THERMODYNAMIC STUDY OF A SYMMETRICAL DISAZO DIRECT DYE DERIVED FROM 4,4 -DIAMINO-BENZANILIDE ON MERCERIZED COTTON

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THERMODYAMIC STUDY OF A SYMMETRICAL DISAZO DIRECT DYE DERIVED FROM 4,4 -DIAMIO-BEZAILIDE O MERCERIZED COTTO SIMU Georgeta Maria, FUAR-TIMOFEI Simona, BALŞ Gianina Institute o Chemistry Timişoara,

In order to ind out the best sorption model o the considered dyes, a theoretical study was also perormed.

Better statistical results were obtained in the case o the Freundlich sorption model. KEY WORDS: Direct dyes, dyeing theory, adsorption isotherms, ernst model, Freundlich model, Langmuir model.

1 THERMODYAMIC STUDY OF A SYMMETRICAL DISAZO DIRECT DYE DERIVED FROM 4,4 -DIAMIO-BEZAILIDE O MERCERIZED COTTO SIMU Georgeta Maria, FUAR-TIMOFEI Simona, BALŞ Gianina Institute o Chemistry Timişoara, Romanian Academy, ROMAIA ABSTRACT: The sorption isotherms o a symmetrical disazo direct dye with symmetrical structure on a mercerized cotton were determined at 60 o, 86 o and 96 o C. In order to ind out the best sorption model o the considered dyes, a theoretical study was also perormed. The experimental data obtained rom the dyeing process was itted by non-linear and linear regression analysis to the classical Freundlich, Langmuir and ernst isotherms. Better statistical results were obtained in the case o the Freundlich sorption model. KEY WORDS: Direct dyes, dyeing theory, adsorption isotherms, ernst model, Freundlich model, Langmuir model. ITRODUCTIO The textile dyeing equilibrium o the direct dyes on cellulose ibres presents a great interest, but a general model which could oer complete explanations o the dye cellulose ibre sorption was not reported yet [-4]. The dye adsorption at equilibrium represents the maximum possible sorption rom the dyebath, under certain conditions. From the inal dye equilibrium concentrations, sorption isotherms are obtained, most o them corresponding to the Freundlich and Langmuir equations []. In the Freundlich model (equation ) the dye is considered as being contained in an internal phase o volume V o the ibre []. [ C] K [ C] s x = () F where: [C] represents the dye concentration in the ibre at equilibrium, in mol/kg dry ibre, and [C] s represents the dye concentration in solution at equilibrium, in mol/l; K F is the equilibrium constant, and x is a sub-unitary power. The ernst adsorption isotherms (equation 2) are considered as a limit case o Freundlich and Langmuir adsorption isotherms [5]. [ C] = K P [ C] s (2) The Langmuir isotherm (equation 3) has been obtained rom kinetics considerations [4]. The basic assumption is related to the idea that the dye adsorption takes place on independent ixed sites, in monomolecular layer and all the adsorption positions are equivalent energetically. = K [ ] [ ] L + (3) C S C s S where S is the saturation value in mols/kg ibre and K L is the equilibrium constant. Some authors reported that the Langmuir model oers a better interpretation o the direct dye cellulose sorption than the Freundlich one [2-3, 6-9]. In this present work, an experimental and theoretical study o the sorption o one disazo direct dye with symmetrical structure on a cellulosic substrate was perormed. The aim o this study was to establish the best sorption model o the considered dye. For this purpose, the equilibrium sorption data o the studied dye were itted by nonlinear regression analysis to the ernst, Freundlich and Langmuir sorption models. 2. THE STUDY General All the chemicals were purchased rom Merck Co, Aldrich Chemical Co and Reactivul Bucureşti. The dye used in this study was a disazo direct dye derived rom 4,4 -diaminobenzanilide. The coupling component was resorcinol. The dye was synthesized, puriied by several recrystallizations 92 Tome VII (year 2009), Fascicule 3, (ISS )

