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Ar

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J. Braz. Chem. Soc., Vol. 20, No. 3, 460-465, 2009.Printed in Brazil - 2009 Sociedade Brasileira de Qumica0103 - 5053 $6.00+0.00

*e-mail: s.m.ghoreishi@kashanu.ac.ir

Interaction of Anionic Azo Dye and TTAB - Cationic Surfactant

Sayed Mehdi Ghoreishi,* Mohsen Behpour and Mehdi Shabani-Nooshabadi

Department of Chemistry, Faculty of Science, University of Kashan, Kashan, I.R. Iran

A interao entre trs corantes aninicos azo: C.I. Vermelho cido 14 (AR14), C.I.Vermelho cido 1 (AR1), C.I. Laranja cido 7 (AO7) e um suractante catinico, o brometo detetradeciltrimetilamnio (TTAB), oi investigada por meio da tcnica de eletrodo seletivo parasuractante. O eletrodo seletivo para TTAB oi construdo e usado para determinar a concentraode monmeros TTAB e, tambm, de ons suractantes ligados aos corantes por medidas de oraeletromotriz. A constante de ormao do complexo corante-suractante, K

1, e a variao da energia

livre de Gibbs, G10, oram obtidas a partir dos dados experimentais. Os resultados indicaram

que no sistema TTAB/AO7, no qual o corante AO7, mais hidrobico, usado, as interaescorante-suractante so mais ortes do que em outros sistemas. Os resultados tambm indicaramque ambas interaes, hidrobica e atrao eletrosttica, so muito importantes para a ormaodo complexo entre os corantes e o suractante. A capacidade mxima de ligao dos corantes decargas opostas e tambm o grau de ligao do suractante aos corantes oram calculados a partirdos dados experimentais.

Interaction between three anionic azo dyes, C.I. Acid Red 14 (AR14), C.I. Acid Red 1 (AR1),C.I. Acid Orange 7 (AO7) and a cationic suractant tetradecyltrimethylammonium bromide (TTAB)has been investigated using suractant selective electrode technique. The TTAB selective electrodewas constructed and used to determine the concentration o TTAB monomers and also suractantions bounded to dyes by electromotive orce data. The dye-suractant complex ormation constant,K

1, and the standard ree energy change, G1

0, could be obtained rom the experimental data. Theresults indicate that in the TTAB/AO7 system, where the more hydrophobic dye AO7 is used, thedye-suractant interactions are stronger than in other systems. The results also indicate that both

the electrostatic attractive and the hydrophobic interactions are very important or the ormation othe complex between the oppositely-charged dyes and the suractant. Maximum binding capacitieso the dyes and also the degree o binding o the suractant to the dyes were calculated rom theexperimental data.

Keywords:ion selective electrode, anionic azo dye, dye-suractant interactions, TTAB, AcidRed 14, Acid Red 1, Acid Orange 7

Introduction

The use o water as a medium or textile processingideally requires that liquid wets the ber suraces quicklyand uniormly, and here suractants play a useul role.In addition, suractants are required or detergency,achievement o level dyeing, and so on. The choice o aparticular suractant or a particular purpose depends onits ability or interaction to bers and/or other componentsin the system. Suractants contain both hydrophobic andhydrophilic moieties and are adsorbed at interaces betweenphases, lowering their interacial tension.1

Suractants are extensively used in our daily lie andalso in various industrial processes such as textiles, pulp and

paper, paints, oil, metallurgy etc. Textile efuents containmany chemical substances arising rom desizing, dyeing,printing and nishing processes. Suractants that are usedas levelling, dispersing and wetting agents in the dyeingprocess, act mostly in two ways. They can orm a complexwith ionic dyes or they can be adsorbed with nonionic dyesonto the ber.2 Although the interaction between dyes andsuractants has been studied in many papers, the studies inthis area are still important and interesting or improving thedyeing process rom theoretical, technological, ecologicaland economical points o view. The investigations intothe behavior o dierent dyes in aqueous suractant

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Ghoreishi et al. 461Vol. 20, No. 3, 2009

solutions can give useul inormation or understanding thethermodynamics and kinetics o the dyeing process and thenishing o textile materials.3

Various parameters, the charge and the alkyl chainlength o the suractants and the type and the position o

the substituents in the aromatic ring o the dye molecules,can aect the interactions between suractant and dyemolecules. It was ound that structure o dye and suractantare important or their mutual interaction as well as dye-berand suractant-ber interaction. Literature survey indicates,beside the electrostatic interaction, the hydrophobicinteraction is also very important or the binding betweenthe oppositely charged dyes and suractants.4

