Korean Journal of Chemical Engineering最新文献

Redox flow battery (RFB) employing oxygen as active material is a promising system because this oxygen can replace expensive conventional active materials. However, its practical application is limited due to the high overpotential of reactions involving oxygen and the necessity of continuous oxygen supply. To overcome the difficulties, in this study, new RFBs using redox reaction of mediator and electrochemical oxygen evolution reaction (OER) are suggested. Here, oxygen acts as a self-sustaining active material for catholyte operating without its external supply and anthraquinone-2,7-disulfonate (AQDS) is employed as a redox mediator to reduce the high overpotential of oxygen reduction reaction, while iron-2,2-bis(hydroxymethyl)-2,2’,2’-nitrilotriethanol complex (Fe(BIS-TRIS)) is considered as the active material for anolyte. A nickel-electrodeposited heat-treated graphite felt (Ni-HGF) electrode is further introduced to simultaneously facilitate the OER and redox reaction of AQDS mediator in cathode. Electrochemical analysis indicates that the Ni-HGF electrode lowers the potential required for oxygen evolution and provides suitable conditions for AQDS-mediated redox reactions, enabling continuous in situ generation and utilization of oxygen during cycling. As a result, in RFB single cell employing Ni-HGF electrode, its discharge capacity after 200 cycles (746 h) (2.34 Ah L^− 1) is well preserved compared to its initial capacity of 2.55 Ah L^− 1. Furthermore, additional oxygen injection does not affect the discharge capacity, indicating that a sufficient amount of oxygen is continuously generated via OER during charging step and such generated oxygen is subsequently utilized during discharging step. This work proves a viability of a self-sustaining oxygen-based RFB that can operate without external oxygen supply, providing a new strategy for establishing a low-cost energy storage system.

MoS₂-based nonvolatile memory devices, including a capacitor and thin-film transistors (TFTs), were fabricated in a metal-MoS₂-insulator-Si (MMIS) architecture with interfacial Au nanoparticles (Au NPs) serving as charge-storage nodes between monolayer MoS₂ and the gate dielectric. An n-type SiO₂ layer (10 nm) was functionalized with an APTES self-assembled monolayer to enable dense Au NP assembly, yielding an M-capacitor with pronounced hysteresis in capacitance-voltage (C-V) characteristics. MoS₂ TFTs were further realized on 300 nm n-type SiO₂, either without Au NPs (M-TFT) or with the Au NP interlayer (MM-TFT). Solution-processed MoS₂ prepared by chemical exfoliation was characterized by TEM, AFM, Raman spectroscopy, and XPS. The M-capacitor exhibited a flat-band voltage shift (ΔV_FB) of 1.73 V under a ± 5 V sweep, while the MM-TFT showed a threshold-voltage shift (ΔV_TH) of 6.32 V for a + 10 to -30 V gate sweep, confirming efficient interfacial charge trapping.

Tetrabromobisphenol A (TBBPA), as the most widely used brominated flame retardant, was characterized by its recalcitrance to degradation and bioaccumulation. To address this limitation, a carbon layer-protected Cu₂O (C-Cu₂O/Cu) cathode was fabricated via in-situ chemical oxidation and calcination followed by glucose impregnation-carbonization, which was subsequently coupled with silver-loaded TiO₂ (Ag-TiO₂/Ti) anode prepared by anodic oxidation and photodeposition to construct an efficient photoelectrocatalytic (PEC) system. By optimizing preparation parameters such as impregnation concentration and calcination temperature, the photocurrent density of the C-Cu₂O/Cu cathode was enhanced to 2.6 times higher than that of Cu₂O/Cu, and it maintained stable performance during 1200 s of light on/off cycles, contrasting with the rapid decay of Cu₂O/Cu. Within the PEC system, the C-Cu₂O/Cu photocathode achieved a TBBPA degradation efficiency of 97.1%, significantly surpassing the 87.2% of Cu₂O/Cu. Systematic investigation of various applied voltages, pH levels, and electrolyte concentrations revealed that the optimal operating parameters were a 1.5 V bias, pH 9.5 and 0.05 mol/L Na₂SO₄. Radical trapping experiments confirmed that hydroxyl radicals (·OH) and superoxide radicals (·O₂⁻) served as the primary reactive species, while GC–MS analysis elucidated the degradation pathway involving debromination, ring cleavage, and mineralization. This study provided a novel strategy for enhancing the stability of Cu₂O photoelectrodes and achieving efficient degradation of persistent organic pollutants with the PEC system.

