Search Results (733)

This study investigates the simultaneous elimination of ethyl acetate (EA), a representative volatile organic compound (VOC), and Escherichia coli aerosols from indoor air using a continuous-flow dielectric barrier discharge (DBD) plasma reactor coupled with a photocatalytic luminous textile system (Cu/TiO₂-coated fibers). The effects of applied voltage, relative humidity, and air-flow rate on pollutant removal and disinfection performance were systematically evaluated. Optimal DBD operation at 18 kV, 1 m³ h⁻¹ airflow, and 70% relative humidity achieved single-process removal efficiencies of 77% for EA and 2 log reduction (CFU mL⁻¹) for E. coli. When photocatalysis was coupled with DBD plasma, a significant combined effect was observed, increasing EA degradation to 87% and bacterial inactivation to 3.8 log (CFU mL⁻¹). The coupling enhanced active-species generation, improved CO₂ selectivity (up to 53%), and reduced residual ozone concentration. Humidity positively affected microbial inactivation due to °OH radical formation but slightly decreased VOC degradation by limiting ozone regeneration. Results demonstrate the efficiency and scalability of the DBD–photocatalysis hybrid system for multi-pollutant indoor air purification, offering rapid, low-temperature treatment suitable for industrial-scale applications. Full article

The presence of xenobiotics in wastewater, particularly emerging contaminants such as pharmaceuticals, poses an ecotoxicological risk to the environment and human health. One of the main pharmaceutical products detected in water is diclofenac, which can be sold without a prescription. The lack of health regulations indicates the necessity of finding environmentally friendly treatment alternatives to remove this type of contaminant. Among these alternatives, biotechnology, specifically biological processes, offers a sustainable option compared to conventional treatments. Current treatment methods used in wastewater treatment plants are ineffective at removing diclofenac, a chlorinated aromatic compound highly resistant to degradation processes. In recent years, new treatment methods have gained prominence due to the favorable results they have yielded, including physicochemical, biological, and advanced processes. Biological treatments are notable for their low cost and the high level of effectiveness and efficiency with which they can remove toxic compounds. For this reason, the aim of this research project was to evaluate the degradation efficiency of a biological treatment in a bioreactor using a microbial community consisting of five bacterial strains, which was isolated from a pharmaceutical effluent and cultivated in a continuous culture system. Removal efficiencies ranging from 99.38 to 99.98% were achieved at various volumetric loading rates (from 0.087 to 1.043 g L⁻¹d⁻¹). Influents and effluents from the biological reactor were analyzed using bioassays to determine any potential toxic effects. The results showed that the effluents did not elicit a negative response in the bioindicators, indicating high toxicity in the influents. Full article

In the present study, Fe₃O₄@hydrothermal carbon was prepared successfully using rice straw waste. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analysis confirmed that the material had rich and strong redox-active centers on its surface, indicating that it has potential to be used as a redox mediator for electron transfer. Fe₃O₄@hydrothermal carbon was added into the anaerobic sludge treatment system for the collaboration of dye decolorization. The results showed that azo dye decolorization efficiency reached the maximum value (98.3%) with the presence of Fe₃O₄@hydrothermal carbon, which was 16.6% higher than control reactor (without Fe₃O₄@hydrothermal carbon added). In addition, Fe₃O₄@hydrothermal carbon exhibits good reusability and the dye decolorization rates in the “anaerobic sludge–material” combining system were significantly higher than that in the “sludge-alone” system during the semi-continuous wastewater treatment process. Mechanistic investigations revealed that the enhanced decolorization is driven by a synergistically constructed interspecies electron transfer pathway. Specifically, the addition of Fe₃O₄@hydrothermal carbon improved the formation of the extracellular polymeric substance (EPS), which had positive effects on sludge stability and its interaction with the material. CV and electron transport system (ETS) activity analysis showed that the sludge exhibited high electrochemical activities with the support of the material, which led to a high electron transfer efficiency between the electron-donating and accepting microbial pairs in the treatment system. The high-throughput sequencing analysis showed that the structure of the microbial community changed during the semi-continuous treatment process; Megasphaera and Clostridium accounted for more than 87.5% of the total abundance of the bacterial community in the anaerobic sludge with material addition. Driven by the material-mediated process, these enriched functional taxa exhibited a high electron transfer efficiency between electron-donating and accepting pairs, accelerating the catalytic cleavage of azo bonds and ultimately improving the overall anaerobic treatment performance. Full article

