Analysis Methods of Chloride Ions With Industrial Applications
Analysis Methods of Chloride Ions With Industrial Applications
Analysis Methods of Chloride Ions With Industrial Applications
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Tomul LX (LXIV)
Fasc. 2
Editorial Board
President: Prof. dr. eng. Ion Giurma, Member of the Academy of Agricultural
Sciences and Forest, Rector of the “Gheorghe Asachi” Technical University of Iaşi
Editor-in-Chief: Prof. dr. eng. Carmen Teodosiu, Vice-Rector of the
“Gheorghe Asachi” Technical University of Iaşi
Honorary Editors of the Bulletin: Prof. dr. eng. Alfred Braier,
Prof. dr. eng. Hugo Rosman,
Prof. dr. eng. Mihail Voicu, Corresponding Member of the Romanian Academy
SUMAR
Pag.
ADRIANA MARINOIU, CONSTANTIN TEODORESCU, DANIELA
MARINESCU, MIHAI VARLAM, CLAUDIA COBZARU,
AMALIA SOARE şi CRISTINA IONESCU, Grafene pentru pile de
combustie (engl., rez. rom.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
ETELKA DAVID şi IOAN MĂMĂLIGĂ, Materiale pe bază de carbon
nanostructurate pentru adsorbŃia compuşilor organici volatili (engl.,
rez. rom.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
LOREDANA FLUERARU, GABRIELA RĂUL, MĂDĂLINA TĂTARU şi
LAURA BULGARIU, Metode de analiză a ionilor clorură cu aplicaŃii
industriale (engl., rez. rom.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
CORINA CERNĂTESCU, CLAUDIA COBZARU, ROXANA CANTA şi
ADRIANA MARINOIU, Sinteza a patru noi hidroxiazometine (engl.,
rez. rom.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
SUSANA SOLANO ARANA şi GABRIELA CIOBANU, Sinteza şi
caracterizarea zeolitului H-ZSM-5 (engl., rez. rom.) . . . . . . . . . . . . . . . 67
IRINA DĂBULEANU, MIHAELA GABRIELA DUMITRU şi AURORA
REISS, ObŃinerea unui biofertilizant pe bază de acizi humici şi
galactomanani extraşi din seminŃele de Gleditsia triacanthos folosit în
fertilizarea extraradiculară a plantelor (engl., rez. rom.) . . . . . . . . . . . . . 75
BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI
BULLETIN OF THE POLYTECHNIC INSTITUTE OF IAŞI
Tomul LX (LXIV), Fasc. 2 2014
CONTENTS Pp.
∗
Corresponding author; e-mail: lbulg@ch.tuiasi.ro
46 Loredana Flueraru et al.
1. Introduction
2. Experimental
2.1. Materials
All reagents were analytical reagents degree and were used without
further purifications. Sodium chloride (purchased from Fluka) was used as
chloride ions source. The stock solution of 0.1 mol·L-1 sodium chloride was
prepared by salt dissolving in doubly distilled water and dilution to 500 mL.
Working solutions of chloride ions were prepared by dilution of a given volume of
stock solution with doubly distilled water. The silver nitrate solution (0.1 mol·L-1)
was obtained by AgNO3 salt (from Reactivul Bucharest) dissolving in doubly
distilled water, following by solution standardization (Bejan et al., 2006).
2.2. Methods
Table 1
Several Characteristics of Tap Water and Wastewater
Samples Used for Recovery Test
Parameter Tap Water Wastewater
Suspension, [mg·L-1] Clear solution 1715.52
pH 6.57 4.32
Chloride, [mg·L-1] 62.53 3748
Fe total, [mg·L-1] 3.23 2204
Zn, [mg·L-1] 1.02 2.43
Pb, [mg·L-1] − 3.11
All the methods considered for chloride analysis in this study are based
on the well known reaction between chloride ions and AgNO3, when a white
precipitate of AgCl is formed, according with the following equation:
The obtained precipitate has a low solubility in water (Ps = 1.7 10-10)
(Dean, 1995) and acid media, and it is soluble only in concentrated ammonia
solution (Bejan et al., 2006). These characteristics makes that the methods
based on this reaction to have a good sensibility and accuracy. In addition,
because only halide and sulfide ions precipitate in presence of AgNO3, such
methods have a good selectivity in quantitative analysis of chloride ions. All
these advantages have been checked in case of examined methods (Mohr
Bul. Inst. Polit. Iaşi, t. LX (LXIV), f. 2, 2014 49
Table 2
Analytical Characteristics of Mohr Method
Analytical Parameter Determined Value
Studied concentration range 177.5 – 35500 [mg Cl-·L-1]
Limit of detection (3σ) 13.62 [mg Cl-·L-1]
Limit of quantification (10σ) 45.40 [mg Cl-·L-1]
Variation coefficient 0.34
Precision (RDS %) 3.15
1.1
Electrical conductibility, [mS]
0.9
(2)
0.8
0.7
0.6 (1)
0.5
0.4
ve
0 2 4 6 8
volume of AgNO3, [mL]
Table 3
Analytical Characteristics of Conductometric Titration Method
Analytical Parameter Determined Value
Studied concentration range 177.5 – 35500 [mg Cl-·L-1]
Limit of detection (3σ) 37.19 [mg Cl-·L-1]
Limit of quantification (10σ) 123.96 [mg Cl-·L-1]
Variation coefficient 0.47
Precision (RDS %) 2.93
Bul. Inst. Polit. Iaşi, t. LX (LXIV), f. 2, 2014 51
Table 4
Analytical Characteristics of Turbidimetric Method
Analytical Parameter Determined Value
Linear dynamic range 2.0 – 10.0 [mg Cl-·L-1]
Limit of detection (3σ) 0.38 [mg Cl-·L-1]
Limit of quantification (10σ) 1.26 [mg Cl-·L-1]
Variation coefficient 0.33
Precision (RDS %) 1.02
analysis of clear samples (because the presence of solid particles reduces the
accuracy of experimental measurements) with low chloride contents (trace
concentrations).
