Abstract This paper explores the role of reactive oxygen species (ROS) and reactive chlorine species (RCS) in the degradation process using detailed kinetic modeling of the solar-activated chlorine degradation of 4-nitrophenol (4-NP). The rate constants for the radical and non-radical routes of hypochlorite and the oxidation of 4-NP by free radicals were determined thanks to the kinetic modeling. Results indicate that the combined action of chlorine and solar illumination in the SunTest model results in a fully synergistic treatment. The observed 4-NP degradation rate constant from the experimental profiles in the control run (pH 10, 500 µM chlorine) is k obs = 2.1 × 10 −3 s −1 ( R 2 = 0.993). The predicted values from the modeling profiles closely matched the experimental ones, with 2 × 10 −3 s −1 ( R 2 = 0.997). To estimate the kinetic constants of the main photolysis reactions [k 2 for R 2 : ClO − + hν → O •− + Cl • , k 3 for R 3 : ClO − + hν → O( 3 P) + Cl − and k 4 for ClO − + hν→ O( 1 D) + Cl − ], several optimization algorithms available in COPASI were tested, but the Nelder–Mead one was ultimately selected because of the stability of its results and its robustness in the optimization of nonlinear parameters. Additionally, the rate constants for the reactions of 4-NP with O •− , Cl • , ClO • , Cl 2 •− , HOCl •− , HO 2 •− , O 2 •− and O( 3 P) were predicted to be k R127 = 4.999 × 10 9 M −1 s −1 , k R129 = 2.44 × 10 9 M −1 s −1 , k R130 = 3.59 × 10 5 M −1 s −1 , k 131 = 3.44 × 10 7 M −1 s −1 , k 132 = 4.19 × 10 4 M −1 s −1 , k 133 = 1.75 × 10 5 M −1 s −1 , k R134 = 4.099 × 10 4 M −1 s −1 , and k R135 = 0.51 M −1 s −1 respectively. At pH 10, the rate constants for the photolysis of ClO − are k R2 = 1.27 × 10 −3 s − , k R3 = 1.68 × 10 −4 s −1 , and k R4 = 0 s −1 . Additionally, profiles of ROS and RCS, along with detailed analyses of radical distribution during 4-NP degradation, were generated and examined under key operating conditions. This enabled the construction of a phase diagram describing radical distribution as a function of the main operational parameters.
Abstract Mechanical agitation is the most dominant engineering technique for achieving efficient solid-liquid multiphase mixing in stirred vessels, playing a core role in multiphase flow transport. Breaking the symmetrical flow field inherent in conventional agitation to enhance whole-tank mixing remains a persistent hotspot and challenge in process equipment. Aiming at the bottlenecks of traditional unidirectional rotating agitation – isolated mixing regions (IMR) and restricted local mass transfer – this study systematically investigates the solid-liquid mixing enhancement mechanism of reciprocating-rotating coupled stirring, based on a coupled computational fluid dynamics-discrete element method (CFD-DEM) framework integrated with the volume of fluid (VOF) multiphase model and overset dynamic mesh technology. This study quantitatively analyze the regulation laws of reciprocating motion functions (sine, trapezoidal, random, chaotic mapping) and stroke amplitudes on particle spatial distribution, and reveal the impeller force response and particle multi-state suspension characteristics via two-way fluid-structure interaction (FSI) analysis. Results show the sine motion function has the lowest spatiotemporal velocity correlation, with robust spatial ergodicity and optimal particle dispersion. When stroke amplitude is 2/3 of the tank diameter, the average particle nearest neighbor distance (NND) peaks, effectively mitigating severe local entrainment and bottom accumulation. FSI dynamic analysis reveals periodic alternating loads induce ∼5,000 Pa concentrated stress at the impeller disk and blade connections, accompanied by high-frequency wall shear stress, posing potential material fatigue and erosive wear risks. High-viscosity systems significantly inhibit particle settling via flu-id damping, achieving up to 85 % suspension rate by the second cycle, with broader property compatibility for diverse particles than low-viscosity systems. This study elucidates the dynamic evolution mechanism of reciprocating-rotating coupled stir-ring, providing explicit quantitative criteria for industrial design and scale-up of novel high-efficiency solid-liquid mixing equipment.
