Search Results (4,237)

5-aminolevulinic acid (5-ALA) affords various positive health effects, including benefits for conditions such as diabetes. Biological fermentation holds potential for efficiently mass-producing biomolecules, including 5-ALA, yet it generally results in a mixture of target molecules and impurities, including byproducts. Pyrazine-2,5-dipropionic acid (PY), a dimer of 5-ALA, can easily form in 5-ALA production and is one of its major impurities. In this study, we developed an integrated purification process for 5-aminolevulinic acid phosphate (5-ALAP) produced via biological fermentation. The process consists of 16 stages, including impurity removal (ion-exchange resins) and crystallization. Three types of ion-exchange resin (IER) columns were combined to remove impurities such as byproducts and pigment. Comprehensive condition setting for crystallization was carried out to reduce the amount of residual poor solvent in the 5-ALAP crystals. The obtained crystals contained significantly fewer impurities (<0.05% vs. 5-ALAP), such as PY, compared with their commercially available counterparts. The residual poor solvent in the 5-ALAP crystals was reduced to below 1000 ppm under the crystallization conditions. We confirmed the high scalability of the purification method developed in this study. Therefore, this article provides an industrially applicable purification process for fermentatively produced 5-ALA. Full article

The large-scale accumulation of titanium-extraction tailing slag (TS) poses environmental concerns, while its application is constrained by high impurity contents and low hydraulic reactivity, which is further exacerbated by the necessary dechlorination process. This study aims to evaluate the effectiveness of synthetic calcium silicate hydrate (C-S-H) nanocrystals in improving the performance of cement pastes incorporating deeply dechlorinated TS (DD-TS). To ensure uniform dispersion and activity, C-S-H seeds with varying crystallinities (55–94%) were prepared via a dynamic hydrothermal method (180 °C for 1–3 h) and incorporated into the composite binder in a wet-powder form at dosages of 0.5–2.0%. Results indicate that C-S-H-1, with the lowest crystallinity, offered the highest efficiency. At 1.5% dosage, the 1 d compressive strength increased by 64.6% to 18.6 MPa, while the initial setting time decreased by approximately 40%. Microstructural analyses reveal that poorly crystalline C-S-H provides abundant nucleation sites, accelerating early hydration and densifying the matrix to levels comparable to 7 d control pastes. These findings demonstrate the potential of C-S-H seeding for enhancing the utilization of DD-TS in cement-based materials. Full article

CO₂-enhanced gas recovery (CO₂-EGR) is a crucial technology for achieving both natural gas production increase and CO₂ geological storage. While pure CO₂ flooding demonstrates favorable recovery performance, the technical challenges and high costs associated with purifying CO₂ remain significant. CO₂ purification from exhaust gas incurs prohibitive costs, while direct injection of an unpurified CO₂–N₂ mixture can greatly cut engineering expenditure. Nitrogen also provides synergistic pressure support, working with CO₂ to drive natural gas displacement. Therefore, from an economic and practical standpoint, employing impure CO₂ mixtures (e.g., CO₂–N₂) for flooding presents a more advantageous approach. To clarify the factors influencing the recovery enhancement in tight sandstone gas reservoirs using CO₂–N₂ mixtures, long-core flooding experiments were conducted at 100 °C. This study systematically investigates the impact patterns of three key factors—injection timing, injection rate, and injection gas composition—on the enhanced recovery of tight sandstone gas reservoirs. The experimental results indicate that: (1) Advancing the injection timing significantly improves the recovery performance for both CO₂ and N₂ flooding. However, the cumulative recovery factor (sum of the depletion recovery and the incremental recovery from gas injection) shows a declining trend. (2) The enhanced recovery effect exhibits a trend of first increasing and then decreasing with the increase in injection rate. When the injection rate exceeds 0.05 mL/min, it tends to cause premature breakthrough of the injected gas, thereby reducing the displacement efficiency. (3) As the proportion of CO₂ in the injected gas increases, the enhanced recovery effect shows a nonlinear rise. The highest incremental recovery (17.02%) was achieved with pure CO₂ flooding, while pure N₂ flooding yielded the lowest result (14.64%). The research findings, from a macroscopic perspective, elucidate the influence patterns of three distinct factors on enhancing gas recovery in tight sandstone reservoirs, thereby providing theoretical foundation and scientific guidance for the development of such reservoirs. In summary, the injection timing, injection rate and CO₂ proportion in injected gas are the key controlling factors for gas flooding enhanced recovery in tight sandstone reservoirs. This study clarifies the macroscopic influence law of each factor, and the optimized development parameters proposed can provide direct theoretical support and technical guidance for the on-site application of gas flooding in tight sandstone reservoirs. Full article

