Effects of Three Ionic Liquids on Microbial Activity of an Organic Soil. Microcalorimetric Study

Ionic liquids are considered as a potential green replacement for traditional volatile organic solvents, but their impact on the environment is not sufficiently studied. The effect of the addition of aqueous solutions of different amounts (from 0% to 75%) of three ionic liquids, two based imidazolium, dimethylimidazolium dimethylphosphate ([MMIM][DMP] and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) and choline dihydrogen phosphate ([Chol][DHP]) on the microbial activity of an acidic, organic soil, was determined in this work. For this propose, an isothermal microcalorimeter, TAM III of TA Instruments was used. This apparatus allows estimating the variation of the metabolic activity through the variation of the heat released after the addition of the ionic liquids (ILs) to the soil. The results showed that the most toxic IL is [BMIM][BF4] which presented a large stress effect and subsequent death on soil microorganisms for the highest concentration of the IL. On the contrary, [Chol][DHP] showed stimulation of the microbial activity for all the concentrations.

Investigations of Oxidation Dependence on Type of Porous Silicon Near Room Temperature by Isothermal Microcalorimeter

Oxidation of porous silicon has been studied using thermal activity monitoring, i.e. isothermal microcalorimeter. It was found that, at room temperature (25 °C) the micro-calorimetric signal from the oxidation of the p+-type porous silicon (PS) reduces exponentially, while in the case of n-type PS, the signal starts to increase slowly, reaching its highest value after some hours. This kind of behaviour is typical of autocatalytic reactions. To clarify the origin of the difference, we varied the preparation parameters of the porous silicon. We determined the activation energy from the measurements near the room temperature (25–70 °C). The results of this research have been compared with the previous observations and the possible origin of the difference has been discussed.