3738
Ind. Eng. Chem. Res. 2009, 48, 3738–3748
Biosurfactants from Urban Wastes As Auxiliaries for Textile Dyeing Piero Savarino,† Enzo Montoneri,*,† Stefano Bottigliengo,† Vittorio Boffa,† Tommaso Guizzetti,† Daniele G. Perrone,† and Raniero Mendichi‡ Dipartimento di Chimica Generale e Chimica Organica, UniVersita` di Torino, C. M. D’Azeglio 48, 10125 Torino, Italy, and Istituto per lo Studio delle Macromolecole (CNR), Via E. Bassini 15, I-20133 Milano, Italy
To promote biobased products for the industry, six biosurfactants isolated from green and food urban residues aged under aerobic digestion for 0-60 days were investigated for their potential to perform as auxiliaries for dyeing cellulose acetate fabric with water-insoluble dyes. The experimental plan included investigation of the chemical nature, surface activity, and power to enhance dye solubility in water, as well as dyeing test performed under a variety of experimental conditions presenting a range of challenge levels. For comparison, the same investigation was performed on commercial synthetic surfactants. The investigated biosurfactants exhibited chemical composition and surface activity properties presumably related to their different biomass sources. However, no significant performance differences in textile dyeing were evident among the biosurfactants and between biosurfactants and synthetic surfactants. The results encourage product and process development for exploitation of biomass residues as a source of chemicals to recycle to the industry. 1. Introduction In the context of the current issues of waste management and exploitation of renewable sources of energy and chemicals for sustainable development, we have recently shown that urban wastes are a rich source of bio-organic matter with excellent surfactant properties.1 This matter is easily available from urban facilities performing aerobic biodegradation of biomass residues to final materials containing up to 60-70% bio-organic substances. Specifically, for two biosurfactants isolated from a 1:1 w/w mix of food and green residues aged for 15 days1,2 and from sole fresh green residues,3-5 we reported data on chemical structure, surfactant properties, and performance in textile dyeing, fabric detergency, dyes photodegradation, and soil washing. The two biosurfactants were found to have some significant differences in chemical structure and surface activity. They were also shown to perform as very promising chemical auxiliaries compared to commercial surfactants. The data indicated the prospect of recycling waste bio-organics to the chemical industry with rather appealing cost and environmental benefits. Although intriguing for expectations, the above-cited results pointed out also the need of both process and product development. The biosurfactants were made available by a known procedure1 involving extraction of the biomass waste with aqueous 0.1 mol · L-1 NaOH and 0.1 mol · L-1 Na4P2O7, using a 1:50 w/v solid/liquid ratio, under N2 blanketing for 24 h at 65 °C followed by precipitation of the biosurfactants with 50% sulfuric acid to pH < 1.5. This procedure, established mainly to recover bio-organic matter from soil, water, and urban refuses for analytical purposes, is clearly not attractive for large-scale operation. Evident reasons are primarily the very high ratio of extraction fluid, the strong alkaline and acid conditions used for the biomass treatment and product recovery, and the burden to recycle and/or dispose of large amounts of reagents. More critical aspects, to be investigated before undertaking process development, are however related to the biological nature of the product source. Indeed, a major concern for using biobased * To whom correspondence should be addressed. E-mail:
[email protected]. † Universita` di Torino. ‡ Istituto per lo Studio delle Macromolecole.
products in industry is the nonsatisfactory reproducibility of their chemical composition, of their structure, and presumably of their performance, as a function of source. For the specific case of biosurfactants sourced from urban wastes treatment facilities, the nature, composition, and aging time of the starting wastes are major parameters most likely expected to affect the recovered products chemical composition and properties.1 On this basis, for promoting biomass wastes as sources of chemicals at the industrial and commercial level, more product investigation seemed necessary to justify and/or focus any research effort on process development. This work reports data on the chemical structure, surface activity, power of enhancing hydrophobic dye solubility, and performance in textile dyeing for six biosurfactants which hereinafter will be referred to by the abbreviation cHALi, i ) 2-7: i.e., cHAL2, cHAL3, and cHAL4 isolated from sole green wastes and cHAL5, cHAL6, and cHAL7 isolated from a 1:1 w/w mix of food and green residues at the start of the aerobic digestion process (cHAL2 and cHAL5), and after 7 days (cHAL3 and cHAL6) and 60 days (cHAL4 and cHAL7) aging. Textile dyeing was chosen as a testing ground of industrial importance since textile processing,6 together with detergents manufacture,7 uses a large portion of the surfactants available in the chemical market. Although mainly addressing applied chemistry, in our experimental plan it was necessary to deal with a number of rather challenging issues related to product chemical structure and properties. First, it should be considered that the cHALi substances are new materials of biological origin with quite complex chemical composition. Previous work performed on similar substances isolated from bio-organic matter present in soil and water (SWS)8-11 and from organic (humid) fraction of city refuses (CRS)1 from different locations reports that the structural determination of these substances is difficult, due to the high polydispersity of the molecular weight and to the content of many organic moieties representing the memory of the main constituents of vegetable matter which are not completely mineralized by biodegradation. Several molecular models have been reported.1,9 They contain a C framework of aliphatic C chains bonded to more or less fused cycloaliphatic and aromatic rings and substituted by several functional groups.
