Values of cell membranes permeability coefficients for water and molecules of cryoprotective agents (CPAs) are the necessary characteristics for developing physical-mathematical models describing mass transfer processes through cell membranes in order to predict optimal cell cooling rates. We carried out a comparative analysis of the permeability coefficients of mouse oocyte membranes for molecules of water, ethylene glycol (EG), propane-1,2-diol (1,2-PD) and dimethyl sulfoxide (Me2SO), determined by applying the classical Kedem-Katchalsky model, which considers only the penetration of non-electrolyte molecules (water and CPA) through the membrane, and the model developed by us, which takes into account the transmembrane transfer of ions and the associated changes in the transmembrane electric potential. We shown that calculations based on the developed modified model provide lower values of the permeability coefficients of the oocyte membrane for water and CPA molecules. What is important that the obtained by our modified model permeability coefficients for water molecules do not depend on the type of cryoprotectant, while the application of the classical model both in our studies and works of other authors always gave different values of these coefficients in solutions with different cryoprotectants. Our modified model also makes it possible to determine the dynamics of the transmembrane electric potential of the cell under the conditions of transmembrane mass transfer and the duration of the membrane being influenced by the changes in electric potential, that is a parameter that can directly affect the viability of cells.

To study the mechanism of heat and mass transfer in porous food material and explore its coupling effect in radio frequency (RF) drying processes, experiments were conducted with potato cubes subjected to RF drying. COMSOL Multiphysics® package was used to establish a numerical model to simulate the heat and mass transfer process in the potato cube and solved with finite element method. Temperature history at the sample center and the heating pattern after drying was validated with experiment in a 27.12 MHz RF heating system. Results showed the simulation results were in agreement with experiments. Furthermore, the temperature distribution and water vapor concentration distribution were correspondent with water distribution in the sample after RF drying. The water concentration within the food volume was non-uniform with a higher water concentration than the corner, the maximum difference of which was 0.03 g·cm-3. The distribution of water vapor concentration in the sample was similar to that of water content distribution since a pressure gradient from center to corner allowed the mass transfer from the sample to the surrounding in the drying process. In general, the moisture distribution in the sample affected the temperature and water vapor concentration distribution since the dielectric properties of the sample were mainly dependent on its moisture content during a drying process. This study reveals the mechanism of RF drying of porous media and provides an effective approach for analyzing and optimizing the RF drying process.

Removal of phenol from wastewater is essential to achieve permitted concentrations according to the recommendations of USEPA. The adsorption capacity of phenol in activated adsorbent with KOH of Enterolobium contortisiliquum (TAC) was evaluated at different temperatures. The Langmuir isotherm represented the equilibrium data of this study. Thermodynamic process was endothermic, spontaneous, and reversible. The mass transfer parameters ranged from KE 0.68 to 0.96 × 10-3 (cm s-1), Ds 8.95 to 14.35 × 10-9 (cm2 s-1), and Dp 5.023 × 10-8 (cm2 s-1). The PVSDM model represented the adsorption kinetics. Intraparticle diffusion limits the mass transfer process Biot > 100. The two-stage process minimized the total amount of TAC required to achieve the permitted specification of phenol concentration in wastewater from different industrial sectors. TAC showed significant performance in the removal of phenol from wastewater.

The present study investigates the wastewater treatment performance of an acoustic cavitation assisted plasma (ACAP) process in a circulating reactor using Rhodamine B (RhB) as a model water pollution. The concept of this process was proposed by the authors recently for a batch type rector. The measurements revealed that combining the ultrasound irradiation with pulsed discharge plasma allows the RhB degradation efficiency to be drastically increased as compared with the plasma-alone case. This effect is especially significant at higher values of solution electrical conductivity examined in a range of 20 ~ 400 μS/cm. Acidic conditions and larger flow rates of solution were found to be favorable for the degradation efficiency. The effect of flow rate was also analyzed through numerical simulation. The results indicated that the mass transfer of RhB to the plasma-cavitation zone is one of the controlling parameters influencing the degradation performance. Behavior of bubbles and pulse discharge frequency were examined using a high-speed video camera. Relatively large bubbles were found to favor the plasma pulse generation and propagation when move near the high-voltage electrode. On the whole, the results of this study suggest that the ACAP process has the potential to synergistically extend the application area of underwater plasma in both research and industry.

A case study is presented that implements two numerical models for simulating a 30-year PAT operation conducted at a large contaminated site for which high-resolution data sets are available. A Markov chain based stochastic method is used to conditionally generate the realizations with random distribution of heterogeneity for the Tucson International Airport Area (TIAA) federal Superfund site. The fields were conditioned to data collected for 245 boreholes drilled at the site. Both MT3DMS and the advanced random walk particle method (RWhet) were used to simulate the PAT-based mass removal process. The results show that both MT3DMS and RWhet represent the measured data reasonably, with Root Mean Square Error (RMSE) less than 0.03. The use of fine grids and the total-variation-diminishing method (TVD) limited the effects of numerical dispersion for MT3DMS. However, the effects of numerical dispersion were observed when compared to the simulations produced with RWhet using a larger number of particles, which provided more accurate results with RMSE diminishing from 0.027 to 0.024 to 0.020 for simulations with 1, 20, and 50 particles. The computational time increased with more particles used in the model, but was still much less than the time required for MT3DMS, which is an advantage of RWhet. By showing the results using both methods, this study provides guidance for simulating long-term PAT systems. This work will lead to improve understanding of contaminant transport and plume persistence, and in turn will enhance site characterization and site management for contaminated sites with large plumes.