Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 115
CHAPTER-5
SELECTIVE LIQUID-LIQUID EXTRACTION OF PALLADIUM(II) FROM SALICYLATE MEDIA BY n-OCTYLANILINE IN XYLENE
5.1 Introduction
Solvent extraction has attracted much attention as an effective and
energy saving type of separation technique for precious metals. This technique,
which has been extensively utilized in the mining industry, is one of the most
important process for the recovery of the precious metals from waste water or
scraps. At present there is a growing demand of precious metals for
technological application due to their outstanding physical and chemical
properties [1].
The abundance of palladium in the earth’s crust is 0.01-0.02 µg ml-1 and
it exists in various natural minerals, soils and rocks [2]. This element is of
immense importance to the electronic industries [3]. Palladium and its alloys
have a wide range of applications both in the chemical industry and in
instrument making. It also has widespread use in dental and medicinal devices
and jewellery manufacture [4]. The carcinogenicity of palladium(II)
compounds in rats and mice and their toxicity to mammals, fish and higher
plants are cause for environmental concern [5]. Therefore, these compounds are
usually considered as environmental pollutants [6].
Palladium(II) forms a number of complexes that are soluble in organic
solvents because of the labile character of its chloro complex, PdCl42- towards
several hydrophobic ligands [7]. This leads to the formation of several highly
extractable complexes at room temperature. Palladium prefers to coordinate
most strongly with polarizable atoms which has focused the development of an
extracting agents on those with donor atoms such as sulfur, phosphorus and
nitrogen. Nitrogen containing reagents, in particular, amines and their
derivatives are efficient extractants for some platinum group metals (PGMs)
and are widely used in technology and analysis. Modern techniques for the
extraction of PGMs provide rational approaches to choosing extractants from
the standpoint of their availability and selectivity and the development of
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
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processes for one-step extraction of the target metal and its separation from the
associate metals.
5.2 Review of literature for liquid-liquid extractive separation of
palladium(II)
In recent years various reagents have been studied for liquid-liquid
extraction of palladium(II). These are hexadecylpyrimidinium bromide [8],
1-octyltheobromine [9], 1-[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-
ylmethyl]-1H-1,2,4-triazole [10], N,N-dimethyl-N,N’-di-n-octyl-thiodigly-
colamide [11], LIX84I(2-hydroxy-5-nonylacetophenone oxime) [12], methyl-
alkylketones, such as 2-octanone, 2-nonanone, 2-undecanone, 2-tridecanone
and ketones containing symmetrical alkyl configuration, such as 5-nonanone,
5-decanone, 5-undecanone, and 6-undecanone exhibited significant extraction
of palladium(II) from nitric acid [13]. 1-Benzoyl-3-[6-(3-benzoyl-thioureido)-
hexyl]- thiourea [14] used for extraction of palladium(II). These methods were
applicable for extraction separation of either individual metal ion or group of
platinum metals and also suffers the incomplete recovery of the palladium [11,
12]. Sastre et.al. have reported selective liquid-liquid extraction of
palladium(II) from hydrochloric acid media by di-(2-ethylhexyl)thiophosphoric
acid (DEHTPA] [15] in kerosene. However, quantitative extraction requires
2 h shaking time. Solvent extraction behaviors of precious metal, palladium(II)
with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) [16] into molten
paraffin wax has been studied in the temperature range from 55 to 750C. The
extraction efficiency was up to 97 % at the experimental pH value. The
extraction properties of bis-acylated diethylenetriamine [17] are studied in the
extraction of palladium(II) from HCl solution. Method required higher reagent
concentration to ensure the complete extraction. Anyun Zhang et.al. have
investigated the extraction behavior of 4-aroyl derivative of 1-phenyl-3-
methyl-pyrazolone-5-one, a weakly acidic chelating extractant 1-phenyl-3-
methyl-4-(2-methoxybenzoyl)-pyrazolone-5-one and a trialkylamine [18] and
4-acylpyrazolone derivative of 1-phenyl-3-methyl-4-trifluoroacetylpyrazolone-
5-one and a tri-n-octylamine [19]. The methods are based on antagonistic
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 117
synergistic extraction of palladium(II) and were used for the separation of
palladium(II) from radioactive fission products. Tri-octylamine [20-23], was
reported for separation of palladium(II) from PGMs. The extraction of
palladium(II) from hydrochloric acid and hydrobromic acid, 5 % tri-iso-
octylamine [22] solution in carbon tetrachloride has been studied.
N-n-octylaniline [4, 24], alamine 336 [25-26], aliquat 336 [27], were reported
for the extraction of palladium. Schiff base extractant NN’-bis[1-phenyl-3-
methyl-5-hydroxypyrazole-4-benzylidenyl]-1,3-propylene diamine in
chloroform extract palladium(II) from nitric acid medium [28]. Extraction of
palladium(II) by bis-acylated diethylenetriamine [29] from hydrochloric acid
solution was studied. Palladium can be separated by this method from non-
noble metals. Extraction of palladium(II) from acidic solution at pH 1-4 by
using two hydrophobic analogs of N,N,N',N'-tetrakis[2-pyridyl-methyl]-1,2-
ethylenediamine (TPEN). N,N,N',N'-tetrakis[4-(2-butyloxy)-2-pyridyl-methyl]-
1,2-ethylenediamine (TBPEN) and N,N,N',N'-tetrakis(2-quinolinylmethyl)-1,2-
ethylenediamine (TQEN) [30] have shown enhanced solvent extraction
performance in more acidic media than TPEN. Liquid-liquid extraction of
palladium(II) and separation of it from other platinum group metals (PGM)
from Cl2/HCl leaching of the ores or concentrations converted into thiourea
eluate resin were studied, with high molecular weight tertiary amines [31] as
extractants. The extraction of palladium(II) from hydrochloric acid solution
with N-benzyl aniline in chloroform was investigated [32].
Extraction of palladium with triphenylphosphine (TPP) [33] in
1,2-dichloroethane from hydrochloric acid medium has been examined,
whereas at low acidity only palladium is quantitatively extracted. Addition of
stannous chloride as labilising agent makes possible a group separation of
platinum metals. Solvent extraction separation and recovery of palladium from
chloride leach liquors of spent automobile catalyst in tributylphosphate [34,
35] was studied. The extraction of palladium(II) by triphenylphosphine sulfide
[36] in benzene from nitric acid solutions has been investigated. The extraction
of palladium(II) was studied using a new series of bifunctional reagent alkane –
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1, ω-diyl bis (0,0-diisobutyl phosphorodithioate) [37] in 1,2-dichloroethane
from chloride solution at pH 3.0. The method is useful for the selective
recovery of palladium from chloride leach sources. An aqueous solution of
palladium(II) in chloride medium at pH 2.4 was shaken with bis-(2,4,4-
trimethylpentyl)-phosphinodithioic acid [38] into chloroform to extract
palladium(II). Similarly, palladium(II) was extracted from same reagent but
from nitric acid medium [39]. p-( I ,1,3,3-tetramethylbutyl)phenyl hydrogen
[N,N-di(2- ethylhexyl)aminomethyl-phosphonate [40] was synthesized as a
novel type of extractant to investigate the extraction behavior of palladium(II)
from aqueous chloride media into toluene. Extraction of palladium(II) from
nitric acid solutions with NN-dialkylcarbamoylmethyl (diphenyl) phosphines
and its oxide was carried out [41]. Palladium(II) from nitric acid medium was
extracted with 1,5-bis-(diphenylphosphinoyl) pentane in toluene [42]. Liquid-
liquid extraction of palladium by a mixture of bis(2-ethyl-hexyl)
dithiophosphate and p-octylaniline [43] was studied. The extraction of
palladium(II) from chloride solutions by di(2-ethylhexyl)dithiophosphates of
tetraoctylammonium, tri-n-octylammonium and di-n-octyl-ammonium in
toluene has been investigated [44]. The extraction of chloropalladium
complexes by solutions of trioctylmethylammonium di(2,4,4-trimethylpentyl)
dithiophosphinate (Cyanex 301) [45] in toluene over a wide range of aqueous
acidities was examined. Liquid-liquid extraction of palladium(II) with Cyanex
921 [46] from aqueous hydrochloric acid media and Cyanex 923 [47] in
chloride media in toluene was studied. Extraction of palladium was carried out
from spent autocatalysts [46,47]. Phosphonium ionic liquid: trihexyl
(tetradecyl) phosphonium chloride (Cyphos®IL 101) [48] has been used as a
novel reagent in the presence of toluene to extract palladium(II) from
hydrochloric acid solutions of various concentrations. Cyphos®IL 101 can be
reused at least in 5 cycles of extraction-stripping process.
