Articles
Renewable Energy (09601481)256
This study presents the development of a mathematical model to accurately predict the dynamics of salt and water transport in a batch electrodialysis system used for either NaCl desalination or LiCl brine concentration. The primary aim of the model is to simulate the desalination of high-salinity water under specified current density conditions. The governing equations for the electrodialysis stack and associated tanks were formulated and solved using numerical methods. Model predictions were validated against experimental data, demonstrating high accuracy: the deviation between measured and predicted tank concentrations was within ±2 % for both NaCl and LiCl systems. In addition, the study investigated how initial salt concentration, current density, and flow rate influence system performance. The results show that system efficiency is significantly affected by the initial brine concentration. Increasing the salt concentration from 5 wt% to 10 wt% and 20 wt% reduced desalination efficiencies by approximately 67 % and 93 %, respectively. Moreover, salt flux improved with higher current density, with a 71 % increase in desalination observed when current density was raised from 100 A/m2 to 400 A/m2. © 2025 Elsevier Ltd
This study explores the experimental and mathematical modeling of energy recovery from hot exhaust gases using a finned tube heat exchanger filled with paraffin. The experimental setup employs air as the heating fluid, water as the cooling fluid, and paraffin with a melting point of 68°C as the phase change material. Key parameters investigated include inlet air temperature, air mass flux during heating, and water mass during cooling. The system's thermal behavior is modeled mathematically by assuming heat accumulation in the paraffin-filled finned tubes. Numerical solutions of the equations are compared with experimental data, and dimensionless parameters are used to evaluate system performance under varying conditions. The model also examines the effects of structural features, such as fin height and the number of fins per unit tube length. The results show that increasing inlet air temperature and reducing air mass flux improve the heating and cooling efficiencies and overall system performance. Enhancing fin height from 0 to 1.5 cm and the number of fins from 0 to 20 within a 10 cm tube length leads to heating efficiency gains of 10.88% and 15%, respectively. © 2025 Wiley Periodicals LLC.
Industrial and Engineering Chemistry Research (15205045)63(36)pp. 15646-15655
The notable reduction in forest coverage and usage of nonrenewable energy resources have resulted in accumulation of carbon dioxide in the atmosphere, thus contributing to the worsening of the phenomenon commonly referred to as global warming. This research undertook an investigation into the efficacy of a distinct absorbent in eliminating CO2 from the air within a spouted bed reactor. By utilizing the Taguchi methodology, the study examined the capacity of sodium carbonate to eradicate CO2 from the atmosphere across a wide range of concentrations (600-1850 ppm), temperatures (55-90 °C), and molar ratios of Na to C in the absorbent (ranging from 1 to 3). The results indicated that this absorbent effectively eliminated 86% of the initial CO2 at a reaction temperature of 55 °C, a molar Na/C ratio of 1.4, and an initial concentration of 1280 ppm. Additionally, the examination of the solid composition postabsorption using X-ray diffraction revealed the formation of sodium bicarbonate during the absorption process. The novelty of this study resides in the introduction of a novel method for capturing CO2 from the atmosphere. Moreover, the viability of regenerating sodium carbonate by liberating CO2 from bicarbonate was also evaluated through thermogravimetric analysis. © 2024 American Chemical Society.
Process Safety and Environmental Protection (17443598)190pp. 1440-1449
The utilization of biogas as a renewable energy source necessitates a reduction in its CO2 content. “Ex-situ biomethanation” is employed to convert CO2 in biogas to CH4 through hydrogenotrophic methanogens. In this study, a biogas stream (32–36 % CO2) originating from cow manure digestion was subjected to treatment in a trickle bed bioreactor (4 liters). The presence of microorganisms on the packing material was confirmed by using a 16 S rRNA test and SEM images. This study stands out by considering all four combinations of thermophilic and mesophilic conditions, monitoring the transition and steady-state phases in a two-reactor series setup. The mesophilic-thermophilic mode yielded the highest purity (92 %) with an 86 % CO2 conversion rate and an energy density of 13,870 kJ/m3. Additionally, the performance consistency was also assessed using a larger TBB (8 liters). Extending the residence time, the thermophilic-thermophilic mode yielded the highest CH4 concentration at 98 %. The 16 S rRNA results revealed that, influenced by the designated growth conditions encompassing culture media, pH, temperature, and reactor retention time, an enrichment of hydrogenotrophic methanogens occurred. Furthermore, promising results in terms of CH4 concentration and process efficiency were demonstrated by the trickled bed bioreactor employing liquid-in-gas dispersion. © 2024 The Institution of Chemical Engineers
Advanced Biomedical Research (22779175)13(1)
Background: Researchers are always searching for chemicals with antioxidant properties. The cell wall polysaccharide of Sargassum angustifolium consists of alginic acid. To use this polysaccharide and investigate on its various effects, it must first be isolated from brown algae and the operational parameters of extraction need to be optimized to reach the maximum antioxidant effect. Materials and Methods: The effects of changing the parameters (temperature, time, and power of ultrasonic waves) used in the extraction of alginic acid were discussed based on changes in the antioxidant effect. After that, M/G (β‑D‑mannuronic acid to α‑L‑guluronic acid ratio) was measured using 1H NMR spectra, and the antioxidant activity of the extracted alginic acid was examined using the DPPH method. Results: The highest antioxidant effect was observed in sample No. 4 with an extraction temperature of 65°C, extraction duration of 25 min, and 640 W of ultrasonication power, whereas the lowest antioxidant effect was observed in sample No. 7 at 45°C, 20 min, and 480 W. Conclusion: Structural changes due to increasing temperature may cause less activity, whereas the optimum temperature was 65°C. There was no direct relationship between M/G and IC50, and it should be examined along with molecular weight. Increasing the intensity of the waves increased the antioxidant activity. The extraction yield can be increased by increasing A/W (Gram of algal sample per mL of solvent). It appears that the extraction under optimum conditions enhances the MM block epimer, which may lead to an increase in the antioxidant activity. © 2024 Advanced Biomedical Research.