Various techniques such as spectrophotometry,5-8membrane selective electrode, 9 polarography, 10potentiometry11 and conductometry12-14 have been appliedor studying o dye-suractant interactions. Considerablestudies have conrmed that suractants can aect thespectra o the solutions o many dyes,15-17 due to aggregationo the dye molecules or dye-suractant ion pairs andcharge transer between dye and suractant molecules.18The spectral changes o a dye observed in the presence ovarying amount o suractants are consistent with sequentialequilibrium involving suractant monomers, micelles, dyeaggregates, premicellar dye-suractant complex and dyeincorporated into the micelle.19,20

This paper presents a potentiometric study o theinteractions between three anionic azo dyes, i.e., C.I.

Acid Red 14 (AR14), C.I. Acid Red 1 (AR1) andC.I. Acid Orange 7 (AO7), and a cationic suractanttetradecyltrimethylammonium bromide (TTAB) insubmicellar concentration ranges. The study o suchsystems can give more inormation about the infuence ohydrophobic and electrostatic eects on the ormation othe dye-suractant complex in aqueous solution at suractantconcentrations below critical micelle concentration (CMC).The suractant selective electrode is sensitive to reesuractant ions (the monomer suractants), thereore theexperimental results allow the direct determination o the

concentration o the monomer suractants (m1) as well as theconcentration o suractant ions bound in the dye-suractantcomplex. The dye-suractant constant, K

1, and the standard

ree energy change, G10, could be also obtained.

Experimental

Materials

The anionic azo dyes C.I. Acid Red 1 (AR1), C.I.Acid Red 14 (AR14), C.I. Acid Orange 7 (AO7) and thecationic suractant tetradecyltrimethylammonium bromide

(TTAB), were purchased rom Aldrich and used withouturther purication.

All solutions were prepared in doubly distilled water.Chemical structures o dyes and suractant are shown inFigure 1.

Potentiometric method

The potentiometric titration was used as an experimentalmethod. The use o the TTA-selective electrode, which was

included the TTA cation-VC containing SO3H (0.1%) anioncomplex incorporated in an Elvaloy 742 gel membrane,21enabled us to determine the concentration o ree TTAsuractant cations in solution. Potentiometric measurementswere carried out in the ollowing electrode cell:

Ag | AgBr | reerence solution: 1 10-5 mol L-1 TTAB +1 10-4 mol L-1 NaBr | polymer membrane | test solution |reerence electrode (SCE)

The relationship between the EMF (E) o the cell andthe TTAB total concentration (C

1) was measured in the

concentration range 110-5 to 110-2 mol L-1 at 25 C. The

calibration curves represent plots o E versus C1 o TTABwithout the addition o the dyes. The binding curves wereobtained when measurements o E versus C1 o TTAB werecarried out in the presence o constant concentration o the dyes(110-3, 510-4 and 110-4 mol L-1). All solutions contained110-4 mol L-1 NaBr. The temperature used was 25 C.

Results and Discussion

Interactions between the dyes and the suractant werestudied or the systems, TTAB/AR14, TTAB/AR1 andTTAB/AO7.

Figure 1. Structures o the dyes and suractants.

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Interaction o Anionic Azo Dye and TTAB - Cationic Suractant J. Braz. Chem. Soc.462

Figure 2 shows plots o measured E versus C1

inaqueous solution when the dierent concentrations o thedye, AR14, (C

d) are added to the solution. It is maniested

rom the gure that the calibration curve is linear over theconcentration range rom 110-5 to 510-3 mol L-1 TTAB

with a good slope, which indicates excellent agreement withthe Nernstian response. In the presence o the dye, AR14,in the test solution, deviation rom the linear response isconsiderable over the whole measured concentration range.This act indicated that the ormation o the dye-suractantcomplex takes place.

These curves also indicate that binding occurs evenat very low TTAB concentrations and that the processcontinues until the dye display no interaction with themonomer o suractant. This point is reached when theEMF values or the solutions with and without dyes mergein the micellar range. This is a result that Wyn-Jones andco-workers22 have obtained previously in connectionwith the binding o sodium dodecylsulate (SDS) to thedendrimers and the cyclodextrins. When the EMF o the

TTAB electrode merge, it shows that the dye is no longerinvolved in any urther binding with TTAB or alternativelythe dye can not interact with bound TTAB. The TTABconcentration corresponding to the merger is denoted T

2.

