Rafael B. Mato

The influence of the energy absorbed from microwave pretreatment on biogas production from secondary wastewater sludge

In this study, microwave treatment is analyzed as a way to accelerate the hydrolysis in anaerobic digestion of municipal wastewater sludge. The influence of the absorbed energy, power and athermal microwave effect on organic matter solubilization and biogas production has been studied. In addition, a novel method that considers the absorbed energy in the microwave system is proposed, in order to obtain comparable experimental results. The absorbed energy is calculated from an energy balance. The highest solubilization was achieved using 0.54 kJ/ml at 1000 W, where an increment of 7.1% was observed in methane production, compared to the untreated sample. Using a higher energy value (0.83 kJ/ml), methane production further increased (to 15.4%), but solubilization decreased. No power influence was found when 0.54 kJ/ml was applied at 1000, 600 and 440 W. Microwave heating was compared to conventional heating in two different experimental setups, providing similar methane yields in all cases.

Thermal degradation of grape marc polyphenols

Bioactive compounds of wine making by-products are of interest in food, cosmetics and pharmaceutical industries. Extraction of antioxidants under mild conditions is time-consuming, giving ground to the development of intensification processes where the operation at high temperature may deteriorate extract quality. This study examined thermal degradation of grape marc and its filtered extract (80, 100 and 150°C). The decrease in anthocyanin content was modelled under non-isothermal conditions by first order kinetics, using the Arrhenius equation. Simulated degradation under isothermal heating showed that the grape marc is more sensitive by one order of magnitude to heat than the filtered extract. This tendency was also confirmed by analyses of the total phenolic content and antioxidant activity. It is suggested that an optimal combination of temperature, treatment time and also raw material environment could be found in process intensification.

Behavior of the LEMF equation for vapor-liquid equilibrium data treatment of systems with negative deviations from ideality

Abstract Mato, R.B., Mato, F.A. and Mato, F., 1991. Behavior of the LEMF equation for vapor-liquid equilibrium data treatment of systems with negative deviations from ideality. Fluid Phase Equilibria, 68: 115-130. The local effective mole fraction (LEMF) equation shows abnormally poor performance in correlating and predicting vapor-liquid equilibrium data of binary and ternary systems when a binary pair exhibits negative deviations from ideality. This abnormal performance becomes progressively worse as the negative deviations from ideality increase, and it is a mathematical consequence of the negative value used in the LEMF equation for the non-randomness parameter αij.