Bio-CO₂ is part of the natural carbon cycle and represents a sustainable carbon source for the production of Renewable Fuels of Non-Biological Origin (RFNBOs), such as synthetic methanol. This study addresses the critical knowledge gap in aligning diverse biogenic CO₂ sources with e-methanol requirements in the EU by providing harmonized mapping, based on datasets, literature sources, and reported industrial statistics at the sectoral and country level. Bio-CO₂ streams from biogas and biogas upgrading, biomass combustion, pulp and paper, bioethanol production, and the food and beverage sector are evaluated for total emissions, CO₂ concentrations and purity, the geographical distribution, seasonality, and impurity profiles. Results show that approximately 350 Mtpa of bio-CO₂ are emitted across the EU, with highly heterogeneous characteristics. Biogas upgrading and fermentation-based processes generate highly pure CO₂ streams (>98–99%), yet their small and dispersed nature complicates logistics. In contrast, biomass-combustion and pulp and paper sectors provide large volumes (around 214.6–298.2 Mtpa and 73.9 Mtpa CO₂, respectively), but in diluted streams (typically 3–15% and 10–20%). Replacing just 10% of the EU maritime fuel demand with e-methanol would require 53.6 Mtpa of bio-CO₂ and 58 GW of electrolyzer capacity, a stark contrast to the current operational 385 MW. The findings highlight the need for infrastructure planning and aggregation hubs to enable the large-scale deployment of RFNBO methanol in the maritime sector. Full article

Renewable hydrogen purification is a critical yet often underemphasised step in enabling its use as a clean energy carrier. Hydrogen produced from biomass-based thermochemical and biological routes typically contains CO₂, CO, CH₄, H₂S, and other impurities that must be removed to meet stringent requirements for fuel cell, industrial, and grid-injection applications. This review provides a critical and up-to-date assessment of renewable hydrogen purification technologies, focusing on their suitability for variable and impurity-rich renewable hydrogen streams. Established benchmark technologies, including pressure swing adsorption and cryogenic separation, are described, with emphasis on their operating principles, material innovations, and process integration strategies. Recent advancements in inorganic, polymeric, and mixed-matrix membranes are highlighted, with particular focus on how advanced porous materials enhance selectivity, permeability, and flexibility. Additionally, a comparative techno-economic assessment is presented, evaluating each purification method based on technology readiness level, capital and maintenance costs, energy efficiency, and operational lifespan. By incorporating recent research trends, this approach facilitates the selection and design of purification systems that are not only efficient and scalable but also cost-effective, tailored to both decentralised and centralised renewable hydrogen production. Full article

PrFeTiO₃ perovskite composite was synthesized, and its structural, morphological, chemical, and optical properties were comprehensively characterized. X-ray diffraction (XRD) and a selected area electron diffraction (SAED) confirm the formation of an orthorhombic distorted perovskite phase with no secondary impurities. Transmission electron microscope (TEM) observations show aggregated nanocrystalline domains, while EDS mapping reveals homogeneous cation distribution (Pr, Fe, Ti, O), confirming successful incorporation of Fe and Ti into the perovskite lattice. X-ray photoelectron spectroscopy (XPS) analysis identifies Pr³⁺, Fe³⁺, and Ti⁴⁺ as the dominant oxidation states, supporting charge-compensated B-site substitution. Optical analysis reveals a bandgap of ~2.0 eV, significantly narrower than pristine titanates, indicating enhanced visible-light absorption. This multi-modal characterization verifies the successful formation of PrFeTiO₃ and highlights its potential as a visible-light-active photocatalyst. Although PrTiO₃ showed little reactivity to visible light, PrFeTiO₃ showed excellent efficiency in visible light photocatalytic reactions. PrFeTiO₃ showed more than 20 times better performance than PrTiO₃ in the photodegradation of methylene blue in the liquid phase and formaldehyde in the gas phase. Furthermore, PrFeTiO₃ showed more than 95% superior bactericidal activity against the pathogenic bacterium Staphylococcus aureus than PrTiO₃. Its high photocatalytic efficiency can be attributed to its strong photosensitivity to visible light and small band gap energy. Full article