10.1021/ie801853x CCC: $40.75 2009 American Chemical Society Published on Web 03/20/2009
Ind. Eng. Chem. Res., Vol. 48, No. 8, 2009 3739
None of these models is however likely to represent the true chemical nature of these substances. Most likely they are mixtures of molecules differing for molecular weight and chemical composition. Given their complexity, these substances are normally characterized by microanalytical data, by the concentration of acid functional groups, and by the ratio of aliphatic to aromatic and/or olefinic structural C. Available analytical data referred to ash-free dry matter for SWS8-11 and for CRS1 from different sources are C 48-69 w/w %, H/C 0.73-1.53 atom/atom, N/C 0.007-0.15 atom/atom, COOH 2.6-5.0 meq · g-1, PhOH 1-1.7 meq · g-1, and aliphatic/aromatic C ratio 0.5-3.3. The data prove the wide variability of chemical composition as a function of source. At the same time they have several problems in the interpretation of surface tension measurements, which introduces the second issue of our work of evaluating product properties and their significance in relation to performance in the intended application. The capacity to lower water surface tension by organic compounds is based on the fact that normally molecules consisting of lipophilic C chains and hydrophilic polar groups occupy the air-water interface, orienting their lipophilic and hydrophilic parts toward the air and the water phase, respectively, until they reach the critical micellar concentration (cmc). Further molecules aggregate orienting their lipophilic part in the inner micelle core and the hydrophilic parts toward the water phase and therefore occupy the bulk water phase. This situation may be represented by the constant12 Kn ) [Sn]/[S]n
(1)
associated to the equilibrium between single (S) and aggregated (Sn) surfactant molecules nS h Sn
(2)
As a consequence, the γ-added surfactant (Cs) plot has a descending tract for Cs < cmc. However, once the cmc value is reached, the specific effect of further added surfactant molecules on γ, i.e., the dγ/dCs slope of the γ-Cs plot, is expected to decrease depending on the aggregation forces and on the compactness of the Sn aggregate. Thus, the stronger the aggregation forces, the higher Kn and the lower dγ/dCs at Cs g cmc are expected. A problem often encountered in surface tension studies is the interpretation of γ-Cs plots and the cmc determination. Indeed, a variety of γ-Cs plots are obtained. In the simplest case, the premicellar C region is clearly distinguished from the postmicellar region by a sharp dγ/dCs change. This is mostly found for simple surfactant molecules with one polar head, such as sodium dodecylbenzenesulfonate (SDBS). For more complex cases, such as small molecule surfactants,1,13 in which two or more polar groups are connected to lipophilic chains of variable length or polymeric molecules,14-16 the transition between the two regimes may be very large. In these cases, the γ-Cs plot in the premicellar region is characterized by different curvatures exhibiting more than one slope change assigned to the formation of premicellar aggregates. One other matter of particular concern in our investigation was to devise an experimental plan for evaluating the performance of the cHALi in textile dyeing in a fair and meaningful way which accounted for either the fact that these substances are new and the complexity of the intended application. To this scope we chose typical dyeing systems comprising cellulose acetate (CA) fiber and hydrophobic dyes6,17 which are normally used in the disperse state. In these systems, uptake of the dyes
having poor water solubility by the CA fiber may occur by hydrophobic and/or polar interaction between the fabric and the dye. The main problem in this type of interaction involving heterogeneous phases arises from the morphology of the fabric and dye particles. Low surface areas available for the dye-fiber interaction cause a nonhomogenous distribution of the dye throughout the fabric solid phase and the accumulation of the dye preferably on the fiber surfaces. These facts are reflected in the undesirable aspect of the dyed fabric and in poor color fastness to washing and/or crocking. Surfactants are expected to improve the performance of the dyeing bath by enhancing the dye dispersion in fine particles and/or its solubility in water through adduct (Dye · · · Sn) formation Dye + Sn h Dye · · · Sn
(3)
In addition to decreasing the dye particle size and increasing the dye surface area, reaction 3 should help control the rate of release of the free dye concentration in solution, the rate and yield of the dye uptake by the fiber Fabric + Dye h Dyed Fabric
(4)
and so improve the three main features of the dyed fabric, i.e., the intensity, homogeneity, and fastness of the color taken up. Reactions 3 and 4 propose the principal components of the dyeing bath, i.e., the dye, the surfactant, and the fiber, as parameters which are very likely to affect the dyed product quality. Under these circumstances, the fairest way to assess the value of the new biosurfactants appeared to be the vis-a-vis performance comparison of the new biosurfactants with major commercial synthetic surfactants under a number of experimental conditions encompassing either the dye or the fabric variability. The authors of this work are well aware that the range of potential applications of surfactants is very wide and multidisciplinary and that highly technical specialized knowledge is required nowadays for the development of new products from laboratory to commercial scale. In this state of the art context, it should be clearly understood that the present work is meant not to provide a recipe to solve specific problems in textile dyeing but rather as a ground for assessing the value of the new cHALi biosurfactant relative to that of commercially established surfactants. The authors ultimate aims are to stimulate specialists in diversified technological applications to join in with efforts for assessing the level at which biomass residues could be a real alternative to synthetic commercial chemical auxiliaries and to foster the development of new processes and products from renewable sources. 2. Experimental Section 2.1. Materials. Ethoxylated castor oil (Ethofor RO 40)17 by ICAI, Bruino (To, Italy), sodium dodecylsulfate (SDS) by Fluka, and all other reagents and synthetic materials by Aldrich, unless otherwise indicated, were used as received. Cellulose acetate (CA) fabrics with weight to surface area ratios (fw/fsa) of 180 g · m-2 (CA1) and 70 g · m-2 (CA2), and regenerated cellulose fabric, were from Testfabrics Inc., West Pittston, PA, products which were supplied by Ausiliari Tessili s.r.l., Milano, Italy. These products are claimed by the manufacturer to be prepared for printing and dyeing and therefore to be desized, scoured, and bleached to contain no sizing, dyes, and resins. The dyes in Table 1 were synthesized as described in previous works18-32 and purified by crystallization from ethanol. The products purity was checked by TLC analysis performed on Macherey-Nagel
3740 Ind. Eng. Chem. Res., Vol. 48, No. 8, 2009 Table 1. Chemical Structure and Experimental Data for Hydrophobic (Disperse) Dyes Used in This Work
a Rf1 and Rf2 found by eluting with SM1 and SM2, respectively (see Experimental Section).
Polygram Sil G/UV 254 0.20 mm thick plates. The dye sample was dissolved in acetone, deposited on the TLC plate, and eluted with one of two solvent mixes (SM): i.e., 70% petroleum ether and 30% ethyl acetate (SM1) or 60% petroleum ether and 40% ethyl acetate (SM2). The dye crystallization from ethanol was repeated until one spot was obtained by elution on the TLC plate. Under this circumstance each final dye product gave the TLC retention factor (Rf) values and melting points reported in Table 1, which were consistent with the literature data. The Rf factor is defined as the ratio between the distance traveled by the product and the distance traveled by the solvent on the TLC plate. Melting points were determined by a Kofler instrument. 2.2. Biosurfactants Isolation. The biosurfactants (cHALi, i ) 2-7) investigated in this work were obtained from ground green wastes or from 1:1 w/w food and green residues mix collected at 0-60 days aging time from aerobic digestion facilities located in the province of Torino, Italy. The cHALi isolation was performed as previously reported.1 In a typical run, the collected waste sample was treated 24 h at 65 °C under N2 with aqueous 0.1 mol · L-1 NaOH and 0.1 mol · L-1 Na4P2O7 at a 1:50 w/v solid/liquid ratio. The resulting suspension was cooled to room temperature and centrifuged at 6000 rpm for 20 min. The separated solid residue was washed repeatedly with distilled water until the supernatant liquid phase was clear. All collected liquid fractions were mixed and acidified with 50% sulfuric acid to pH < 1.5. The precipitated solid was centrifuged as above, washed with water until the final washing had a neutral pH, vacuum dried at 60 °C, and weighed. The final product (cHALi) yield was 12-14% of the starting waste dry matter. 2.3. Chemical Characterization. C, H, and N microanalytical data were obtained with a C. Erba (Rodano, Milan, Italy) NA-2100 elemental analyzer. The determination of the free phenol and carboxylic acid groups content was accomplished by potentiometric titration as previously reported.3 Deionized water was boiled under nitrogen to remove dissolved CO2. This water was used to make the required sample and reagents solutions. The cHALi sample was dissolved at 0.6 g · L-1 concentration in 1 N KOH. The total alkali content in the
