Asia-Pacific Journal of Chemical Engineering最新文献

This study unveils a numerical paradigm that amalgamates the partially saturated lattice Boltzmann method (PSLBM) with the non-isothermal quantitative phase-field (PF) model. This innovative integration equips us with a prognostic tool ready to elucidate the progression and motion of solid-air dendritic growth in the presence of both natural and forced convection. The PSLBM is employed to compute the flow of the solution and the interaction forces between the fluid and solid dendrites. Concurrently, the PF model is utilized to simulate the formation of solid-air dendrites. The reliability of calculating of interaction forces between the fluid and solid was confirmed through a numerical case study involving fluid flow around a stationary cylinder. The results indicate that this model is applicable for simulating the growth and evolution of single/multiple solid-air dendrites under the influence of convection, whether they are stationary or in motion. The promotion of the upstream side dendritic arms and the inhibition of the downstream dendritic arms increase with the intensification of natural convection. As the initial undercooling is raised, the capacity of natural convection to reshape dendritic morphology gradually diminishes. With the enhancement of forced convection intensity, due to alterations in the flow pattern, the downstream dendritic arms do not consistently exhibit growth suppression. The motion of solid-air dendrites induced by forced convection counteracts the influence of convection, resulting in slightly faster growth of the downstream dendritic arms compared to the upstream arms. Simultaneously, it fosters the formation of secondary dendritic branches in the upstream zone.

In this study, V₂O₅ nanoparticles with flake or prism-like morphology were synthesized using a two-step solvothermal synthesis and calcination process for the first time. These nanoparticles exhibited intrinsic oxidase-like activity, catalyzing the oxidation of 3,3′,5,5′-tetramethylbenzidine to produce blue oxidized 3,3′,5,5′-tetramethylbenzidine even in the absence of H₂O₂, with a characteristic absorption peak at 652 nm. Upon the introduction of glutathione (GSH), the solution color gradually lightened, correlating with a reduction in absorbance. Leveraging these properties, we developed a simple, sensitive, and highly selective colorimetric biosensor utilizing V₂O₅ nanoparticles for GSH detection in human serum. The developed method demonstrated excellent linearity over a range of 1–30 μM, with a low detection limit of 4.04 nM. Additionally, it exhibited outstanding selectivity against common interfering substances in human serum. Furthermore, this biosensor enabled both naked-eye detection and spectrophotometric quantitative analysis of GSH. Successful application to spiked serum samples yielded recoveries ranging from 97.1% to 101.7%. Overall, this method offers a promising approach for determining GSH content in human serum, with significant potential for biomedical testing applications. Its rapid and accurate detection capability may contribute to early diagnosis and treatment of various fatal diseases, including cancer and cardiovascular diseases.

The synthesis of Cu/Al₂O₃ nanoparticles (NPs) was conducted by the citric acid sol–gel technique. We used the synthesized NPs to enhance PVC membranes and create PVC-Cu/Al₂O₃ nanocomposite membranes. The quantities of NPs utilized were 0, 0.5, 1, 1.5, and 2 wt.% of solid phase. The point of this study was to look into how PVC-Cu/Al₂O₃ membranes can be used to remove natural organic matter (NOM) from polluted water in submerged membrane systems. The membranes treated with NPs exhibited increased porosity, improved hydrophilicity, and smoother surface. Results revealed that the incorporation of 1 wt.% NPs into PVC (PVC-CA1) demonstrated the highest degree of hydrophilicity and porosity. Moreover, PVC-CA1 exhibited an increased number of pores, with larger pores present on the top surface and larger macrovoids on the cross-sectional surface. The PVC-CA1 exhibited the highest flux recovery ratio (FRR) and highest rejection rate for HA, with values of 82.6% and 92.6%, respectively. PVC-CA1, which had an irreversible fouling ratio (IFR) of 17.3%, demonstrated the greatest resistance to fouling. Generally, incorporation of NPs into PVC resulted in increased hydrophilicity, enhanced porosity, uniform dispersion, smoother surface characteristics, and consequently improved antifouling properties. Furthermore, among the fabricated membranes, PVC-CA1 had the most favorable antifouling performance.