The pre-prepared meal industry is a vital engine for food sector upgrading in China. This study investigates the key drivers of consumer purchasing decisions and identifies strategic pathways to support high-quality industry development. Grounded in behavioral decision theory and the stimulus–organism–response framework, we propose two central research questions: (1) What are the dominant determinants of consumer purchase intention for pre-prepared meals? and (2) How do these determinants interact in nonlinear and asymmetric ways to shape final decisions? To address these questions, we analyzed 805 valid questionnaires collected in Jilin Province using an integrated machine learning framework. Data quality and validity were ensured through baseline balance tests, and sample imbalance was corrected using the SMOTE–Tomek algorithm. Six models, including Random Forest (RF) and XGBoost, were optimized via Gaussian process-based Bayesian optimization. The RF model achieved optimal performance on the test set, with an F1 score of 0.907, an AUC of 0.928, and a prediction accuracy of 0.876. To enhance model interpretability, Mean Decrease Impurity (MDI) was integrated with the SHAP framework. Our findings reveal that: (1) purchase decisions are predominantly willingness-driven, with behavioral tendency—especially recommendation willingness—accounting for over 72% of predictive importance; (2) rational considerations, such as convenience and channel accessibility, serve as foundational enablers; and (3) recommendation willingness exhibits a significant S-shaped nonlinear threshold, where a shift to “relatively willing” marks a critical marketing intervention window. SHAP force plot analysis further uncovers an asymmetric decision logic: high willingness can compensate for perceived product shortcomings, whereas the absence of core intention functions as a non-compensatory barrier. Theoretically, these findings synthesize machine learning outputs with classical behavioral models (e.g., the Theory of Planned Behavior and Prospect Theory) by empirically quantifying bounded rationality and nonlinear activation mechanisms. These findings suggest that enterprises should transition from traffic-centric to retention-oriented strategies by leveraging word-of-mouth and proximity-based channels. Moreover, establishing a collaborative governance system is essential to mitigate risk perception and ensure long-term industry prosperity. Full article

The valorization of agro-industrial residues represents a strategic approach to advancing sustainability and circular bioeconomy principles in the food sector. Although bacterial cellulose (BC) production from waste substrates has been widely explored, limited attention has been given to the role of nitrogen source modulation in complex fermentation systems. This study evaluated passion fruit peel hydrolysate (PFPH), a cellulose- and hemicellulose-rich by-product, as an alternative carbon source for BC production using a symbiotic culture of bacteria and yeast (SCOBY) under static conditions. Acid hydrolysis and detoxification were performed to obtain fermentable sugars while minimizing inhibitory compounds. Different nitrogen sources and purification strategies were comparatively assessed. The highest purified BC yield (81 g L⁻¹ of culture medium) was obtained using ammonium sulfate, whereas sodium nitrate promoted greater impurity removal (77.51% mass reduction). Structural and chemical analyses (FTIR, XPS, and XRD) confirmed effective delignification, enhanced surface purity, and increased crystallinity. SEM revealed a homogeneous nanofibrillar network, and thermogravimetric analysis indicated thermal stability up to approximately 300 °C. Soil burial assays showed 26% mass loss after 42 days, demonstrating controlled biodegradation consistent with food packaging requirements. Overall, PFPH proved to be an efficient and sustainable substrate for BC biosynthesis. The modulation of nitrogen source significantly influenced both production yield and structural properties, highlighting the potential of this system for developing environmentally responsible biopolymer materials for food packaging applications. Full article