A two-stage tandem process combining CO₂ Fischer-Tropsch synthesis (CO₂-FTS) with downstream zeolite upgrading provides a practical route for converting broad Anderson-Schulz-Flory (ASF)-type hydrocarbons into light olefins. In this study, hierarchical MFI zeolites with systematically tuned mesoporosity were synthesized using the amphiphilic organosilane [3-(trimethoxysilyl)propyl]hexadecyldimethylammonium chloride (TPHAC) and compared with commercial microporous ZSM-5 (Si/Al = 15). TPHAC preserved the MFI framework while increasing the external surface area and mesopore volume. The upstream K/Fe-Cu-Al catalyst produced a stable ASF-type hydrocarbon stream at 300 °C and 2.5 MPa. In the temperature-screening tandem reaction, TPHAC-4% showed the best performance, affording the highest C₂-C₄ olefin selectivity of 52.34% on a hydrocarbon basis at 500 °C while suppressing BTEX formation. Under the 150 h long-term operation at the same temperature, it maintained an average C₂-C₄ olefin selectivity of 56.77% over TOS 40–150 h. A 1-octene model reaction reproduced the same trend, indicating that the hierarchical pore structure promoted light-olefin formation while suppressing competing aromatic pathways. Post-reaction coke analysis further showed reduced coke accumulation in the micropores. Overall, the hierarchical pore architecture created a more favorable environment for light-olefin production.

Biphasic absorbents have attracted considerable attention because they can reduce the energy requirements of solvent regeneration during CO₂ capture. In this study, a water-lean biphasic solvent system was developed by introducing polyether solvents into an aqueous amine solution. As the n-octanol-water partition coefficient (log P) of the polyether solvents increased, the solvent system transitioned from a homogeneous phase to a liquid-liquid biphasic system during CO₂ absorption. Solvent screening identified the 3-(methylamino)propylamine (MAPA) / triethylene glycol monobutyl ether (TEGMBE) /water system as a promising formulation due to its high cyclic capacity and low viscosity. ¹³C NMR analysis revealed that CO₂ absorption products such as MAPA-carbamate, protonated MAPA, and CO₃^2-/ HCO₃^- were predominantly located in the lower phase. TEGMBE was predominantly distributed in the upper phase and functions as a physically inert phase-separating component. The cyclic loading and volume distribution of the rich phase were affected by TEGMBE concentration. When the TEGMBE content is 50 wt%, the CO₂-rich phase loading (α_rich) and corresponding cyclic capacity (Δα) within the rich phase reached 279 gCO₂/Lsolvent and 143 gCO₂/Lsolvent, respectively, representing increases of 250% in rich loading and 220% in cyclic capacity compared with a conventional 5 M monoethanolamine (MEA) aqueous solution. In addition, the volume of the CO₂ rich phase was reduced by 54% relative to the MEA aqueous solution. This high concentration significantly reduces the liquid volume to be processed in the subsequent regeneration step, thereby offering substantial potential for energy savings in the desorber.

This study presents the sequential extraction of dichromate (Cr₂O₇²⁻) anions using a continuous multi-dropped liquid membrane (MDLM) system. Trioctylphosphine oxide (TOPO) dissolved in kerosene was employed as the mobile carrier in the organic phase. To determine the optimal operational conditions, both chemical variables (e.g., donor phase acid type, acceptor phase composition, and carrier concentration) and physical parameters (e.g., temperature, phase volume ratios, flow rate, and reactor frit porosity) were systematically investigated. Unlike earlier studies, this work uniquely emphasizes the critical influence of the reactor’s hydrodynamic and physical design on overall mass transfer efficiency. Kinetic evaluations confirmed that the dichromate transport strictly adheres to consecutive first-order irreversible reaction kinetics, enabling the precise calculation of fundamental kinetic parameters (k₁, k₂, t_max, (:{R}_{m}^{max}), (:{J}_{d}^{max}),(::{J}_{a}^{max})). Furthermore, the activation energy of the process was determined to be 14.60 kJ·mol^− 1 (3.49 kcal·mol^− 1), demonstrating that the extraction is fundamentally a diffusion-controlled mechanism. Under the optimized physicochemical conditions, the MDLM system achieved a maximum overall dichromate extraction efficiency of 96.31%.