Mechanical stirring during the flotation conditioning process is a commonly employed and efficient method to enhance the effectiveness of slurry conditioning. However, excessive stirring intensity can lead to the desorption of collectors from the surface of coal slurry particles, compromising the conditioning efficacy. Thus, determining the optimal range of stirring intensity to enhance conditioning performance is necessary. The influence of stirring speed on the adsorption rate of coal oil and the desorption behavior of coal oil on the surface of coal slurry was investigated. Adsorption rates were measured and calculated using a UV spectrophotometer. An in-house desorption test apparatus and a high-speed motion capture system were employed to study the contact angle, adsorption area, deformation degree, and the forces acting on the adsorbed oil droplets under stirring conditions. Results indicated that the stirring speed significantly impacted the adsorption rate of the coal slurry. On increasing the stirring speed, the adsorption rate exhibited three distinct phases, that is, an increase, decrease, and stabilization. A maximum adsorption rate of 78.37% was observed at a stirrer rotation speed of 800 r/min, highlighting the crucial role of optimal stirring speed during conditioning. Both excessively high and low speeds were found to be detrimental to the conditioning process. As the stirring speed increased, the contact angle and contact area of the adsorbed oil droplets also increased, leading to an enhanced adsorption effect. Furthermore, the degree of deformation of the oil droplets increased with rising speed, accompanied by a reduction in stability.

To discover the “coordinative effect” within MEA-polyamines, the non-catalytic CO₂ absorption-desorption tests were conducted within tri-solvents of “MEA-TETA (triethylenetetramine)-DEEA (N, N-diethylethanolamine)/AMP(2-amino-2-methyl-1-propanol)” at specific concentrations of .1 ~ .5 + 2 + 2 mol/L for the first time. The energy efficient combinations were detected of MEA-TETA based tri-solvents with solid acid catalysts, from catalytic CO₂ desorption experiments onto MEA-TETA-DEEA/MEA-TETA-AMP with several commercial solid acid catalysts: blended γ-Al₂O₃/H-ZSM-5 = 2:1, H-mordenite, H-Beta (Hβ), HND-580, and HND-8. Three parameters were adopted to evaluate desorption activity: average desorption rate, heat duty, and desorption factors (DFs). After analyses, the .1 + 2 + 2 mol/L MEA-TETA-AMP with catalyst HND-8 possessed the best CO₂ desorption at 95–98°C with biggest DF. The desorption ability of DEEA was better than AMP, but with aid of solid acid catalyst, the AMP can release more CO₂ than DEEA due to weak stability of AMP-CO₂⁻ carbamate.

Ethyl levulinate (EL) production from steam-exploded corn straw (SCS) in a cascade of reaction using a Brønsted (B) acid and a Lewis (L) acid in ethanol was studied. The entangled structure of corn straw could be obviously damaged through steam explosion when the pressure was 1.5 MPa holding 10 min. The content of cellulose can be increased from 35.9% to 46.8%, and the contents of hemicellulose and lignin were changed from 16.7% to 8.8% and 22.6% to 27.5%, respectively. EL yield was significantly increased from 10.7 to 24.6 wt% under optimal reaction conditions (L/B = 1/20 [mol/mol], 205°C, 90 min, 1.8 g of SCS, 60 mL of ethanol). According to kinetic models, the activation energies for the main and side reactions were 56.8 and 110.5 kJ mol⁻¹, respectively. It suggested that SCS was more easily to be converted to EL rather than other by-products. The highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy gaps (HOMO-LUMO gaps) of cellobiose over the mixed acids in ethanol were significantly reduced with frontier molecular orbital (FMO) theory. This work provides an effective strategy for EL production from agricultural waste straws.

The precise prediction of NOx generation concentration in coal-fired boilers serves as the foundational cornerstone for the judicious optimization and control of selective catalytic reduction denitrification (SCR) systems. Owing to the intricate nature of the denitrification process within SCR, there exists a temporal delay in regulating the ammonia injection rate based on the monitored data of NOx concentration at the SCR inlet. Such delays can give rise to ammonia leakage and subsequent obstruction of the air preheater. In light of this, a predictive model, CEEMDAN-LSTM-SA, is proposed as an amalgamation of data decomposition and the LSTM (long short-term memory) fusion self-attention mechanism within a deep learning network, which is introduced to forecast the NOx emission concentration at the SCR inlet of coal-fired units. To mitigate the impact of data outliers on the training effectiveness of the model, a clustering method coupled with a statistical testing strategy is initially applied to refine the dataset first. CEEMDAN data decomposition technology is leveraged to facilitate the breakdown of data, alleviating its non-stationary and intricate characteristics. Subsequently, through spectral analysis, the decomposed components are grouped and aggregated to form novel data elements, which are then subjected to prediction by the constructed LSTM-SA deep learning network. The ultimate NOx emission concentration prediction value is derived through a process of fusion. Upon scrutinizing and comparing the predictions derived from various models using coal-fired power plant data, it is evident that the performance metrics of CEEMDAN-LSTM-SA predictions exhibit a mean absolute error of 7.425, mean absolute percentage error of 2.415%, root mean square error of 9.715, R-squared (R²) value of .789, mean absolute relative error of 2.109%, and a Theil's information criterion of .016. In contrast to other models, including traditional self-attention networks, LSTM, and LSTM-SA combination networks, CEEMDAN-LSTM-SA proposed in this study demonstrates superior prediction accuracy and enhanced generalization capabilities. Consequently, this predictive model stands poised to furnish an efficacious framework for the SCR ammonia injection strategy within thermal power units.

