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Surface charge localization and inferior charge transfer efficiency seriously restrict the supply of reactive hydrogen and the reaction dynamics of CO2 photoreduction performance of photocatalysts. Herein, chemically bonded BiVO4/Bi19Cl3S27 (BVO/BCS) S-scheme heterojunction with a strong internal electric field is designed. Experimental and density function theory calculation results confirm that the elaborated heterojunction accelerates the vectorial migration of photogenerated charges from BiVO4 to Bi19Cl3S27 via the interfacial chemical bonding interactions (i.e., Bi-O and Bi-S bonds) between Bi atoms of BVO and S atoms of BCS or Bi atoms of BCS and O atoms of BVO under light irradiation, breaking the interfacial barrier and surface charge localization of Bi19Cl3S27, and further decreasing the energy of reactive hydrogen generation, CO2 absorption and activation. The separation efficiency of photogenerated carriers is much more efficient than that counterpart individual in BVO/BCS S-scheme heterojunction system. As a result, BVO/BCS heterojunction exhibits a significantly improved continuous photocatalytic performance for CO2 reduction and the 24 ​h CO yield reaches 678.27 ​μmol·g−1. This work provides an atomic-level insight into charge transfer kinetics and CO2 reduction mechanism in S-scheme heterojunction. [ABSTRACT FROM AUTHOR]

Surface charge localization and inferior charge transfer efficiency seriously restrict the supply of reactive hydrogen and the reaction dynamics of CO2 photoreduction performance of photocatalysts. Herein, chemically bonded BiVO4/Bi19Cl3S27 (BVO/BCS) S-scheme heterojunction with a strong internal electric field is designed. Experimental and density function theory calculation results confirm that the elaborated heterojunction accelerates the vectorial migration of photogenerated charges from BiVO4 to Bi19Cl3S27 via the interfacial chemical bonding interactions (i.e., Bi-O and Bi-S bonds) between Bi atoms of BVO and S atoms of BCS or Bi atoms of BCS and O atoms of BVO under light irradiation, breaking the interfacial barrier and surface charge localization of Bi19Cl3S27, and further decreasing the energy of reactive hydrogen generation, CO2 absorption and activation. The separation efficiency of photogenerated carriers is much more efficient than that counterpart individual in BVO/BCS S-scheme heterojunction system. As a result, BVO/BCS heterojunction exhibits a significantly improved continuous photocatalytic performance for CO2 reduction and the 24 ​h CO yield reaches 678.27 ​μmol·g−1. This work provides an atomic-level insight into charge transfer kinetics and CO2 reduction mechanism in S-scheme heterojunction.

The study characterized the water outflow dynamics during artificial drying of plantain (Plantago major L.) and linden (Justicia pectoralis J. var. ‘Pectoralis’). The trials were conducted at 40 °C temperature and 50 % relative humidity. The post-harvest flow and the determination of the initial moisture content of each plant were initially established by the gravimetric method. The kinetic characterization was carried out based on the determination of the drying constants and diffusion coefficients of each species. The drying constants were obtained from the mathematical adjustment of five models and the diffusion coefficient was obtained through the analytical solution of Fick’s second law. The best fitting equation was the Henderson and Pabis equation. That model characterized the moisture loss over time when using a technology with 40 °C temperature and 50 % relative humidity and described the diffusion mechanism occurring in the leaves of the species under study. The drying time of linden in 45 h as opposed to plantain, which takes 77 h, is associated with the few adsorption points with relatively strong bonds that the plant presents. The results constitute a contribution to the knowledge that allows optimizing the drying processes of the species under study in the technological conditions of Cuba. [ABSTRACT FROM AUTHOR]

The study characterized the water outflow dynamics during the artificial drying of plantain (Plantago major L.) and linden (Justicia pectoralis J. var. ‘Pectoralis’). The trials were conducted at 40 °C temperature and 50 % relative humidity. The post-harvest flow and the determination of the initial moisture content of each plant were initially established by the gravimetric method. The kinetic characterization was carried out based on the determination of the drying constants and diffusion coefficients of each species. The drying constants were obtained from the mathematical adjustment of five models and the diffusion coefficient was obtained through the analytical solution of Fick’s second law. The best-fitting equation was the Henderson and Pabis equation. That model characterized the moisture loss over time when using a technology with 40 °C temperature and 50 % relative humidity and described the diffusion mechanism occurring in the leaves of the species under study. The drying time of linden is 45 h as opposed to plantain, which takes 77 h, is associated with the few adsorption points with relatively strong bonds that the plant presents. The results constitute a contribution to the knowledge that allows optimizing the drying processes of the species under study in the technological conditions of Cuba.