Clay mineral authigenesis and transformation are key diagenetic processes that influence the evolution of sandstone reservoir quality. Although smectite formation and its transformation to illite have been widely studied in clay-rich and feldspathic systems, their development in highly quartz-rich sands remains less well constrained. This study investigates the experimental formation of authigenic smectite and its subsequent illitization in a quartz-dominated sand under controlled hydrothermal experiments. Quartz-rich glass sand from the Middle Jurassic Mariedal Formation (Skåne, Sweden) was reacted with natural Red Sea water in sealed reactors at 80, 150, 200, and 250 °C for 14 days to simulate progressive burial diagenesis. Mineralogical, textural, and geochemical changes were evaluated using thin-section petrography, SEM-EDS, WD-XRF, XRD, and ICP-OES. The starting material is composed predominantly of quartz (91.3%), with minor K-feldspar (6.2%) and muscovite (1.4%), providing limited but sufficient reactive components for clay mineral formation. Dissolution of K-feldspar and muscovite began at 80 °C and continued throughout the experiments. Authigenic smectite was first detected at 150 °C as discontinuous grain-coating phases, indicating nucleation through dissolution–precipitation reactions linked to feldspar alteration and uptake of Mg from the reacting fluid. At 200 °C, the smectite coating became thicker and more extensive, with the onset of transformation to illite through mixed layer stages. By 250 °C, illite becomes the dominant clay mineral, recording progressive smectite illitization with increasing temperature. Fluid chemistry shows systematic variations with temperature, including decreasing Mg and evolving K concentrations, reflecting progressive mass transfer between solid and fluid phases. These results demonstrate that even highly quartz-rich sands can generate authigenic clay minerals when minor reactive phases and suitable fluid chemistry are present. The experiments provide a process-based analogue for clay mineral evolution in quartz-rich sandstone reservoirs and highlight the importance of coupled mineral–fluid reactions during burial diagenesis. Full article

The quantitative measurement of nuclear material hold-up in the process equipment is one of the technical challenges in nuclear material measurement for nuclear facilities. Its results are directly related to the optimization of radiation protection, the criticality safety control of nuclear materials, and the accurate accounting of nuclear material. As a key core equipment in the nuclear material reprocessing process, the precipitation reactor is restricted by the complex on-site environment, compact spatial layout, and continuous operation process, making it difficult for traditional measurement technologies to conduct accurate quantitative analysis of the internal hold-up. To address this issue, this paper proposes a method for measuring and analyzing the hold-up in the precipitation reactor based on the passive neutron counting method. A laboratory model of the precipitation reactor is constructed, and a multi-detector neutron measurement system is developed in this work. By combining Monte Carlo (MC) simulation with experimental calibration of standard point sources, a mathematical model suitable for hold-up measurement of the precipitation reactor is established. Meanwhile, uncertainty analysis of key data was carried out, and the accuracy of the model was verified by operational Pu samples of various masses, effectively reducing the measurement deviation caused by the uneven distribution of hold-up in the equipment and model assumptions. This research provides a more reliable technical reserve and reference paradigm for the measurement of nuclear material hold-up in nuclear facilities. Full article

In this study, a sustainable calcium-rich biochar was synthesized via co-pyrolysis at 800 °C of marble waste, animal manure, and lignocellulosic biomass. This biochar (MWM–B) was comprehensively characterized and then valorized for phosphorus (P) removal from real effluent and synthetic solutions in both batch and continuous stirred tank reactor (CSTR) modes. Characterization results confirm the formation and deposition of significant amounts of calcium oxides and calcium hydroxides on the biochar surface, which enhance the biochar’s surface chemistry and textural properties. In batch mode, MWM–B efficiently removes P with a removal capacity (108.4 mg g⁻¹) that is 5.3 times higher than that observed in the CSTR system. This efficiency drop is due to the limited contact time between phosphate species and the biochar particles. Interestingly, the presence of calcium and magnesium in the continuously renewed real effluent in the CSTR system increases P removal efficiency by approximately 136% compared with synthetic solutions. A detailed analysis of MWM–B before and after P removal suggests that this process occurs mainly through precipitation as hydroxyapatite, complexation with hydroxyl functional groups, electrostatic interactions, and hydrogen bonding. This work confirms that MWM–B generated at 800 °C is an attractive material for P removal from effluents. Full article