A number of extractants for platinum group metals have been
developed, however, the majority of them are those of sulphur atom donating
ligand type. The sulphide podand 1,12-di-2-thienyl-2,5,8,11-tetrathiadodecane
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 119
(TTD) [49] in chloroform or 1,2-dichloroethane has been used to extract
palladium(II) from hydrochloric acid medium but for phase separation 15 min
time was required. Di-octyl sulphoxide [50] in xylene was applied for
extraction of palladium(II) from nitric acid medium and spectrophotometric
determination using arsenazo III. The extraction of palladium(II) nitrate by
bis(2-ethylhexy1) sulphoxide (BBSO) [51] was evaluated over a wide range of
acidity. 1,2-Bis-(tert-hexylthio) ethane [52] has been used as an extractant in
toluene for palladium(II) from hydrochloric acid medium. A new extractant
bis-(2-butylthioethyl) sulfide in chloroform was used for palladium(II)
extraction [53]. Extraction of palladium(II) with dihexyl sulfide (DHS) [54-56]
from chloride solution, and the degradation of DHS to dihexyl sulfoxide
(DHSO) were investigated in this study. The solvent extraction of palladium(II)
from hydrochloric acid solution by some dialkyl sulfoxides were reported [57].
The solvent extraction and separation performances of Pd(II) and Pt(IV) from
hydrochloric acid solutions were investigated by using di-Bu sulfoxide [58]
diluted in kerosene. Separation was carried out from several common
impurities like Fe(II), Cu(II) and Ni(II). Extraction and separation of palladium
with normal Bu benzothiazole [59] sulfide ether was studied.
2-Mercaptobenzothiazole in chloroform [60] extracts palladium(II) from
acidified solutions of platiniferous samples. NN-dialkyl-N’-benzoylthiourea
extracts palladium(II) in Solvesso 150 [61]. Method is applicable for extraction
and separation of platinum group metals from solution containing base metals.
But the optimal pH range is narrow. N’N’-dihexyl and phenyl and N’-hexyl
and phenyl derivatives of N-benzoyl thiourea [62] extract palladium(II) from
chloride medium in toluene but the method demands large volume of the
extracting solvent to effect the quantitative recovery of metal. Extraction of
palladium(II) with NN-diethyl-N’benzoylthiourea (DEBT) [63] in toluene from
hydrochloric acid media has been also reported. Methyl isobutyl ketone
extracts palladium(II) from hydrochloric acid medium [64, 65] and also
β-diketone [66] have been reported for the extraction of palladium(II). The
chloroform extraction of palladium(II) from 0.1-8 M sulphuric acid in the
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
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presence of potassium ethyl xanthate [67] has been studied. N-benzoyl-N’,N’-
diethylthiourea [68] was used for extraction of palladium(II). Theophylline
derivatives [69] was used in extraction of palladium(II). Extraction of
palladium(II) with thiocyanate [70] complexes by MIBK was reported.
N,N-Di(2-ethylhexyl) aminomethylquinonline [71] has been newly
synthesized to develop selective extractants for palladium(II). Mixture of protic
ionic liquids trioctylammoniumbis(trifluoromethanesulfonyl)amide ([TOAH]
[NTf2]) and trioctylammonium nitrate ([TOAH][NO3]) [72] were investigated
for palladium(II) extraction. The extractability of palladium(II) using
N,N,N’,N’- tetra-n-octyl-thiodiglycolamide (TOTDGA) [73] diluted with a
mixed solution of n-dodecane and 2-ethylhexanole were investigated by
solvent extraction and FT-IR measurements. Selective solid-phase extraction
and separation of trace palladium using activated carbon modified with ethyl-3-
(2-aminoethylamino)-2-chlorobut-2-enoate [74]. Liquid-liquid extraction of
palladium(II) was carried out with acylthioacetamides [75]. An aliquot
containing palladium(II) solution was extracted with 1,2,3-benzotriazole in
isobutyl methyl ketone from acetic acid-sodium acetate buffer at pH 4 [76].
The extraction behaviour of palladium(II) from the aqueous ammonium
chloride solution with the 7-tridecanone oxime in toluene was investigated in
terms of equilibrium and kinetics [77]. Dibenzylammonium dibenzyldithio-
carbamate (DBADBDC) was used as an extractant for palladium(II) into
chloroform at pH more than 4 [78]. N,N'-dimethyl-N,N'-diphenyl-
tetradecylmalonamide (DMDPHTDMA) [79] in 1,2-dichloroethane has been
investigated as a solvent extraction reagent to mainly perform the separation of
palladium from other PGMs and from some commonly associated elements
contained in concentrated hydrochloric acid media. The developed separation
scheme was applied to an automobile catalytic converter leaching solution.
Palladium contents in geochemical reference samples, rocks [80] were
determined by graphite furnace-atomic absorption spectrometry after digestion
of sample with aqua regia and HF and extraction of palladium as iodide by
methyl isobutyl ketone. Extraction of palladium(II) from hydrochloric acid
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 121
solutions with pyridinecarboxamides and ACORGA®CLX50 [81], was studied.
An extremely sensitive, reliable and simple procedure for extraction of
palladium(II) from human urine at pH 4 with pyrrolidinedithiocarbamate into
4-methyl-2-pentanone has been described [82]. Extraction mechanism of
complex in the presence of chloride ion was also discussed. Palladium(II) was
quantitatively and selectively extracted into a chloroform solution of
3-hydroxy-4 (1H-tetrazol-5-ylazo)- naphthalene –2,7-disulphonic acid [83] and
benzalkonium chloride and determined by atomic absorption spectrometry.
The extraction was investigated of halo complexes of palladium(II) by
dipyrazolonylmethanes [84] and method was developed for the chemical
atomic emission determination. Solvent extraction of the platinum and
palladium chloro complexes by tetraoctylhexylenediamine salts with di(2-
ethylhexyl)-phosphoric and dithiophosphoric acids [85] were studied.
Determination of palladium(II) from various geological samples by graphite
furnace-AAS [86, 87] was reported. The use of commercially available solid
phase extraction (SPE) [88] anion exchange cartridges for the separation and
preconcentration of palladium(II) was reported. A method for the separation of
bromide complex anions of palladium(II) with liquid solid extraction system of
polyvinylpyrrolidone-salt-water [89] was investigated. Cetylpyridinium
chloride (CPC) [90] used for separation of palladium(II). 1-[2-(2,4-
dichlorophenyl)-4-propyl-1,3-dioxolan-2-ylmethyl]-1H-1,2,4-triazole [91] was
studied for the extraction of palladium(II). N,N-di(2-ethylhexyl)
aminomethylquinoline (DEQ) [92] and separation and preconcentration of
palladium(II) by octadecyl- silica membrane disks [93] was reported. Di-(2-
ethylhexyl) thiophosphoric acid (DEHTPA) [94] in high sensitive sepration
method was reported. Separation of palladium(II) by bulk liquid membranes
during electrodialysis [95] was reported by Sadyrbaeva et. al.
Formazans-I in dichloromethane [96], Kelex 100 in toluene [97, 98],
Calix[4]arene in chloroform [99], 2,2 dithiodianiline [100], 18-crown-6,1,4,
7,10,13,16-hexa- azaoctadecane (hexacyclen) [101], Caffeine in chloroform
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
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[102] were reported as extractants for palladium(II) mostly from hydrochloric
acid media.
