Incorporation of silver to titanium dioxide is of great interest for photocatalytic disinfection applications since in addition to the enhancement of the electron-hole separation and interfacial charge transfer and the increase in the visible light response, silver compounds present a strong bactericidal effect. Ag/TiO 2 materials used in suspension and immobilized in two different configurations (catalytic wall and fixed-bed reactors) have been prepared, characterized and tested using Escherichia coli as model microorganism. Although the incorporation of silver to powdered Degussa P25 TiO 2 increases the activity, the thermal treatment required for the stabilization of the supported metal particles reduces the global efficiency. The comparison with experiments of dye photodegradation indicates that the activity of Ag/TiO 2 is mainly due to the bactericidal role of silver and not to the enhancement of the photocatalytic mechanism. The best tested system has been proved to be the Ag/TiO 2 catalytic wall reactor with a 0.6 wt% of Ag loading, showing a high activity both in relative (per gram of TiO 2 ) and absolute terms, an optimal use of the radiation source, and a good stability of the film with negligible silver lixiviation, allowing the continuous treatment of water.

Actually, there is a growing interest in the biotechnological production of lactic acid by fermentation aiming to substitute fossil fuel routes. The development of an efficient method for its separation and purification from fermentation broth is very important to assure the economic viability of production. Due to its high reactivity and tendency to decompose at high temperatures, the study of lactic acid thermal behavior is essential for its separation processes and potential application. In the present study, differential scanning calorimetry (DSC) analyses showed endothermic peaks related to the process of evaporation. Data of thermogravimetry (TG/DTG) were correlated to Arrhenius and Kissinger equations to provide the evaporation kinetic parameters and used to determine the vaporization enthalpy. Activation energies were 51.08 and 48.37 kJ·mol−1 and frequency values were 859.97 and 968.81 s−1 obtained by Arrhenius and Kissinger equations, respectively. Thermogravimetry, coupled with mass spectroscopy (TG-MS), provided useful information about decomposition products when lactic acid was heated at 573 K for approximately 30 min.

Lignin has gained momentum as a renewable material because it is the largest natural source that can provide aromatic compounds in a wide range of applications. However, its heterogeneity in terms of high polydispersity molar mass distribution and variety of functional groups has limited the direct production of added-value lignin-derivatives. Among the alternatives to obtain more homogeneous lignin cuts is solvent fractionation. However, it is not well understood how different solvents influence lignin partition, and thus it is difficult to establish a rational solvent order to perform it. Thus, the purpose of this work was to understand Eucalyptus urograndis kraft lignin partition in organic solvents through the application of three solubility parameter theories: Hildebrand, Hansen (HSP), and Functional (FSP). Through the theories studied, FSP provided the best representation of lignin partition in organic solvents. In addition, the influence of solvents’ solubility parameters on lignin solubility was investigated by multiregression analyses, which revealed that only the polar solvent parameter showed statistical relevance to describe lignin solubility. The results of this work may contribute to the effective development of technical lignins’ fractionation, allowing the production of higher-value lignin derivatives, increasing the profitability of biorefineries, and establishing a sustainable bio-based economy.

No abstract

No abstract