This study focuses on the design, optimization, and evaluation of a biodiesel production process involving the transesterification of waste cooking oil (WCO) using a heterogeneous calcium oxide (CaO) catalyst derived from waste eggshells. The work is divided into two main parts. The first focuses on the laboratory preparation, characterization, and performance of the CaO catalyst, while the second translates the experimentally optimized conditions into a process-scale model using Aspen HYSYS to assess industrial feasibility. Waste eggshells were cleaned, dried, ground, and calcined at high temperature to produce the CaO heterogenous catalyst. The catalyst was characterized by Simultaneous Thermogravimetric-Differential Scanning Calorimetry (TG-DSC) and Fourier Transform Infrared Spectroscopy (FTIR). Transesterification experiments were conducted in a batch round-bottom flask reactor where CaO was added to sunflower oil and methanol, and multiple operating parameters were varied to determine the optimal conditions. The catalyst exhibited its best performance after calcination at 900 °C for 2 h. A maximum biodiesel yield of 95 wt.% was obtained at a methanol-to-oil molar ratio (MOMR) of 9:1, reaction time of 2 h, stirring speed of 700 rpm, temperature of 60 °C, and catalyst amount of 3 wt.%. In addition, the eggshell-derived CaO catalyst maintained a biodiesel yield close to 95% over three consecutive reuse cycles, demonstrating good reusability and catalytic stability. The produced biodiesel complied with ASTM standards. Based on these results, the process was then scaled up by simulating a continuous industrial biodiesel production plant using Aspen HYSYS. The model proved practical, achieving a biodiesel purity of 99.85%. Further process optimization, including methanol recovery and heat integration, reduced fresh methanol consumption by 60% and overall energy requirement by 25%. The combined experimental and simulation results demonstrate that energy efficiency and waste valorization enable a biodiesel production pathway that is both environmentally and economically sustainable and aligned with circular economy principles and sustainable development goals. Full article

Greenhouse gas generated from wastewater treatment plants has attracted much attention as it has the potential to be recovered and used as an energy source. In this study, a membrane biofilm reactor was designed to simultaneously enhance nitrate removal and reduce methane (CH₄) emissions during methane oxidation coupled with the denitrification process. The enrichment of CH₄-driven denitrification microbes with a relatively short hydraulic retention time (HRT) and its effects on the stable operation of the reactor were studied within 250 d. With an increasing HRT from 8 to 20 h, a removal rate of up to approximately 0.51 mg/L·h⁻¹ was achieved, which also kept the effluent NO₂⁻-N below 0.5 mg/L. Microbial community analysis showed that the diversity and uniformity of microorganism communities decreased with the addition of CH₄ as a carbon source, and the microbial structure changed significantly. Compared with that of seed sludge at the phylum level, the relative abundance of Proteobacteria increased significantly, Alphaproteobacteria and Sphingobacteriia continued to become enriched, and the abundance of Methylocystis increased significantly. Neither denitrifying anaerobic methane oxidation (DAMO) archaea nor bacteria were found in the sequencing analysis. Methylocystis was the dominant CH₄ oxidizing bacteria, in synergy with the co-occurrence of autotrophic and heterotrophic denitrifying bacteria, which likely join up in nitrogen removal. Unlike the systems described in most methane-driven denitrification studies, our system achieved nitrate removal without detectable DAMO microbes. Full article