In this work, n-octylaniline-salicylate system was studied to investigate
the extraction of aqueous palladium(II) solution as a function of concentration
of extractant, different weak organic acids, pH, various strippants etc. The
proposed method is used for rapid and selective separation of palladium(II)
from associated elements. It is also tested for the separation and determination
of palladium(II) from real samples such as alloy and catalysts. The review of
literature for comparison of liquid-liquid extractive separation of palladium(II)
is given in Table 5.1.
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 123
Table 5.1 Review of literature for comparison of liquid-liquid extractive
separation of palladium(II)
System Aqueous phase
Organic phase
Special features Ref.No.
Hexadecylpyrimidinium bromide (HDPB)
HCl Chloroform Shaking time only few min
% recovery of Pd(II) 99 %
8
1-Octyltheobromine HCl Toluene Study was carried out at 303 K
9
1-[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-ylmethyl]-1H-1,2,4-triazole
HCl Toluene The extraction follows the
anion-exchange mechanism
10
N,N-dimethyl-N,N’-di-n-octyl-thiodiglycol-amide (MOTDA)
HCl - Extraction was nearly 100 % and very fast
11
LIX84I (2-hydroxy-5-nonylacetophenone oxime)
HCl - Pd(II) extraction was about 86 %
Thermodynamic values like ΔS, ΔH, G determined
Common impurities like Fe(III), Al(III), Zn(II), Cu(II), Ni(II) were separated
12
Methylalkylketones HNO3 - Pd(II) extraction behavior was fully investigated.
13
1-benzoyl-3-[6-(3-benzoyl-thioureido)-hexyl]- thiourea
HNO3 1,2-Dichloroethane
Stoichiometry of the extracted complexes has been determined
14
Di-(2-ethyl-hexyl)thiophosphoric acid (DEHTPA)
HCl Kerosene Selective extraction of palladium(II) over Pt(IV), Rh(III), Cu(II), Fe(III) and Zn(II)
15
1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP)
- - Extraction has been studied in the temperature range 55 to 75oC.
Extraction efficiency was up to 97 %
16
Bis-acylated diethylenetriamine
HCl - Required higher reagent concentration to ensure the complete extraction
17
1-phenyl-3-methyl-pyrazolone-5-one
HNO3 Chloroform Synergistic extraction with trialkylamine (TiOA)
18
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
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1-phenyl-3-methyl-4-trifluoroacetylpyrazolone-5-one
HNO3 - Antagonistic synergistic extraction (TOA)
19
Tri-octylamine HCl
Kerosene The extraction sequence of platinum metals was Au(III) > Pd(II), Pt(IV), Ir(IV) > Ir(III), Ru(III).
Separation of Pd(II) from PGMs.
20- 23
8.0 M HCl Thiourea
- Method was applicable for Pd(II) and Au(III)
Column packed with divinylbenzene
homopolymeric microcapsule
21
HCl< 4M CCl4 Rapid procedure 22
N-n-octylaniline HCl, Salicylate
Xylene Extraction of metal from synthetic mixture, alloys and catalyst.
4, 24
Alamine 336 (A336) pH, 2-3
- Pd(II) and Pt(IV) separated from each other by selective stripping with thoicyanate and thiourea.
25
HCl HClO4, Na2CO3 and thiourea used as stripping agents.
26
Aliquat 336 Salicylate Xylene Proposed method was described the scheme for the separation of Pt(IV), Ni(II), Cu(II), Co(II),Zn(II), Mn(II)
27
NN’-bis[1-phenyl -3-methyl-5- hydroxypyrazole -4-benzylidenyl] -1,3-propylene diamine
HNO3 or HClO4
Chloroform or toluene
The separation of palladium(II) from the mixed solution of Pd(II)-Pt(IV) was achieved.
28
Bis- acylated diethylenetriamine
HCl - In extraction process Pd(II) separated from non-noble metals
29
Nitrogen-donor ligand TPEN and TBPEN,TQEN
pH, 1-4 - More effective in more acidic media.
30
Tertiary amines Cl2/HCl - Palladium(II) separated from other PGMs from Cl2/HCl leaching of the ores or concentrations converted into thiourea eluate resin were studied
31
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 125
N-benzyl aniline HCl, < 1 M
Chloroform Thiourea excellent stripping agent.
32
Triphenylphosphine HCl 1,2-Dichlo- roethane
Stannous chloride used as labilizing agent. Useful for group concen-
tration before determination by AAS. Palladium was
quantitatively extracted at low acidity.
33
Tri-butyl phosphate HCl, 3.5-6 M
Toluene Monomeric anionic chloro complexes and polymeric aquachloro or aqua-oxo-complexes produced.
34
HCl Kerosene Palladium(II) recovery 99.9 %.
35
Triphenyl phosphine sulfide
HNO3, 2.5 M
Benzene No interference of the commonly associated radio -nuclides
36
Alkane-1, ω-diyl bis(o,o-diiso- butyl phosphoro-dithioate)s (ADBDiBPDT)
Chloride solution 1.0 M pH, 3.0
1,2-Dichloro-ethane
Extractibility increases with the increase in the length of the alkane-1 ω chain-separating the two phosphorodithioate groups.
37
Bis-(2,4,4-trime -thylpentyl)pho-sphinodithioic acid (HBTMPDTP)
Chloride, 0.1 M pH, 2.4 HNO3
Chloroform Separation of palladium(II) from platinum(IV)
38, 39
P-(1,1,3,3-tetramethyl butyl)phenyl H N,N-di(2-ethylhexyl) amino-methyl phosphonate (HR)
HCl, 0.01-6 M
Toluene Extractant for precious metals. High lipophilicity leads to
higher extraction than that from N,N-di(2-ethyl/hexyl) amino methylphosphoric acid. Fe(III) interference.
40
NN-dialkylcarba- moylmethyl (diphenyl) phos- phines, NN-dial- kylcarbamoylmethyl(diph-enyl)phosphine oxide.
HNO3 - Extraction of Pd(II) 41
1,5-Bis(diphenyl phosphinoyl) pentane
HNO3 Toluene Pd(II) Successfully extracted
42
Mixture of bis(2-ethyl-hexyl) dithiophosphate and p-octylaniline.
- - Flameless atomic absorption determination
43
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Di(2-ethylhexyl) dithiophosphates of tetraoctyl ammonium, tri-n –octylammonium and di-n-octylammonium
Chloride Toluene When binary extractants used in excess, palladium(II) complexed with reagent distributes into the organic phase.
44
Trioctylmethylammonium di(2,4,4-trimethylpentyl)dithiopho-sphinate (Cyanex 301)
HCl Toluene Increase in acidity and reagent concentration increase the percentage extraction.
45
Cyanex 921 HCl Toluene Recovery from spent autocatalysts
46, 47
Cyanex 923 HCl Toluene 1:1 HCl + HClO4 strippant. Method applicable for
recovery of metal ions from synthetic solution
47
Trihexyl(tetradecyl)phosphonium chloride (Cyphos®IL 101)
3 M HCl Toluene. 0.5 M ammonia solution used as strippant.
48
Sulphide podand 1,12-di-2-thienyl –2,5,8,11-tetra-thiadodecane
HCl Chloroform 15 min required for phase separation. Rate of extraction
considerably higher than dioctyl sulphoxide
49
Dioctyl sulphoxide HNO3, 0.5-1.5 M
Xylene Back extracted into a mixture of 2 M sodium carbonate and 0.05 M ammonia
50
Bis-(2-ethyl-hexyl)sulphoxide
HNO3, 8 M
Toluene Recovery of extractant by sodium thiosulfate.
51
1,2-bis(ter-hexyl thio)ethane
HCl Toluene Study was carried out at 303 K
52
Bis-(2-butylthio ethyl) sulfide
- Chloroform Decontamination factor 3x105.
53
Dihexyl sulphide (DHS) Chloride Insoluble substance was decreased by the addition of modifier like alcohol.
