Band 42, Heft 5

Standard method of surfactant determination is UV/VIS determination and a long time — consuming standard flask extraction with chloroform, in which very large quantities of harmful organic solvent are employed. In this work, ultrasonic solvent extraction of anionic, cationic and non-ionic surfactants was compared with the traditional shake-flask extraction method and both methods were applied on laundry wastewater samples. Separation, identification and quantification of surfactants were done by thin layer chromatography and video densitometry. Ultrasonic extraction procedure was optimized with regard to the amount of solvent and duration of extraction. This extraction method proved to be much better because it was faster and more efficient. Due to the application of much less organic solvent, it is both economically and ecologically favorable.

The two last decades have been marked by an increasing environmental awareness. In relationship to detergents, renew-ability, biodegradability, and ecotoxicity have become important issues in the study, development and application of surfactants. In this respect, rapeseed methyl ester ethoxylates are an interesting new class of nonionic surfactants that gain more and more interest on the market. They are easily to formulate into attractive liquid detergents with high cleaning performance and show a more favorable ecotoxicological profile compared to fatty alcohol ethoxylates.

The effect of counterions and temperature on the association (critical micelle concentration, thermodynamics of micellization) and partition balances (experimental partition coefficient) of three quarternary ammonium surfactants (CPX) having a common hexadecylpyridinium cation and different anions (chloride, bromide, iodide) were studied in aqueous solutions at the temperature range 20–50°C, using conductometry, potentiometry, UV spectroscopy and measurement of surface tension. All methods used gave closely similar values for critical micelle concentration. From calculated thermodynamics parameters the process of micellization was found to be spontaneous and exothermic. Experimental partition coefficient of hexadecylpyridinium halides increased from chloride to iodide. The objective of this work was to check whether surfactant counterions can affect the micellization and partition processes. From the results obtained it seems that the differences found in micellization and partitioning of all compounds studied, may be attributed to the different physicochemical properties of chloride, bromide and iodide anions as their differences in mobility etc.

Addition of electrolytes to surfactant solutions does change the temperature at which the clouding phenomena occur. Electrolytes have a large effect on the cloud point (CP) of hexa ethyleneglycol mono-n-dodecyl ether (C 12 E 6 )/water system, because of their effect on water structure and their hydrophilicity. In this work we report the effect of electrolytes (KCl, NaCl and Na 2 CO 3 ) on the (CP) of C 12 E 6 /water system. It has been observed that the cloud point as a function of electrolyte's concentration, depends mostly on the electrolyte's charge. Furthermore it has been observed that the two factors, temperature and salt concentration mainly affect equivalently the phase separation of C 12 E 6 /water system. Moreover, ionic surfactants such as sodium dodecyl sulfate (SDS) and carboxylate ethoxyle (TDC) have been used to investigate their effect on CP of C 12 E 6 .

In this study the thermodynamic properties of various Oxo-alcohol ethoxylates related to their adsorption at the air/water interface and to their micellization have been studied. The effect of various additives, including electrolytes, alcohols, polar aromatic solutes, and ionic and nonionic surfactants on the cloud point of aqueous solutions of the same surfactants has also been investigated. Salting-out electrolytes lower the cloud point while salting-in species raise it. Except for the totally water-miscible alcohols, most hydroxylated compounds lower the cloud point. Phenols, aromatic alcohols, and amines seem to interact preferentially with the ethylene oxide groups of the micelles, leading to strong dehydration, and consequently lowering the cloud point. On the contrary, by forming mixed micelles, an anionic surfactant strongly raises the cloud point of the nonionic.

The adsorption kinetics of the non-ionic surfactant C 10 E 4 was studied by maximum bubble pressure (MPT-2) and drop/bubble shape analysis tensiometry (PAT-1). The two methods complement each other and show good agreement in the overlapping time range if the problem of the so-called initial load at the drop/bubble surface is considered properly. The adsorption appears to be diffusion-controlled, giving an average diffusion coefficient of the order of 110 −10 m 2 s −1 . At higher surfactant concentrations, the adsorption rate tends to change to a non-diffusional mechanism, which is possibly caused by surface active impurities.

Monotriethanolammonium salts of N -acylated N -carboxyethylglycine were obtained. Acid chlorides were used in the acylation reaction. The products contained about 25% of fatty acid under acylation conditions, which resulted from the adopted synthesis conditions. Triethanolammonium salts of N -acyl- N -carboxyethylglycine offered good surface active properties — these were confirmed in tests of standard detergent formulations, which were compared to those of corresponding commercial products.