solution was in excess relative to the total sample carboxyl and phenoxide content determined by 13C NMR spectroscopy. This solution with a pH of about 13.8 was titrated with standardized 1 N aqueous HCl. Similar titration was performed on a blank solution containing the same amount of alkali as the above sample solution but no cHALi. The titrations were performed at 25 °C using an automatic Cryson Compact Titrator with a resolution of 1 µL of titrant in a thermostatted glass cell under nitrogen blanketing to prevent dissolution of atmospheric carbon dioxide in the sample. Under these experimental conditions, it was possible to obtain potentiometric curves of satisfactory quality showing two inflection points which allowed calculating the COOH and PhOH concentration by the data elaboration previously reported.3 Solid-state 13C NMR spectra were acquired at 67.9 MHz on a JEOL GSE 270 spectrometer equipped with a Doty probe. The cross-polarization magic angle spinning (CPMAS) technique was employed, and for each spectrum about 104 free induction decays were accumulated. The pulse repetition rate was set at 0.5 s, the contact time was 1 ms, the sweep width was 35 KHz, and MAS was performed at 5 kHz. Chemical shifts (δ, ppm) of NMR resonances are referred to tetramethylsilane. Typical 13C NMR spectra showed signals whose resonance range and assignments were 0-53 ppm aliphatic C, 53-63 ppm O-Me or N-alkyl C, 63-95 ppm O-alkyl C, 95-110 ppm di-O-alkyl C, 110-140 unsaturated (aromatic and/or olefinic) C, 140-160 ppm phenol or phenyl ether C, 160-185 carboxyl C, 185-215 keto C. The aliphatic to unsaturated C ratio in Table 2 was determined by the ratio of the aliphatic C signal area to the sum of the unsaturated (aromatic and/or olefinic) and phenol or phenyl ether C signal areas. Molecular weight investigation was performed through fractionation and characterization by a multiangle laser light scattering (MALS) detector online to a size exclusion chromatography (SEC) system as previously reported.3 2.4. Surface Tension, Particle Size, and Dye Solubility Measurements. Surface tension (γ, mN · m-1) measurements of aqueous solutions containing the sample of the investigated substances at variable concentration (Cs ) 0.005-3 g · L-1) were carried out at 25 °C and pH 7 with a Kruss K100 automatic tensiometer. Dye solubility (DS) in water was determined by saturating with 0.1 w/v % dye the sample (surfactant or biosurfactant) solutions at pH 7 containing 10 v/v % 0.1 M tris buffer, stirring at 80 °C for 24 h, filtering, and diluting the sample-dye (SD) solution with ethanol containing 10 v/v % dimethylsulfoxide and tris buffer in a 1/1 v/v ratio in order to lower the sample concentration to 0.08 g · L-1. The dye concentration in the SD solutions was determined by absorption spectroscopy at 505 nm against a solution in the reference beam which had identical composition as the SD solution but contained no dye. Absorption-dye concentration calibration curves performed under the same conditions gave 0.999 linear correlation coefficients. The results are reported as γ-Cs and DS-Cs plots in Figure 1. Dynamic light scattering (DLS) measurements of surfactants particle size in solution, in the absence and presence of dye, were obtained with a ZetaSizer (Malvern, U.K.) instrument, which has a detection window included between about 0.6 nm and 5 µm. The measurements were carried at pH 7.0 and 25 °C after filtering the cHALi sample solution on a cellulose acetate disk (Schleicher & Schuell) with a size cutoff of 0.8 µm. As in previous work,3 the CONTIN method was used to analyze the DLS data for calculating the intensity-average hydrodynamic diameter (DH) of the molecules or aggregates in solution.
Ind. Eng. Chem. Res., Vol. 48, No. 8, 2009 3741 Table 2. Analytical Data for cHALi Isolated from Different Urban Wastes Aged under Aerobic Digestion for 0-60 Days atom/atom ratiosc cHALia
H2O, w/w %
ash, w/w %
Cb,c w/w %
H/C
N/C
COOHb,d meq g-1
ArOHb,d meq g-1
Cal/Cune
MW,f kg mol-1
cHAL2 cHAL3 cHAL4 cHAL5 cHAL6 cHAL7
7.6 6.3 7.4 6.3 6.0 6.9
1.0 2.1 2.1 1.0 1.0 3.8
65.0 63.5 60.4 64.5 62.7 61.7
1.07 1.10 1.01 1.13 1.23 1.07
0.062 0.075 0.064 0.066 0.073 0.071
3.2 3.2 3.4 3.1 2.9 3.2
1.0 1.8 2.1 1.6 2.3 1.3
3.1 2.6 2.2 4.9 4.5 2.9
97–200 186–267 200–273 120–271 195–300 165–297
a cHAL2, cHAL3, and cHAL4 isolated from sole urban wastes aged under aerobic biodegradation for 0, 7, and 60 days, respectively; cHAL5, cHAL6, and cHAL7 isolated from 1:1 w/w green/food residues mix aged under aerobic biodegradation for 0, 7, and 60 days, respectively. b Referred to ash-free dry matter. c Determined by microanalysis. d Determined by potentiometric titration. e Aliphatic to unsaturated C ratio determined by 13C NMR spectroscopy. f Apparent molecular weight by SEC-MALS.
Figure 1. Surface tension (γ) and dye 2 solubility (DS) versus concentration (Cs) of SDBS and cHALi (i ) 2-7) in water at pH 7.
2.5. Textile Dyeing Trials. Cellulose acetate (CA1 and CA2) fabrics were treated with the dyes reported in Table 1 according to a previously published procedure.2,4 Both fabrics were soluble in acetone at room temperature and showed softening at 175-190 °C and melting at 240 °C when analyzed by a Koffler apparatus. Before use, the fabrics were washed as reported in the literature6 with 1 g · L-1 Marsiglia soap at a 1:50 w/v solid/ liquid ratio and 45 °C for 1 h, rinsed with water, and dried at room temperature. This treatment was performed to remove possible dirt or other accidental contaminants from the fabrics. Under these conditions the washed fabric samples had the same solubility and thermal properties as the starting fabric, proving that the washing treatment had not altered the chemical structure of the starting cellulose acetate. Fabric dyeing was performed on a Linitest apparatus (Hanau, Germany) using 0.1 M Tris buffer at pH 7 by introducing the prewashed fabric into the dye bath at 40 °C, heating to 80 °C over 20 min, and maintaining the bath at this temperature for 1 h. Typical dyeing experimental conditions, unless otherwise indicated, were 5 v/w liquor volume to good (fabric) weight ratio (LGR, mL · g-1), 1% dye depth (percentage of dye related to the fabric weight), and bath sonication by Vibra-Cell 120 W Ultrasonic Apparatus at 4 W for 1.5 min. The dyed fabric samples were then removed, rinsed,
washed at 40 °C with water solution containing soap (2.5 g · L-1) and sodium carbonate (2.5 g · L-1) at 200:1 v/w LGR, rinsed again, and dried at room temperature. Surfactants performance (Figures 2-4) in the dyeing trials was assessed by tristimulous colorimetry, using a Minolta CR200 instrument.33 Tristimulous colorimetry measurements allow the indirect evaluation of dye uptake based on the color difference (∆E) between the dyed and undyed fabric and also of the color uniformity based on the standard deviation (σ∆E) around the mean ∆E value of replicate measurements over the fabric specimen.17 Figure 5 shows an example of undyed and dyed specimen next to the measured ∆E and σ∆E values for the dyed specimen. In this work, the reported ∆E value is the mean of five determinations performed over five different sites comprised in a 2.5 cm2 specimen area. Provided that each specimen had 10 × 10 cm2 size, in some cases replicate ∆E and σ∆E values for the same specimen were obtained by repeating the set of five determinations on a different 2.5 cm2 specimen area. Replicate measurements are identified in Figures 2-4 by the different histogram rectangles for the same dye and surface active agent. Dyed specimen were compared also for color fastness to washing (WF) and to crocking (CF) according to standard procedures.33,34 For WF measurements a composite sample was prepared by sawing on the two faces of the dyed specimen two samples of witness fabrics, i.e., a plain undyed cellulose acetate fabric on one face and a regenerated cellulose (viscose) fabric on the other face of the dyed specimen. The composite sample was washed at 50 °C with 5 g · L-1 Marsiglia soap at 50:1 v/w LGR for 45 min in Linitest apparatus. The dried composite sample was analyzed for (i) color change (CCWF) of the dyed specimen relative to the unwashed dyed specimen, (ii) color staining (CSWF-CAW) of the cellulose acetate witness, and (iii) color staining (CSWF-VW) of the viscose witness. Color fastness to dry (DCF) and wet (WCF) crocking was evaluated by rubbing off the surface of the dyed fabric with a dry or wet cotton cloth by crockmeter and evaluating the cotton cloth for color change. Color change in CCWF, DCF, and WCF measurements and color staining in CSWF-CAW and CSWF-VW measurements were evaluated using the empiric gray scales for assessing change in color and staining approved and issued by the British Standard Institution (Manchester, U.K.) in collaboration with the Society of Dyers and Colorists (Bradford, U.K.). According to these scales, WF or CF values by color change or staining are rated from 1 (worst value) to 5 (best value). 3. Results 3.1. Chemical Nature. The chemical composition and molecular weight (MW) data of the investigated cHALi substances are reported in Table 2. The data confirm the dependence of chemical composition on the substances source which has
3742 Ind. Eng. Chem. Res., Vol. 48, No. 8, 2009
Figure 2. Values for ∆E measured on cellulose acetate fabric CA1 treated with Table 1 dyes in the absence and presence of cHALi (i ) 2-7) and other synthetic surfactants at 2 g · L-1 under the conditions reported in the Experimental Section. Letters on top of the histogram rectangles indicate ∆E inequalities at the 95% confidence level:43 i.e., a < b < c < d < e < f < g. Error bars indicate σ∆E values reported in Figure 3. Differences are related to the surfactant exhibiting the lowest ∆E value for each dye.