In 2024, China generated approximately 130 million tons of food waste. This study focuses on food wastewater characterized by exceptionally high organic strength (chemical oxygen demand (COD) > 80 g·L⁻¹, total suspended solids (TSS) > 20 g·L⁻¹) content. Conventional continuous stirred tank reactors (CSTRs) inherently couple hydraulic retention time (HRT) and sludge retention time (SRT), making them prone to microbial washout under high organic loading. To overcome this limitation, this study employed two anaerobic sequencing batch reactors (ASBRs) for treating such high-strength food wastewater. This study systematically evaluated the impacts of temperature (mesophilic: 37 °C and thermophilic: 55 °C) and organic loading rate (OLR) on fermentation performance. Under stable operation (OLR = 5.6 kg_COD·m⁻³·d⁻¹; HRT = 16 days), the mesophilic ASBR achieved a specific methane yield of 307 mL CH₄·g_CODremoved⁻¹, an average COD removal efficiency of 81%, and a volatile fatty acids-to-total alkalinity (VFA/TA) ratio of 0.2, indicating robust process stability. In contrast, the thermophilic ASBR exhibited a VFA/TA ratio of 0.5, signaling incipient acidification. Microbial community analysis revealed significantly higher bacterial and archaeal alpha diversity in the mesophilic system. Notably, Methanothrix—a versatile acetoclastic methanogen—dominated the mesophilic archaeal community (66.65%), conferring functional redundancy and resilience against organic shock loads. By contrast, the thermophilic system was overwhelmingly dominated by the hydrogenotrophic Methanothermobacter (99.28%), resulting in low functional diversity and structural fragility. Compared with a benchmark mesophilic CSTR (specific methane yield: 276 mL CH₄·g_CODremoved⁻¹; COD removal efficiency: 70.6%), the mesophilic ASBR improved methane yield by 11%, COD removal efficiency by 15%, and operational stability (VFA/TA = 0.2 vs. 0.6). This work addresses a gap in ASBR applications for high-strength food wastewater treatment and provides experimental validation of the performance, stability, and scalability of mesophilic ASBRs. The proposed process represents a technically feasible, resource-efficient, and operationally robust solution for the valorization of organic wastewater with COD > 80 g·L⁻¹ and TSS > 20 g·L⁻¹. Full article

A livestock farm in southern Taiwan produces wastewater with high concentrations of nitrogen and organics, which inhibit anaerobic methanogens and limit the efficiency of its biogas system. To enhance energy recovery, this study developed a liter-scale microbial fuel cell (MFC) system aimed at harvesting electricity from livestock wastewater, serving as a supplementary energy recovery pathway alongside the biogas process. According to the five analyses, the chemical oxygen demand (COD) of raw wastewater ranged from 14 to 21 g L⁻¹, with acetate concentrations ranging between 40 and 112 mM. Propionate and butyrate were consistently below 32 mM and 18 mM, respectively. Ammonium ranged from 1.1 to 1.7 g-N L⁻¹, indicating the wastewater’s high organic load and elevated nitrogen content. Two liter-scale MFCs, ch5 and ch7, were operated for over 70 d. From days 7 to 28, both MFCs employed a fill-and-draw mode, achieving optimal COD removal exceeding 80%. After resolving leakage issues between days 30 and 40, the system was restarted on day 40, yielding 76% (ch5) and 82% (ch7) of COD removal. Continuous operation began on day 59, and both reactors maintained COD removal rates above 80% for most of the subsequent two-week period. The best power outputs for ch5 and ch7 reached 1.11 and 0.82 W m⁻³, respectively. Although both liter-scale reactors achieved COD removal and measurable power output, the most important finding was obtained from the inoculum comparison experiments. After 54 days of acclimating to raw wastewater solids, no significant current was observed. In contrast, digestate solids acclimated with carbon powder for 22 d produced a peak current of 42.5 A m⁻³ at 147 h, with COD removal rates of 67–73% and complete removal of organic acids. The key conclusion of this study is that anaerobic digestate exhibits electroactive microbial potential, whether operated in liter-scale reactors or acclimated with carbon powder. Further investigation into the microbial community structure is warranted to optimize system performance. Full article