Abstract Photocatalysis is a sustainable and light-driven technology increasingly recognized for its potential to address pressing environmental and energy challenges. Incorporating nanomaterials has notably enhanced photocatalytic performance by offering high surface area, tunable optical and electronic properties, and increased chemical reactivity. This review summarizes recent developments in photocatalytic nanomaterials, with a focus on titanium dioxide due to its cost-effectiveness and stability, along with other materials such as zinc oxide, metal sulfides, carbon-based nanomaterials (e.g., fullerenes, nanotubes, graphene, graphitic carbon nitride), perovskites, and metal–organic frameworks. Strategies to enhance photocatalytic activity include bandgap engineering for visible-light activation, suppression of charge carrier recombination through heterostructure formation, and using cocatalysts. Applications span environmental remediation (e.g., water and air purification, soil decontamination) and energy-related processes (e.g., hydrogen generation, CO 2 reduction, biomass conversion). Despite considerable progress, challenges remain in long-term stability, full-spectrum light absorption, testing standardization, scalability, and potential environmental toxicity. Future research directions involve developing advanced hybrid systems, integrating with energy storage technologies, utilizing artificial intelligence for material design, and implementing green synthesis methods. These developments aim to overcome current limitations and advance the practical implementation of photocatalysis based on nanomaterials in sustainable environmental and energy solutions.
Abstract The efficiency of Proton Exchange Membrane Fuel Cell, which is one of the promising energy-converting technologies, strongly depends on the design of the flow fields of such systems. The architecture of the fuel cell becomes an essential factor that ensures the adequate distribution of the gases and control of heat and water in the fuel cell. To understand the impact of the architecture of fuel cells on the efficiency of PEMFCs, a comprehensive computational model has been developed that considers four various geometries of channels with identical cross-section areas in the parallel flow field configuration. The objective of this research was to explore the impact of the channel geometry on the behavior of PEMFC concerning gas transport, heat transfer, and water balance. Notably, the square channel geometry outperformed the other designs, exhibiting a 17.20 % improvement in efficiency compared to the semi-circular channel also at 0.40 V, the maximum velocities in square, rectangular, semicircular, and triangular channels are 4.28618 m/s, 4.1856 m/s, 4.17292 m/s, and 4.78493 m/s, respectively. This is attributed to the more optimized flow profile and reduced parasitic losses in the square channel design.
Abstract This study investigates the photocatalytic performance of synthesized cerium oxide (CeO 2 ) nanoparticles for the degradation of Direct Blue 14 (DB14), a model organic pollutant, in comparison with titanium dioxide (TiO 2 ). CeO 2 nanoparticles were synthesized via the chemical precipitation method and characterized using Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and Raman spectroscopy. The presence of Ce–O and O–Ce–O stretching vibrations in the FTIR spectra confirmed the successful formation of CeO 2 nanoparticles. XRD and Raman analyses revealed that the nanoparticles possess a crystalline structure, with an average crystallite size of approximately 10 nm and a face-centered cubic (FCC) lattice. Photocatalytic tests demonstrated that both CeO 2 and TiO 2 exhibited significant activity in degrading DB14 under UV irradiation, with enhanced performance observed in acidic media at ambient temperature. CeO 2 nanoparticles achieved optimal degradation efficiency at a dosage of 6 mg, compared to 30 mg required for the TiO 2 /UV system. Overall, CeO 2 nanoparticles exhibit greater activity than TiO 2 representing five-fold higher mass-specific activity. Thermodynamic analysis indicated that the photodegradation process of DB14 is endothermic and non-spontaneous at low temperatures. Additionally, the composition of water matrices significantly influenced photocatalytic efficiency. The presence of ions such as Na + , Cl − , SO 4 2− , K + , Mg 2+ , Ca 2+ , Br − , and HCO 3 − was found to inhibit chemical oxygen demand (COD) removal, thereby reducing the effectiveness of both CeO 2 /UV and TiO 2 /UV systems. Similarly, the use of tap water and seawater led to a decrease in photocatalytic efficiency in both systems.