The effect of various foreign ions that can interfere in chloride ions
determination has been quantified, for each examined method, by the selectivity
coefficients. The selectivity coefficients (aCl,j) were calculated as the ratio
between chloride concentration and interfering ions concentration which gives a
5% property change (equivalence volume or turbidity) in a reference solution
that contains 5 mg Cl-·L-1 in case of turbidimetric method and 50 mg Cl-·L-1 in
case of Mohr method and conductometric titration. The interferences cased by
various foreign ions (Table 5) were noted with “+” – which means that
interfere, if the selectivity coefficient are equal or higher than 1, and with “-” –
which means that do not interfere, if the values of selectivity coefficients are
lower than unit.
Table 5
Effect of Various Foreign Ions in Chloride Ions
Determination by Considered Methods
Foreign Mohr Conductometric Turbidimetric
Ion Method Titration Method
K+ − − −
Ca2+ +* − −
Mg2+ − − −
SO42- − − −
HCO3- − − −
CO32- − − −
Ba2+ + − −
Pb2+ + − −
Fe3+ +* − −
Zn2+ +* − −
Cd2+ − − −
*concentration higher than 250 mg·L-1.
It can be observed from Table 5 that K+, Mg2+, HCO3-, CO32-, SO42- ions
that are fairly abundant in most industrial aqueous samples do not interfere in
the chloride determination, in none of the studied methods. Also, the presence
of some heavy metals, such as: Ca2+, Ba2+, Pb2+, Fe3+ or Zn2+, do not interfere in
the chloride analysis by conductometric titration and turbidimetric method, but
have serious interferences in case of Mohr method, in special at higher
concentrations. This means that the Mohr method cannot be used for analysis of
Bul. Inst. Polit. Iaşi, t. LX (LXIV), f. 2, 2014 53
industrial samples that contains beside chloride ions and important quantities of
such metal ions. In such conditions it is recommended that the determination of
chloride ions to be done by conductometric titration (if the chloride ions
concentration in analyzed samples is higher) or by turbidimetric method (if the
samples contains trace of chloride ions).
Table 6
The Recovery Test
Tap Water Wastewater
Analysis CL-ADD
- -
Method [Mg·L-1] Cl found Recovery Cl found Recovery
[mg·L-1] [%] [mg·L-1] [%]
177.5 237.12 98.36 − −
Mohr 355.0 418.53 100.28 − −
method 532.5 596.12 100.20 − −
177.5 239.02 99.43 3925.51 100.03
Conductometric 355.0 419.34 100.51 4104.98 100.55
titration 532.5 595.92 100.16 4279.92 99.89
177.5 236.43 97.97 3922.47 98.29
Turbidimetric 355.0 415.85 99.53 4103.86 100.24
method 532.5 592.54 99.24 4279.32 99.78
The results presented in Table 6 shows that in case of tap water, a good
recovery of chloride ions was obtained for all considered methods, indicating
that the constituents of tap water sample do not interfere significantly, and each
method can be successfully used for chloride ions analysis. In case of
wastewater, where can be present important quantities of other metal ions, a
good recovery of chloride ions was obtained only in case of conductometric
54 Loredana Flueraru et al.
titration and turbidimetric method (Table 6). For chloride ions analysis in such
samples the Mohr method is inadequate due to the presence some heavy metals
(such Pb2+, Fe3+, in this case) that will precipitate with the indicator (K2CrO4),
making it impossible the visualization of equivalence point. It should also noted
that the less accurate recovery of chloride ions by turbidimetric method, both
from tap water and wastewater samples, is mainly determined by multiple
dilutions required for to obtain a chloride ions concentration that lies the linear
dynamic range. Even this method has excellent analytical characteristics and
high selectivity, it is recommended to be used for chloride ions analysis in
samples where its concentration is low (trace concentrations).
4. Conclusions
REFERENCES
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(Rezumat)
Standardul românesc recomandă ca analiza ionilor clorură din diferite probe industriale
să se facă utilizând metoda Mohr. Din păcate, metoda Mohr nu poate fi utilizată
întotdeauna. În acest studiu am examinat comparativ trei metode diferite care pot fi
utilizate pentru determinare ionilor clorură din probe apoase industriale, pentru a stabili
limitele de aplicabilitate pentru fiecare caz. Aceste trei metode, şi anume: metoda Mohr,
titrarea conductometrică şi metoda turbidimetrică, au la bază reacŃia dintre ionii clorură
şi o soluŃie standardizată de AgNO3. Parametrii analitici (cum sunt: domeniul de
concentraŃie utilizabil, limita de detecŃie, precizia, etc.) au fost calculaŃi din rezultatele
experimentale. InterferenŃele cauzate de unii ioni comuni şi ioni ai metalelor grele, care
pot fi prezenŃi în probele industriale, au fost identificate. Rezultatele experimentale arată
că aceste trei metode se completează una pe cealaltă şi permit analiza ionilor clorură
dintr-o gamă mult mai variată de probe.