The potato chip processing (PCP) industry generates huge amounts of wastewater heavily polluted with organic matter and nutrients. The current treatment technology of PCP wastewater uses dissolved air flotation (DAF) and an activated sludge sequential batch reactor (SBR); both consume large amounts of chemicals and represent energy-intensive systems. This study explores the utilization of algae for the sustainable treatment of PCP wastewater, nutrient recovery, and algal biomass production. Conical flasks (1-L) and 6-L transparent plastic bottles were used as lab-scale algae photobioreactors (APBRs). Raw wastewater, an anaerobically pre-treated effluent and a DAF–SBR or shortly SBR effluent were used in the first, second, and third APBR. Three feed volumes from each source (150 mL, 300 mL, and 500 mL for first and second APBR and 400 mL, 600 mL, and 800 mL for third APBR) to a fixed volume of algal seed (200 mL) were tested to select the optimal feed volume and harvest time using a 1-L APBR. System performance and impact of water characteristics on quantity and quality of algal biomass were explored at pre-selected feed volume and harvest time in 6-L APBRs. All experiments were carried out in a growth chamber with continuous light (148.75 μmol.m⁻².S⁻¹). The results showed that 150 mL is the optimal feed volume for the first and second APBR at 10 days and 9 days growth cycles. An amount of 500 mL and 6 days were selected as the optimal feed volume and growth cycle for the third APBR. The average dry biomass yields at the pre-selected optimal conditions were 65.3 ± 11.4, 69.9 ± 12.0, and 100.6 ± 11.7 mg/L.d in the first, second, and third APBR, respectively. The first APBR achieved removals of 99.2 ± 0.4%, 98.7 ± 0.8%, 89.1 ± 4.3%, and 97.5 ± 1.4% for turbidity, COD, TKN, and TP, respectively, on average. Corresponding removal in the second APBR is 97.6 ± 2.6%, 91.6 ± 7.5%, 93.6 ± 4.5%, and 96.1 ± 1.4%, respectively, while the third APBR achieved 98.5%, 76.2%, and 97.0%, respectively. Additionally, the results of protein content and amino acids profiles indicate significant impacts of feed water quality on both parameters. The protein content was 30.64%, 32.53%, and 35.65% in the first, second, and third APBR, respectively. Similarly, the amino acids profile indicated a significant higher percentage of the amino acids in the third reactor compared with the first and second reactor. Full article

This paper presents a theoretical engineering feasibility analysis of the RK-X photocatalytic process for In Situ Resource Utilisation (ISRU) on Mars. Experimental validation under simulated Martian conditions is the essential next step before any mission deployment claim can be made. The RK-X process converts the two most abundant Martian resources, atmospheric carbon dioxide (CO₂) and subsurface water ice (H₂O), into formic acid (HCOOH) and oxygen (O₂) through a fulvic acid-based photocatalytic cycle validated at the industrial scale in Hungary. A reference module processing 10 tonnes of CO₂ per Earth year yields 10.459 tonnes of formic acid and 3.636 tonnes of oxygen, sufficient to sustain a six-person crew for approximately two Earth years with a 198% safety margin over nominal respiratory demand. The economic analysis indicates that importing equivalent oxygen from Earth costs $1.82–$3.64 million per year; equivalent energy storage (Li-ion) costs $30.5–$61 million for one-time use. Formic acid stores 15.25 MWh of energy in ambient-stable liquid form at a round-trip efficiency of 68.64% without cryogenic infrastructure. A photovoltaic array of 55.37 m² provides the primary energy source; a kilowatt-class nuclear fission reactor constitutes the strategic opportunity for continuous, dust-storm-immune operation with free thermal co-generation. Three critical research gaps have been identified requiring laboratory validation before Mars deployment: (i) catalyst performance at the Martian CO₂ partial pressure (p(CO₂) < 10 mbar, T = 15 °C); (ii) water ice and dry ice extraction at an operational scale; and (iii) integrated closed-loop system demonstration. Built on Earth-proven chemistry with identified, addressable development pathways, the RK-X process theoretically resolves the problems of oxygen supply, seasonal energy storage, water management, and cryogenic infrastructure within a single closed-loop chemical cycle. Full article