The Soret and Dufour effects play a crucial role in various fields such as geosciences, groundwater pollutant migration, chemical reactor operations, binary alloy solidification, and isotope separation. This study focuses on examining the impact of mixed convective flow on hybrid nanofluid through an exponentially stretching sheet with Soret and Dufour effects. The flow is affected by factors like variable viscosity, radiation, viscous dissipation, and activation energy. Instead of the no-slip condition at the boundary, velocity slip, thermal slip, and concentration slip are considered. The physical problem is modeled using boundary layer theory, and flow patterns are expressed using partial differential equations (PDEs). These governing fluid flow equations are transformed into non-linearly coupled ordinary differential equations (ODEs) using exponential similarity transformations. These simplified ODEs are resolved using the MATLAB bvp4c package. The effects of physical parameters on velocity, temperature, and concentration are illustrated through figures. Additionally, the drag force coefficient and heat and mass transfer rates are calculated for various parameters and presented graphically and in tabular form. It is observed that compared to nanofluids, the drag force coefficient of hybrid nanofluids increases by up to 21.05% with various solute buoyancy parameters (δ). Also, the mass transfer rate of hybrid nanofluids can be increased by .96% by the chemical reaction rate (σ_m). A comparison of this work with previously published research has been reported.

Over 218 million tonnes of oil palm trunks (OPT) waste is produced annually by Malaysian oil palm industry, which can be converted to biofuels via wet torrefaction. This study assessed the fuel characteristics of wet torrefied OPT (WT-OPT) using proximate analysis, higher heating value (HHV) analysis, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy–energy dispersive X–ray spectroscopy (SEM–EDX). Increasing wet torrefaction temperature and residence time increased the fixed carbon content and HHV of OPT. SEM–EDX revealed the presence of microspheres of 5-hydroxymethylfurfural (5-HMF) in OPT wet torrefied at 180 and 220°C for 72 h, an intermediate compound that can contribute to the HHV enhancement in WT-OPT. FTIR and EDX results revealed that higher temperature and residence time concentrate the carbon content of OPT. Wet torrefaction at 180°C for 72 h decreased the activation energy and pre-exponential factor of OPT from 301.88 to 171.70 kJ mol⁻¹ and from 4.43 × 10²⁸ to 3.25 × 10¹² s⁻¹, respectively, during pyrolysis. The estimated thermodynamic parameters, particularly the change in entropy which generally decreased by more than 140 J mol⁻¹ K⁻¹, indicated increase in stability of certain WT-OPT.

This study explores the development of environmentally sustainable, high-quality packaging materials by incorporating poly(hydroxybutyrate) (PHB) with different polymers. To accomplish this objective, pure PHB was blended with poly(ethylene glycol) (PEG) in a precise 9:1 ratio. Subsequently, this blend was further combined with 50 wt% of various polymers, namely, polycaprolactone, poly(vinylacetate), and polylactic acid (PLA), using a solvent-casting method. Further, the research investigates the multifaceted properties of these materials, including their thermal characteristics, morphological structures, mechanical strengths, barrier properties, and degradation behaviors. Among these blends, the film consisting of PHB, PEG, and PLA (PHB/PEG/PLA) emerged as a standout performer, displaying exceptional attributes. Notably, the PHB/PEG/PLA composite film exhibited remarkable thermal stability, boasting a high tensile strength of 26.6 MPa. Additionally, it demonstrated an outstanding ability to serve as a barrier against water vapors. These findings imply that the PHB/PEG/PLA composite film holds significant potential for a wide range of applications, particularly in the field of packaging and beyond.