Volume 48, Issue 2

We present a case study of surfactant enhanced oil recovery using Alkyl polyglucoside/1-naphthol formulations. Alkyl polyglucosides are a green, non-toxic and renewable surfactant class synthesized out of agricultural raw materials. We measured interfacial tensions versus n-octane and viscosities of these formulations and conducted one coreflood enhanced oil recovery (EOR) experiment where we recovered 82.6 % of initial oil in place demonstrating that these formulations are efficient EOR agents.

The work refers to the already published modification of widely used method for anionic active agents determination which concerns the replacement of the mixed indicator, consisting of Acid Blue 1 and carcinogenic Dimidium Bromide, applied in the International Standard ISO 2271:1989 with solvatochromic dye i.e. 5-(3-bromo-4-hydroxy-5-methoxyphenyl)-7,7-dimethyl-7H-indolo[1,2-a]quinolinium perchlorate (1). The value of pK a for examined dye (1) amounts to 6.59 thus the influence of different pH values of the probes on the analysis results was studied i.e. precision of determination of titration endpoint and the same the result of the quantitative analysis. The change of pH for aqueous and apparent pH for organic phase were determined during the titration process. It was shown that there is no effect of the pH change in its range varying from 3.5 to 5 on the results. The modification of the method for the probes which pH do not fit to the range mentioned above is presented.

The coal ash (Φ) was used as an adsorbent for the removal of tartrazine from aqueous solution at room temperature. The adsorption capacity of tartrazine increased as the adsorption time was increased and then remains constant after 30 min adsorption duration. It was found that the Φ removed more than 40% of tartrazine from the aqueous solution within 1 h contact time. The equilibrium adsorption was also analyzed by Langmuir isotherm and it was found that the data followed the Langmuir isotherm models.

Removal of acid blue 1 from aqueous solution on activated carbon produced from Salvadora oleoides was investigated. The samples were characterized by BET surface area, BJH pore volume and pore diameter, XRD, SEM, EDS and FTIR analysis. The surfaces contain functional groups like ketones and hydroxyl which disappeared at high activation temperature; relatively high amount of carbon w.r.t. oxygen was found with the increase in activation temperature; the increase in surface area and development of porous structures showed a positive effect on the adsorption capacity. Adsorption of the dye on carbon at 10 and 45°C showed that the first order, Bangham and Elovich and parabolic diffusion equations apply to the kinetic data. The adsorption rate increased with the temperature and with thermal activation of the sample. Thermodynamic parameters like ΔE ≠ , ΔH ≠ , ΔS ≠ and ΔG ≠ were calculated from the kinetic data. The negative values of ΔS ≠ reflect decrease in the disorder of the system at the solid-solution interface during adsorption. Gibbs free energy (ΔG ≠ ), which represents the driving force for the affinity of dye for the carbon, increased with the increase in activation temperature.

Recently, a novel concept has been proposed to interpret the nonequilibrium character of oppositely charged polyelectrolyte/surfactant mixtures. According to this approach, at low surfactant-to-polyelectrolyte ratios the system is a thermodynamically stable solution. In a given composition range colloidal dispersions of the polyelectrolyte/surfactant nanoparticles are formed. In the presence of surfactant excess, the dispersions can be stabilised via the adsorption of the surfactant ions on the surface of the hydrophobic polyelectrolyte/surfactant nanoparticles. In the presence of polyelectrolyte excess, charge stabilised polyelectrolyte/surfactant dispersions might also be prepared if the charge of the macromolecules is large enough. These latter colloidal dispersions are stabilised by the uncompensated charges of the polyelectrolyte. The colloidal dispersion concept provides several options to control the formation of self-assemblies and the kinetic stability of the mixtures. In this paper, the effect of solution preparation protocols and different additives (including non-ionic polymers or surfactants) on the mentioned properties of oppositely charged macromolecule/surfactant systems is discussed.

New double-tail trisiloxane surfactants of the general formula R 1 NR 2 CH 2 CH(OH)CH 2 O(CH 2 CH 2 O) x CH 3 (R 1 = Me 3 SiOSiMe(CH 2 ) 3 · OSiMe 3 ; R 2 = Me 3 SiOSiMe((CH 2 ) 3 OCH 2 CH(OH)CH 2 )OSiMe 3 ; x = 8.4, 12.9, 17.5, 22) have been synthesized. The spreading ability (SA) values of the double-tail trisiloxane surfactants solutions (1.0 × 10 −3 mol/L) with average ethoxy units of 8.4, 12.9 and 17.5 on ficus microcarpa leave surface are more than 9 within 3 minutes, and their SA values on the parafilm surface are over 15 within 10 minutes at a concentration of 5.0 × 10 −3 mol/L. In alkaline environment (pH = 10.0) the hydrolysis resistant ability (HRA) of the double-tail trisiloxane surfactant containing average ethoxy units of 8.4 with the surface tension of aqueous solution (1.0 × 10 −3 mol/L) of less than 23 mN/m over 170 days, is far better than the others’. It is suggested that a more flexible spacer between hydrophobic groups and hydrophilic groups in double-tail trisiloxane surfactants molecules, not only can improve their SA on low-energy solid surfaces, but also improve their HRA.

A novel series of dibenzothiophenedioxide sulphonamide derivatives were synthesized and tested as antimicrobial agents. The chemical structures of the prepared compounds were confirmed by micro elemental analysis, fourier transform infrared (FT-IR) and proton nuclear magnetic resonance spectroscopy (H-NMR). The surface parameters of two of the prepared compounds were determined at 35°C including, surface tension, effectiveness, maximum surface excess and minimum surface area. Also the standard free energy of micellization and adsorption were recorded. The results showed that the prepared sulphonamides have good surface properties and effective antimicrobial activity against thirty three test organisms isolated from cooling towers.

The micellar and interfacial properties of three sulfobetaine surfactants of the type C n H 2n+1 N + Me 2 (CH 2 ) 3 SO 3 − (n = 10; SB3-10 n = 12; SB3-12, n = 16; SB3-16) have been studied by conductometry and surface tension measurements. The critical micellar concentration (CMC), surface excess concentration (Γ max ), minimum surface area per molecule of surfactant (A min ), Gibbs free energy of micellization (ΔG o m ), Gibbs energy of transfer (ΔG o trans ), the surface pressure at CMC (π CMC ) and the Gibbs energy of adsorption (ΔG o ads ) of these surfactants have also been determined. Effect of formamide has been studied at higher temperature conductometrically. Results show that alkyl chain length and the amount of solvent composition influences micellization and surface properties of sulfobetaines. Increment in the CMC, ΔG o m and ΔG o trans , can be accounted for changes in the polarity of the bulk phase. Γ max , and π cmc decreases where as A min increases with increase in the organic solvent. It was also observed that micellization in water-formamide mixture was even slower than in the case of ethylene glycol.

Present work includes experimental studies related to the viscosimetric behaviour of microemulsions that consist of three compounds: isooctane (organic phase), water (aqueous phase) and Aerosol OT (surfactant). The effect of the microemulsion composition, based on the ω parameter value, and the effect caused by the temperature have been analysed in this work. In relation to the influence of temperature and the use of microemulsions in different processes, one important characteristic of this kind of systems (the percolation phenomenon) must be taken into account in the discussion of the experimental results.