Search Results (1,614)

Zeolites are porous aluminosilicate crystalline materials that are widely used for the adsorption of volatile organic compounds (VOCs). The synthesis of zeolites without organic structure-directing agents (OSDAs) is attractive because of its low cost and environmental friendliness. In this study, analcime and the ZSM-5 zeolite were synthesized from natural diatomite under OSDA-free conditions through different crystallization routes. Analcime was prepared by regulating the hydrothermal conditions, while the ZSM-5 zeolite was synthesized by combining hydrothermal condition regulation with seed-induced crystallization. Hydrochloric acid modification was further used to improve the pore structures and adsorption properties of the zeolites. The optimum acid treatment conditions were 1.0 mol·L⁻¹ HCl for analcime and 0.5 mol·L⁻¹ HCl for the ZSM-5 zeolite. After acid modification, the specific surface area and pore volume of analcime increased to 271.7 m²·g⁻¹ and 0.130 cm³·g⁻¹, respectively, and its tolune adsorption capacity increased from 18.3 mg·g⁻¹ to 23.2 mg·g⁻¹, corresponding to a 26.6% improvement. For the ZSM-5 zeolite, the optimal modified sample showed a specific surface area of 307.9 m²·g⁻¹, a pore volume of 0.172 cm³·g⁻¹, and a toluene adsorption capacity of 65.4 mg·g⁻¹, which was 5.5% higher than that of the unmodified sample. Adsorption kinetic analysis indicated that pore diffusion played an important role in toluene adsorption, while acid modification introduced additional acid sites that contributed to chemisorption. Overall, the ZSM-5 zeolite showed a higher adsorption capacity than analcime because of its larger surface area, higher pore volume, and more accessible adsorption sites. This study provides a low-cost and environmentally friendly route for preparing diatomite-derived zeolite adsorbents for VOC removal. Full article

Waste aluminum dust generated from aluminum refining and machining processes contains high fractions of Al₂O₃ and SiO₂, making it a potential secondary aluminosilicate resource for zeolite synthesis. In this study, waste aluminum dust was converted into functional zeolite materials through dry fusion purification, NaOH-assisted hydrothermal synthesis, acid purification, Si/Al ratio control, and cation-exchange modification. The raw dust was subjected to dry fusion at 1600 °C under an Ar atmosphere to remove metallic impurities and obtain an aluminosilicate precursor. Na-type zeolite was then synthesized using 50 wt.% NaOH solution at 90 °C for 24 h. The as-synthesized Na-type zeolite exhibited an estimated chemical purity of 97.501 wt.% based on measured residual impurities, with Mg, Ca, K, and Ti remaining as major impurities. HCl leaching at 0.25 M for 24 h increased the estimated chemical purity based on measured residual impurities to 98.469 wt.% while retaining the major zeolitic diffraction features. The Si/Al ratio was further controlled using water glass, and the maximum Si/Al ratio of 1.77 was obtained at a Na-type zeolite-to-water-glass mass ratio of 1:2 after reaction at 90 °C for 6 h. The purified and composition-controlled zeolite was subsequently modified with Mg²⁺ and K⁺ ions to prepare Mg-modified and K-modified zeolites. Under fixed batch conditions using a relatively high zeolite dosage and a single initial concentration, Mg-modified zeolite reduced Pb, Hg, Cr(VI), and Cd concentrations from 100 ppm to 0.004, 0.00059, 0.018, and 0.004 ppm, respectively, while K-modified zeolite reduced the total hardness of synthetic hard water from 308.3 to 40.13 ppm as CaCO₃. These results should be interpreted as preliminary batch-performance results under the tested conditions rather than as maximum adsorption capacities or a complete adsorption-mechanism evaluation. Overall, this study demonstrates the feasibility of valorizing waste aluminum dust into purified and cation-modified zeolite materials for potential water-treatment applications. Further adsorption isotherm, kinetic, dosage-dependent, BET surface area, pore-volume, pore-size distribution, and quantitative phase analyses are required to evaluate adsorption capacity, adsorption mechanism, true zeolite phase purity, and framework–performance relationships. Full article