Dye-laden wastewater presents a critical global environmental issue, requiring sustainable and bio-based treatment strategies for the effective removal of hazardous pollutants. The adsorption of methylene blue (MB), a cationic dye, using raw cupule scale (CR) as a natural bioadsorbent was investigated in this study. Additionally, untreated cupule scales were selected for further evaluation of the cationic dye adsorption process. The physicochemical characterization of the adsorbents was carried out using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and the determination of the point of zero charge (pHPZC) (7.2). The influence of key operational parameters, including contact time, adsorbent dosage, solution pH, and initial dye concentration, was systematically investigated and optimized using the Box-Behnken Design (BBD). The equilibrium data showed an excellent fit to the Langmuir isotherm model with correlation coefficient R2 = 0.99 at 20 degrees C while kinetic analysis indicated that the pseudo-second-order model best described the adsorption behavior, suggesting a chemisorption-controlled mechanism with a maximum adsorption capacity of 102.315 mg/g. Among the advanced isotherm models evaluated, the double-energy monolayer model provided the most accurate description of MB adsorption on CRs (R2 greater than 0.9981, MRSE little than 0.015), revealing a multimolecular adsorption mechanism with a primary receptor site density (Nm1) reaching up to 318.2 mg/g. Thermodynamic analysis confirmed that the adsorption process is exothermic and spontaneous, with adsorption efficiency decreasing at higher temperatures. These findings underscore the potential of CR as an effective, natural, and cost-efficient adsorbent for mitigating MB contamination in aqueous systems.
Abstract This work is carried to review the second edition of The Chemical Reactor from Laboratory to Industrial Plant by Riccardo Tesser and Elio Santacesaria. The book stands out through a systematic and problem-based approach, which integrates thermodynamics, catalysis, kinetics and mass transfer phenomena into a unified framework for reactor scale-up. Compared with the first edition, the book has significant improvements, adding two chapters on polymerization and bioreactor, reflecting the needs of contemporary industry. An important teaching advantage is that a large number of MATLAB codes for numerical solutions can make reader go beyond the analytical approximation. The book excels in the strict treatment of non-ideal thermodynamics, Langmuir-Hinshelwood kinetics, efficiency factor calculation, and multiphase mass transfer using two-layer theory. However, several limitations are also found: too dense content may make it difficult for novices to understand; computational fluid dynamics is not discussed; the description of non-ideal flow characteristics is also very simple. Compared with Froment & Bischoff’s, Fogler’s, and Levenspiel’s classic works, this book presents a unique European perspective. It not only emphasizes physical chemistry, but also combines engineering practice. The review of the book points out that although there are some minor shortcomings, the book is still a valuable resource for graduate students, process engineers and researchers seeking practical and computational guidelines for the design and scale-up of chemical reactors.
The catalytic epoxidation and subsequent conversion of waste cooking oil (WCO) to dihydroxystearic acid (DHSA) were investigated using a synergistic acid system consisting of citric acid and sulfuric acid via an in situ peracid mechanism. The study aims to valorize WCO as a sustainable feedstock for bio-based chemical production while addressing limitations in selectivity and process efficiency. A synergistic acid system consisting of 5 g citric acid and 1.2 g sulfuric acid was employed as the catalytic medium for the epoxidation of waste cooking oil. The effects of reaction temperature (60-80 degrees C) and acetic acid molar ratio (0.5-1.5 mol) on relative oxirane content (RCO) were evaluated. The optimum epoxidation condition was achieved at 70 degrees C, while a molar ratio of 0.5 provided the highest RCO, indicating favorable epoxide formation prior to ring-opening. FTIR analysis confirmed the formation of oxirane rings and their subsequent conversion into vicinal diols, validating DHSA production. The simulated results showed good agreement with the experimental data, with a low sum of error value of 0.2083, indicating satisfactory predictive accuracy of the developed model.