The same results obtained or TTAB/AR1 and TTAB/AO7 systems. Figure 3 or example shows plots o EMFversus C

1or TTAB/dye (510-4 mol L-1) systems in

110-4 mol L-1 NaBr.Maximum binding capacity o the dyes is also obtained

rom the data. The values o T2-m

1, where m

1is the

concentration o the TTAB monomers at T2, are listed in

Table 1.These values represent the maximum amount o TTAB

that can bind to one dye molecule. At TTAB concentrationsapproaching the end o binding (T

2) the complex involve

one dye containing 0.2-3.8 bound monomers o TTABdepending on the size and type o dyes.

At any C1

(the total concentration o suractant), theconcentration o ree suractant, m

1, was determined

rom the calibration curve at the same EMF value.A typical m

1 versus C

1plot is shown in Figure 4 or

TTAB/dye (110-3 mol L-1) systems. Figure 4 clearlyshows that in the presence o the dye the concentrationo ree suractant, m

1, is negligible (nearly zero) at low

suractant concentration and so, these results conrmthat the ormation o the dye-suractant complex takes

place even at very low suractant concentration. A slightincrease in m1

with increasing C1

is exactly the behaviorexpected when suractant exclusively bind to the dye anda sudden increase in m

1with increasing C

1shows that

Figure 2. Plot o the EMF o the TTAB electrode as a unction o thetotal TTAB concentration or the TTAB/AR14 system in the presence odierent concentrations o dye: () 0 mol L-1 (calibration curve); ()

110-3 mol L-1; () 510-4 mol L-1; () 110-4 mol L-1.

Figure 3. Plot o the EMF o the TTAB electrode as a unction o thetotal TTAB concentration or TTAB/dye (510-4 mol L-1) systems in110-4 mol L-1 NaBr: () pure TTAB; () TTAB + AR14; () TTAB +AR1; () TTAB + AO7.

Table 1. Binding parameters or the TTAB/dye (5 10 -4 mol L-1) systems in 110-4 mol L-1 NaBr

Dye T2/(mmol L-1) m

1at T

2/(mmol L-1) T

2 m

1/(mmol L-1) [TTAB]/[Dye] at T

2/(mmol L-1)

AO7 4.34 2.46 1.88 3.76

AR14 2.61 2.01 0.6 1.2

AR1 1.31 1.21 0.1 0.2

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Ghoreishi et al. 463Vol. 20, No. 3, 2009

there is no interaction between the dye and the monomero suractant. When m

1decreases or remains almost

constant with increasing C1, it represents the ormation

o ree micelles in solution.

The experimental data also permit the calculation othe degree o binding o suractant to dyes, , dened asthe concentration o bound suractant divided by the dye

concentration ( ) (commonly known as

a binding ratio). Figure 5 shows the binding isotherms o

TTAB/dye (110-3 mol L-1) systems, where is plottedversus m

1.

It can be seen rom Figure 5 that the degree o TTA cationbinding to AO7 anions is much higher than o TTA cationsto AR14 and AR1 anions. The binding ratio o TTAB/dyesystems is small at low suractant concentrations.

The dye-suractant complex ormation constant, K1, is

calculated according to the method proposed by Simoncicand Kert23 were applied.

I the values o/m1 are plotted against m1, the value K1 isobtained by the extrapolation to zero ree TTAB concentration.In Figure 6 the determination o complex ormation constantsor some typical studied systems are shown. The values o K

1

or TTAB/dye systems are collected in Table 2.Furthermore, rom the values o K

1, the standard ree

energy change or complex ormation is calculated, asollows:24

G10 = RT lnK

1

These results are also reported in Table 2. It is evidentthat the value o K

1slightly increases by increasing the

dye concentration.The results show that the strength o dye-suractant

interaction and the stability o complex ormed increasewith the increasing in K

1value and consequently with

the decrease in G1

0 value. Strength o interaction alsoincreases with the increase in hydrophobicity o the dye.

Similar results were reported by Tunc and Duman25

andAkbas and Kartal.26 They studied the interaction betweenanionic dyes and cationic suractants using a conductometrictechnique. The calculated K

1andG1

0 values in the presentpaper are comparable with their results.

The lowest o the G1

0 values and also the largest otheK

1values or TTAB/dye systems are in the case o

interactions between TTAB and AO7 whose hydrophobicgroups are larger than those o AR14 and AR1. These dataindicate that in the TTAB/AO7 system, the dye-suractantinteraction is stronger than that in the TTAB/AR14 andTTAB/AR1 systems.

Figure 4. Plot o the TTAB monomer concentration (m1) as a unction

o the total TTAB concentration (C1) or TTAB/dye (110-3 mol L-1)

systems in 110-4 mol L-1 NaBr: () TTAB + AR14; () TTAB + AR1;() TTAB + AO7.

