International Journal of Chemical Engineering

In this study, we performed a comparative analysis of the combustion behavior of pyrite, pyrrhotite, and pyrite-pyrrhotite mixture (mixed mineral) powders in an air atmosphere. To study the influence of the pyrrhotite content in mixed mineral powders on the combustion behavior in the air, thermogravimetric mass spectrometry, X-ray diffraction analysis, and scanning electron microscopy were employed. The results indicated that pyrrhotite lead to a weight gain in the mixed minerals during the combustion process. Pyrrhotite particles are more easily adsorbed on the surface of pyrite particles during mixed mineral combustion due to their strong ability to absorb oxygen, which accelerates pyrite combustion. The weight loss of mixed minerals decreased during the combustion process with increasing pyrrhotite content, resulting from pyrite encapsulation by agglomerated and sintered pyrrhotite during combustion. The calculated kinetic parameters and phase analysis results suggested that pyrite combustion is consistent with the shrinking core mechanism, and in the combustion process, the irregular pyrite particle shrank into a spherical particle; the combustion products of pyrrhotite grew in a layer-by-layer manner. Pyrrhotite combustion corresponded to the three-dimensional diffusion mechanism, and mixed mineral combustion was dominated by the shrinking core mechanism and supplemented by the three-dimensional diffusion mechanism. SO₂, as the main combustion product, was continuously generated and volatilized in the reaction, signifying that the combustion reaction of pyrite is a two-phase reaction involving gas and solid.

Polymer-based soil stabilization has fascinated substantial interest in the field of research intending to gain a better knowledge of the anticipated soil characteristics after polymer treatment. Intricate research on the engineering performance of expansive soil which is highly challenging due to its swell and shrink nature based on variations in water regime, treated with guar gum, a biopolymer made from gum along with polyethylene terephthalate fibre, one of the most generated plastics, resulting in massive waste, is accomplished through this entire experimental investigation. Comprehensive geotechnical tests and microstructural examinations have been performed to optimize the guar gum for enhancement of soil properties and to comprehend the interactive mechanism with the soil. The biopolymer at dosages 0.5%, 1%, 1.5%, and 2% was added to the soil. Polyethylene terephthalate Fibre with an aspect ratio of 28 is used with the soil at an increment of 0.4% up to 1.6%. The optimum dosage of biopolymer was mixed with polyethylene terephthalate fibres, and its effect on geotechnical properties was carried out separately. From the experimental investigations, it is comprehended that there is a reduction of 27% and 40% in plasticity index and swelling, respectively, at an optimum dosage of 0.5% GG when compared to untreated soil. Furthermore, there is a marginal decrease of 24% in dry density, 310% increase in CBR value, and 33% reduction in compressibility of the soil treated with 0.5% GG with 1.6% PET fibre, when compared to virgin soil. The present study was conducted to improve the subgrade soil strength beneath the pavements. The usage of biopolymer and its combination with polyethylene terephthalate fibres shows that there is a considerable improvement in modifying the geotechnical properties, and its coupling effect contributes to higher California bearing ratio values. According to the outcomes of this investigation, it is proven that biopolymer and polyethylene terephthalate fibre is definitely an alternate to conventional materials. The present study was conducted to improve the subgrade soil strength beneath the pavements.