already been observed for other similar bio-organic matter1,11,35 present in soil, water, and city refuses from other locations. Basically, the substances isolated from sole green wastes (cHAL2-4) seem to contain relatively more aromatic C than those isolated from the mix of green and food residues (cHAL5-7). Also, for each group comprising substances isolated from the same waste type, increasing the aging time seems to cause a relative decrease of the content of aliphatic C and an increase of acid functional groups. This trend appears well consistent with the more recalcitrant nature of aromatic moieties to bio-oxidation compared to aliphatic C. Some trend might be picked out for the molecular weight as a function of the nature and aging time of the substance source, i.e., cHAL2-4 seem to have slightly lower MW values than cHAL5-7; for the substances isolated from the same type of biomass waste, MW seems to increase upon increasing the waste aging time. 3.2. Surface Activity Properties. Figure 1a reports surface tension (γ) versus concentration (Cs) plots for the new cHALi substances and for solution of the commercial SDBS surfactant. As expected, the plot for SDBS presents a sharp dγ/dCs change, whereas those for the more complex cHALi substances are characterized by different curvatures exhibiting more than one
slope change before reaching the final plateau. To provide quantitative evidence of the difference between these substances, we divided each plot in Figure 1 into four tracts. These were analyzed by linear regression analysis, yielding the results shown in Table 3. The calculated values for the slopes standard deviation and for the linear regression coefficient evidence that linearity is maintained in all cases, except for the fourth tracts of the cHAL2-4 plots where the slope (dγ4/dCs) values are not significantly different from zero. It may be also observed that the slope changes in the first three tracts are much more pronounced for all cHALi than for SDBS. This is likely to mean that the cHALi, by virtue of their complex chemical nature, undergo several changes of molecular conformation and/or aggregation before reaching the final micellar structure. According to their significance (see Introduction), the dγ4/dCs values in Table 3 indicate that cHAL2-4 form the most compact micellar aggregates, followed by SDBS, and by the least compact cHAL5-7 micelles. The cmc value (Table 3) of SDBS measured in this work is consistent with literature data36-39 reported for this surfactant. This consistency is an indirect validation of our procedure for measuring surface tension. Interesting for the scope of this work is the fact that the cmc and degree of micellar compactness
Ind. Eng. Chem. Res., Vol. 48, No. 8, 2009 3743
Figure 3. Color uniformity (σ∆E) values of cellulose acetate fabric CA1 samples listed in Figure 2. Letters on top of the histogram rectangles indicate σ∆E inequalities by the F test at the 95% confidence level at 4 degrees of freedom:43 i.e., a < b < c < d < e. Differences are related to the surfactants exhibiting the lowest σ∆E value across the entire samples set, regardless of the dye and/or fabric type.
appear relatively constant within each group of cHALi substances obtained from the same source material (i.e., cHAL2-4 and cHAL5-7) but change significantly from one group to the other (i.e., from cHAL2-4 to cHAL5-7). 3.3. Solubility and/or Dispersion Power. To address specifically the technological applicability of cHALi in textile dyeing, we studied their capacity to enhance dye solubility (DS) in water. To this purpose we chose dye 2 in Table 1 as the hydrophobic probe molecule since this dye is commonly used in textile dyeing in the disperse state.4 In Figure 1b we report the DS-Cs plots in the presence of SDBS and of cHAL2 and cHAL5 as representatives of the two groups distinguished on the basis of cmc values, i.e., the cHAL2-4 with 0.73-0.77 g · L-1 cmc and the cHAL5-7 with 0.98-1.01 g · L-1 cmc. It may be observed that all three compounds enhance significantly the dye water solubility. However, cHAL5 seems to yield significantly lower DS values than cHAL2 and SDBS at the same Cs value. An apparent relationship of this behavior with cmc values may be picked out in Figure 1. Each DS-Cs plot (Figure 1b) seems to exhibit a plateau at nearly the cmc value indicated by the corresponding γ-Cs plot (Figure 1a and Table 2). These results prove that both the species in the premicellar region and the final micellar aggregates are capable of interacting with the dye and enhance its water solubility. The plateaus in the DS-Cs plots occurring at the border between the premicellar and
postmicellar regions show that when the cmc is reached and the final micellar aggregate starts to form, no further enhancement of dye solubility occurs upon increasing Cs over the plateau width. Our explanation is that over the plateau Cs range the concentration of the premicellar species is likely to remain nearly constant due to the fact that the added biosurfactant is mostly used for the formation of the final micellar aggregate. Once the final micellar aggregate is formed and a critical number of micelles builds up, further added surfactant contributes to increase the number of micelles in solution and the dye solubility increases again. The plateau width is likely to depend on the complexity and number of molecules participating to the formation of the final micellar aggregate. For SDBS this process is expected to be much simpler than for cHALi, and indeed, the plateau extent for the former is much smaller. In this process involving interaction of the dye with both premicellar and postmicellar surfactant or biosurfactant species, it is interesting to observe that the premicellar species of cHAL2 seem to have the highest solvent power for the dye, whereas in the postmicellar region the SDBS micelles seem mostly effective in enhancing the dye solubility. The plots indeed evidence that the specific dye solubility (dDS/dCs) in the cHAL2 solution in the postmicellar region is significantly lower than in the premicellar region. The behavior of cHAL2 was found to be
3744 Ind. Eng. Chem. Res., Vol. 48, No. 8, 2009
Figure 4. Values for ∆E and σ∆E measured on cellulose acetate fabrics CA1 and CA2 treated with dye 2 listed in Table 1 in the absence and presence of cHALi (i ) 2-7) and other synthetic surfactants at 2 g · L-1 under the conditions reported in the Experimental Section, except for CA2 dyeing bath sonicated 10 min at 1.5 W. Legends for letters on top of the histogram rectangles as in Figures 2-3.