2 OF EGIEERIG. TOME VII (year 2009). Fascicule 3 (ISS ) rom distilled water and characterized by means o electronic spectra (VIS) and mass spectroscopy (MS-FAB) and its homogeneity was determined by thin layer chromatography (TLC). Electronic spectra were recorded on a Cecil CE 7200 spectrophotometer. Mass spectra were recorded on a ermag R 0-0 spectrometer, rom nitrobenzylalcool and glycerol as matrix. The TLC data were taken rom silica gel plates (Merck 60F-25) and i-propanol/methylethylketone/h 4 25%=4:3:3 (v:v:v) as eluting system. In the experimental study o the dye sorption on a cellulosic substrate, samples o mercerized cotton (00 %) were used. The samples were soaked in a bath with a liquor ratio o 20: at 80 o C or 60 minutes, rinsed with distilled water and air - dried. Procedures Synthesis o resorcinol 4, 4 -diaminobenzanilide resorcinol A suspension o.5 g 4,4'-diaminobenzanilide (0.05 mol), 70 ml water, 26 ml (0.27 mol) 35% HCl and 50 g ice was bis-diazotised by the direct method [0]..4 g (0. mol) o resorcinol were dissolved in a solution containing 0.5 g sodium acetate in 90 ml water. The solution was cooled to 5 o C and was added dropwise to the solution o bis-diazonium salt obtained above, in a 45 minutes period. The temperature o the reaction mixture was kept around 5 o C and the ph o the reaction was maintained around 8.5 by addition o 0.5 mol/l a 2 CO 3 aqueous solution. The mixture was stirred or three hours at 5-0 o C. The dye was precipitated by salting out with natrium chloride and was separated by vacuum iltration. The yellow disazo dye was obtained in 88% yield. Samples o the synthesized dye, ree o sodium chloride were obtained by dyeing cotton abric in boiling solutions containing 5 g o dye in 250 ml water. Ater rinsing the dyed abrics, the dye was extracted using solutions o 50-60% aqueous pyridine. The extracts were then evaporated, giving a dye ree o salts. Dyeing system and measurements The dyeing processes were carried out in round lasks, equipped with a stirrer, a condenser and a thermometer. The dyeings were made at three temperatures, namely 60 o, 86 o and 96 o C (± o C). The cotton samples weight in every case was near 70 mg (±0. mg). The liquor ratio was 50:. The initial dyebath concentrations o the studied dye varied rom 0.5 g/l to 5 g/l. Sodium chloride concentrations in the dyebath were in every case mol/l. The time necessary or reaching equilibrium or each dye and each dyeing temperature was evaluated in a series o preliminary experiments. The dyed cotton samples were removed rom the hot dyebath and rinsed or about 30 seconds in ice water to remove the adhering dye liquor. The dye was extracted rom the dyed samples with 25% aqueous pyridine at 80 o C. The molar extinction coeicients were determined at one wavelength rom the Lambert-Beer law. The dye concentrations in the dyebath as well as the extracted dye rom the substrate were recorded spectrophotometrically, using a Specord M40 UV-VIS spectrophotometer. Other details on the dyeing system can be ound in reerences [6-9]. In order to ind out the model which describes best the sorption o the studied dyes on mercerized cotton, the experimental data thus obtained were itted to the classical ernst, Freundlich and Langmuir sorption models by nonlinear regression analysis. For this purpose, the STATISTICA sotware [] was used CF CS Figure. Freundlich adsorption isotherm at 60 o ( points and large interrupted itting line), 86 o ( points and continuous itting line) and 96 o ( points and small interrupted itting line) 3

3 OF EGIEERIG. TOME VII (year 2009). Fascicule 3 (ISS ) The standard deviation (expressed in [%]) o the experimental values obtained or the concentration o the dye on the substrate (C ) rom the calculated ones) was calculated according to equation (4). 2 C C i exp icalc (4) SS = 00 i C = icalc where the suixes "exp" and "calc" reer to experimental and calculated values, respectively; suix "i" reers to the number o sorption data. Figure presents the Freundlich dye adsorption isotherm at 60 o, 86 o and 96 o. 3. DISCUSSIOS In the present study, the sorption isotherms o a symmetrical disazo direct dye on mercerized cotton were determined at 60 o, 86 o and 96 o C. The studied dye (I) contains 4,4 -diaminobenzanilide as diazo component and resorcinol as coupling component. 2 COH 5 Dye I The dye was prepared in a two steps procedure, as shown in Scheme. H 2 COH H Cl 2 COH 2 Cl 2 COH Scheme. ao 2, HCl, 0 o C, hour, 2. Resorcinol, :2 molar ratio, ph = 8.5-9, 5-2 o C, 3 hours. The bis-diazotization o 4, 4 -diaminobenzanilide was carried out by the direct method, in aqueous HCl solutions. The coupling step was conducted at a ph value o 8.5-9, and with a 2-3% excess o coupling component. The progress o the coupling reaction was monitored by the usual way (drop reaction) and by thin layer chromatography (TLC), when the ormation o dye I was examined. Dye I was obtained with overall high yields and was characterized by means o VIS spectra and negative (-) FAB MS spectroscopy. Dye homogeneity was examined by TLC. The chromatographic mobility (R ) o dye I was ound equal to The VIS spectrum was examined in the region o 350 to 800 nm. The spectra contain one maxim o absorption at about λ max = 435 nm ( ε g / L cm I = 52) in 0. mol/l aqueous a solution. The molecular peak [MS(FAB-)] was ound at m/z. The disazo dye I was urther used in the experimental study o the dye sorption on mercerized cotton, as shown in Experimental section. Dyeings were carried out until equilibrium was reached, at three dierent temperatures and in presence o sodium chloride. The experimental equilibrium dye concentrations in ibre [C] and in solution [C] s were itted to equations () and (2) by nonlinear regression analysis and to equation (3) by linear regression analysis, in order to provide the best model o sorption o the studied dye on cotton. The values o the thermodynamic parameters K F, K L respectively S have been evaluated by means o nonlinear least squares it o experimental sorption data to respective equations (, 2), respectively by linear regression it o experimental sorption data to equation (3) or K P. The multiple 94 copyright FACULTY o EGIEERIG - HUEDOARA, ROMAIA

