic phase can be determined by the equation:

 

RESULTS AND DISCUSSION:

Spectrophotometric Studies:

Laboratory prepared azo derivative 2-[(4-Formyl phenyl) azo]-4,5-diphenyl imidazole (FPAPI) was dissolved in chloroform at concentration 1×10^-4M give UV-Vis spectrum as in Figures (2,3):

 

Fig.1. UV-Vis spectrum for organic reagent FPAPI

 

The results show that wavelength for the maximum absorbance of FPAPI dissolved in chloroform was at λ_max=462nm.

To pinpoint the wavelength of maximum absorbance to ion pair association, complexes of Pb²⁺ and Cd²⁺ were extracted into chloroform by applying a general method for extraction 100μg of each metal ion under study at fixed optimum pH and UV-Vis. Spectrum demonstrates λ_max=533nm for ion pair complex of Pb²⁺ and λ_max=543nm for ion pair complex of Cd²⁺, as in Figures (4,5):

 

 

Fig.2. UV-Vis spectrum for ion pair complex of Cd²⁺ with FPAPI

 

 

Fig.3. UV-Vis spectrum for ion pair complex of Pb²⁺ with FPAPI

 

 

Fig.4. Calibration curves for determination Pb(II), Cd(II) ions in aqueous solution

Effect of pH:

Extraction of 100μg of Pb²⁺ and Cd²⁺ in 5mL aqueous solution each one alone was at different pH values using 5mL of 1×10^-4M FPAPI dissolved in chloroform after shaking the dual layers for 10 minutes. The outcomes have been as in the Figures (6,7):

 

 

Fig. 6. Consequence of pH on formation and stability of extracted ion pair association complex

 

 

Fig.7. Consequence of pH on extraction efficiency and D-Values

 

The consequences show that the optimal pH value for giving higher extraction efficiency of Pb²⁺ and Cd²⁺ were 8 and 9 respectively. At these pH values, reaching to maximum rate of forward direction of thermodynamic is for forming ion-pair association complex of metal ions under study with best distribution into organic phase, because at these pH values, gate favorable coordinately binding between organic reagent FPAPI and metal ion with higher stability at any pH is less than optimal value. It does not arrive the finest equilibrium and declines extraction efficiency. At pH value more than the optimum value, extraction efficiency is decreased by the effect of forming a stable compound between metal ions and hydroxyl ion in aqueous solution^[22,23].

 

Effect of Shaking Time:

From 5mL aqueous solution having 100μg of Pb²⁺ ion and Cd²⁺ ion at pH=8, 9 respectively, extracted metal ion as ion-pair association complex was by1×10^-4M FPAPI dissolved in chloroform by shaking the two phases for different shaking times ranged from 5 to 20 minutes in an electrical shaker. The procedure was completed using the general method and the consequences have been illustrated as in Figures (8,9):

 

Fig.8. Consequence of shaking time on formation and stability of extracted ion pair association complexes

 

 

Fig.9. Consequence of shaking time on extraction efficiency and D- values

 

Thermodynamic:

According to the general procedure, extracted Pb²⁺ and Cd²⁺ ions were at the optimum condition at the different temperature. The corresponding consequences were as in Figures (10, 11):

 

 

Fig.10. Result of temperature on formation and stability of ion pair association complex extracted of Pb²⁺ and Cd²⁺

 

 

Fig.11. Result of temperature on extraction efficiency and D values for Pb²⁺ and Cd²⁺

The relation of Log K_ex and 1/T K for both ions was demonstrated in Fig.(12).

 

 

Fig.12. Variation extraction constant for extraction Pb²⁺ and Cd²⁺

 

Thermodynamic data^[24] calculated for extraction Pb²⁺ and Cd²⁺ ions were explained in Table (1).

 

Table 1. Thermodynamic data for extracted Pb²⁺ and Cd²⁺ ions

Metal ions	ΔHex( ) kJmol-1	ΔGex (ΔGex= -RT ln Kex)  kJ.mol-1	ΔSex (ΔGex= ΔHex -TΔSex ) J.mol-1.K-1
Pb2+	0.0952	-64.62	203.51
Cd2+	0.0981	-63.99	201.53

 

Organic Solvent Effect:

Extraction of 100μg of Pb²⁺ and Cd²⁺ each one alone was according to a general method by using 1×10⁴M organic reagent FADPI dissolved in different organic solvents differed in dielectric constant values. The corresponding consequences have been stated in Table (2).