Figure 5. Aspect versus ∆E and σ∆E values reported in Figure 4 for cellulose acetate CA2 fabric samples undyed (upper left) and dyed with 2 g · L-1 aqueous Na2CO3 in the absence of added surface active agents (upper right) and in the presence of 2 g · L-1 SDBS (lower left) or cHAL3 (lower right).
common to cHAL3 and cHAL4. The three biosurfactants exhibited identical DS-Cs plots. To assess the nature of the dye particle size in the presence of the surfactants, the average particles hydrodynamic diameter (DH) in the sole surfactant and in the surfactant-dye solutions was measured by DLS. For SDBS, due to the small molecular size, the scattered intensity was too low and could not be well distinguished from the background noise until Cs was not much above the cmc value. Reliable measurements at 10 g · L-1 Cs gave 3.7 ( 0.1 nm DH, compared to 2.5 nm reported40 for spherical SDBS micelle at room temperature and 0.2 M concentration. For cHAL2, representing the typical behavior of
the investigated cHALi substances, DH was found to be 105-168 ( 1.3-3.6 nm in the 0.2-2 g · L-1 Cs range at 25-60 °C. Consistent with the molecular weight data in Table 2, the DLS results confirm the presence of polymeric molecules or quite large molecular aggregates for the biosurfactant. In the dye-SDBS or dye-cHAL2 solutions no significant DH changes were observed compared to the sole SDBS or cHAL2 solutions. Checked against the dye solubility measurements, the DLS results in the presence of the dye indicate that the dye particle size in solution is likely to be at the molecular level and therefore not large enough to be distinguished from the background noise and/or affect significantly the large aggregate size of cHAL2 by interaction according to reaction 3. Although these results offered scope for further studies, no other investigation was carried out into the nature of the biosurfactant species and their solution interactions with hydrophobic compounds. 3.4. Performance in Textile Dyeing. To account for the fabric morphology and the dye nature effects on surfactants performance, we performed our dyeing tests with the 12 hydrophobic dyes listed in Table 1 and with two types of cellulose acetate fibers differing in weight to surface area (fw/ fsa) ratio, i.e., CA1 with fw/fsa ) 180 g · m-2 and CA2 with fw/fsa ) 70 g · m-2, using as surface active agents the cHALi substances, and the commercial SDBS, SDS, and the Ethofor products. In our experimental plan, each system component has features expected to affect the quality of the end product. The 12 dyes contain four functional groups, i.e., OH, CN, NO2, and OMe, which by their different polarity are expected to affect the dye solubility and interaction with the surfactant and the fabric. The two types of cellulose acetate fabric with different weight to surface area (fw/fsa) ratio dyed with the same 5 liquor volume to a good weight ratio at 1% depth yield two values of the dye weight per fabric surface area unit (dw/fsa) available in the bath, i.e., dw/fsa ) 0.18 mg · cm-2 for CA1 and 0.07 mg cm-2 for CA2, with the lower one expected to make the test harder for the investigated surfactants. The above surfactants have very different chemical features and cmc values. The three commercial surfactants are small molecules surfactants, with SDS and SDBS being anionic surfactants with cmc values1,3 of 0.5-1.4 and 2.3 g · L-1, respectively, and Ethofor being a nonionic surfactant with a cmc value of 0.03-0.3 g · L-1.41,42 On the other hand, the cHALi substances are polymeric-like materials falling in the category of anionic compounds by their molecular mass and the content of their COOH functional groups (Table 2) and have a cmc of 0.70-1.0 g · L-1 (Table 3). As the above cmc values range from a few milligrams to approximately 2.0 g · L-1, we performed our dyeing tests at the added surfactant concentration of 2 g · L-1, which corresponds approximately to the highest cmc value presented by SDS, in order to ensure that all surfactants were present in micelle form for best performance. Indication for using the surface active agent at added concentration above its cmc value came from previous work performed with SDBS, SDS, and cHAL2.4 Figures 2-4 report the results of our dyeing trials as values of the ∆E and σ∆E parameters. To realize how these parameters relate to the dyed product quality in this work, it should be understood that the color difference measured by the ∆E parameter results from a different amount of dye taken up by the dyed specimen compared to the undyed fabric and that a higher ∆E value is a qualitative indication of higher color intensity resulting from higher dye uptake. Consequently, the σ∆E parameter, being the standard deviation of the mean color difference measured over several different specimen surface sites, is related to the distribution of the adsorbed dye over the
Ind. Eng. Chem. Res., Vol. 48, No. 8, 2009 3745 Table 3. Data Extrapolated from γ-Cs Plots in Figure 1 SDBS -dγ1/dCs R1 -dγ2/dCs R2 -dγ3/dCs R3 -dγ4/dCs R4 pmc1-2 pmc2-3 cmc3-4 γmc1-2 γmc2-3 γcmc3-4
61.1 ( 0.997 56.7 ( 0.994 22.1 ( 0.982 0.52 ( 0.940 0.08 0.32 0.52 49.8 38.3 34.6
3.0 1.1 2.4 0.06
a
cHAL2
cHAL3
cHAL4
cHAL5
cHAL6
cHAL7
71.9 ( 9.9 0.985 20.2 ( 1.4 0.990 6.3 ( 0.3 0.985 0.03 ( 0.01 n.s.b 0.089 0.28 0.77 44.9 41.1 38.0
147.7 ( 27 0.995 22.8 ( 1.2 0.989 4.5 ( 0.3 0.966 0.04 ( 0.02 n.s.b 0.055 0.27 0.75 45.6 40.7 38.0
75.1 ( 6.4 0.988 11.1 ( 0.6 0.990 2.5 ( 0.5 0.880 0.03 ( 0.05 n.s.b 0.11 0.39 0.73 41.9 38.9 38.1
105 ( 16 0.897 13.1 ( 1.5 0.941 7.1 ( 0.2 0.998 2.5 ( 0.1 0.977 0.13 0.34 0.99 37.2 36.7 30.3
150 ( 23 0.931 29.6 ( 4.3 0.918 7.1 ( 0.1 0.994 2.2 ( 0.1 0.971 0.087 0.22 1.01 39.2 37.5 30.2
182.7 ( 27 0.893 18.3 ( 1.3 0.962 5.0 ( 0.2 0.983 1.3 ( 0.1 0.949 0.11 0.39 0.98 45.6 40.8 38.0
a Slope values and their standard deviations for four linear tracts (dγi/dCs, mN · L · m-1 · g-1, i ) 1-4), associated linear regression coefficient (Ri, i ) 1-4), concentrations at which slope changes occur (pmc1-2, pmc2-3, and cmc3-4 in g · L-1) and surface tension values at slope change points (γpmc1-2, γpmc2-3, γcmc3-4 in mN · m-1) obtained at the intersection of the following tracts: 1 and 2 for pmc1-2 and γpmc1-2, 2 and 3 for pmc2-3 and γpmc2-3,, 3 and 4 for cmc3-4, and γcmc3-4. b Not significant.
