دوماهنامه مهندسی شیمی ایران
پیاپی 126 (فروردین و اردیبهشت 1402)

The aim of this study was to investigate the distribution of lactic acid in polymer-salt aqueous two phase systems. Accordingly, four temperatures of 25, 30, 35 and 40°C were considered and at each temperature, three different salts including sodium sulfite, disodium tartrate dihydrate and sodium dihydrogen phosphate and two different molecular masses of polyethylene glycol 30% by weight (4000 and 8000 g/mol) was tested in aqueous two-phase system. Also, the percentage of acid extraction at pH 5 to 9 and the effect of polymer concentration were investigated. The effect of polymer molecular mass, polymer concentration, salt type, salt concentration and temperature change on the extraction percentage was evaluated. It was observed that in all three systems, with increasing the molecular weight of the polymer, temperature, salt concentration, polymer concentration and pH, the extraction efficiency decreases. The optimum values of polymer molecular weight, temperature, salt concentration and pH were determined as 4000 g/mol, 25 °C, 25% by weight of sodium sulfite, disodium tartrate dihydrate and sodium dihydrogen phosphate and 5.5 to 6.5, respectively. In addition, the optimal polymer concentration was determined to be 30% by weight. Finally, the extraction values for sodium sulfite, disodium tartrate dihydrate and sodium dihydrogen phosphate were calculated to be 53.205, 50.149 and 19.549%, respectively.

In recent years, fuel cells have attracted considerable attention due to their high energy efficiency with zero emissions. Electrocatalysts are some of the key materials used in low-temperature fuel cells such as the polymer electrolyte membrane fuel cell(PEM). Creating high-performance and stable/durable catalysts is widely recognized as a key step for the further development and commercialization of PEMs. Catalysts supported on high surface area carbon black are widely used in PEMs. However, the corrosion of carbon black has been recognized as one of major causes of performance degradation and durability issues of PEMs under high-potential conditions. So the need for alternative supports with outstanding physical and mechanical properties to carry out the successful reaction in catalyst layer and give a longer lifetime for the electrocatalysts is inevitable. The emergence of nanothechnology has opened up new avenues of materials development for PEMs. This study presents the PEMs performance with a variety of nanostructured based materials as a catalyst support. The improved electrochemical activity of the nanostructured electrocatalysts are highlighted.

Magnesium hydroxide is a substance with the chemical formula Mg(OH)2 that is found in nature as an inorganic mineral of brucite. This chemical compound can be synthesized in the form of a solid white powder. It has very little solubility in water. Magnesium hydroxide belongs to a group of compounds of a unique nature due to its large number of desirable properties and applications. Magnesium hydroxide is one of the main antacid compounds such as magnesium milk as well as laxatives. Of course, this compound is also used in other fields such as the food industry, water, and wastewater treatment, and the production of fire retardant sprays.In industrial laboratories, this compound is also used to form and synthesize many chemical compounds such as magnesium oxide. This compound is known as a food additive by the U.S. Food and Drug Administration completely wholesome. For this reason, manufacturers of pharmaceutical products and dietary supplements use this compound. There are many factors that cause the acidification of industrial effluents and wastewater. One of the steps that are necessary for the process of water treatment and distance is pH neutralization. Researchers use magnesium hydroxide for this purpose. Considering the importance of this material in this study, applications and methods of preparation of magnesium hydroxide including precipitation, sonochemical, electrochemical, microwave radiation, etc. were investigated and the factors affecting it were investigated. The advantages and disadvantages of each method and the parameters affecting the final product have been investigated in each method.

Measurement of sulfur compounds in the tail gas flow in the sulfur recovery unit is necessary in order to fine control the combustion furnace airflow and efficiency enhancement. In this research, required equations for calculation of air demand in feedforward and feedback control loops in the sulfur recovery unit of Ilam Gas Treating Plant are developed. First, the process was simulated. Then, using MLP neural network and nonlinear regression, K factor was determined for tail gas analyzer air demand calculation. Total required air is sent to the combustion furnace through two lines: trim and main, such that 92.5% of air is passed through the main line. Meanwhile, tail gas analyzer air demand is in the range of -5 to +5 % of the total required air. The presented equations in this research can be employed for other sulfur recovery units.

In this study, the effect of adding nanoclay and carbon black to SBR on curing behavior, oil absorption and mechanical properties such as tensile strength and strain at break, hardness and abrasion resistance were investigated. At the end, we investigated the effect of carbon black (CB) and replacement a portion of CB with modified clay on tensile strength, elongation at break, hardness and abrasion resistance of SBR. Tensile strength and elongation at break were significantly improved upon addition of nanoclay and the optimum amount of nanoclay was 10 phr. The rheometric test indicated that as the nanoparticles loading increases, the scorch time and optimum cure time decrease and the cure rate increases. Adding nanoparticles to the polymer matrix improved the abrasion resistance and the abrasive volume of the samples decreased significantly with addition of nanoclay content. Adding 10 phr nanoclay to SBR containing 20 phr carbon black elongation at break and tensile strength exhibited a siginificant increase of 300% and 3 MPa respectively indicationg synergisty of carbon black and nanoclay in improving mechanical properties of SBR. Upon replacement of 10 phr CB with clay tensile strength, elongation at break and hardness improved 30%, 24% and 5% respectively and oil absorption and abrasive volume decreases 23% and 11% respectively.

The most important parameter in the design and fabrication of an artificial lung consisting of hollow membranes is the oxygen transfer rate (OTR). OTR determination methods in the artificial lung are complex and require highly accurate sensors and instruments. The fluids used to determine OTR in the artificial lung are blood, water, and a mixture of water and glycerol, each of which has multiple drawbacks and problems. In this paper, the sulfite system (SS) is considered as a fluid that can replace blood in determining OTR and does not have blood problems and the need for special relationships and tools. For this purpose, the OTR conditions in the artificial lung are first optimized by determining the appropriate concentration of catalyst (cobalt) in SS (flow (gas and sulfite solution) 2000 mL/min). The results of SS at a flow rate (500-2000 mL/min) are then compared with blood data in an artificial lung. The results show that the mean OTR of SS is less than 10% different from the mean OTR of blood at 2000 mL / min flow.