Real-time and accurate acquisition of the wheat impurity rate is a key technology for realizing intelligent cleaning operations, and it directly influences the quality of wheat harvest. This study proposes a novel impurity rate regression network named Segmentation is Not The Purpose (SNTP). SNTP integrates a semantic segmentation network and an impurity rate regression network into a single neural architecture and replaces the DeepLabV3+ backbone with MobileNetV4, which serves as the segmentation branch of SNTP. Furthermore, a Transformer block is introduced into the regression branch to enable global feature extraction, and a Generalized Categorical Regression head is designed based on Distribution Focal Loss to improve regression accuracy. The SNTP model ultimately achieves an MIoU of 77.7%, an MPA of 83.3%, an MAE of 0.045, and an MSE of 0.005 on the validation set, with only 9.51M parameters and 17.98 GMACs of computation, successfully solving the overfitting problem in impurity rate regression networks and achieving high regression accuracy. SNTP is easy to optimize, requires no additional prior knowledge, and the performance of the SNTP model is unaffected by camera mounting height, making it exceptionally versatile for deployment and enabling real-time impurity rate detection, which is the key technology for intelligent cleaning. Full article

Lithium manganese iron phosphate [LiMn_xFe_1−xPO₄ (x ≤ 0.5)]-based cathode materials were synthesized via a hydrothermal method to investigate their composition effect on structure and electrochemical performance. The X-ray diffraction results confirmed a single-phase olivine structure (Pnma) for all the compositions, with minor lithium phosphate (Li₃PO₄) impurities detected at high manganese (Mn) contents (x ≥ 0.4). The morphological evolution from small particles with low Mn content to compact rod-like particles at x = 0.3 indicates optimized crystal growth and improved interparticle connectivity. Electrochemical testing revealed that the discharge capacity initially increased with the substituted Mn content to a maximum of 140 mAh g⁻¹ at 0.5 C for LiMn_0.3Fe_0.7PO₄/C with remarkable cycling stability. This high capacity is attributed to the activation of Fe²⁺/Fe³⁺ and Mn²⁺/Mn³⁺ redox couples and the minimal formation of electrochemically inactive phases. Further Mn incorporation (x > 0.3) caused structural distortion, Li₃PO₄ formation, and overall capacity loss. Codoping with Mg (LiMg_0.05Mn_xFe_1−xPO₄) improved stability but lowered discharge capacity owing to the electrochemical inactivity of Mg²⁺ and impurity formation. Notably, an optimal x value of ~0.3 exhibited an effective balance between high energy density, rate capability, and structural integrity in Mn-doped LiFePO₄ cathodes for next-generation lithium-ion batteries. Full article

The purity of titanium sponge is crucial for determining the performance of final titanium alloys, underscoring the importance of impurity control in its precursor, TiCl₄. Among these impurities, VOCl₃ is particularly challenging to remove due to its similar boiling point and complete miscibility with TiCl₄. Although organic reagents are widely employed for vanadium removal, their complex compositions complicate the identification of key active components. This study systematically compares the vanadium removal efficiency of six organic compounds bearing different functional groups. Results demonstrate that 1-dodecene exhibits superior performance, achieving a VOCl₃ removal efficiency of 93.35%. Mechanistic studies reveal that 1-dodecene initially undergoes cyclization to form cyclododecane, followed by aromatization and subsequent carbonization through stacking, dehydrogenation, and coking, ultimately yielding partially graphitized amorphous carbon. In this process, VOCl₃ interacts not only with the incompletely carbonized organic precursor but also directly with the alkenes. These findings elucidate the reaction pathway and central role of linear α-alkenes in vanadium removal, providing a theoretical foundation for developing efficient and stable vanadium removal agents. Full article

The electrochemical reuse of spent graphite from the negative electrodes of lithium-ion batteries is influenced by regeneration-induced changes in near-surface chemical and defect states. These states govern solid electrolyte interphase (SEI) re-formation, particularly when bulk contaminants are suppressed. Acidic malic-acid leaching and ethylenediaminetetraacetic acid chelation under alkaline conditions (pH 8.7) were compared under similar operating parameters to isolate the role of the leaching environment. This was followed by heat treatment at 1200 °C to decouple chemical cleaning from structural restoration. Both methods reduced the total impurities from 217.85 ppm to ~1.8 ppm, approaching that of commercial graphite. Despite the comparable bulk purity, depth-resolved X-ray photoelectron spectroscopy after formation cycling revealed distinct outermost surface states relevant to SEI re-formation: acidic processing yielded a more oxygenated carbon signature and higher LiOH fraction at the outermost surface (~16%), whereas alkaline chelation produced a more graphitic, carbonate-dominated surface with lower LiOH (~7%). Electrochemical and impedance measurements were consistent with these differences, suggesting that after the bulk impurities were minimized, resistance development was largely governed by the leaching-conditioned near-surface state, which biased the SEI composition. The comparison under matched conditions linked the regeneration environment to SEI-relevant surface speciation and provided a mechanistic basis for selecting regeneration routes to reuse spent graphite as a negative-electrode active material. Full article

