No abstract

Semi-volatile organic compounds (SVOCs) are hazardous contaminants found in several products - ranging from personal care products to plastic products and the environment. Their chemical migration into food substances, raising environmental and health concerns, has been well documented. The dispersion/diffusion and solubility of SVOCs in food simulants is an indicator of their migration from food packaging materials. Here, we employed molecular dynamics simulations to investigate molecular mass transfer/diffusivity and intersolubility of three (S)VOCs from various sources into water. The simulation results illustrated that the molecular weight of SVOCs affects their dispersion and solubility in water. SVOC molecules are also much easier to diffuse into water at higher temperatures and longer time periods. The intersolubility of SVOCs in water according to the Flory-Huggins parameter (χ) and Hildebrand solubility parameter (δ) occurs in the following order: methyl isocyanate > caprolactam > naphthalene. The solubility of SVOCs increases with temperature, as evident by the decreasing δSVOCs and χsvocs. These results will play a key role in expanding the knowledge base of chemical migration of small molecules into food simulants.

No abstract

This study investigated the use of fractional condensation, following the fast pyrolysis of three different ashrich biomass feedstocks, to optimize the composition of aqueous pyrolysis condensates (ACs) for downstream microbial conversion. Optimum conditions were first predicted and established theoretically by means of vapor−liquid equilibrium flash calculations that employed the modified UNIFAC Dortmund (UNIFAC-DMD) model. Thereafter, theoretical models were experimentally validated on a 10 kg/h fast pyrolysis setup. Model predictions revealed that a temperature combination of 120 and 50 °C on the first and second staged condensers, respectively, returned optimum production of AC yield and substrates at the expense of inhibitors. Satisfactory agreement existed between most experimental data and model predictions, and the qualitative trend was mostly reproduced correctly. Some noteworthy deviations were, however, observed, most especially for inhibitory compounds, which were blamed on the limitation of the UNIFAC-DMD model in accurately predicting the phase behavior of organic compounds at such very low concentrations as well as the scarcity of precise vapor pressure data for some of these organic compounds. Nonetheless, the study demonstrated how valuable theoretical phase equilibrium models are in predicting the composition of fast pyrolysis bio-oils and how fractional condensation proves to be a key upstream pre-treatment for valorizing ACs.