54-56
Extraction of platinum(IV) increased by increase of contact time and decrease of palladium(II) concentration.
Dialkyl sulphoxide HCl - Pd(II) extract at low acidity
57
Di-bu sulfoxide
HCl Kerosene Separation was carried out from several common impurities like Fe(II), Cu(II) and Ni(II).
58
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 127
Butyl benzothiazole - - Extraction 80 % of platinum(IV)
In two stage total extraction 98.7 %
59
2-mercaptobenzothiazole - Chloroform Method successfully applied for analysis of solid platiniferrous samples.
60
N-benzoyl-NN’-dihexylthiourea
pH, 3 Solvesso 150
Analysis of geological samples. Cu, Fe, Ni interfere in the extraction.
61
NN’-dihexyl and-phenyl and N’-hexyl and phenyl derivatives of N-benzoyl thiourea.
HCl, pH, 1-3
95oC temperature required. Separation from other platinum group metals and base metals.
62
NN’-diethyl-N’-benzoylthiourea (DEBT)
HCl, 1 M Toluene Extraction selectivity in order Pd(II)>Pt(IV)> Ru(III)>Rh(III) > Ir(III).
63
Methyl isobutyl ketone HCl Methyl isobutyl ketone
Palladium can be extracted quantitatively from small amounts of sample.
Analysis of converter matte. Useful for analysis of standard ore PTC-1.
64, 65
β-diketone (LIX 51) pH, 3.2 –6.0
- Palladium can be extracted quantitatively
66
Potassium alkyl xanthate H2SO4, 0.1-8 M
Chloroform Determination from organic phase by a a.s.
67
N-benzoyl-N’,N’-diethylthiourea
pH, 1-2
- Palladium can be extracted quantitatively
68
Theophylline derivatives
- - Selective extraction method for palladium(II)
69
Thiocyanate HCl MIBK At room temptature Pd(II) only form complex with thiocyanate. More than 95 %
extraction was observed. Extraction of secondary
PGMs
70
N,N-Di(2-ethylhexyl) aminomethylquinonline
HCl Toluene This method also applicable for Pt(IV)
71
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur
128
Trioctylammoniumbis(trifluoromethanesulfonyl)amide ([TOAH][NTf2]) and Trioctylammonium nitrate ([TOAH][NO3])
HNO3 - Reagent was applicable for Pt(IV) Method was recyclable,
easy to handle, safe, and environmentally friendly. Slightly co-extracted
Na(I), Mg(II), K(I), Ca(II), Mn(II),Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Ru(III), Rh(III)
72
N,N,N’,N’- tetra-n-octyl-thiodiglycolamide(TOTDGA)
HNO3- HCl
Mixture of n-dodecane and 2-ethyl hexanole
Extraction depends on the reagent concentration.
73
ethyl-3-(2-aminoethylamino)-2-chlorobut-2-enoate
- - Determination of Pd(II) by ICP-AES
74
Benzoylthioacetanilide (Acyl thioacetamides)
- Benzene Palladium extracted over wide pH range.
75
1,2,3-Benzotriazole Acetic acid Sodium acetate-acetic acid buffer pH, 4
MIBK Determination by γ-ray spectrometer
CN-, SCN-, S2O32-, Fe(III),
W(VI), Se(IV), Ag(I), Au(III), Co(II), Cu(II), Zn(II) interfered.
76
7-Tridecanone oxime (TDO)
HCl, 0.01M
Toluene Equilibrium and kinetics of extraction investigated
77
Dibenzylammonium dibenzyl- dithiocarbamate (DBADBDC)
pH =>4 Chloroform Extraction mechanism discussed
78
N,N'-dimethyl-N,N'-diphenyltetradecylmalona-mide (DMDPHTDMA)
HCl 1,2-Dichloroethane
Method was applicable for separation of palladium from other PGMs
79
MIBK - MIBK Platinum contents geochemical reference samples rocks were determined by graphite furnace atomic absorption spectrometry
80
Pyridinecarboxamides HCl - At low acidity Pd(II) separated from Pt(IV)
81
Pyrrolidinedithiocarbamate PH, 4 4-Methyl-2-pentenone
Extremely sensitive, reliable and simple procedure
82
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 129
3-Hydroxy-4-(1H-tetrazol-5-ylazo) naphtha- lene-2,7-disulphonic acid Benzalkonium chloride
- Chloroform Method applicable for determination of Pd(II) in sludges and pharmaceutical processes.
83
Dipyrazolonylheptane H2SO4, 0.25 M NH4Cl, 0.1 M
Chloroform Determination by emission spectroscopy Mercury interfered
84
Di(2-ethylhexyl)-phosphoric (II) and -Dithiophosphoric acids
- Toluene Decrease in acidity of aqueous phase diminution in phase contact in the organic phase.
85
Methyl isobutyl ketone - MIBK Palladium contents in geochemical reference samples rocks were determined by
graphite furnace atomic absorption spectrometry.
86, 87
Solid-phase extraction cartridges (SPE)
HCl - Method was used for group extraction
88
Polyvinylpyrrolidone-salt-water
HBr - Separation of Pd(II) from other PGMs
89
Cetylpyridinium chloride (CPC)
- - Process also studied for Rh(III), Pt(IV).
90
1-[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-ylmethyl]-1H-1,2,4-triazole
HCl Toluene Method was used for group extraction
91
N,N-di(2-ethylhexyl) aminomethylquinoline(DEQ)
HCl Toluene Method was used for group extraction
92
Octadecyl- silica membrane disks
- - Separation of Pd(II)from other PGMs
93
Di-(2-ethylhexyl) thiophosphoric acid (DEHTPA)
HCl Kerosene Highly selective in separation of Pd(II) against Fe(III), Pt(IV), Rh(III) and Zn(II)
94
Bulk liquid membranes - 1,2-Dichloroet-hane
Separation of Pd(II) from Pt(IV)
95
Formazans-I - Dichloro-methane
Prolonged shaking (24 h) required.
96
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur
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Kelex 100 [7-(4-ethyl-1-methyloctyl) quinoline-8-ol]
Chloride, 1M Thio-cyanate
Toluene Equilibrium period 60 h. Presence of tin affects the extraction behaviour of noble metals. Stripping increases with increase in concentration of oxidizing agent
97, 98
Calix[4]arenes - Chloroform Introduction of amide functional group improved Pd(II) extraction.
Na interference.
99
2,2 dithiodianiline (DTDA)
pH, 1-6
MIBK Trace amount of Pd(II) was determined.
100
18-crown-6,1,4, 7,10,13,16-hexa- azaoctadecane (hexacyclen)
pH 3-11 Methyl isobutyl ketone
Separation of Pd(II) from iron, silver, mercury, copper and platinum.
101
Caffeine HCl Chloroform High selectivity over base metals and platinum(IV).
102
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 131
5.3 Experimental
5.3.1 Apparatus
Elico digital spectrophotometer model 12 Chemito 215D with 1 cm
quartz cells was used for absorbance measurements and pH measurements were
carried out using an Elico digital pH-meter model LI-127. All weighing
operations were done by using Tapson’s analytical single pan balance model
200 T having 0.001 gm accuracy.
5.3.2 Reagents
A stock solution of palladium(II) was prepared by dissolving 1 g of
palladium chloride hydrate (Johnson Matthey, UK) [103] in dilute analar HCl
(1 M) and diluting to 250 mL with water and standardized. A working solution
of 100 µg/mL was made by diluting the stock solution with water.
n-Octylaniline
The reagent n-octylaniline was prepared by the method of Pohlandt’s
[104] and its 0.07 M solution was prepared in xylene. All solutions were
prepared from A. R. grade reagents. Aqueous solutions were prepared with
water. Double distilled water was used throughout the experimental study.
Preparation of 4’-ChloroPTPT
1-(4’-Chlorophenyl)-4,4,6-trimethyl-(1H,4H)-pyrimidine-2-thiol (4’-
ChloroPTPT) were prepared by the method of Mathes [105-108]. A stock
solution (0.02 M) was prepared by dissolving 0.5329 g 4’-ChloroPTPT in
100 mL chloroform. Reagent solution was colorless and stable.