Abstract The demand for eco-friendly epoxides has driven significant growth in vegetable oil-based epoxidation. This paper highlights the significance of epoxidized nonedible oils as sustainable chemical precursors, offering a biodegradable and renewable alternative to traditional petrochemical resources. With applications spanning lubricants, plasticizers, and polymer precursors, vegetable oil-based epoxides provide versatility for diverse industries. The study explores the epoxidation reaction’s core principles, focusing on the transformation of unsaturated vegetable oil bonds into epoxide functional groups through oxidants and catalysts. It also examines optimization strategies to improve process efficiency, yield, and selectivity, while addressing challenges like degradation and stability. By prioritizing nonedible oils, this research aligns with global sustainability goals, reducing competition with food resources and advancing eco-friendly materials through green chemistry.
Abstract The accelerating global shift toward renewable energy has intensified the demand for reliable solar power generation. Concentrated solar power (CSP) plants offer a promising utility-scale solution due to their inherent dispatchability, yet their performance is constrained by the intermittency of solar irradiation. Thermal energy storage (TES) mitigates this limitation by storing excess heat during peak insolation and delivering it during low-solar periods, enabling stable and flexible power output. This review examines key TES pathways – sensible heat storage (e.g., molten salts), latent heat storage using phase-change materials (PCMs), and thermochemical energy storage (TCES) – and their roles in improving CSP system performance. TES integration can increase CSP capacity factors from 25–30 % to 40–50 % while reducing the levelized cost of electricity. Current molten-salt systems provide 6–15 h of storage, whereas PCMs and TCES offer up to two- to three-fold higher energy densities compared with conventional sensible-heat media. This review critically compares these technologies in terms of performance, scalability, and integration challenges, identifies key research gaps in high-temperature materials and system design, and outlines future strategies to advance CSP–TES deployment in sustainable energy systems.
Abstract The synthesis of zeolite nanoparticles has gained significant attention for their application in advanced oxidation processes for treating wastewater. In AOPs, zeolite nanoparticles act as catalysts to enhance the production of oxygen species that are reactive, which include hydroxyl radicals, can effectively breakdown a wide spectrum of organic contaminants into non-toxic end products. The literature study focused the efficiency of zeolite nanoparticles in wastewater treatment which was evaluated through batch experiments targeting persistent organic pollutants (POPs) under varying operating conditions such as pH, temperature, and pollutant concentration. The overall results demonstrate a significant enhancement in pollutant degradation rates when zeolite nanoparticles are employed in conjunction with AOPs like Fenton’s reaction and photocatalysis. Additionally, the versatility and durability of the nanomaterials were evaluated to determine their economic viability. The integration of zeolite nanoparticles in AOPs presents a promising solution for addressing global wastewater challenges, paving the way for eco-friendly and effective treatment technologies. This study contributes to the advancement of nanomaterial-based approaches in environmental engineering, with implications for sustainable water management.
The autocatalytic epoxidation of a hybrid neem oil-oleic acid system using lactic acid as an oxygen carrier was investigated as a greener alternative to conventional mineral-acid epoxidation routes. A feasibility study demonstrated rapid oxirane formation during the early reaction stage, achieving a maximum relative conversion of approximately 28 % within 20-30 min before gradual decline due to ring-opening side reactions. Process optimisation using the Taguchi L16 design identified temperature as the dominant factor influencing epoxidation efficiency, with the optimal condition achieved at 55 degrees C, a low oxidant ratio and moderate agitation. FTIR analysis confirmed successful epoxidation by the appearance of characteristic oxirane bands and the simultaneous reduction in C=C absorbance. Kinetic modelling using MATLAB produced an excellent fit between simulated and experimental data, reflected by a high R 2 value of 0.9982, validating the proposed reaction mechanism. The results highlight the feasibility of lactic-acid-mediated epoxidation and demonstrate that hybrid feedstocks can enhance double-bond availability while maintaining reaction controllability. This study offers a promising pathway to produce bio-epoxides under milder and more environmentally acceptable conditions, supporting future development of renewable polymer precursors.