A lignosulfonate-derived iron–carbon composite catalyst was fabricated via hydrothermal pyrolysis and employed to activate peroxydisulfate (PDS) for tetracycline hydrochloride (TCH) degradation. The optimized LFC possessed a porous carbon matrix uniformly decorated with Fe⁰/Fe₃O₄/Fe₂O₃ crystals, providing abundant active sites for catalytic reactions. The LFC/PDS system achieved nearly 100% TCH removal within 30 min at neutral pH and exhibited high efficiency over a broad pH range, strong anti-interference ability, and good universality for various organic pollutants. Mechanistic investigation confirmed that TCH degradation was dominated by a singlet oxygen (¹O₂)-mediated non-radical pathway, with minor contribution from radical species. The synergistic effect of iron cycle and surface functional groups promoted the generation of reactive oxygen species and ¹O₂. This research provides a low-cost, eco-friendly and efficient strategy for antibiotic wastewater treatment. Full article

Warming profoundly influences soil respiration in terrestrial ecosystems, thereby altering global carbon cycling. Understanding the trends and drivers of soil respiration changes in forest ecosystems under warming is essential for assessing regional carbon budgets and ecosystem carbon sink/source dynamics. In this study, a one-year warming experiment was conducted using open-top chambers in a Taxodium hybrid (Zhongshanshan) ecosystem in the northern Jiangsu coastal area, China. Treatments included control (CK) and warming (W), focusing on soil respiration components (soil respiration, Rs; heterotrophic respiration, Rh; autotrophic respiration, Ra) and associated soil hydrothermal and nutrient factors. Results showed that both warming and season significantly affected Rs, Rh, and Ra, all exhibiting a unimodal seasonal pattern peaking in summer. Warming increased winter Ra by 117.39% (p < 0.001). Bivariate models (temperature and moisture) explained more variation in respiration (R² = 0.720–0.893) than univariate models. Correlation analysis indicated that under control conditions, Rs components were significantly positively correlated with microbial biomass carbon (MBC), ammonium nitrogen (NH₄⁺-N), and available phosphorus (AP). After warming, these positive correlations with MBC and AP persisted; however, negative correlations emerged with soil organic carbon (SOC) and its stoichiometric ratios (C:N, C:P). Additionally, Ra showed negative correlations with easily oxidizable carbon (EOC), total nitrogen (TN), and N:P. Overall, these findings suggest that climate warming may enhance soil respiration in the Taxodium hybrid (Zhongshanshan) ecosystem by altering soil thermal-hydrological and nutrient factors, although further validation is needed. Full article

This manuscript proposes to valorize the macauba endocarp (E) wastes from the macauba processing by a pyrolytic + hydrothermal process to produce activated carbon (ACE), followed by chemical treatment with H₂O₂ (ACEA) and HNO₃ (ACEB). Elemental analysis, surface area, pore-size distribution, and surface functional groups are investigated for the different prepared materials. ACEA and ACEB offer a higher surface area and functionality than Vulcan XC-72R (VC), making them suitable as carbon supports for Pd nanoparticles. The prepared Pd/ACEA and Pd/ACEB are physicochemically characterized by X-ray diffraction and Transmission Electron Microscopy. Their electrochemical performance is initially evaluated in a 3-electrode glass cell and is found to surpass that of Pd/VC in glycerol electro-oxidation. This trend is confirmed in the glycerol acid-alkaline electroreformer, where hydrogen and electricity were simultaneously produced, achieving a maximum power density of 0.28 kW m⁻² and H₂ flux of 0.6 STP m³ m⁻² h⁻¹ at 80 °C. Full article

The increasing generation of solid waste has become a critical environmental and economic challenge worldwide, demanding innovative strategies for sustainable management and resource recovery. In this context, the conversion of solid waste into green materials has emerged as a promising approach to reduce environmental impacts associated with waste disposal. This review provides an overview of recent advances in the transformation of various solid waste streams (including agricultural residues, food waste, industrial by-products, and municipal solid waste) into value-added green materials. Particular emphasis is placed on innovative synthesis processes such as thermochemical conversion, hydrothermal treatments, biological transformations, and advanced physicochemical methods that enable the production of functional materials with enhanced properties. The review also discusses the potential applications of these materials in areas such as environmental remediation, catalysis, energy storage, and construction materials. Overall, the valorization of solid waste into green materials represents a sustainable pathway to reduce environmental burdens while generating high-value products for diverse industrial sectors. Full article