Transport phenomena through hollow fiber membrane contactors (HFMCs) indicate the exchange of a component between the two phases, inside and outside of hollow fibers. In this research, we designed and fabricated lab-made HFMCs to assess the difference between water and air as sweeping media for CO₂ exchange. The effects of flow rates and temperature ratios on aqueous CO₂ absorption were investigated accordingly. A semiclosed circuit incorporating our fabricated HFMCs was set up to regulate the operating parameters and evaluate the aqueous CO₂ concentration using an initiative pH-based method. The results of our experiments remarkably reveal that air tends to remove aqueous CO₂ more than water when aqueous CO₂ concentration is higher than 3.53 × 10⁻⁶ mlCO₂/l. However, water would surpass air in lower concentrations. Nevertheless, tripling the flow rate of sweeping media from 500 to 1500 ml/min shifts up this cutoff point 50 times to around 1.66 × 10⁻⁴ mlCO₂/l. The experiments performed at three different temperature ratios of 22 : 22, 44 : 12, and 22 : 12°C (CO₂-rich liquid: sweeping medium) demonstrated that a higher temperature gradient deteriorates the CO₂ absorption capacity of sweeping media. Nonetheless, temperature gradient becomes highly effective in aqueous CO₂ concentrations lower than 1.57 × 10⁻⁶ CO₂/l. The results of this research could be applied in performance optimization of aqueous CO₂ absorbing HFMCs, even in sophisticated medical procedures such as arterio-venous and veno-venous CO₂ removal systems where both water and air could be used as blood’s CO₂ sweeping media.

In this study, a mathematical model of the copolymerization of AN-VA in a continuous stirred tank reactor (CSTR) was developed considering charge-transfer complexes (CTCs). CTC formation between acrylonitrile (AN) and vinyl acetate (VA) was demonstrated using UV-VIS spectrophotometry and molecular orbital theory. The rate constants and equilibrium constants of the complexes were calculated from a model of the simultaneous participation of complexes and free monomers and the molar ratio method. Furthermore, the participation of CTCs in propagation was included because of their high reactivity. All the simultaneous equations defined to analyze the reactor parameters were analytically solved, and the results of the model were in terms of operative variables such as monomer conversion, average molecular weight, and the mole fraction of monomer 2 (i.e., VA) in the polymer formed. The results of the predictions of the developed model were compared with the experimental data for validation. This prediction was also compared with the reactor model solution without considering the CTC, which showed deviations that were more significant than those of the CTC model. These results represent a quantitative way to analyze the order of magnitude of the impact of the formation of the complexes in the analyzed polymerization system.

A better understanding of the reaction mechanism and kinetics of dry reforming of methane (DRM) remains challenging, necessitating additional research to develop robust catalytic systems with high catalytic performance, low cost, and high stability. Herein, we prepared a zirconia-alumina-supported Ni-Fe catalyst and used it for DRM. Different partial pressures and temperatures are used to test the dry reforming of methane reaction as a detailed kinetic study. The optimal reaction conditions for DRM catalysis are 800°C reaction temperature, 43.42 kPa CO₂ partial pressure, and 57.9 kPa CH₄ partial pressure. At these optimal reaction conditions, the catalyst shows a 0.436 kPa² equilibrium constant, a 0.7725 /g_Cat/h rate of CH₄ consumption, a 0.00651 /m²/h arial rate of CH₄ consumption, a 1.6515 /g_Cat/h rate of H₂ formation, a 1.4386 mol_CO/g_Cat/h rate of CO formation. This study’s findings will inspire the cost-effective production of robust catalytic systems and a better understanding of the DRM reaction’s kinetics.

The goal of this research was to employ copper-doped zinc oxide nanoparticles (Cu/ZnONPs) as an adsorbent to remove the potentially toxic azo dye Congo red (CR). The Cu/ZnONPs were made using a chemical coprecipitation method, and their characteristics were examined using XRD, SEM, EDS, and FTIR methods. The response surface methodology (RSM) central composite design (CCD) is used to optimize the operational parameters’ agitation time, adsorbent dosage, solution pH, and initial concentration of CR solution during the adsorption process. The agitation period of 29.48 min, the Cu/ZnONP dosage of 0.301 g/L, the solution pH of 6.96, and the CR initial concentration of 90 mg/L resulted in a maximum CR adsorption of 94.14% and a desirability of 0.976. The kinetic findings fit the pseudo-second-order kinetic equation, and the equilibrium data agreed with the Langmuir isotherm (maximum uptake capacity q_max = 250 mg/g). During the thermodynamic experiments, endothermic, spontaneous, and physical adsorptions were observed.