Novel ternary photocatalyst TiO 2 -ZnO/g-C 3 N 4 was synthesized via a ball milling-assisted sol-gel method and its photocatalytic performance was tested in the photocatalytic degradation of methyl orange (MO) and metoprolol (MTP) under UV-LED and visible light. The samples were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen physisorption (BET), UV-visible diffuse reflectance spectroscopy (UV–Vis DRS), X-ray photoelectron spectroscopy (XPS) and positive hole production. Optical measurements confirmed that the combination of TiO 2 , ZnO, and g-C 3 N 4 extended the visible light absorption to 2.63 eV. SEM, TEM, FTIR and XPS revelated correct coupling between the three semiconductors, and hole density analysis suggested a synergistic effect, reducing the charge recombination. Additionally, reusability tests demonstrated the chemical stability of the material. In terms of pollutant degradation, the TiO 2 -ZnO/g-C 3 N 4 composite efficiently removed 97.75 % of MO under UV-LED light and 98.57 % under visible light in 180 min. Similarly, MTP degradation test reached 86.42 % and 86.08 % under UV-LED and visible light, respectively, after 180 min. These results highlight the mate-rial’s potential for environmental applications, particularly in contaminant removal through photocatalysis.
Radical and non-radical peroxymonosufate (PMS) activation using heterogeneous metal-based catalysts has received particular focus for its efficiency in the removal of refractory contaminants across diverse water matrices. In this study, Co 3 O 4 was synthesized through a mild wet chemical process. The resulting catalyst was then characterized using various technics (XRD, FT-IR, SEM, and BET). The catalytic activity of Co 3 O 4 in activating PMS to degrade naproxen (NPX) was investigated, revealing 90.7 % NPX degradation rate in just 15 min and total organic carbon removal of 67.95 %. Key parameters such as PMS dosage and pH were optimized and their impact on NPX degradation was assessed. Furthermore, the contribution of reactive species was evaluated via quenching tests and the results identified singlet oxygen ( 1 O 2 ) as the primary species involved in the degradation of NPX. The efficiency of the process was assessed in various water matrices, and the results revealed that ubiquitous inorganic anions had a negligible effect, whereas organic matter inhibited the process. Finally NPX mineralization was evaluated using total organic carbon (TOC) analysis.
Efficient and sustainable hydrogen generation is fundamental to the transition to a clean energy economy. Water dissociation is a key method for producing green hydrogen when powered by renewable energy sources. The substitution of cations such as strontium and cobalt in the lanthanum chromite crystal lattice induces structural modifications that increase oxygen vacancies, thereby modulating electronic conductivity and enhancing surface catalytic activity for water dissociation. Furthermore, it is possible to create materials sensitive to specific wavelengths; this tuning capability is essential in photovoltaics, photocatalysis, and optoelectronics. In this work, we investigate the modifications in the electronic and catalytic properties of lanthanum chromite induced by strontium and cobalt doping. To assess the material's potential for hydrogen production using thermochemical water splitting, thermogravimetric analysis was conducted, yielding a hydrogen production capacity of 0.252 mmol/g. Analysis performed using reflectance spectroscopy showed that the band gap can be tuned within a range of 1.69-2.88 eV. Furthermore, the solar absorbance of the materials was observed to increase from 92 % to 98 % in the UV-Vis range due to doping, this improvement in absorption increases power conversion efficiency.