fabric specimen surface. Thus, lower σ∆E values indicate a more homogeneous dye distribution and, therefore, better color uniformity. The letters on top of the histogram columns in Figures 2-4 indicate sample inequalities at 95% of confidence: samples marked with different letters have significantly different ∆E or σ∆E values based on statistical analysis performed according to the literature.43 Figure 5 allows the visual appraisal of the significance of ∆E and σ∆E values in relation to fabric appearance. The color intensity and uniformity of the samples yielding 84.6-86 ∆E and 0.3-0.4 σ∆E units appears clearly much higher than that of the sample with 67 ∆E and 29 σ∆E. The experimental results for CA1 (Figures 2 and 3) dyed in the presence and absence of surfactants show that the ∆E and σ∆E values depend on the type of dye. For instance, in the absence of surfactants dye 3 yields the lowest color intensity (∆E ) 52.0), dyes 3, 10, and 12 yield the worst color uniformity (σ∆E ) 5.9-7.3), and dye 11 yields the highest color intensity (∆E ) 100.3) coupled to the best color uniformity (σ∆E ) 0.5). Thus, dye 11 seems to yield the best results and therefore to be least challenging for the surfactants, whereas the other dyes offer more scope for surfactants-assisted dyeing. The results indeed show that in the case of dyes 3 and 12 all surfactants give large improvements of both the color intensity and uniformity, whereas with dye 11 no further improvement in the product quality seems to be obtained by the presence of the surfactants. An overview of Figures 2 and 3 shows that most improvements due to the added surface active agents are on color uniformity rather than on color intensity. Generally, in all cases except dyes 1 and 11 most of the surfactants significantly improve the color uniformity. For the cHALi biosurfactant the results allow two major conclusions: (i) they rank in most cases at the same level of the best synthetic surfactants for the degree of improvement of σ∆E, and (ii) they do not no show definite clear performance differences which may be related to their source. Figure 4 shows also the vis-a`-vis comparison of the cHALi performance in the dyeing tests carried out with dye 2 and CA1 and CA2 fibers. It may be observed that, according to expectations, in the absence of surfactants CA2 yields both much lower intensity and much lower color uniformity than CA1. As a consequence, both the ∆E and σ∆E indicators show that compared to the case of the dye 2-CA1 fabric system, in the more challenging dye 2-CA2 fabric dyeing bath the improvement brought by the biosurfactants is more evident. Our duplicate tests show a larger variability between dyeing runs
performed with CA2 compared to CA1, presumably due to the more challenging dyeing conditions in the former case. Such performance variability is evident either in the presence of the biosurfactants or in the presence of the synthetic surfactants. Results for color fastness measurements performed on the same dyed samples to which Figure 2 refers are reported in detail in Figures 1s-5s of the Supporting Information. Values for washing (WF) and crocking (CF) fastness were in the following ranges: 3-5 for CCWF (Figure 1s), 2.5-4.5 for CSWF-CAW (Figure 2s), 4-5 for CSWF-VW (Figure 3s), 4-5 for DCF (Figure 4s), and 4.5-5 for WCF (Figure 5s). The values for dry (DCF) and wet (WCF) crocking fastness prove good or excellent penetration of the dyes through the fabric bulk solid phase. The values for washing fastness, measured by the color change of the dyed fabric (CCWF) or by the color staining of the cellulose acetate witness (CSWF-CAW) or the viscose witness (CSWF-VW) prove satisfactory to excellent dye fixation to the dyed fabric, except in a few cases (10 out of 288) rated at the 2.5 level by the color staining test on the cellulose acetate, but at higher level by the CCWF and CSWF-VW values. Major differences in WF and CF values were due to different dyes. With the dyes yielding the worst WF and/or CF values, improvements were shown in most cases by the presence of the investigate surface active agents. No definite important differences due to the type of surface active agent was however apparent. The results proved the same good to excellent dye stability in the samples dyed in the presence of the investigated cHALi or of the commercial surfactants. 4. Discussion Our work reports chemical, properties, and performance data on biobased substances (cHALi) isolated from urban refuses collected in the province of Torino, Italy. As these substances are new and complex by their nature, we needed to find in the literature and/or collect the same types of experimental data on known substances with assessed chemical, properties, and performance data in the same investigated application of this work. This was necessary either to validate our experimental procedures or to assign a reliable relative performance value to the new substances. By the data reported in Table 2 we have shown that the chemical nature of the cHALi substances is of the same type reported for other biobased substances isolated from soil or water natural organic matter8-11,35 and from urban refuses of other locations.1 We have also shown that the surface tension (Table 3) and DLS data measured for SDBS are
3746 Ind. Eng. Chem. Res., Vol. 48, No. 8, 2009
consistent with literature values.36-40 These facts constitute validation of the experimental procedures used in this work and therefore allow a number of reliable conclusions based on the experimental data collected for the cHALi substances. The scopes of this work were basically threefold. The first was to assess possible source effects on chemical composition, properties, and performance reproducibility by the biobased cHALi substances. The second was to find out if chemical composition data and surface activity data for cHALi could provide indications for their performance and best use in textile dyeing. The third was to compare the biosurfactans performance with that of synthetic surfactants. The data in Table 2 point out that both the nature and aging time of the source wastes influence the chemical composition of the isolated cHALi. The data reported in Figure 1 and Table 3 indicate however that most of the effect of the source material on the surface activity and on the power to enhance dye solubility of the cHALi substances is due to the source nature and not to the aging time. These data point out that the chemical parameters listed in Table 2 are capable to evidence source effects on chemical composition for the isolated substances but do not provide enough structural information to use when trying to establish structureproperties relationships. We accomplished the chemical characterization of the cHALi substances using methods and parameters available by the current state of art for similar natural substances.1,8-11,35 To develop procedures for a more comprehensive characterization of the chemical structure of these substances was not in the scope of this work. Notwithstanding this limitation, our experimental data on surface tension and dye solubility were found to be mostly informative and valuable for interpreting the behavior and for the use of the investigated biosurfactants in textile dyeing. The data in Figure 1 and Table 3 prove that the cHALi substances have the basic properties to perform according to reaction 3 and to compete with commercial synthetic anionic surfactants. Similarly to SDBS, the biosurfactants are capable of lowering by nearly 50% the water surface tension at their cmc value and of forming micelles at relatively low Cs values. Also, they can effectively enhance the water solubility of the hydrophobic dyes listed in Table 1. The correlation evidenced between the surface tension data and the capacity to enhance dye solubility by both cHALi and SDBS provides justification for previous findings suggesting use of surface active agents above their cmc values for best performance in textile dyeing.4 The particle size measurements indicate that the higher quality of the dyed products achieved in the presence of the biosurfactants is likely to be due to the solubilization of the dye at molecular level size by reaction 3. The results of the dyeing trials in Figures 2-4 show that the dye solubilization effect on the dyed product quality, compared to dyeing in the absence of surfactants, is more evident in the more challenging trials with the CA2 fabric. It appears that, for the CA1 fabric, the dyeenhanced solubilization by the surfactants is evidenced primarily by the more homogeneous color distribution over the fabric surface area. In this case, the amount of available dye per fabric unit surface (0.18 mg cm-2) seems to be enough to guarantee satisfactory color intensity even in the absence of surfactants. This result is consistent with expectations based on reaction 3 controlling primarily the rate of the dye uptake by the fiber, whereas the color yield is assured as well, even in the absence of surfactants, by the total amount of available dye for reaction 4. By comparison, in the dyeing trials for the CA2 fiber, where the available dye weight per fabric unit surface area (0.07