Standard solution of diverse ions were prepared by dissolving AR grade
reagents in water or dil HCl. All the organic solvents were used after double
distillation. All chemicals used were of AR grade.
5.3.3 General procedure for extraction and determination of palladium(II)
To an aliquot containing 200 µg palladium(II) in 25 mL volumetric flask,
0.034 gm of sodium salicylate was added to get the concentration of solution
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
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0.085 M. The pH of the resulting solution was adjusted to 1.5 with dilute HCl
and NaOH solution. The aqueous solution was shaken with 10 mL 0.07 M
n-octylaniline in xylene for 5 min in separator funnel. After the phase
separation, the organic phase was stripped with three 10 mL portions of 5 M
ammonia. The back extracts were evaporated to moist dryness in order to
remove excess of ammonia. The residue was dissolved in minimum amount of
aqua regia, and evaporated with two 2 mL portions of concentrated HCl to
remove oxides of nitrogen. The residue was dissolved in 0.1 M HCl and
palladium(II) was determined spectrophotometrically by 4’-ChloroPTPT [109].
All the experiments were repeated on an average five times and the accuracy
determination of the metal concentration in the loaded organic phase was
realized by mass balance and checked by complete stripping of the loaded
organic phase followed by analysis of the stripped solution.
5.4 Results and Discussion
5.4.1 Extraction as a function of pH
The effect of pH on the percentage extraction of palladium(II) was studied
in the pH range of 0.3 to 10 with n-octylaniline in xylene in presence of
0.085 M sodium salicylate (Table 5.2). The extraction of palladium(II) was
found to be quantitative in pH range 1.0 to 2.0. Hence, all the extractions of
palladium(II) were carried out at pH 1.5 with 0.07 M n-octylaniline in xylene
(Fig 5.1).
5.4.2 Extraction as a function of n-octylaniline concentration
In the effect of reagent concentration, extractions were carried out with
various molar concentrations of n-octylaniline in xylene (Table 5.3). The
extraction of palladium(II) was quantitative with 10 mL of 0.060 - 0.080 M
n-octylaniline in xylene. However, 10 mL of 0.070 M n-octylaniline in xylene
was used for general extraction procedure (Fig 5.2).
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 133
5.4.3 Extraction as a function of weak organic acid concentration
The extraction of palladium(II) was carried out at pH 1.5 with 10 mL of
0.07 M n-octylaniline in xylene in presence of varying concentrations of
salicylate, succinate and malonate as weak carboxylic acid media (25 mL)
(Table 5.4). The extraction of palladium(II) was found to be quantitative in the
range of 0.080 to 0.095 M sodium salicylate. However, the extraction of
palladium(II) was incomplete in succinate (0.01 to 0.1 M) and malonate (0.01
to 0.1 M) media. Thus, 0.085 M concentration of salicylate (0.034 gm) was
used throughout the experimental work.
5.4.4 Effect of diluents
The studies were performed to find out the most suitable solvent for
n-octylaniline to ensure quantitative recovery for palladium(II) by the
extraction. The solution of n-octylaniline (0.07 M) in benzene, toluene, xylene,
n-butyl alcohol, amyl alcohol provides quantitative extraction of palladium(II).
The extraction of palladium(II) was incomplete if n-octylaniline is dissolved in
chloroform (% E = 25.1 %), carbon tetrachloride (% E = 61.0 %), methyl
isobutyl ketone (% E = 91.9 %), 1, 2-dichloroethane (% E = 51.9 %), kerosene
(% E = 46.4 %) and amyl acetate (% E = 28.3 %). Xylene showed minimum
toxicity and it provides better phase separation, as compared to other diluents
so it was recommended for general procedure (Table 5.5).
5.4.5 Effect of stripping agents
Stripping is the reverse of extraction, so it should be promoted by
those factors that affect extraction negatively, such as alkalies and salt media.
Acids were unsuccessful because the anion complex adhered in the organic
medium under these conditions. Ammonia solution (5 M) was preferred
because it was easier to remove from the aqueous phase by evaporation prior to
determining palladium(II) spectrophotometrically with 4’-ChloroPTPT as
compared to ammonia buffer solution. Hence, ammonia and ammonia buffer
are the most effective stripping agents for palladium(II) from organic layer.
The stripping percentage was calculated relative to the initial amount of
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur
134
palladium(II) in organic layer. It was found that stripping was incomplete in
HCl, H2SO4, HNO3, NaOH, KOH, water and acetate buffer. In this work, three
10 mL portions of 5 M ammonia were used as a strippant (Table 5.6).
5.4.6 Effect of equilibration time
The period of equilibration was varied from 1 to 30 min (Table 5.7). The
extraction of palladium(II) was quantitative over a period of 3 min shaking of
the solution, but with prolonged shaking over 20 min (Fig. 5.3) there was
decrease in the percentage extraction of palladium(II) due to the dissociation of
ion-pair complex. Thus, equilibration time for 200 μg palladium(II) extraction
was kept about 5 min throughout the study.
5.4.7 Extraction behavior of palladium(II) as a function of metal loading
capacity
Varying concentrations of palladium(II) (100 to 5000 µg/mL) were
extracted with 10 mL portions of 0.07 M n-octylaniline in xylene from 0.085 M
sodium salicylate media. It was observed that extraction of palladium(II) was
quantitative up to 1500 µg/mL with 10 mL of 0.07 M n-octylaniline
(Table 5.8).
5.4.8 Extraction behavior of palladium(II) as a function of aqueous to
organic volume ratio
Palladium(II) was extracted from 10 mL to 50 mL aqueous solutions
containing 0.085 M sodium salicylate with 10 mL of 0.07 M n-octylaniline in
xylene. The extraction was quantitative when aqueous to organic volume ratio
was in the range 1:1 to 5:1 and above this ratio the extraction decreased
(Table 5.9)
5.4.9 Nature of extracted species
The probable composition of extracted species was ascertained by
plotting the graphs of log D[Pd(II)] against log C[n-octylaniline] at fixed sodium
salicylate concentration (0.085 M). The graphs were found to be linear and
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 135
having the slopes of 0.89 and 0.82, values at pH 4.0 and 7.0, respectively
(Fig. 5.4). Also, plots of log D[Pd(II)] against log C[Salicylate] at fixed n-octylaniline
concentration (0.07 M) were linear and the slope values were found to be 2.8
and 2.7 at pH 4.0 and 7.0, respectively (Fig. 5.5). The probable composition of
the extracted species was calculated as 1:3:1 (Metal: Acid: Extractant).The
possible mechanism of ion- pair complex is as follow:-
CH3(CH2)7C6H4 NH2(org) + H + (aq) [CH3(CH2)7C6H4NH3]+
(org) (5.1)
Pd2+(aq) + 3C7H5O3
-(aq) [Pd(C7H5O3)3]-
(aq) (5.2)
CH3(CH2)7C6H4NH3+
(org)+[Pd(C7H5O3)-3](aq) [CH3(CH2)7C6H4NH3
+Pd(C7H5O3)3-](org) (5.3)
The possible mechanism of the ion-pair complex extracted
appears to be protonated n-octylaniline which form cationic species as
CH3(CH2)7C6H4NH3+
,while salicylate combines with palladium(II) to form
anionic species as Pd (C7H5O3)-3 and both of them associate to form ion-pair of
the type [CH3(CH2)7C6H4NH+3Pd(C7H5O3)-
3](org), which being neutral
constituted extractable species.
5.4.10 Effect of temperature
The effect of temperature in the range 302-314 K on the extraction of
palladium(II) in a solution of ionic strength of 0.085 M sodium salicylate and
having pH 5.0, by 0.07 M n-octylaniline in xylene was studied. It was found
that in the extraction of palladium(II) by n-octylaniline in xylene, the
distribution coefficient increases with rise in temperature.