Figure 5. Binding isotherm in the orm o a plot o C1-m

1, as a unction o

monomer TTAB concentration or TTAB/dye (110-3 mol L-1) systems in110-4 mol L-1 NaBr: () TTAB + AR14; () TTAB + AR1; () TTAB +AO7.

Figure 6. Plots o values o/m1versus m1 obtained or TTAB/dye(510-4 mol L-1) systems in 110-4 mol L-1 NaBr: () TTAB + AR14;() TTAB + AR1; () TTAB + AO7.

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Interaction o Anionic Azo Dye and TTAB - Cationic Suractant J. Braz. Chem. Soc.464

The values oG1

0, which is an indication o thetendency or the ormation o the dye-suractant complex,show that TTAB interacts with AO7 is more avorably andstronger than AR14 and at the same conditions. The resultsare also conrmed by data rom Figures 2-5.

In the studied systems (TTAB/dyes) in addition tocomplex ormation between dye and suractant, precipitateormation was also observed. The precipitation o dye withsuractant at special concentration o suractant takes placeand the precipitation range are also collected in Table 2.

According to these data, the necessary concentrationranges or the precipitation and dissolution are dierentin TTAB/dye systems. In the TTAB/AO7 system

the beginning o the precipitation depends on thedye concentration and with any increase in the dyeconcentration the precipitation takes place at highersuractant concentrations. The dissolution o ormedprecipitate occurs at higher suractant concentration atcomparison to the beginning place o the precipitation(and below the CMC, < 4 10-3 mol L-1).

Thereore whenever the dye concentration is small,the necessary suractant concentration range or theprecipitation and dissolution is lower. Namely, when the dyeconcentration increases, the precipitation and dissolution

take place at larger suractant concentration range.The TTAB/AR14 system is dierent rom the TTAB/AO7 system in some cases. First, the precipitation occursat higher suractant concentration. Secondly, the necessarysuractant concentration range or the ormation andstability o precipitate is much lower and the precipitateater ormed dissolves with addition o small amount osuractant. The precipitation and dissolution have not beenobserved at 110-4 mol L-1 o dye.

The TTAB/AR1 system diers rom the two previoussystems. The precipitation takes place at very low suractantconcentrations and the dissolution o precipitate has not

been observed even at suractant concentrations higherthan CMC.

Conclusions

Potentiometric measurements using suractant selectiveelectrode was used to investigate the interaction betweenthree anionic azo dyes and a cationic suractant. With thismethod the dye-suractant complex ormation constantcan be directly determined rom the electromotive orcemeasurements.

It was ound that TTAB binds to all o the threedyes, AO7, AR14 and AR1, at suractant concentrations

lower than 110-5 mol L-1. Our results also show that theinteraction between AO7 and TTAB is stronger than thatbetween other dyes and TTAB accompanied with thehighest value o K

1and the lowest value oG

10.

The results also indicate that both the electrostaticattraction and the hydrophobic interactions are veryimportant or the ormation o the complex between theoppositely-charged dyes and suractants.

Acknowledgment

The authors grateully acknowledge nancial supportrom Kashan University.

References

1. Datyner, A.; Surfactant Science Series, Marcel Dekker: New

York, 1983, vol. 2.

2. Majewska-Nowak, K.; Kowalska, I.; Kabsch-Korbutowicz, M.;

Desalination 2006, 198, 149.

3. Tehrani Bagha, A. R.; Bahrami, H.; Movassagh, B.; Arami, M.;

Menger, F. M.;Dyes Pigm.2007, 72, 331.

4. Simoncic, B.; Span, J.;Dyes Pigm. 1998, 36, 1.

Table 2. Complex ormation constant (K1), the standard ree energy change (G

10) and the precipitation range o TTAB/dye systems (N means no dissolution

was observed)

Dye Dye Conc. / (mol L-1) K1 10-5/ (L mol-1) G1

0/ (kJ mol-1) Precipitation range / (mmol L-1)

AO7 0.001 2.5 30.8 0.33-2.96

0.0005 1.75 29.9 0.25-2.61

0.0001 0.6 27.3 0.05-0.45

AR14 0.001 1.3 29.2 0.64-1.12

0.0005 1.1 28.8 0.45-0.54

0.0001 0.6 27.3 clear

AR1 0.001 0.4 26.3 0.05-N

0.0005 0.3 25.5 0.05-N

0.0001 0.125 23.4 0.05-N

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