Abstract: This study describes an application of model-based control techniques to a liquid–liquid extraction process. The control design is based on a reduced order model of the process obtained by system identification. A multi-loop decentralized control system, in the framework of internal model control (IMC), is initially selected to control the 2 × 2 control loops of the extraction column. The interaction of loops is then investigated to explore the feasibility of such multi-loop control structure. A centralized multivariable control system is synthesized with a model predictive control (MPC) technique. The simulation results demonstrate good servo and regulatory characteristics for both control system designs. However, the MPC control of extraction proved to be superior to the IMC one in terms of speed of response, stability, robustness, and loops interaction. MPC has also shown ability to handle control operation under input variables constraints, which has significant practical importance. [Copyright &y& Elsevier]

Abstract: The liquid–liquid extraction process is well-known for its complexity and often entails intensive modeling and computational efforts to simulate its dynamic behaviour. However, rigorous mathematical models are usually impractical or are of limited usefulness for control system design. Therefore, there is a need to derive simpler models for this process. Reduced-order linear models can be derived through applying system identification on the input–output simulation data. As a first step, a rigorous model for dynamic simulation of an extraction process is developed. This model employs an improved detailed stage-wise mixing stage with backmixing and it takes into account the variation in hydrodynamics, mass transfer, and physical properties throughout the length of the extraction column. It also approximates end effects by incorporating two mixing stages at both ends in addition to calculation of mass transfer within calming zones through the use of a mass transfer weight factor. The model is validated with dynamic experimental data for a nine stage Scheibel extraction column of type I. The simulation model is shown to be accurate for prediction of process behaviour under different operating conditions. Dynamic analysis of the process is conducted on the developed rigorous simulation model. Then, system identification is applied to derive linear time-invariant reduced-order models, which relate the input process variables (agitator speed, solvent feed flowrate and concentration, feed concentration and flowrate) to the output process variables (raffinate concentration and extract concentration). The identified model predictions are found to be in a good agreement with the rigorous ones. [Copyright &y& Elsevier]

Background: Prunella vulgaris (PV) is a low-growing perennial herb, which can be found in different parts of the world as Asia, Europe and North America. It is traditionally used for medicinal treatment in various cultures in India, China, Japan, Korea, Russia, and Eastern Europe for treating different ailments, such as fever, and healing wounds. In our previous article, we showed the anti-tumorous effect of the volatile organic compounds (VOCs) of PV and characterized the steam distillation process in the extraction of VOCs from PV. This has never been done before as we are aware of. To use the VOCs as drugs, there is a question of how much of the VOCs are lost before the prepared drugs reach the patients. Thus, the first aim of the present article is to try to explore the time depletion effect on the VOCs in the PV extracts. Then, the second aim is to extend the work in the previous paper and further understand the dynamics of the distillation process of PV by changing the steam flow rate in the extraction process., Methods: To achieve the first aim to explore the aging effect of how much VOCs are depleted after they are extracted, the VOCs were first extracted by the same method as before, i.e., using steam distillation. Then, tubes of the aqueous solution containing the VOCs were then stored in a 5°C refrigerator. They were then taken out for GC-MS analysis according to a preplanned schedule up to 8 weeks after the VOCs were extracted. The chemical composition of the distillate could then be evaluated. This revealed the changes in the abundance of VOCs with aging. At the same time, the cell viability of SCC154 oral squamous cells treated by these herbal solutions, which were at different aging stages, was evaluated using a tetrazolium-based colorimetric reagent, Cell Counting Kit-8. To achieve the second aim of exploring the dynamics of the steam distillation process, the steam flow rate was adjusted by changing the temperature setting of the hot plate. GC-MS was again used to quantify the chemical constituents of the distillates., Results: By using GC-MS to measure the abundance of volatile compounds at different time points after the distillation process, it was found that the volatile compounds persist for a very long time, or over 8 weeks, which was the longest period of our experiment. The aging of the distillates also did not depreciate much the cell cytotoxicity of the PV distillate on the cancer cells. With respect to the dynamics of the steam distillation process, it was found that, at a low steam flow rate, volatile compounds of lower molecular weight are more efficient to be extracted, while at a high steam flow rate, volatile compounds of higher molecular weight are more efficiently extracted., Conclusion: Our findings demonstrate that the VOC compounds extracted and present in aqueous form do not deplete much for at least 2 months after the extraction process, neither they exhibit cell cytotoxicity. The experiments on the dynamics of the steam distillation process demonstrate that the mass of herb present in the flow path of the steam has significant effects on the relative amounts of VOCs extracted., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)