Résumé -Production de biosurfactants sur un substrat économique et dégradation du gasoil par une souche du genre Rhodococcus -L'aptitude d'une souche bactérienne du genre Rhodococcus à produire des agents tensioactifs à partir d'une huile de friture résiduelle de tournesol (RSFO) a été testée en milieu non renouvelé. Durant la culture avec RSFO comme seule source de carbone, à la concentration de 3 % (vol/vol), la souche bactérienne a synthétisé des substances de nature extracellulaire qui induisent une émulsification du milieu de culture avec un indice d'émulsion E 24 de 63 %. Sous leur forme non purifiée, les substances extraites du milieu de culture abaissent la tension superficielle de l'eau jusqu'à 31,9 mN m -1 . La croissance exponentielle de la bactérie utilisant RSFO comme seule source de carbone s'est développée au taux spécifique de μ = 0,55 d -1 (d = jour). La concentration micellaire critique de l'extrait brut a atteint la valeur de 287 mg L -1 (γCMC = 31,9 mN m -1 ). Après methylesterification, la fraction lipidique du biosurfactant a été analysée par GC-MS / EI, qui révèle la présence d'esters méthyliques d'acide gras. Le micro-organisme a été également cultivé avec le gasoil comme seule source de carbone à la concentration de 1 % (vol/vol): la phase de croissance exponentielle s'est développée au taux de μ = 0,02 d -1 , sans production de substances émulsifiantes : le microorganisme semble développer différents modes d'assimilation de substrat, selon la nature de la source de carbone. Les agents tensioactifs synthétisés à partir de l'huile de tournesol résiduelle de friture par Rhodococcus erythropolis 16 LM.USTHB pourraient être utilisés, de manière rentable, dans l'industrie pétrolière avec des spécifications minimales de pureté pour la restauration des sites contaminés par les hydrocarbures et dans la récupération du pétrole brut. Abstract
To develop a new method for the manufacture of anionic surfactants such as alkanesulfonates, which are completely biodegradable, we used linear aliphatic hydrocarbons C 12 and C 14 as raw material. These hydrocarbons were transformed into the corresponding sulfochlorides in quantitative yield by photosulfochlorination with sulfuryl chloride. The operating conditions led to reaction mixtures containing all the position isomers of sulfochlorinated and chlorinated alkanes. These compounds have been identified by gas chromatography-mass spectrometry. The isomeric distribution of different reaction products, as well as the molar ratio of the main product, the alkanesulfochlorides, vs. the by-products, the alkanechlorides, were determined by the gas chromatography method. The particular isomeric distribution observed during these reactions was different from that of classic chain reactions, as highlighted by the values of calculated relative reactivities. After separation, purification, and alkaline hydrolysis steps, the resulting dodecane and tetradecanesulfonates showed good surface activity. Indeed, the values of the surface tensions at the critical micelle concentration (CMC) compare well with those in the literature. CMC values of these mixtures are given, and the influence of isomeric distribution on CMC values and on the surface tension values at the CMC is presented.
Patent Blue V has been applied in a solvent extraction spectrophotometric method for the determination of cationic surfactants (CS) in industrial wastewaters. The method is based on the introduction of Patent Blue V as an anionic dye, and the formation of an ion pair association with CS in chloroform under the studied extraction conditions. The maximum wavelength of absorption for the ion pair is located at 627 nm, and a molar absorption coefficient of higher than 3.6 9 10 5 l mol -1 cm -1 was obtained. The calibration curve was linear between 0 and 5.48 9 10 -6 M, and exhibited a significant coefficient of correlation. Based on the calculated values for the relative standard deviation (%) over the studied concentration range, the method was found to be highly sensitive, and the deduced limit of detection for the method was found to be very low (8.6 9 10 -8 M of CTAB). It was also found that a washing step was necessary for the organic extract in order to remove interferences caused by foreign ions and species present in unknown samples. To validate this method, the procedure was used to determine the CS contents of samples collected from textile industry wastewaters in the Algiers region. The results obtained showed good agreement for the proposed method.
Using different reaction conditions of photosulfochlorination of n-dodecane, two samples of anionic surfactants of sulfonate type are obtained. Their micellar behavior has been already reported and the relationship between their isomeric distribution and their chemical structures and micellar behaviors have been more thoroughly explored. In this investigation, we screened the foaming properties (foaming power and foam stability) by a standardized method very similar to the Ross-Miles foaming tests to identify which surfactants are suitable for applications requiring high foaming, or, alternatively, low foaming. The results obtained for the synthesized surfactants are compared to those obtained for an industrial sample of secondary alkanesulfonate (Hostapur 60) and to those of a commercial sample of sodium dodecylsulfate used as reference for anionic surfactants. The foam formation and foam stability of aqueous solutions of the two samples of dodecanesulfonate are compared as a function of their isomeric distribution. These compounds show good foaming power characterized in most cases by metastable or dry foams. The highest foaming power is obtained for the sample rich in primary isomers which also produces foam with a relatively high stability. For the sample rich in secondary isomers we observe under fixed conditions a comparable initial foam height but the foam stability turns out to be low. This property is interesting for applications requiring low foaming properties such as dishwashing liquid for machines. The best results are observed near and above the critical micellar concentrations and at 25°C for both the samples.
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