Polycrystalline diamond compact (PDC) has excellent wear resistance, making it widely utilized in drill bits and bearings of downhole tools within the oil industry. However, the harsh conditions underground and the friction place higher demands on the performance of PDC. However, the harsh conditions underground and the friction place higher demands on the performance of PDC, leading to a severe deterioration in both wear resistance and chemical stability. To address this issue, the present work investigates cobalt removal PDC subjected to high-temperature annealing to evaluate its degree of graphitization and chemical stability. The annealing experiment was carried out by box resistance furnace. The microstructure of PDC after annealing and friction wear was examined using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Additionally, the evolution of chemical bonds after PDC wear was analyzed by X-ray photoelectron spectroscopy (XPS). The results show that with increasing annealing temperature, the area of PDC wear-resistant interface transfer film is increasing. In contrast, the non-cobalt removal PDC not only failed to develop a transfer film at the wear interface but also exhibited pronounced graphitization. These experimental findings and mechanistic insights offer a theoretical basis for guiding the application of PDC in downhole tools for petroleum drilling.
This study presents the development of a cost-effective ceramic membrane derived from waste inorganic fly ash for efficient dye removal from aqueous solutions, leveraging the synergistic properties of fly ash and a supporting substrate through a combination of chemical grafting. A wider particle size distribution of fly ash results in a denser membrane structure with reduced porosity. The membrane was fabricated using the uniaxial pressing technique, specifically through dry uniaxial compaction, and was analyzed using Fourier-Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Thermogravimetric Analysis (TGA). Additionally, porosity and permeability tests were conducted using pure water. The particle size of fly ash significantly affects the properties of the ceramic membrane, including porosity, surface area, mechanical strength, and filtration efficiency. The membrane featured varying compositions and sintering temperatures ranging from 600 degrees C to 900 degrees C. The porosity of the membranes was found to be 31.31 %, with an average hydraulic pore radius of 0.311 & micro;m, leading to an increase in pure water flux from 0.022 to 0.15 L/m(2) min bar within a transmembrane pressure range of 1-4 kg/cm(2). The membrane surface displayed a negative charge within the pH range of 4-12, indicating that adsorption played a key role in removing the cationic dye. This work emphasizes the significant potential of these membranes for treating dye-containing aqueous solutions, considering factors such as transmembrane pressure, feed concentration, flux, and rejection. At a pressure of 1 kg/cm(2), the highest dye removal efficiency is 99.86 % at a feed concentration of 20 mg/L.
A proper experimental design is of central importance for carrying out an efficient parameter estimation of heterogeneous reaction kinetics. The outcome of parameter estimation impacts the design, analysis, and optimization of chemical reactors. Commonly, practitioners conduct experiments based on heuristic or ad hoc designs, which can induce statistical bias, excessive amplification of experimental errors, and unnecessary costs. With this in mind, optimal design of experiments (DOE) is an alternative for establishing experimental configurations that are both statistically and economically efficient. Optimal DOE dates back at least 100 years, but its extensive use in chemical kinetics is still limited. One possible reason for this limitation is that optimal DOE relies on rigorous statistical and mathematical methods, which are generally intractable for many practitioners. The aim of this work is to explore optimal DOE for Langmuir-Hinshelwood kinetics from a more intuitive than rigorous perspective. The motivation is to promote the use of systematic DOE techniques that are accessible to practitioners with an elementary background in calculus and algebra.
Hydrogen-based flash ironmaking, which combines hydrogen reduction with flash smelting, enables the rapid reduction of iron ore powder in a suspended state and represents a new approach to low-carbon ironmaking. Existing research has largely focused on macroscopic reduction behaviour, with insufficient attention paid to the gas-solid two-phase flow characteristics and control mechanisms within the reaction tower; there is a lack of systematic understanding regarding the influence of nozzle configuration on particle dispersion and gas-solid contact efficiency. This study takes the hydrogen-based flash ironmaking reaction tower as its subject and employs the CFD-DEM method to systematically investigate the impact of five nozzle arrangement schemes on gas-solid flow characteristics. The results indicate that a double-layer, three-nozzle staggered arrangement increases the proportion of particles retained in the reaction zone by over 80 %, significantly prolonging residence time and enhancing gas-solid contact, thereby providing favourable flow conditions for efficient reduction. The study elucidates the regulatory mechanisms of gas-solid mixing governed by nozzle structure, providing a theoretical basis for reactor structural optimisation and process control.