mg · cm-2) is less than one-half that for CA1, the effect of the dye-enhanced solubilization by the surfactants contributes both better color homogeneity and better color intensity of the dyed fabric. These considerations may have important implications for optimizing dyeing experimental conditions as a function of fabric morphology and dye nature. For the more specific scopes of this work, our dyeing trials prove that that the cHALi biosurfactants are effective in enhancing the color homogeneity and/or intensity of the investigated cellulose acetate fabric as well as in maintaining or improving the dye penetration into and fixation to the fabric solid phase. The performance data in Figures 2-4 show the following major facts for the biosurfactans used above their cmc values, either in the case of the CA1 dyeing trials or in the case of the more challenging trials with CA2, i.e., (i) the six cHALi do not exhibit significant performance differences which can be traced to their different biomass sources and aging conditions, and (ii) the cHALi do no exhibit any significant or important differences compared to the best major commercial surfactants such as SDBS and Ethofor. 5. Conclusions We investigated in this work the potential of six biosurfactants (cHALi) isolated from urban wastes to perform as auxiliaries in textile dyeing, with specific reference either to their performance level or to the effect of their source on their performance reproducibility. To this purpose we performed physicochemical studies of surface activity properties and dyeing tests. The investigated biosurfactant source parameters were the biomass nature ranging from sole urban green to 1:1 w/w green/kitchen urban residues mixes and the aerobic biodegradation time ranging from 0 to 60 days. We found that the above source parameters cause some differences in the isolated biosurfactants chemical nature, surface activity properties, and power to enhance the solubility of hydrophobic dyes in water. However, these differences do not seem to affect critically the performance of the isolated biosurfactants in dyeing cellulose acetate. Our surface activity studies for cHALi and SDBS have shown very interesting correlation between the measured cmc values and the capacity to enhance the water solubility of hydrophobic dyes. Our experimental plan for dyeing cellulose acetate encompassed a variety of parameters and conditions presenting a range of challenge levels for chemical auxiliaries with surface activity properties. In the most challenging conditions, significant improvements of the dyed product quality have been demonstrated by the use of either synthetic surfactants or biosurfactants. No significant or important performance differences between synthetic surfactants and biosurfactants or among biosurfactants has been assessed. The results therefore allow concluding that the cHALi may perform at the same level as the major synthetic surfactants. Also, for the biosurfactants the variability of the biomass source parameters does not appear to be critical for supplying potential users with products having reproducible performance. This perspective does not necessarily imply that the source nature and treatment process are absolutely unimportant for the formation of biobased surfactant like compounds. One should investigate different biomasses for a reliable assessment of source-product relationships. The nature of the processed waste is indeed likely to be a very important variable. Different types of biomass residues, containing different pools of vegetable and animal residual species, sourced from different locations under different climate and aging conditions, are likely to exhibit different sensitivities to aerobic or anaerobic degrada-
Ind. Eng. Chem. Res., Vol. 48, No. 8, 2009 3747
tion and yield a large variety of biosurfactants for a variety of tailored applications and uses. Both the results of our physicochemical studies on surface activity connected to dye solubility enhancement and of our applied chemistry experimental plan offer intriguing and worthwhile scope for further investigation into the nature of the biosurfactant species and their solution interactions with hydrophobic compounds, and into the application of biosurfactants for other chemical technologies where commercial synthetic surfactants are used. The perspective to use the cHALi biosurfactants in place of synthetic surfactants allows to envision a number of beneficial expectations for the industry and society. These are lower materials cost and lower consumption of synthetic surfactants, and in turn significant environmental benefits deriving from lower CO2 emission, lower fossils consumption, and lower concern for disposal practices of exhausted dyeing baths. The results of this work encourage both process and product development work for industrial production of biosurfactants from biomass residues of different sources. Acknowledgment This work was carried out with Regione Piemonte Cipe 2006 funds. Supporting Information Available: This material is available free of charge via the Internet at http://pubs.acs.org. Literature Cited (1) Quagliotto, P. L.; Montoneri, E.; Tambone, F.; Adani, F.; Gobetto, R.; Viscardi, G. Chemicals from wastes: compost-derived humic acidlike matter as surfactant. EnViron. Sci. Technol. 2006, 40, 1686, and references therein. (2) Savarino, P.; Montoneri, E.; Biasizzo, M.; Quagliotto, P. L.; Viscardi, G.; Boffa, V. Upgrading biomass wastes in chemical technology. Humic acid-like matter isolated from compost as chemical auxiliary for textile dyeing. J. Chem. Technol. Biotechnol. 2007, 82, 939. (3) Montoneri, E.; Boffa, V.; Quagliotto, P. L.; Mendichi, R.; Chierotti, M. R.; Gobetto, R.; Medana, C. Humic acid-like matter isolated from green urban wastes. Part I: structure and surfactant properties. Bioresources 2008, 3, 123. (4) Montoneri, E.; Savarino, P.; Bottigliengo, S.; Musso, G.; Boffa, V.; Bianco Prevot, A.; Fabbri, D.; Pramauro, E. Humic acid-like matter isolated from green urban wastes. Part II: performance in chemical and environmental technologies. Bioresources 2008, 3, 217. (5) Montoneri, E.; Boffa, V.; Savarino, P.; Tambone, F.; Adani, F.; Micheletti, L.; Gianotti, C.; Chiono, R. Use of biosurfactants from urban wastes compost in textile dyeing and soil remediation. Waste Manage. 2009, 29, 383. (6) Wang, J.; Zhu, Y. Surfactants applications in textile processing, Handbook of Detergents. Part D: Formulation 9; Showell, M. S., Ed.; Taylor & Francis: Boca Raton, FL, 2006; pp 279-303. (7) Watson, R. A. Laundry detergents formulations, Handbook of Detergents. Part D: Formulation 3; Showell, M. S., Ed.; Taylor & Francis: Boca Raton, FL, 2006; pp 51-104. (8) Gasˇparovic, B.; Cosovic, B. Surface-active properties of organic matter in the North Adriatic Sea. Estuarine Coastal Shelf Sci. 2003, 58, 555. (9) Tan, K. H., Ed. Humic Matter in Soil and EnVironment. Principles and ControVersies; Marcel Dekker, Inc.: New York, 2003; Chapter 6. (10) von Wandruszka, R. Humic acids: Their detergent qualities and potential uses in pollution remediation. Geochem. Trans. 2000, 1, 10. (11) Malcom, R. L.; MacCarthy, P. Limitations in the use of commercial humic acids in water and soil research. EnViron. Sci. Technol. 1986, 20, 904. (12) Tanford, C. The hydrophobic effect, 2nd ed.; Wiley: New York, 1980. (13) Rauter, A. P.; Lucas, S.; Almeida, T.; Sacoto, D.; Ribeiro, V.; Justino, J.; Neves, A.; Silva, F. V. M.; Oliveira, M. C.; Ferreira, M. J.; Santona, M. S.; Barbosa, E. Synthesis, surface active and antimicrobial properties of new alkyl 2,6-dideoxy-L-arabino hexopyranosides. Carbohydr. Res. 2005, 340, 191.