The change of the extraction equilibrium constant Kex with temperature
is expressed by van’t Hoff equation (5.4)
Δ log Kex /Δ (1/T)=Δ H/(-2.303 R) (5.4)
where T is absolute temperature and R is the gas constant.
The plot of Kex versus 1000/T is linear with a slope value of -3.407 and the
enthalpy change of the extraction carried out at constant pH 5.0 was evaluated
as Δ H = 65.23 KJ mol-1 which means it is an endothermic process. The free
energy ΔG and entropy ΔS were calculated form equation (5.5) and (5.6) and
are reported in Table 5.10.
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
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ΔG= -2.303 RT log K (5.5)
ΔS = (ΔH – ΔG) / T (5.6)
The negative values of free energies imply that reaction is spontaneous.
The positive enthalpy value indicates that the extraction of palladium(II) with
n-octylaniline in xylene is favorable with rise in temperature (Fig. 5.6).
5.4.11 Effect of various diverse ions on percentage of extraction
The effect of a large number of foreign ions on the extraction of
200 µg/mL of palladium(II) with n-octylaniline was investigated following the
recommended procedure. The tolerance limit of individual foreign ions was
set so that error in percentage recovery was not more than ± 2 %. Thiourea,
tartarate, oxalate, EDTA, thiocyanate, thiosulphate, ascorbate interfere in the
extraction procedure of palladium(II) (Table 5.11).
5.5 APPLICATIONS
5.5.1 Separation of palladium(II) from associated metal ions
The method permits separation and determination of palladium(II) from
binary mixtures containing Pt(IV), Rh(III), Ir(III), Cu(II), Fe(III), Co(II),
Ni(II), Se(IV), Au(III) and Te(IV) (Table 5.12). Palladium(II) was separated
from these associated metal ions, under the optimum extraction conditions of
palladium(II) where, all the added metal ions were remained quantitatively in
aqueous phase from which they were determined spectrophotometrically by
standard methods [109-114]. Palladium(II) from organic phase was stripped
and estimated spectrophotometrically by 4’-ChloroPTPT method. Palladium(II)
was separated from Ru(III) by masking with 25 mg of citrate when
palladium(II) was extracted with 0.07 M n-octylaniline in xylene at pH 1.5.
While, Ru(III) remained in aqueous phase. Palladium from the organic phase
was stripped with ammonia and determined spectrophotometrically. The
masked Ru(III) was demasked with concentrated HClO4 and determined
spectrophotometrically by standard method.
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 137
5.5.2 Sequential separation of palladium(II), rhodium(III) and
ruthenium(III) form their mixture
Palladium(II) and rhodium(III) are used as auto exhaust catalyst as well
as palladium(II) and ruthenium(III) are used as hydrogenation catalyst in
organic chemistry. Hence, their separation and determination from mixture has
great importance (Table 5.13).
Palladium(II) was separated from ternary mixtures of rhodium(III) and
ruthenium(III) at pH 1.5, from 0.085 M sodium salicylate media by 0.07 M of
n-octylaniline in amyl alcohol. Rhodium(III) and ruthenium(III) remain
quantitative in aqueous phase while, palladium(II) was extracted into organic
phase. Separation is based on the use of amyl alcohol as a solvent for
palladium(II). Palladium(II) from organic phase was stripped with 5 M
ammonia (3 × 10 ml). The ammonia was evaporated and palladium(II) was
determined by 4’-ChloroPTPT [109].
The aqueous phase was evaporated to moist dryness and adjusted to
0.03 M sodium malonate, and then pH was adjusted to 9.0. Rhodium(III) was
extracted with 0.1 M of n-octylaniline in xylene . It is back stripped with 1 M
HCl (2 × 10 ml). It was determined spectrophotometrically by KI + SnCl2
method [110].
The aqueous phase containing ruthenium(III) was again evaporated to
moist dryness. It was adjusted to 0.05 M sodium malonate, the pH was
maintained 3.5 and extracted into 0.1 M of n-octylaniline in xylene. The
organic phase was stripped with 2 % NaCl + 1 M HCl (4:1) solution. Back
stripped ruthenium(III) in aqueous phase was estimated by 4’-ChloroPTPT
[109] (Flow sheet 5.1).
5.5.3 Determination of palladium(II) from synthetic mixture and
synthetic mixture corresponding to alloys
The proposed method was applied to the extraction and determination of
palladium(II) from salicylate media at pH 1.5 in various ternary mixtures.
Palladium(II) is extracted with 0.07 M n-octylaniline in xylene while Pt(IV),
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
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138
Ir(III), Te(IV), Se(IV) remained unextracted in the aqueous phase. However,
Ru(III) masked by 25 mg citrate. The extracted palladium(II) was stripped with
5 M ammonia ( 3 × 10 mL portions) and determined by 4’-ChloroPTPT
method spectrophotometrically (Table 5.14).
Similarly, the proposed method was applied for analysis of synthetic
mixture corresponding to alloys such as oakay alloy, jewellery alloy, copper
alloy, antimony alloy. The real samples of these alloys were not available at
working place, which forced us to use synthetic mixture with corresponding
composition to alloys, the palladium(II) was extracted under its optimum
extraction conditions and determined spectrophotometrically, the result of
analysis are reported in Table 5.15.
5.5.4 Determination of palladium(II) in catalysts
A known weight of catalyst was dissolved in a mixture of concentrated
HCl and HNO3 (3:1). After the reaction was over, the solution was heated with
two 5 mL portions of concentrated HCl until complete removal of oxides of
nitrogen. The residue was dissolved in 10 mL of 1 M HCl and filtered to
remove carbon and barium sulphate. The residue was washed with diluted
hydrochloric acid. The filtrate and washings were collected and diluted with
water in standard volumetric flask. An aliquot of the sample solution was taken
and palladium(II) was extracted and determined by using the recommended
procedure (Table 5.16).
5.6 CONCLUSIONS
The developed method is reliable, as can be seen from the complete
agreement of the results observed for the analysis of various practical
samples with added palladium(II).
The satisfactory recovery of palladium(II) from these samples also indicated
that the developed method is suitable for the separation and concentration
of palladium(II) from solution of complex composition. It permits the
separation of palladium(II) from other platinum group metals, gold and base
metals.
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 139
The method is highly selective, rapid, and reproducible and permits the
rapid separation and determination of micro amount of palladium(II). The
extraction of palladium(II) with n-octylaniline in xylene is an endothermic
reaction.
n-Octylaniline synthesized by low cost with high yield in best purity and
recovered for reuse without loss of extraction efficiency. Low reagent
concentration (0.07 M) is required for quantitative recovery of
palladium(II). It is free from interference of large number of foreign ions
which are commonly associated with palladium(II) in its natural occurrence.