 

Table 2. Organic Solvent effect on extraction efficiency of Pb²⁺ and Cd²⁺

Biological Solvents	εr	Pb(II)		Cd(II)
		Abs. at λmax=533nm	D	Abs. at λmax=543nm	D
Amyl alcohol	15.80	0.303	27.44	0.345	28.48
1,2-Dichloro ethane	10.65	0.485	41.47	0.566	50.89
Dichloro methane	9.080	0.518	46.71	0.598	58.34
Chloroform	4.806	0.597	51.17	0.623	63.86
Benzene	2.804	0.365	35.66	0.417	41.71
Toluene	2.438	0.546	50.22	0.608	61.11

 

The results show that there is no linear relationship among the dielectric constant of organic solvents and extraction efficiency that means there is no any influence for polarity on extraction efficiency but there is the influence for organic solvent structure because it participates in the formation of ion-pair association complexes extracted into an organic phase^[25].

 

 

Stoichiometry:

For identification, the structure of the ion-pair complex for extracted Pb²⁺ and Cd²⁺ ions has employed four spectrophotometric methods: Slope analysis, Slope ratio, Mole ratio and Job method. The consequences have been depicted in Figures (13-16):

 

 

Fig.13. Slope analysis technique

 

Fig.14. Slope ratio method (a) and (b)

 

Fig.15. Mole ratio method a) Pb(II) and b) Cd(II)

 

Fig.16. Contiueons variation method a) Pb(II) and b) Cd(II)

 

The results show that the most likely structure of extracted ion pair association complex were [1:1]²⁺, anion: [Pb-FPAPI]²⁺, 2NO₃^-, [Cd-FPAPI]²⁺, 2NO₃^-.

 

Effect of Methanol:

Extraction of 100μg of Pb²⁺ and Cd²⁺ ions from 5mL aqueous solution was according to the general method in the presence of a rising percentage of methanol. The consequences have been presented in the Figures (17-18):

 

 

Fig.17. Result of methanol percentage presence on formation and stability of ion pair association complex extracted

 

 

Fig.18. Result of methanol presence on extraction efficiency and D values

 

The fallouts indicate increased extraction efficiency by the existence of methanol in aqueous solution with rising percentage of CH₃OH to optimum value of 35% with Pb²⁺ ion and 40% with Cd²⁺ ion, because methanol has effect to decrease the dielectric constant of water, destroy hydration shell of metal ions and increase binding with FPAPI to increase realization and stability of ion pair association complexes^[26].

 

Influence of Electrolytes:

Extracted metal ions were under study according to general procedure at optimum conditions and in the presence of some electrolyte salts in aqueous solution at 0.01M. The consequences have been as in Table (3).

 

Table 3. Influence of electrolyte on extraction efficiency of Pb²⁺ and Cd²⁺.

Electrolyte	Pb(II)		Cd(II)
	Abs. at λmax=533nm	D	Abs. at λmax=543nm	D
LiCl	0.985	96.4	1.13	105.4
NaCl	0.866	84.3	0.921	92.7
KCl	0.743	72.6	0.854	88.3
Mg2Cl2	0.899	87.5	0.985	96.6
CaCl2	0.671	66.2	0.743	78.5

The results depict enhancement in the extraction efficiency in the presence of electrolyte in aqueous solution. Because the effect of destroying the hydration shell of metal ions, the chances of binding with FPAPI is increased to form ion-pair association complexes, and this increase in extraction efficiency varies with different electrolytes according to its performance in aqueous solution.

 

Interferences:

Extracted metal ion under study was according to general procedure in the presence of foreign metal ions at 0.01M. The consequences were illustrated in Table (4).

