Volume 43, Issue 6

Interaction between surfactants forms micelles that typically lead to a reduction of the irritation potential of the mixture. The objective of this study is to illustrate that such antagonism between surfactants is applicable to actual cases of consumer products e.g. laundry detergent products. The Zein test is an in vitro assay measuring corn protein denaturation by solutions of surfactant(s) and often used to predict their acute irritation potential. The Zein test data for the surfactant mixtures from nine representative laundry detergents demonstrate that the protein denaturation by the mixtures is, in all cases, lower than the cumulative score of protein denaturation by the different surfactants tested separately. The data clearly indicate that antagonism occurs between the actual surfactants present in their exact proportions as found in the consumer laundry detergent products. These data support the view that the hazard classification of detergent products as (irritant) by the dangerous preparation directive should not be based on a simple cumulative score of the irritation properties of the individual components of the products.

A new spectroscopic method was proposed for evaluating detergency of laundry detergents. In the determination process, salad oil labeled by Sudan Red IV was the simulated lipidic dirt, which was distributed on textile by a centrifugal way adding ultrasonic to simulate the washing mechanical force. The residual oil left after washing was determined according to the maximum absorbance of Sudan Red IV at 502nm. The method precision was satisfactory with a relative standard deviation of RSD = 2%. The relative deviation between the spectrometric and the gravimetric method was less than 2%.

Activated charcoal prepared from the animal bones at different temperatures (600–1000°C) was characterized for surface area, pore volume and by FTIR, EDS, SEM and XRD techniques. The surfaces contained functional groups like carboxyl's and ketones which disappeared at above 800°C, favoring exposure of porous structural surfaces; resulting in enhancement of the adsorption capacity. At the high temperatures the carbon content in the charcoal increased while oxygen got decreased. Adsorption kinetics of acid yellow 34 on the prepared activated charcoal was studied at 10°C and 45°C. Bangham and Parabolic diffusion kinetic models fitted the adsorption data. The two components of the intraparticle diffusion plots suggested that the adsorption process proceeded by surface adsorption and intraparticle diffusion. The thermodynamic parameters of adsorption, such as rate constant (kad), activation energy (DE¿), enthalpy (DH¿) and entropy (DS¿) were evaluated from the first order rate kinetics. The enthalpy of activation (DH¿) indicated that the process was endothermic in nature and its values decreased with the increase in activation temperature. The negative entropy of activation DS¿ reflect the affinity of charcoal toward dye and it decreased with the increase in activation temperature indicating that the dye molecules take more oriented position on the surface of charcoal.

Critical micelle concentrations (cmc) were obtained from tensiometric method on binary mixtures of decyl and dodecyl glucopyranoside nonionic surfactants with hexadecyl-triphenyl and tributyl phosphonium bromide and trimethylammonium bromide surfactants in aqueous media. The cmc data have been analysed in the context of pseudophase separation model. The interaction parameter (b) determined by using the regular solution theory (RST) was found to be negative and composition dependent. The values of interaction parameters were found to be more negative for C 1 0 glucopyranoside mixtures. Employing Maeda's Theory, the chain/chain contribution parameter B 1 was obtained and related to the Gibbs free energy of mixed micelle formation. Thermodynamics of adsorption, surface excess and minimum area occupied by surfactant molecules were also evaluated.

A series of ethoxylated sodium monoalkyl sulfosuccinate (ESMASS) ester surfactants were prepared by reaction of polyethylene glycol (M. wt. 600) with sodium mono alkyl sulfosuccinate (SMASS). The esters were prepared by reaction of octyl, lauryl or cetyl alcohol with sodium sulfosuccinate (SSS) to prepare E(14)SMOSS, E(14)SMLSS and E(14)SMCSS. The chemical structures of the prepared surfactants were confirmed by FTIR and 1 HNMR spectroscopy. The surface tension of the synthesized surfactants was measured at 25°C individually or mixing at different molar fraction with the sodium dioctyl sulfosuccinate. The surface active properties were calculated and micellization process of the mixture was investigated. The molar ratio of anionic (SDOSS) and anionic-nonionic surfactants moiety [E(14)SMOSS, E(14)SMLSS and E(14)SMCSS] in the mixed aggregates were deduced using the regular solution approximation equations. Depending on the critical micelle concentration values for each surfactant individually and mixed systems, the minimum surface tension was exhibited at mixture of [0.6 SDOSS and 0.4 E(14)SMCSS]. The micellar composition of the mixed aggregates were explained and discussed based on the effect of their chemical structures. Activity coefficient (f 1 , f 2 ), interaction parameter (b) and ideality of anionic-nonionic mixed aggregates were evaluated.

Polyoxyethylated nonionic surfactants (POSs) are more soluble in cold than in hot water. On heating, they precipitate reversibly from aqueous solution at and above characteristic temperatures, which are called cloud points (CPs) because the solutions turn cloudy/opaque. The CPs of normally distributed POSs are correlated with the average number p of oxyethylene units per molecule by the linear equation (p – p 0 )/CP=A+B(p – p 0 ). In a homologous series of POSs, the smallest value of p conducive to solubility in ice-cold water, p 0 , belongs to the surfactant with CP=0°. Its hydrophile-lipophile balance, HLB 0 , is a quantitative measure of the hydrophobicity of the parent fatty alcohols, C m H 2 m+1OH, fatty acids and alkylphenols. New CPs, especially of POSs with p approaching p 0 , are combined with published CPs in this study. The order of increasing HLB 0 and hydrophobicity of the parent compounds, accompanied by decreasing CPs of their ethoxylates, is: saturated linear primary alcohols [m=18 (lowest HLB 0 =8.2), 16, 14.6, 13.3, 12.7, 12.0]<oleyl alcohol<saturated primary alcohols with multiple methyl branches (m=10, 13)<Guerbet alcohols (2-hexyldecanol, 2-butyloctanol)<p-nonyl (i.e., triisopropyl)phenol<p-octyl (i.e., diisobutyl)phenol<esterified saturated linear acids [m=18, 12 (highest HLB 0 =11.4)]. Interpolation by means of the equation above with the appropriate values of p 0 , A and B supplies the CP for any homologous POS belonging to one of the 14 groups investigated, based on its degree of ethoxylation p.