The sintering process represents a primary source of dust, SO₂, NOx, and CO₂ emissions in steel mills. Utilizing high-grade concentrate with low impurity content can directly reduce slag generation at the source, thereby decreasing fuel consumption and minimizing associated emissions. This study investigated the physicochemical properties, microstructure, and elemental distribution of hematite concentrates (H2 and H3) and H1 sinter fines. Sinter pot tests were conducted to evaluate the effects of blending these two concentrates on sintering performance and key quality indices. Microstructural analysis and quantitative phase composition statistics of the sintered products were performed to elucidate the mechanisms by which these concentrates influence sintering outcomes. Results demonstrated that replacing 33% H1 sinter fines with 33% H2 or H3 concentrates reduced the tumbler index from 73.6% to 68.5% and 73.2%, respectively. The productivity coefficient decreased to 68.5% and 73.2%, while solid fuel consumption increased from 73.9 kg/t to 90.5 kg/t and 81.2 kg/t. RI declined from 80.0% to 77.9% and 78.4%, whereas RDI improved from 72.9% to 76.8% and 75.8%. Full article

Thermal energy storage (TES) plays a crucial role in improving the efficiency and reliability of solar thermal systems, particularly when low-cost and readily available materials are desired. This study experimentally investigates the performance of a water–salt thermal energy storage system using sodium chloride (NaCl) at different concentrations in a simple solar collector setup. Experiments were conducted using a laboratory-scale solar thermal energy system under controlled conditions, with water serving as the heat transfer fluid and a fixed flow rate of 15 L/h. The storage medium consisted of water mixed with salt, which was obtained from the Dead Sea before any treatment. In its raw form, this type of salt contains impurities, mainly sand, at a fixed concentration of approximately 1% by weight. The effects of salt concentration on storage temperature, system efficiency, and effective heat capacity were analyzed. The results show that moderate NaCl concentrations improved the average storage temperature by up to 12–18%, increased thermal storage efficiency by approximately 1%, and enhanced the effective specific heat capacity compared to pure water. In contrast, higher salt concentrations resulted in a performance reduction of up to 8–12% due to increased thermal resistance and reduced heat transfer effectiveness. An optimal salt concentration range was identified at which maximum storage efficiency and heat capacity were achieved. These findings demonstrate that common sodium chloride can serve as an effective and economical enhancement material for thermal energy storage when properly optimized. The study provides quantitative evidence and practical insights for the development of low-cost, salt-based thermal energy storage systems for solar thermal applications. This study highlights the importance of concentration optimization and provides practical insights for the development of low-cost, salt-based thermal storage systems for solar energy applications. Full article

The extraction of high-purity sodium tungstate from complex wolframite concentrates presents significant challenges due to the limitations of conventional processing methods, which are often energy-intensive and generate substantial secondary waste. In this study, we propose a novel phase-regulated alkali fusion approach for the one-step production of high-purity Na₂WO₄. Using phase-diagram calculations with FactSage in the Na-Fe-Mn-Si-O system, SiO₂ was introduced to regulate slag formation, promoting immiscibility between the silicate slag and Na₂WO₄ melt. This resulted in a clear stratification of the phases at 1000 °C, enabling spontaneous separation of the Na₂WO₄-rich salt phase from the slag. The optimized conditions achieved a sodium tungstate purity of 98.76%, with a tungsten recovery rate of 98.91%. Furthermore, impurity elements such as Fe and Mn were preferentially retained in stable silicate/oxide phases within the slag, contributing to the high purity of the sodium tungstate product. This method offers a simplified and environmentally friendly alternative to traditional hydrometallurgical and pyrometallurgical processes, with significant implications for the efficient utilization of complex tungsten resources. Full article