 

Table 4. Influence of interferences on extraction efficiency of Pb²⁺ and Cd²⁺

Foreign ions	Pb(II)		Cd(II)
	Abs. at λmax=533nm	D	Abs. at λmax=543nm	D
Zn(II)	0.243	36.5	0.445	41.7
Hg(II)	0.315	43.2	0.514	50.1
Ag(I)	0.111	18.6	0.253	24.2
Cu(II)	0.222	22.7	0.372	35.8

 

The results show that there are different interferences with different foreign ions in aqueous solution because these ion participations form ion pair association complexes and decrease ion-pair association for Pb²⁺ and Cd²⁺ ions formation^[27].

 

CONCLUSIONS:

1.    The overshadowed application method entirety accommodates for separation and determination of other metal cation with different organic reagents.

2.    The value of pH is a highly imperative limitation in the solvent extraction of the cation.

3.    Shaking time represents the kinetic side of the extraction process.

4.    All foreign ions were used for interference with ions under study.

5.    Using electrolyte in aqueous solutions facilitates to increase extraction efficiency.

 

ACKNOWLEDGMENTS:

We thank Prof. Dr. Shawket Kadhim Jawad from the Faculty of Education for Girls- University of Kufa for his assistance with methodology, and for comments that greatly improved the manuscript.

 

REFERENCES:

1.     Shawket, K.J., Fawzi, Y. W., and Ghosoon. F. H., 2010, Complexation and Extraction Studies of 2-[(Benzothiazolyl) azo]-4-benzylphenol with Cd+2 Ion. J. of Kufa for Chemical Science, 1(1), 15-23.

2.     Shawket, K. J., and Safa. M. H., 2011, Separation and Extraction Micro Amount of Cadmium (II) and Mercury (II) with Liquid Anion Exchange Method, Ibn Al- Haitham J. for Pure & Appl. Sci., 24 (2),152-161.

3.     Shawket, K. J., and Ghusoon J. A., 2012, Spectrophotometric determination for micro amount of Lead(II) in environmental and vital samples by 2-[Benzo thiozolyl azo]-4-Benzyl phenol, Al-Qadisiya J. for Science,17(1), 1-10.

4.     Aleksandra, W.K., WieszczyckaIrmina W., and Andrzej, O., 2017,Lead(II) extraction from aqueous solutions by pyridine extractants, Separation and Purification Technology J., 177(28), 239-248.

5.     Alafara, A. B., and Folahan, A. A., 2013, Solvent extraction of Pb(II) and Zn(II) from a Nigerian galena ore leach liquor by tributylphosphate and bis (2,4,4-trimethylpentyl) phosphinic acid. J. of King Saud University - Science, 25(4), 297-305.

6.     Shawket, K.J., and Jihan .R. M., 2012, Cloud Point Extraction Methodology for Separation and Microamounts Determination of Lead(II)and Cadmium(II) Ions, Iraqi National J. of Chemistry, 47, 401-412.

7.     Shawket, K.J., and Safa, M. H., and Sahar, A. H., 2014, With Solvent Extraction Method, and via new Organic Reagent 2-(Benzo thiazolyl azo)-4,5- Diphenyl Imidazole for Spectrophotometric Determination of Copper (II) in different Samples, Baghdad Science J.,11(1) 147-157.

8.     Shawket, K.J., and Zainab, A.H. 2008, Solvent Extraction Method for Extraction Cd2+ ions as cations from aqueous media by use 2-[(4-Chloro-2-Methoxyphenyl) azo]-4, 5-diphenyl imidazole, J. of Al-Qadisiya, Pure Science, 13(1), 1-20.

9.     Shawket, K.J. 2010, Solvent Extraction and Spectrophotometric Determination of Cd by using the Ligand 2-[4-Carboxy methyl phenyl azo]-4,5-diphenyl imidazole, J. of Thi -Qar University, 6(1), 7-22.

