INTRODUCTION:
More active and sensitive method by incorporation Cloud point method and Solvent extraction was used for separating and determining Iron (III) and mercury (II) by used [methyl phenylthiozolyl azo]-3-methyl-4-methoxy-2-naphthol(MPTAN) in presence TritonX-100,the limit detection are 0.016 ppm for Fe3+ and 0.041 ppm for Hg2+[7]. Determination trace amount of silver Ag+ in water by CPE method coupled flame atomic absorption spectrometry[8]. Liquid ion exchange method giving high sensitivity to extracted Fe (III) as ion-pair association complex and sensitive determination in biological samples by using crown ether DB18C6 and Triton X-100[9].
By using of many applications of cloud point extraction method for separation and determination several metal ions by using different organic reagent[10-12]. Even lanthanum (III) Extracted and Determination via Cloud point extraction method joined with solvation method by Triton X-100 as surfactant[13]. There is another several application of cloud point method for extraction and determination trace elements as (Fe, Co, V, Pb)ions[14-18].
In the present work, we have applied ternary liquid ion exchange for cloud point extraction by the spectrophotometric method for determination of the manganese as MnO4- quantities in the real samples by using azo compound (4-hydroxyphenylazo)-4-Benzen naphthol HPABN with Triton X-100.
EXPERIMENTAL:
For spectrophotometric studies and absorbance measurements, we used Double beam UV-Vis spectrophotometer Biochrom model (80-7000-11) based on Libra 560 Cambridge CB40FJ.
Reagent and solution:
Analytical grads are the chemicals used in all experiments without furthermore purification. Stock solution of 1mg\mL for manganese (VII) as MnO4- was organized by dissolving (0.2876g) in 100mL distilled water by using volumetric flask. Other working solutions were prepared by dilution with distilled water, for determining the reminder amount of Mn(VII) in aqueous solution followed the special solution method[19]. Prepared 1×10-3 M solution of (4-hydrxyphenylazo)-4-Benzennaphthol (HPABN) by dissolved (0.0340g) in 100mL distilled water containing several drops of Tritonx-100 in volumetric flask.
Principal Technique:
10 mL aqueous solution contains 100 µg of Mn(VII) as MnO4- with 1×10-4M organic reagent HPABN and optimum concentration of hydrochloric and 0.5mL of TritionX-100. Heat the solution in electrostatic water bath for finest temperature and time until formation of CPL and separate the CPL from the aqueous phase and dissolve in 5mL ethanol. Then, measure the absorbance of alcoholic solution in λmax=292 nm determined throughout the spectrophotometric study in contradiction of blank prepared at the same manner in absence metal ion Mn(VII). So that the aqueous phase can be treated according to the special solution spectroscopic method[19]. Then, return to the calibration curve as in Fig(1) for determination the remainder amount of Mn(VII) in aqueous solution after extraction. Afterward, subtract the remaining amounts from the original amount of metal ion to regulate the transfer quantities of Mn(VII) to CPL as ion-pair association complex. At latter calculate Distribution ratio (D).
RESULT AND DISCUSSION:
Spectrophotometric Study:
Preparing 10mL aqueous solution contain 100µg Mn(VII) as MnO4-, 0.1MHCl, 1×10-4 M HPABN and 0.5 mL surfactant TritonX-100. Heat the solution in electrostatic water bath at 80ºC for 20 minutes up to the forming of CPL. Subsequently, separate CPL from aqueous phase and dissolve in 5mL ethanol and take UV-Vis spectra for alcoholic solution Vis blank organized by the identical method without metal ion Mn(VII). The results are depicted in Figure (2).
Figure (1): Calibration curve for determining Mn(VII) in aqueous solution by special solution spectroscopic method
Figure (2): UV-Visible absorption band for ion-pair association complex for Mn(VII) with HPABN
The spectrum in Figure (2) depicts wavelength for maximum absorbance of ion-pair complex of Mn(VII) with HPABN organic reagent was λmax=292 nm.
Effect of Hydrochloric Acid Concentration:
Preparing a series of 10 mL aqueous solution contain 100 µg of Mn(VII) as MnO4- and 1×10-4 M HPABN with rising concentration of hydrochloric acid HCl (0.01→0.5) M and 0.5 mL of surfactant TritonX-100. Afterword heating these solutions in electrostatic water bath at 80ºC for 20 min up to CPL formation. At that point, separate the CPL from the aqueous phase, dissolve in 5 mL ethanol and measure the absorbance of alcoholic solution against blank prepared at the identical routine in absence of metal ion MnO4-. So that treated the aqueous phase according to special solution spectroscopic method[19] detailed in principal method and determined distribution ratio D. The results were as in Figures (3, 4).
Figure (3): Outcome of HCl concentration on formation and stability of ion-pair association complex
Figure (4): Outcome of HCl concentration on extraction efficiency and D magnitudes
The results illustrate that 0.2MHCl was the optimum concentration necessary to higher formation and stability of ion-pair association complex. According to thermodynamic equilibrium below:
Any concentration less than optimum concentration not allow to reach necessary equilibrium for higher extraction efficiency as well as any concentration of HCl bigger than optimal magnitude drops formation of liquid ion exchanger (H-HPABN)+, Cl-. So that may be effect to reduction some of Mn(VII) to Mn2+ and formation stable compound MnCl2 in aqueous solutions.
Effect of Metal Ion Concentration:
Preparing aqueous solutions 10 mL in volume contain rising concentration of metal ion Mn(VII) as MnO4-and 1×10-4 M of HPABN, 0.2 M from hydrochloric acid in existence of 0.5 mL of non-ionic surfactant TrtionX-100. Heat these solutions in electrostatic water bath at 80ºC for 20 min up to CPL formation. Finish the work as in principal method. The results are as in Figures (5,6).