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
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Table 5.2 Extraction of palladium(III) as a function of pH
Palladium(II) = 200 µg Sodium salicylate = 0.085 M
Aq:Org ratio = 2.5: 1 Extractant = 0.07 M n-Octylaniline in xylene
Strippant = 5 M ammonia (3×10 mL)
pH Percentage extraction, (% E) Distribution ratio, (D)
0.3 77.7
8.71
0.5 83.7
12.83
0.7 88.9
20.02
1.0 100 ∞
1.5* 100 ∞
1.7 100 ∞
2.0 100 ∞
3.0 77.4
8.56
4.0 72.8
6.69
5.0 66.7
5.00
6.0 61.7
4.02
7.0 52.6
2.77
8.0 19.3
0.59
9.0 18.7
0.57
10.0 17.5
0.53 * Recommended for general extraction procedure
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 141
Table 5.3 Extraction of palladium(III) as a function of reagent
concentration
Palladium(II) = 200 µg Sodium salicylate = 0.085 M
Aq:Org ratio = 2.5: 1 pH = 1.5
Strippant = 5 M ammonia (3×10 mL)
n-Octylaniline
concentration, M Percentage
extraction, % E Distribution
ratio, D 0.00 0.00 -
0.010 50.0 2.50
0.020 72.3 6.52
0.030 79.0 9.40
0.040 82.6 11.86
0.050 85.4 14.62
0.060 100 ∞ 0.065 100 ∞
0.070* 100 ∞
0.075 100 ∞
0.080 100 ∞ 0.090 95.5 53.0
0.10 92.0 28.75
0.11 79.0 9.40
0.12 61.3 3.95
0.13 54.6 3.00
0.14 46.9 2.20
0.15 36.0 1.40
0.16 26.5 0.90
0.20 21.9 0.70
0.25 20.8 0.65
* Recommended for general extraction procedure
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur
142
Table 5.4 Extraction behavior of palladium(II) as a function of weak
organic acid concentration
Palladium(II) = 200 µg pH = 1.5
Aq:Org ratio = 2.5: 1 Extractant = 0.07 M n-octylaniline
Strippant = 5 M ammonia
(3×10 mL)
Acid concentration
(M)
Sodium salicylate Sodium malonate Sodium succinate
% Ea Db % E Db % E Db
0.010 70.3 5.91 14.9 0.43 18.9 0.58
0.020 73.3 6.86 20.9 0.66 22.0 0.70
0.030 75.8 7.83 47.9 2.29 25.8 0.86
0.040 84.5 13.62 58.9 3.58 30.3 1.08
0.050 87.5 17.50 61.8 4.04 37.0 1.46
0.060 88.2 18.68 48.8 2.38 46.9 2.20
0.070 93.7 37.18 35.2 1.35 55.3 3.09
0.080 100 ∞ 27.9 0.96 68.3 5.38
0.085* 100 ∞ 20.0 0.62 51.3 2.63
0.090 100 ∞ 11.0 0.30 50.0 2.5
0.095 100 ∞ 10.3 0.28 38.8 1.58
0.10 95.5 53.0 - - 19.8 0.61 * Recommended for general extraction procedure a = Percentage extraction b= Distribution ratio
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 143
Table 5.5 Extraction of palladium(II) with various diluents
Palladium(II) = 200 µg pH = 1.5
Aq:Org ratio = 2.5: 1 Sodium salicylate = 0.085 M
Extractant = 0.07 M n-octylaniline Strippant = 5 M ammonia (3×10 mL)
Solvent Dielectric constant, ε
Amount of Pd(II) extracted, %
Distribution ratio, D
Xylene* 2.30
100
∞
Toluene
2.38
100
∞
Benzene
2.27
100 ∞
Chloroform
4.80
25.1 0.83
Amyl Acetate 4.80 28.3 0.98
Methyl iso butyl ketone (MIBK)
13.10
91.9
28.36
1,2-Dichloro ethane
10.50 51.9 2.69
Amyl alcohol 13.9 100 ∞
n-Butyl alcohol
17.80
100
∞
Kerosene - 46.4 2.16
Carbon tetrachloride
2.24 61.0 3.91
*Recommended for general extraction procedure
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur
144
Table 5.6 Choice of electrolyte solution for the stripping of
palladium(II) from the organic extract
Palladium(II) = 200 µg pH = 1.5
Sodium salicylate = 0.085 M Extractant = 0.07 M n-octylaniline in
Aq:Org ratio = 2.5: 1 xylene Strippant M / pH % E
Ammonia* 1-10 100.0
HCl 1-5 48.1
H2SO4 1-5 5.5
HNO3b 1-5 No stripping
Acetic acid 1-5 20.1
Water - 4.7
NaOH 0.1-0.2 13.7
KOH 0.1-0.2 18.7
Acetate buffer pH-4.7 39.3
Ammonia buffer pH-10 100.0
*Recommended for general extraction procedure, b organic extract decomposes in presence of HNO3.
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 145
Table 5.7 Extraction behavior of palladium(II) as a function of
equilibrium time
Palladium(II) = 200 µg pH = 1.5
Aq:Org ratio = 2.5: 1 Sodium salicylate=0.085 M
Extractant = 0.07 M n-Octylaniline in xylene
Strippant = 5 M ammonia (3×10 mL)
Time in min
% E D
1 65.9
4.83
2 93.9
38.48
3 100
∞
4 100
∞
5*
100
∞
6 100
∞
7 100
∞
8 100
∞
9 100
∞
10 100
∞
15 100
∞
20 100
∞
25 63 4.25
30 34.3 1.30
* Recommended for general extraction procedure % E = Percentage extraction of Pd(II) D = Distribution Ratio.
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur
146
Table 5.8 Loading capacity of n-octylaniline
pH = 1.5 Sodium salicylate = 0.085 M
Aq:Org ratio = 2.5: 1 Extractant = 0.07 M n-Octylaniline in xylene
Strippant = 5 M ammonia
(3×10 mL)
Metal concentration, μg
Percentage extraction, % E
Distribution ratio, D
100 100 ∞
200* 100 ∞
400 100 ∞
800 100 ∞
1000 100 ∞
1500 100 ∞
2000 93.3 34.81
2500 77 8.36
3000 63 4.25
4000 48 2.30
5000 32 1.17
*Recommended for general extraction procedure
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 147
Table 5.9 Extraction of palladium(II) as a function of aqueous to
organic volume ratio
Palladium(II) = 200 µg pH = 1.5
Sodium salicylate = 0.085 M Strippant = 5 M ammonia (3×10 mL)
Extractant = 0.07 M n-octylaniline
* Recommended for general extraction procedure
Aqueous to organic volume ratio
Percentage extraction,
( % E )
Distribution ratio, ( D )
10:10 100 ∞
20:10 100 ∞
25:10* 100 ∞
30:10 100 ∞
35:10 100 ∞
40:10 100 ∞
50:10 100 ∞
70:10 94.7 44.66
100:10 50.4 2.46
150:10 45.8 2.11
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur
148
Table 5.10 Effect of temperature and thermodynamic functions related
to palladium(II) extraction system
Palladium(II)= 200µg Sodium salicylate = 0.085 M
Aq:Org ratio = 2.5: 1 Extractant = 0.07 M n-Octylaniline in
Strippant = 5 M ammonia xylene
(3×10 mL) Temperature
(K)
Log Kex -∆ G
(KJ/mol)
∆ S
(J/ K/mol)
∆ H
(KJ/mol)
302
2.20
-12.75
275.58
305
2.22
-13.00
278.11
308
2.33
-13.74
291.2
65.23
311
2.43
-14.48
303.82
314
2.54
-15.31
318.33
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 149
Table 5.11 Effect of foreign ions on the extraction palladium(II)
Palladium(II) = 200 µg pH = 1.5
Sodium salicylate = 0.085 M Aq:Org ratio = 2.5: 1
Extractant = 0.07 M n-octylaniline in xylene
Strippant = 5 M ammonia (3×10 mL)
Ratio of ions
Palladium: ion Mass tolerated /
mg Foreign ion
2:500 50 Iodide
2:250 25 Citrate, malonate, Zn(II)
2:150 15
Ni(II),Te(IV),Tl(III),Mo(VI), Se(IV), Ba (II), Ce (IV)
2:100 10 Mg(II), Cd(II), Sb(III),V(V), Pb(II), Sn(II), Bi(III), fluoride
2:50 5 Cu(II), Co(II), Fe(III)
2:20 2 Fe(II), Hg(II), Cr(VI)
2:6 0.6 Ag(I), Pt(IV), Rh(III)
2:5 0.5 Au(III)
2:4 0.4 Ru(III)a a Masked by 25mg citrate.
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur
150
Table 5.12 Separation of palladium(II) from associated metal ions
Palladium(II) = 200 µg pH = 1.5
Sodium salicylate = 0.085 M Aq:Org ratio = 2.5: 1
Extractant = 0.07 M n-octylaniline in xylene
Strippant = 5 M ammonia (3×10 mL)
Metal ions Mass taken,µg
R* %
Chromogenic ligand
Ref. No.
Pd(II)
Ru(III)a
200
400
99.6
99.5
4’ChloroPTPT
[109]
Pd(II)
Ir(III)
200
100
99.7
99.6
SnCl2 - HBr
[110]
Pd(II)
Pt(IV)
200
300
99.7
99.6
SnCl2
[110]
Pd(II)
Rh(III)
200
200
99.8
99.5
KI + SnCl2
[110]
Pd(II)
Fe(III)
200
1000
99.7
99.6
Thiocynate
[110]
Pd(II)
Au(III)
200
150
99.8
99.6
SnCl2
[110]
Pd(II)
Cu(II)
200
2000
99.8
99.6
4’ChloroPTPT
[111]
Pd(II)
Co(II)
200
1000
99.7
99.6
Thiocynate
[112]
Pd(II)
Ni(II)
200
5000
99.8
99.6
DMG
[112]
Pd(II)
Se(IV)
200
300
99.8
99.7
4’-BromoPTPT
[113]
Pd(II)
Te(IV)
200
200
99.7
98.4
4’-BromoPTPT
[114]
a Masked by 25 mg citrate, * Average recovery Pd(II).
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 151
Table 5.13 Sequential separation of palladium(II), rhodium(III) and
ruthenium(III) form their mixture
Metal ion
Amou-nt
taken, µg
Aqueous phase (25 mL)
Stripping agent
Determination method
Recovery percentage*
Pd(II)a 200 pH =1.5, 0.085 M salicylate, 0.07 M n-octylaniline in amyl alcohol
5 M(3×10mL)
4’-ChloroPTPT [109]
99.7
Rh(III)a 200 pH =9.0, 0.03 M malonate, 0.1M n-octylaniline in xylene
1 M HCl (2×10 mL)
SnCl2 +KI [110]
99.6
Ru(III) 200 0.05 M malonate, pH =3.5, 0.1M n-octylaniline in xylene
2 % NaCl + 1 M (4:1)
4’-ChloroPTPT [109]
99.6
*= Average of Six determination
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur
152
Table 5.14 Determination of palladium(II) in synthetic mixtures
Palladium(II) = 200 µg pH = 1.5
Sodium salicylate = 0.085 M Aq:Org ratio = 2.5: 1
Extractant = 0.07 M n-octylaniline Strippant = 5 M ammonia
in xylene (3×10 mL)
Synthetic mixture
Ions
Metal mass/µg
Palladium(II) found, (µg) R (%) R.S.D.
(%)
Pd(II)
Ru(III)a
Pt(IV)
200
100
100
199.2 99.6 0.4
Pd(II)
Ir(III)
Pt(IV)
200
100
100
199.4 99.7 0.3
Pd(II)
Ir(III)
Ru(III)a
200
100
100
199.2 99.6 0.4
Pd(II)
Pt(IV)
Te(IV)
200
200
200
199.4 99.6 0.4
Pd(II)
Pt(IV)
Se(IV)
200
200
200
199.5 99.8 0.2
aMasked by 25mg citrate, R (% ) = Extraction recovery of Pd(II).
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 153
Table 5.15 Determination of palladium(II) from synthetic mixture
corresponding to alloys
Palladium(II) = 200 µg pH = 1.5
Sodium salicylate = 0.085 M Aq:Org ratio = 2.5: 1
Extractant = 0.07 mol/L n-octylaniline in xylene
Strippant = 5 M ammonia (3×10 mL)
Alloys Metal mass, (µg)
Palladium(II) mass found,
(µg) R (%) R.S.D.
%
Oakay alloy Pd10.5,Pt20, Ni60,V9.5. Pd18.2,Pt18,Ni54,V9.1
105 104.5 99.5 0.5
Jewellery alloy Pd95.5,Rua 4.5
105 104.5 99.5 0.5
Pd-Cu alloy 190 189.6 99.7 0.3
Pd60,Cu40 120 119.6 99.6 0.4
Pd75,Sb25 150 149.7 99.8 0.3
a masked by 25mg citrate. R (%) extraction recovery of Pd(II).
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur
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Table 5.16 Determination of palladium(II) in catalysts
Catalyst Palladium(II)
mass found /µg
R (%)
R.S.D.
(%)
PdCl2 on Carbon 239.2 99.2 0.8
PdCl2 on Carbon (5%) 239.5 99.3 0.7
PdCl2 on Carbon (10%) 239.2 99.2 0.2
PdCl2 on CaCO3 239.5 99.3 0.7
PdCl2 on BaSO4 239.7 99.4 0.6
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 155
Flow Sheet 5.1
Sequential separation of palladium(II) , rhodium(III) and ruthenium(III) form their mixture.
Pd(II)+Rh(III)+Ru(III) (200 µg in each)
Adjust the acidity to 0.085 M sodium salicylate in total volume of 25 mL and pH 1.5, extract with 0.07 M n-octylaniline in amyl alcohol for 5min.
Aqueous phase Organic phase Pd(II) Rh(III)+Ru(III) backstripped with 5 M adjust the acidity 0.03 M ammonia (3 × 1 mL) sodium malonate in total volume of 25 mL and pH 9.0, extract with 0.1 M n-octylaniline in xylene for 3 min Aqueous phase estimated by
4’-ChloroPTPT [109] (R=99.7 %)
Aqueous phase Organic phase Ru(III) Rh(III) backstripped Adjust the acidity 0.05 M with 1M (2 × 10 mL) sodium malonate in total volume of 25 mL and pH 3.5, extract with 0.1M n-octylaniline Aqueous phase in xylene for 5 min. Rh(III) estimated by KI+SnCl2 [110] (R=99.6%) Aqueous phase Organic phase Rejected Ru(III) backstripped with 2% NaCl+1M HCl (4:1) Aqueous phase Ru(III) estimated by
4’-ChloroPTPT [109] (R = 99.6 %)
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur
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0
10
20
30
40
50
60
70
80
90
100
0 1 2 3 4 5 6 7 8 9 10
pH
Perc
enta
ge e
xrac
tion
(% E
)
Fig. 5.1 Plot of pH versus percentage extraction of palladium(II)
(200 μg/mL) from salicylate medium (0.085 M) by using
n-octylaniline (0.07 M) as an extractant in xylene with 5 min
shaking time.
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 157
0
10
20
30
40
50
60
70
80
90
100
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 0.22 0.24 0.26
n-octylaniline (M)
Perc
enta
ge e
xtra
ctio
n (%
E)
Fig. 5.2 Extraction of palladium(II) (200 µg/mL) at pH 1.5 from
0.085 M sodium salicylate as a function of n-octylaniline
concentration.
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur
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0
10
20
30
40
50
60
70
80
90
100
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Time in min.
Perc
enta
ge e
xtra
ctio
n (%
E)
Fig. 5.3 Extraction of palladium(II) (200 µg/mL) at pH 1.5 from
0.085 M sodium salicylate as a function of equilibration
period.
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 159
▲Slope at pH 4 = 0.89■ Slope at pH 7= 0.82
-0.17
-0.07
0.03
0.13
0.23
0.33
0.43
0.53
0.63
0.73
-2.1 -1.9 -1.7 -1.5 -1.3 -1.1 -0.9
Log C [n-octyaniline]
Log
D[P
d(II
)]
Fig 5.4 log D[Pd(II)] against log C[n-octylaniline] at fixed sodium salicylate
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur
160
▲ Slope at pH 4 = 2.8
■ Solpe at pH 7 = 2.7
-0.45
-0.25
-0.05
0.15
0.35
0.55
0.75
-1.8 -1.7 -1.6 -1.5 -1.4 -1.3
Log C [salicylate]
Log
D[P
d(II
)]
Fig 5.5 log D[Pd(II)] against log C[Salicylate] at fixed n-octylaniline
concentration
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur 161
Slope = -3.407
2
2.1
2.2
2.3
2.4
2.5
2.6
3.17 3.19 3.21 3.23 3.25 3.27 3.29
1000/K
Log
Kex
Fig 5.6 Effect of temperature on palladium(II) extraction
Chapter 5 – Selective liquid‐liquid extraction of palladium(II) from salicylate media by n‐octylaniline in xylene
Analytical Chemistry Laboratory, Dept. of Chemistry, Shivaji University, Kolhapur
162
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