Lipases have been added to detergents in an attempt to develop more environmentally friendly and energy efficient products for triglyceride-based stains. However, more research is needed to improve the efficiency of lipase-containing detergents. In this work we have examined all the factors affecting lipase performance in detergent formulations, particularly for hard surface cleaning. Several issues, such as thermal and hydrodynamic stability, kinetic aspects, and surfactant compatibility, both in solution and at the oil/water interface, have been addressed and the conditions for an optimal performance have been established. The role of some stabilizers in preventing lipase deactivation has also been considered, and some insight on the mechanisms of lipase deactivation under washing conditions is provided. Finally, washing tests conducted in a continuous flow device which simulates a clean-in-place (CIP) system have demonstrated that, under optimal conditions, a reduction of the surfactant dosage was possible upon the incorporation of lipases in detergent formulations.

Thermal lens spectrometry (TLS) and photopyroelectric (PPE) techniques were used to obtain the thermal diffusivity and effusivity of different nanofluid samples. The thermal effusivity of these samples was obtained by the PPE technique in a front detection configuration. In the case of the determination of the thermal diffusivity, TLS was used for the different solvents in the presence of gold nanoparticles (nanofluids). In this technique, an Ar + laser and intensity stabilized He-Ne laser were used as the heating source and probe beam, respectively. The experimental results showed that thermal diffusivity values of the studied solvents (water, ethanol, and ethylene glycol) were enhanced by the presence of gold nanoparticles. Comparisons with literature values show good agreement with pure solvents. These techniques are applicable for all kind of liquid samples, including semitransparent ones.

Thermal and optical properties of two different nanofluids containing SiO 2 and TiO 2 semiconductor nanoparticles were studied by thermal lens spectrometry (TLS) and spectrophotometry. In the case of SiO 2 nanofluids the transmission electron microscopy technique was used to obtain the SiO 2 nanoparticle sizes to investigate the size effect of these nanoparticles on the sample thermal diffusivity which is important in some medical applications such as photothermal-modulated drug delivery systems. On the other hand for the case of TiO 2 nanofluids, the photopyroelectric technique, TLS, scanning electron microscopy, and X-ray diffraction were employed to investigate the concentration effect on the thermal properties of these nanofluids. Thermal diffusivities and effusivities as functions of the TiO 2 nanoparticle concentrations were obtained. From the experimental results, an incremental increase in the thermal diffusivities and effusivities was observed when the nanoparticle concentration was increased, indicating that the nanoparticle concentration is an important factor to be considered to obtain nanofluids with more thermal efficiency which are required for some applications, such as degradation of residual water.

No abstract

No abstract

No abstract

No abstract

The degradation of linear alkylbenzene sulfonates (LAS) in aqueous solutions by ozone has been investigated. The ozonation process was performed in a stirred tank reactor with recirculation which simulates the clean-in-place process used in many industrial facilities. The gas-liquid mass transfer of ozone in a buffer solution at different temperatures (25-55°C) was also studied in the same device, revealing that ozone decomposition can be considered negligible under the experimental conditions assayed. The effect of the initial LAS concentration, temperature, and ozone concentration on the concentration of homologues and total LAS were analysed as a function of time. Both concentrations diminished with time, this effect being more significant when higher temperatures were assayed. The relative proportion of homologues shows that the homologues of higher chain length are degraded in a greater proportion than are the homologues with shorter chain lengths.