Figure (5): Outcome of Mn(VII) concentration on formation and stability of ion-pair association complex
Figure (6): Outcome of Mn(VII) concentration on extraction efficiency and D magnitudes
The results show100µg Mn(VII) in 10mL aqueous solution was the favourable concentration to giving best thermodynamic equilibrium to formation ion-pair association complex with higher stability. The concentration less than the finest magnitude shall not allow to reach the equilibrium and decline complex formation. So that any concentration bigger than finest concentration magnitude will decrease extraction efficiency magnitude based on mass action law.
Variation Surfactant Volume:
A series of aqueous solutions 10 mL in volume contain 100 µg Mn(VII) as MnO4- with 1×10-4 M HPABN, 0.2 M HCl and rising volume of surfactant TritonX-100. Heating these solutions in electrostatic water bath at 80ºC for 20 min until formation CPL. Finish the work as in principal method and the consequences were shown in Figures (7,8).
Figure (7): Consequence of Triton X-100 volume on formation and activity of CPL for separation
Figure (8): The relation between extraction efficiency and surfactant volume
The results shows 0.5 mL of TritonX-100 giving higher extraction efficiency because this volume allow to reach critical micelles concentration CMC to form best CPL any volume less or more that is not allowed to that.
Variation of Temperature:
Organise 10 mL aqueous solution of 100 µg of MnO4- , 0.2 M HCl, 0.5 mL TritonX-100 and 1×10-4 M HPABN. Heating these solutions at different temperature for 20minutes after formation of CPL. Separate CPL from aqueous solution and finish the experiments as in principal approach. The results are illustrated in Figures (9,10).
Figure (9): CPL formation = f TºC
Figure (10): D = f TºC
After computation of extraction constant Kex, the results are as in Figure (11):
Figure (11): Kex =f (T K)
According to the straight lineslope in Figure (11) and the thermodynamic relation[20], thermodynamic data of extraction are computed as in Table (1).
Table (1): Thermodynamic records for extraction MnO4-
|
ΔSex |
ΔGex |
ΔHex |
|
165.026 Jmol-1K-1 |
-58.185 kJmol-1 |
0.0692 kJmol-1 |
Variation Heating Time:
Prepare 10 mL aqueous solutions contain 100 µg Mn(VII), 0.2 M HCl, 0.5 mL TritonX-100 , 1×10-4 M HPABN. Heat these solutions in electrostatic water bath at 80ºC for different time. The results are illustrated in Figures (12,13).
Figure (12): Outcome of heating time on formation CPL
Figure (13): Outcome of heating time on extraction efficiency
The results show that 20 minutes was the optimum heating time which is suitable to formation best CPL and giving higher extraction efficiency. Any volume less or more optimum volume is not suitable to extraction.
Effect of Electrolyte:
Prepare aqueous solutions 10 mL in volume contain 100 µg of Mn(VII) as MnO4-, 1×10-4 M HPABN , 0.2 M hydrochloric acid HCl and 0.5 mL of surfactant Triton-100 in existence of 0.1 M from different electrolyte salt. Afterward, heat these solutions in electrostatic water bath at 80ºC for 20 min up to CPL formation. Separate CPL layer from aqueous solution and dissolve in 5 mL ethanol. Then, finish the work as in principal method. The results were as in Table (2).
Table (2): Consequence of electrolyte on extraction efficiency of Mn(VII)
|
D |
Abs at λmax=292 nm |
0.1 M electrolyte |
|
60.11 |
0.954 |
LiCl |
|
40.54 |
0.876 |
NaCl |
|
31.14 |
0.825 |
KCl |
|
13.006 |
0.784 |
NH4Cl |
|
38.9 |
0.895 |
MgCl2 |
|
36.72 |
0.842 |
CaCl2 |
|
28.18 |
0.795 |
AlCl3 |
The results depict the existence of electrolyte in aqueous solution effect to enhancement extraction efficiency because it is effect to increase ion-pair association complex formation after destroy the hydration shell of metal ion Mn(VII) and increase dehydration to formation good CPL to give quantitation extraction of ion-pair complex.
Effect of Interferences:
Prepare aqueous solutions 10 mL in volume of 100µg Mn(VII) as MnO4- , 1×10-4 M HPABN, 0.2 M HCl and TritonX-100. Heat these solutions in electrostatic water bath at 80ºC for 20 min up to formation of CPL. Later, separate CPL from aqueous phase and finish work as the steps of principal routine and the results were as in Table 3.
Table (3): Interferences results on extraction efficiency of Mn(VII)
|
D |
Abs at λmax=292 nm |
Interferences 0.1 M |
|
23.44 |
0.425 |
Fe 3+ |
|
30.6 |
0.515 |
Hg2+ |
|
21.45 |
0.388 |
Cd2+ |
|
26.53 |
0.476 |
Ni2+ |
|
33.21 |
0.52 |
Co2+ |
|
18.72 |
0.375 |
Zn2+ |
The results illustrate that all these cations have the effect to decline extraction efficiency of Mn(VII) by effect of interferences these cations through formation ion-pair association complex and consumption apart of HPABN[21].
Stoichiometry:
In order to evaluate the most feasible structure of extracted ion-pair complex, adopt spectrophotometric method with slope analysis method and slope ratio method at optimum condition. The outcomes have been depicted in Figures (13-15).
Figure (13): Slope analysis technique
|
Figure (14): Consequence of metal ion concentration on formation ion-pair complex extracted
|
Figure (15): Consequence of HPABN concentration on formation ion-pair complex extracted
(6959.50)
slope ratio = ––––––––––––=1.1~1
(5959.59)
The most probable structure of ion-pair complex was 1:1: