Based on light scattering intensity measurements, a critical concentration for micelle formation can be assigned to sodium taurodeoxycholate in aqueous electrolyte solutions. For sodium taurocholate a progressive aggregation even at very low concentrations of bile salt is indicated. Surface tension and diffusion coefficients are also reported.Key words: Bile salts, Sodium taurodeoxycholate, Sodium taurocholate, Micelles, Critical micellar concentration.The detergent-like properties and the propensity to form micellar aggregates are related to the most importance physiological functions of bile salts. Yet, in spite of numerous investigations, partly summarized in several review articles [1][2][3], there is a great deal of disagreement even about such common parar~-eters as the critical micellar concentration (cmc) and the micellar aggregation number which, for specified temperature and solvent composition, are characteristic for any micelle-forming amphiphilic compound. This lack of agreement among many experimental observations, not unusual for surfactants [4, 5], can be ascribed to such obvious causes as the presence of impurities in the samples of bile salts and the use of inappropriate experimental techniques, or to the more subtle factors, for instance, those related to the inadequate or incomplete treatment of the experimental data [4,6,7]. Notably lacking are the systematic, comparative studies on carefully purified materials using several complementary experimental techniques. In this report we compare the reversible aggregation behaviour of a dihydroxy bile salt, sodium ;aurodeoxycholate (NaTDC) and a trihydroxy compound, sodium taurocholate (NaTC), in aqueous electrolyte solutions over a broad range of solute concentrations. The light scattering intensity measurements at 25 ~ were supplemented by surface tension and diffusion experiments. The state of aggregation of two bile salts at low concentrations was explored in detail. For this purpose we made use of two favorable properties of EM 642 bile salts for the light scattering measurements, namely, a relatively high molar mass of the monomer and the large refractive index increment. Consequently, our results are particularly relevant to the currently debated question of the existence of cmc in solutions of bile salts [8][9][10][11][12][13][14][15][16][17][18][19].The results of the light scattering experiments are presented in figure 1 as Debye plots in terms of the total bile salt concentration, c~, and the Rayleigh ratio in excess of the solvent (0.15 m or 0.60 m NaCI), Rg0.The logarithmic scale is used in order to incorporate in a single diagram the data over almost three orders of magnitude in c~ and to emphasize those at low c~. These plots are different from the customary Debye plots for treatment of light-scattering intensity measurements on surfactant micelles, in which the micellar concentration, c2 = e~ -cmc, and Rayleigh ratio in excess of that at the cmc are used. Consequently, the apparent aggregation numbers, Na*, indicated on ...

Photochemical activation routes are gaining the attention of the scientific community since they can offer an alternative to the traditional chemical industry that mainly utilizes thermochemical activation of molecules. Photoreactions are fast and selective, which would potentially reduce the downstream costs significantly if the process is optimized properly. With the transition towards green chemistry, the traditional batch photoreactor operation is becoming abundant in this field. Process intensification efforts led to micro- and mesostructured flow photoreactors. In this work, we are reviewing structured photoreactors by elaborating on the bottleneck of this field: the development of an efficient scale-up strategy. In line with this, micro- and mesostructured bench-scale photoreactors were evaluated based on a new benchmark called photochemical space time yield (mol·day−1·kW−1), which takes into account the energy efficiency of the photoreactors. It was manifested that along with the selection of the photoreactor dimensions and an appropriate light source, optimization of the process conditions, such as the residence time and the concentration of the photoactive molecule is also crucial for an efficient photoreactor operation. In this paper, we are aiming to give a comprehensive understanding for scale-up strategies by benchmarking selected photoreactors and by discussing transport phenomena in several other photoreactors.

No abstract

Monolith structures are a common method to scale flow chemistry tools up to industrial throughput. Internally illuminated monolith reactors (IIMRs) were their versions for photochemistry. The channels inside the monolith were illuminated with optical fibers coated with a photocatalyst such as TiO 2 . The majority of the light in an IIMR was however not utilized to illuminate the reaction medium. Furthermore, the monolith was always made of opaque materials, making it impossible for unabsorbed light to illuminate other channels, lowering the photochemical space-time yield (PSTY), a benchmark for the overall energy efficiency of a photoreactor. In this paper, the potential of a translucent monolith structure for scalable photochemical process design was tested. Due to the translucent nature of the monolith, there was no need for optical fibers or multiple light sources to provide the necessary photon flux and distribution. There has never been a study of translucent monoliths in the open literature and no design parameters have been investigated. This research studies the first translucent monoliths and their design principles by varying the channel size, channel distance as well as the amount of unit cells with a ray tracing algorithm in COMSOL Multiphysics. A model was developed, validated and used to design a monolith for the photodegradation of micropollutants in a case study. A theoretical improvement of seven orders of magnitude in PSTY was obtained compared to IIMRs making this reactor design a promising candidate for more efficient photochemical processes. K E Y W O R D Sadditive manufacturing, COMSOL multiphysics, modeling and simulation, process intensification, ray tracing, translucent monolith