4 OF EGIEERIG. TOME VII (year 2009). Fascicule 3 (ISS ) regression coeicient (R) and the standard deviation (SS) calculated by equation (4) were used as statistical criterions in the regression analysis. The thermodynamic data and the statistical results obtained or the studied dyes are presented in tables, 2 and 3. TABLE o dye I according to equation [ C] = K [ C] F s x (Freundlich model)* T [ o C] KF [L/lg] x R SS [%] *KF represents the Freundlich partition constant; x- the subunitary power; R- the multiple regression coeicient and SS-the standard deviation. TABLE 2 o dye I according to equation [ C] S [ C] K L + S s = (Langmuir model)* T [ o C] S [mol/kg] KL [L/mol] R SS *S represents the saturation value; KL - Langmuir partition constant; R the multiple regression coeicient and SS-the standard deviation TABLE 3 = (ernst sorption model)* o dye I according to equation [ C] K P [ C] s T [ o C] KPx0-2 [L/mol] R SS * KP - ernst partition constant; R- the multiple regression coeicient and SS-the standard deviation. Comparing the obtained data presented in Tables, 2 and 3 it could be seen that or the studied dye, overall high values o R respectively low standard deviation (SS) values were obtained or the Freundlich sorption model as compared to the classical ernst and Langmuir models. 4. COCLUSIOS The equilibrium sorption isotherms o a symmetrical disazo direct dye on cotton were determined at three temperatures and one sodium chloride concentration. Experimental data were itted to the standard known adsorption isotherms o ernst, Freundlich, and Langmuir by nonlinear regression. The results indicated best statistical values in the case o the Freundlich sorption model. AKOWLEDGEMETS This work was supported by the Grant contract 7 GR o the MEC (Romania) REFERECES [] Vickersta T., The Physical Chemistry o Dyeing, Imperial Chemical Industries Limited: London, 954. [2] Porter J. J., Perkins W. S., A Study O The Thermodynamics O Sorption O Three Direct Dyes On Cellophane Film, Textile Res J, 40, 8-87,

5 OF EGIEERIG. TOME VII (year 2009). Fascicule 3 (ISS ) [3] Bairathi A., Dyeing Sorption Isotherms O Three Direct Dyes And Their Mixtures On Puriied Cotton, Textile Chem. Color., 25, 4-46, 993. [4] Peters R.H., Textile Chemistry. The Physical Chemistry o Dyeing, Elsevier Amsterdam, Vol. III, 975. [5] Rys P., Zollinger H., Fundamentals o the Chemistry and Application o Dyes, Wiley- Interscience: London-ew York-Sydney and Toronto, 972. [6] Simu G., Funar-Timoei S., Hora S., Schmidt W. E., Kurunczi L., Şişu E., Morin., Coloranti Directi Derivati ai 4,4 -Diaminobenzanilidei. I. Sinteza si Studiul Izotermelor de Adsorbtie pe Bumbac ale unui Colorant Disazoic Direct cu Structura Asimetrici, Rev Chim (Bucharest), 53, , [7] Simu G., Funar-Timoei S., Hora S., Kurunczi L., Experimental and Theoretical Study o the Adsorption o a Trisazo Direct Dye Derived rom 4,4'-Diaminobenzanilide on a Cellulose Substrate, Molec Cryst Liq Cryst, 46, 97-04, [8] Simu G., Funar-Timoei S., Kurunczi L., Schmidt W., A Thermodynamic Study o the Sorption o an Asymmetric Disazo Direct Dye on Mercerized Cotton, Rev Roum Chim, 49(3-4), , [9] Simu G., Funar-Timoei S., Kurunczi L., Hora S., Schmidt W., Grad M., Synthesis and Study o Adsorption Isotherms o a Trisazo Direct Dye on Cotton Fibre, Cellulose Chem Technol, 38 (5-6), , [0] Simu G. M., Chicu S. A., Morin., Schmidt W., Sisu E., Direct Dyes Derived rom 4,4 - Diaminobenzanilide. Synthesis, Characterization and Toxicity Evaluation o a disazo symmetric direct dye, Turk J Chem, 28, , [] STATISTICA 7., StatSot Inc, Tulsa, OK, USA 96 copyright FACULTY o EGIEERIG - HUEDOARA, ROMAIA

Annals of West University of Timisoara

Annals of West University of Timisoara Series Chemistry 13 (1) (2004) 27-32 SYNTHESIS IN NON-AQUEOUS MEDIUM OF SOME SYMMETRICAL DISAZO DIRECT DYES DERIVED FROM 4,4 -DIAMINOSTILBENE-2,2 -DISULPHONIC ACID