To address the problems of short-circuit flow and dead zones, complicated operation and control caused by intermittent influent, and the mismatch between aeration rate and oxygen demand in the Cyclic Activated Sludge System (CASS), a novel Multi-Compartment Fixed-Biofilm Cyclic Activated Sludge System (MCFCASS) was developed. This system operated in continuous-flow mode, and the aeration rate of each compartment was redistributed using a mathematical model. The results show that the plug flow ratio of the MCFCASS reactor increased from 18.75% to 31.25% compared with the CASS reactor. After aeration rate redistribution, the average total nitrogen (TN) removal efficiency of the MCFCASS reactor rose from 83.34% to 86.80%, and the effluent TN concentration consistently met the Grade I-A limit (15 mg/L) specified in the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB 18918-2002). The average removal efficiencies of chemical oxygen demand (COD) and ammonium nitrogen (NH₄⁺-N) increased from 91.58% and 93.39% to 92.98% and 94.57%, respectively. Microbial community analysis revealed that after aeration rate redistribution, the relative abundances of Pseudomonadota, Bacteroidota, and Bacillota in the pre-reaction zone of MCFCASS were 39.17%, 17.78%, and 10.33%, respectively. In addition, the abundances of some functional bacterial groups in the first and fourth compartments of the main reaction zone shifted adaptively in response to the aeration rate redistribution, consistent with the trends in pollutant removal contributions in these compartments. Hierarchical clustering and principal coordinate analysis (PCoA) further indicated that aeration rate redistribution influenced the microbial community structure. The above laboratory-scale optimization results may provide a preliminary reference for aeration control and improvement of denitrification performance in similar processes. Full article

Monoethanolamine (MEA) remains the predominant solvent for carbon dioxide (CO₂) capture due to its rapid reaction kinetics, substantial absorption capacity, and demonstrated industrial effectiveness. Despite its established status, MEA-based systems are undergoing continuous development to lower energy requirements, enhance solvent stability, and expand operational adaptability. This review provides a critical assessment of recent progress in MEA-based CO₂ capture, encompassing molecular-level understanding, advancements in reactor and process design, solvent modification strategies, and system-wide optimization. Recent theoretical and experimental research has improved the understanding of CO₂ absorption mechanisms in MEA, highlighting the effects of reaction-product buildup, interfacial phenomena, and free amine availability on mass-transfer efficiency. Reboiler duty and comparable work have significantly decreased as a result of advances in process intensification, improved regeneration systems, and energy-integration techniques. New hybrid strategies that partially decouple capture from thermal regeneration, such as combined absorption–mineralization pathways, show promise for long-term CO₂ sequestration. To address regeneration energy, corrosion, degradation, and cyclic stability, this review examines advances in MEA-based solvents, including aqueous blends, non-aqueous and biphasic systems, ionic liquids, and deep eutectic solvent hybrids. It also critically assesses the trade-offs of developments in intensified contactors, surfactants, nanomaterials, and catalysts. The growing role of digital optimization, machine learning, and computational modeling in MEA process design and control is highlighted. Overall, this analysis underscores MEA’s continued importance as a versatile platform for next-generation carbon capture, utilization, and storage. Full article

This study investigates the continuous-flow hydrolysis reaction of propylene oxide (PO) in a spiral microchannel reactor, integrating experiments, computational fluid dynamics (CFD) simulations, and response surface methodology (RSM). To the best of our knowledge, experimentally determined apparent Arrhenius parameters for PO hydrolysis under microscale continuous-flow conditions remain rarely reported, and afterwards they were incorporated into CFD-based numerical simulations. This combined experimental–numerical framework provides a robust methodology for quantifying and optimizing liquid-phase kinetics in microscale flow environments. Subsequently, CFD simulations were employed to examine key process parameters, including reaction system temperature, inlet flow rate, and reactor length. Finally, RSM was utilized to identify the optimal process conditions (reaction system temperature of 298.15 K, inlet flow rate of 6 × 10⁻³ m·s⁻¹, and reactor length of 4 m), achieving a predicted PO conversion rate of 81.68%. The study provides a reference for designing and optimizing spiral microchannel reactors for PO hydrolysis. Full article