10.   Manis, K. J., Vinay, K., Jinki, J., and Jae-chun, L. 2012, Review on solvent extraction of cadmium from various solutions, Hydrometallurgy, 111-112, 1–9

11.   Zhen, Q., Jinxi, Q., Daoyan, J., Junhong, L., Ailiang, C., Yutian, M., and Yan, Z. 2018, Removal of Cadmium from Cobalt Sulfate by Solvent Extraction Using Cyanex 301, the journal of the Minerals, Metals & Materials Society 70(1)

12.   Cristina, M., Alexandra, R.M., Irina, P., Cristina, C., Firas, H.K. 2015, Zinc, Cooper and Cadmium Solvent Extraction at Equilibrium in Liquid-liquid Systems, Revista de Chimie –Bucharest, 66(9),1257-1260

13.   Preston, J.S., Patrick, J.H., and Steinbach, G. 1994, The selective solvent extraction of cadmium by mixtures of carboxylic acids and trialkylphosphine sulphides. Part 2. Practical applications in the separation of cadmium from zinc and nickel, Hydrometallurgy, 36(2), 143-160.

14.   Smirnova, S. V., Baulin, V. E., Torocheshnikova, I. I., Pletnev, I. V. 2016, Extraction of cadmium, lead, cobalt, copper, and zinc ions from aqueous solutions into hydrophilic–hydrophobic ionic liquids, Moscow University Chemistry Bulletin, 71(1), 81–86.

15.   Øien, A., and Gjerdingen, K. 1977, Determination of Cadmium and Lead in Soils by Means of Solvent Extraction and Atomic Absorption, Acta Agriculturae Scandinavica, 27:1, 67-70.

16.   Sadeddin, K. 2011, Extraction of cadmium from phosphoric acid by trioctylphosphine oxide/kerosene solvent using factorial design, Chemical Engineering, 55(2), 45–48.

17.   Manis, K.J., Vinay, K., Jinki, J., and Jae-chun, L. 2018, Study of Cadmium Extraction with Aliquat 336 from Highly Saline Solutions, J. of Solution Chemistry, 47(6),1-23.

18.   Shawket, K.J., and Maha, A.H. 2017, Separation and Determination Micro Amount Cd+2 Ion byUsing Cryptand C221 via Liquid Ion Exchange Methodology, Oriental Journal of Chemistry, 33(5), 2452-2458.

19.   Shawket, K.J., and Luay, A. K. 2016, Cloud Point Extraction Methodology for Separation and Determination Lead (II) By Use New Azo-Derivative, International Journal of Scientific Research and Modern Education, I(I), 56-64.

20.   Zuhair, A.A.K., Ibtehaj, R.A., and Shawket, K.J. 2012, Cloud Point Extraction and Micro Amount Determination of Cadmium as Chloro Anion Complex in Real Samples by using Molecular Spectrophotometry, J. of Kufa for Chemical Science, 1(6), 67-85.

21.   Fatin K. Abod, 2009, MS.c Thesis, Faculty of education for girls-Kufa University.

22.    Marczenko, Z., and Balcerzak M., 2000, Separation, preconcentration and spectrophotometry in inorganic analysis, 1st ed. Amesterdam: ELSEVIER.

23.   Shawket, K.J., and Safa, M. H., and Sahar, A. H., 2013, Solvent extraction of Copper(II) from aqueous solutions by new organic reagent 2-[(3-Hydroxy phenyl)azo]-4,5-diphenyl imidazole, Al-Qadisiya J. for Science, 18(1), 66-80.

24.   Atkins, P., and Paula, J.de., 2010, Physical Chemistry, 9th ed. Great Britain: Oxford University Press.

25.   Safa, M. H., Al-Kubaisy R. K. and Khalil, I. H., 2015, Liquid Ion Exchange Method for Extraction of Pb (II) as Anion by Using 15C5 Coupled with Spectrophotometric Determination in Different Samples, J. of Kufa for Chemical Science, 1 (10), 21-37.

26.   Shawket, K.J., and Safa, M. H., 2017, Extraction of Cd(II) and Hg(II) by Liquid Ion Exchange Methodology, Noor Publishing.

27.   Shawket, K.J., and Abed, A. S. 2015, Efficient Method Cloud Point Extraction for Separation Preconcentration and Trace amount Determination of Bismuth (III) from Different Samples by New Laboratory Prepared Azo Derivative, J. of Natural Sciences Research, 5(7), 39-51. 14

 

 

 

 

 

Received on 14.02.2019          Modified on 16.03.2019

Accepted on 18.04.2019        © RJPT All right reserved