(14) An, S. W.; Thomas, R. K.; Baines, F. L.; Billingham, N. C.; Armes, S. P.; Penfold, J. Neutron reflectivity of an adsorbed water-soluble block copolymer at the air/water interface: the effects of pH and ionic strength. J. Phys. Chem. B 1998, 102, 5120. (15) Baines, F. L.; Armes, S. P.; Billingham, N. C.; Tuzar, Z. Micellization of poly(2-(dimethylamino)ethyl methacrylate-block-methyl methacrylate) copolymers in aqueous solution. Macromolecules 1996, 29, 8151. (16) Lowe, A. B.; Billingham, N. C.; Armes, S. P. Synthesis and properties of low-polydispersity poly(sulfopropylbetaine)s and their block copolymers. Macromolecules 1999, 32, 2141. (17) Savarino, P.; Viscardi, G.; Quagliotto, P.; Montoneri, E.; Barni, E. Developments in dyeing technology based on microemulsion technology. J. Dispersion Sci. Technol 1995, 16, 51. (18) Johri, S.; Varshney, H. Synthesis of some new disperse dyes. J. Indian Chem. Soc. 1996, 73, 629. (19) Fedorov, L. A.; Savarino, P.; Dostovalova, V. I.; Viscardi, G.; Carpignano, R.; Barni, E. 1H NMR spectra of a series of disperse azo dyes. Magn. Reson. Chem. 1991, 29, 747. (20) Bridgeman, P. Synthesis and electronic spectra of some 4-aminoazobenzenes. J. Soc. Dyers Color. 1970, 86, 519. (21) Matsui, M.; Kawase, R.; Funabiki, K.; Muramatsu, H.; Shibata, K.; Ishigurec, Y.; Hirota, K.; Hosoda, M.; Tai, K. Perfluoroalkylsulfonylsubstituted azobenzenes as second-order nonlinear optical chromophores. Bull. Chem. Soc. Jpn. 1997, 70, 3153. (22) Komach, L. D.; Zinchenkov, Y. Y.; Rodionova, G. N.; Karpov, V. V.; Popov, E. V. IR spectroscopic study of polymorphic forms of disperse dyes. J. Appl. Chem. U.S.S.R. 1990, 63, 1502. (23) Bassignana, P.; Cogrossi, E. Absorption IR du groupe N)N en colorants azoı¨ques. Tetrahedron 1964, 20, 2361. (24) Sigman, M. E.; Leffler, J. E. Supercritical carbon dioxide. The cis to trans relaxation and pi-pi* transition of 4-(diethylamino)-4′-nitroazobenzene. J. Org. Chem. 1987, 52, 3123. (25) Bortolus, P.; Monti, S.; Albini, A.; Fasani, E.; Pietra, S. Physical quenching and chemical reaction of singlet molecular oxygen with azo dyes. J. Org. Chem. 1989, 54, 534. (26) Albini, A.; Fasani, E.; Moroni, M.; Pietra, S. Photochemical decomposition of 4-arylazo- and 4-arylazoxy-N,N-dialkylaniline N-oxides. J. Chem. Soc., Perkin Trans. 1986, 2, 1439. (27) Haessner, C.; Mustroph, H. Untersuchungen zum UV/Vis-Spektralverhalten von Azofarbstoffen. XVIII. Substituenteneinflu¨sse auf die Absorptionsmaxima der n rarr pi*- und pi f pi*-Banden von 4-N, N-Diethylaminoazobenzenen. J Prakt. Chem. 1987, 329, 493. (28) Park, K. H.; Twig, R. J.; Ravikiran, R.; Rhodes, L. F.; Shick, R. A.; Yankelevich, D.; Knoesen, A. Synthesis and Nonlinear-Optical Properties of Vinyl-Addition Poly(norbornene)s. Macromolecules 2004, 37, 5163. (29) Lee, M. J.; Piao, M. G.; Yeong, M. Y.; Lee, S. H.; Kang, K. M.; Yeo, S. J.; Lim, T. G.; Cho, B. R. Novel azo octupoles with large first hyperpolarizabilities. J. Mater. Chem. 2003, 13, 1030. (30) Ho, M. S.; Natansohn, A.; Barrett, C.; Rochon, P. Azo polymers for reversible optical storage. 8. The effect of polarity of the azobenzene groups. Can. J. Chem. 1995, 73, 1773. (31) Zemskov, A. V.; Rodionova, G. N.; Tuchin, Y. G.; Karpov, V. V. IR spectra and structure of some azo dyes, p-azobenzene derivatives, in various aggregate states. J. Appl. Spectrosc. 1988, 49, 1020. (32) Simova, S.; Radeglia, R.; Fanghaenel, E. 1,2,3-Triazabutadiene. XV. Einfluβ der Substituenten auf die 15N- und 13C-chemischen Verschiebungen in Triazabutadienen und Azobenzenen. J. Prakt. Chem. 1982, 324, 777. (33) Parlati, S.; Gobetto, R.; Barolo, C.; Arrais, A.; Buscaino, R.; Medana, C.; Savarino, P. Preparation and application of a beta-cyclodextrindisperse/reactive dye complex. J. Inclusion Phenom. Macrocycl. Chem. 2007, 57, 463. (34) Rong, L.; Feng, G. Dyeing Properties of PECH-Amine Cationized Cotton with Acid Dyes. J. Appl. Polym. Sci. 2006, 100, 3302. (35) Gauthler, T. D.; Seltz, W. R.; Gran, C. L. Effects of structural and compositional variations of dissolved humic materials on pyrene K Values. EnViron. Sci. Technol. 1987, 21, 243. (36) Chun, C. L.; Lee, J. J.; Park, J. W. Solubilization of PAH mixtures by three different anionic surfactants. EnViron. Pollut. 2002, 118, 307. (37) Sulthana, S. B.; Bath, S. G. T.; Rakshit, A. K. Solution properties of sodium dodecylbenzenesulfonate (SDBS): effects of additives. Bull. Chem. Soc. Jpn. 2002, 73, 281. (38) Fachini, A.; Joekes, I. Interaction of sodium dodecylbenzenesulfonate with chrysotile fibers. Adsorption or catalysis. Colloids Surf. A 2002, 201, 151. (39) Flaming, J. E.; Knox, R. C.; Sabatini, D. A.; Kibbey, T. C. Surfactant effects on residual water and oil saturations in porous media. Vadose Zone J. 2003, 2, 168.
3748 Ind. Eng. Chem. Res., Vol. 48, No. 8, 2009 (40) Kumar, S.; Sharma, D.; Ghosh, G.; Din, K. U. Structural modifications of aqueous ionic micelles in the presence of denaturants as studied by DLS and viscometry. Langmuir 2005, 21, 9446. (41) Pramauro, E.; Pelizzetti, E. Surfactants in Analytical Chemistry. Applications of Organized Amphiphilic Media; Elsevier Science BV: Amsterdam, 1996; Chapter 1 (Comprehensive Analytical Chemistry XXXI). (42) Wang, W. Z.; Feng, L. J.; Wang, H. J.; Cui, Z. G.; Li, G. Z. Effectiveness of Surface Tension Reduction by Nonionic Surfactants with Quantitative Structure-Property Relationship Approach. J. Dispersion Sci. Technol. 2005, 26, 441.
(43) Natrella, M. G. Experimental Statistics; Besson, F. S., Astin, A. V., Eds.; National Bureau of Standards Handbook 91; U.S. Government Printing Office: Washington, D.C, 1996.
ReceiVed for reView December 3, 2008 ReVised manuscript receiVed February 10, 2009 Accepted February 12, 2009 IE801853X