This study developed a novel composite polymer flocculant, polyaluminum zinc silicate-cationic guar gum (PSAZ-CGG) and investigated the effects of preparation conditions and flocculation parameters on the removal of Congo Red (CR) and Reactive Blue 19 (RB-19). The synthesized flocculant and flocs were characterized using techniques such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy–energy dispersive spectroscopy (SEM/EDX), elemental analyzer (EA), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). These findings suggest the successful fabrication of the composite flocculant and its favorable flocculation performance. Single-factor flocculation experiments revealed maximum removal rates of 97.7% and 95% for CR and RB-19. The kinetic and isotherm data were better fitted by the pseudo-second-order and Langmuir models, respectively. These models were used as empirical tools to describe the apparent dye removal behavior. Furthermore, maximum uptake values of 454.55 mg g^− 1 (CR) and 393.33 mg g^− 1 (RB-19) were measured for the PSAZ-CGG composite in aqueous solution. XPS analysis further supports the interaction between PSAZ-CGG and the dye molecules during the flocculation process. The primary flocculation mechanisms are likely to include sweep flocculation, adsorption bridging, and charge neutralization. The recycling study further suggests that the flocculant possesses good chemical stability and eco-compatibility.

Graphical Abstract

All-iron redox flow batteries (AIRFBs) have attracted increasing attention as cost-effective and sustainable large-scale energy storage systems due to the natural abundance and low cost of iron. However, their performance is often hindered by the crossover of iron species through the membrane, leading to electrolyte contamination, capacity decay, and reduced coulombic efficiency. In this study, we report a reinforced anion exchange membrane based on poly(phenylene oxide) (PPO) functionalized with 1,4-diazabicyclo[2.2.2]octane (DABCO) for AIRFBs. The membrane was modified through vinylbenzyl functionalization followed by thermal crosslinking and integrated with a porous polyethylene support to fabricate a reinforced composite membrane (DAB-PPO-RX). Structural characterization confirmed functionalization, crosslinking, and integration with the support layer while maintaining mechanical robustness and stability. When applied in AIRFBs, DAB-PPO-RX exhibited improved electrochemical performance compared with the non-reinforced membrane and commercial Selemion DSV membrane. The cells using DAB-PPO-RX delivered a coulombic efficiency of 93.7% and an energy efficiency of 64.9% with stable cycling over repeated charge–discharge cycles. The improved performance is attributed to the reinforced membrane structure, which suppresses iron crossover while maintaining efficient ion transport. These results demonstrate that DAB-PPO-RX provides an effective strategy for improving membrane selectivity and stability in AIRFBs, highlighting its potential for large-scale energy storage.

The effects of the different diffusivities of the displacing and displaced components on the growth of miscible viscous fingering in a radial porous medium are analyzed theoretically and numerically. By considering viscosity profiles determined by the diffusivity ratio and the log-viscosity parameters, six stability regimes are identified. For each regime, the influences of physical parameters on the onset and the growth of the radial viscous fingering are examined using linear stability analysis (LSA) and numerical simulations. In the present regime IV_U, where viscosity decreases monotonically with an inflection point, a new dynamic stability criterion is proposed to explain the instabilities without viscosity mismatch, and its validity is demonstrated through linear stability analysis (LSA) and numerical simulations. Although the system is initially stable, double-diffusive effects render it unstable in the present regime V. Unlike a system with identical diffusivities, the Péclet number delays the onset and suppresses the growth of fingering motion in regimes IV_U and V. Because of the differences in the spatio-temporal domains between the linear stability analysis (LSA) and the numerical simulations, visible motion is not observed in the present simulations, particularly for instabilities that grow slowly.

The separation of azeotropic mixtures, such as methyl acetate and methanol remain a major challenge in chemical process design due to strong molecular interactions and low relative volatilities. In this study, a green and efficient deep eutectic solvent (DES) based on choline chloride (ChCl) and ethylene glycol (EG) (1:3) was introduced as a sustainable entrainer to disrupt the azeotrope at 323.15 K. Vapor–liquid equilibrium (VLE) and vapor–liquid–liquid equilibrium (VLLE) experiments revealed complete azeotrope elimination at only 0.4 wt% DES loading, confirming its superior selectivity and phase-splitting capability. Beyond the experimental findings, a Physics-Guided Artificial Neural Network–Gaussian Process Regression (PI-ANN + GPR) hybrid framework was developed to predict key thermodynamic properties. The hybrid model outperformed conventional regression methods by achieving near-perfect parity and statistically calibrated uncertainty bounds (PICP₉₀ ≈ 0.90). This integrated experimental–computational approach not only validates ChCl: EG as a viable green entrainer but also demonstrates a scalable machine learning route for data-efficient, uncertainty-aware design of DES-assisted separations, establishing a new benchmark for reliability-driven solvent screening.