Global requirement of clean, cost-effective and sustainable energy has stimulated massive research and development in photocatalytic materials that have the potential to harvest solar based energy while mitigating the environmental issues. Among various materials, perovskite oxides have emerged as a promising energy resource. Owing to the structural versatility, optical and electrical properties, chemical inertness allows the use of material of multifunctional prospects. Currently Strontium titanate (SrTiO₃), a vital perovskite oxide having a band gap nearly ~3.2 eV, is showing significant function for photocatalytic water splitting, carbon dioxide conversion and degradation of organic pollutants. Though within the UV spectrum, its intrinsic photocatalytic behavior is limited to approaches such as graphene junctions, noble-metal support, and post-synthetic heat treatment seem to promote the adsorption within visible-light. Strontium titanate also demonstrates photo charge separation efficiency, and long-term catalytic durability. Moreover, modifications and hydrothermal synthesis have proven extremely efficient for nano-based engineering, control over crystal diameter, defects, and shape, which can result in magnificent composites that can be promising substitutes. Therefore, further research is imperative regarding these material application prospects. This comprehensive review provides insights into details on the potential of nanoengineering and composite approaches to reduce the inherent limitations of perovskite oxides, especially Strontium titanate, and enabling additional applications in next-generation photovoltaic and solar energy harvesting technologies. Full article

Hydrothermal carbonization (HTC) is a promising thermochemical process for valorizing wet biomass and organic waste streams, generating hydrochar, gas, and a liquid phase commonly referred to as HTC process liquid or the aqueous phase. Depending on feedstock type and process severity, hydrochar typically accounts for approximately 40–70 wt.% of the initial dry feedstock, the liquid phase for about 30–60 wt.% in lignocellulosic and agricultural residues, and the gas phase for about 1–10 wt.%, while highly hydrated waste streams may generate even higher liquid-phase shares. Although hydrochar has traditionally been considered the main energy product, the liquid phase may retain approximately 20–65% of the initial feedstock carbon and around 15–25% of the initial energy content. However, its high chemical oxygen demand, elevated organic carbon content, variable biodegradability, toxicity, and inhibitory compounds often lead to its classification as a wastewater stream requiring treatment. The crucial novelty of this review is its system-oriented evaluation of HTC process liquid as an energy-bearing and system-integrating stream rather than merely as a wastewater by-product or as a substrate for isolated valorization routes. Therefore, this review evaluates the role of HTC process liquid in energy systems, focusing on its formation mechanisms, chemical composition, energy potential, valorization pathways, integration strategies, and environmental implications. The reviewed evidence shows that HTC process liquid contains a complex mixture of dissolved organic compounds, including volatile fatty acids, sugars, furans, phenols, ketones, aldehydes, amino acids, ammonia, and nitrogen-containing heterocycles. These compounds may support anaerobic digestion, dark fermentation, aqueous phase reforming, electrochemical conversion, nutrient recovery, and process-water recirculation. Among these routes, anaerobic digestion is currently the most mature, although its efficiency depends strongly on HTC severity, feedstock type, inhibitor formation, and microbial adaptation. Hydrogen-oriented and electrochemical pathways offer additional opportunities but still require further validation using real HTC liquids, standardized yield reporting, and long-term stability assessment. Overall, HTC process liquid should not be regarded solely as an environmental burden, but as a chemically complex and energy-rich stream that may improve the performance of integrated HTC-based bioenergy systems. Future research should focus on standardized liquid-phase energy metrics, long-term process integration, toxicity control, and experimentally validated techno-economic and life-cycle assessments. Full article

Water and nitrogen management influences farmland productivity and greenhouse gas emissions by regulating the soil micro-environment. However, the synergistic optimization strategy among yield improvement, economic benefit, and emission reduction in intercropping systems in arid regions remains unclear. Based on a two-year field experiment using an intercropping system of wolfberry and alfalfa, this study established four irrigation levels [full irrigation (W0), mild water deficit (W1), moderate water deficit (W2), and severe water deficit (W3)] and four nitrogen application levels [0 (N0), 150 (N1), 300 (N2), and 450 kg·ha⁻¹ (N3)]. The effects of water and nitrogen regulation on soil hydrothermal conditions, greenhouse gas emissions, crop yield, and economic benefits were systematically analyzed. The results showed that soil water content increased with higher nitrogen application rates but decreased with a more severe water deficit. In contrast, soil temperature exhibited the opposite trend, with the W3 treatment increasing by 2.23–2.41 °C compared to W0 during the full fruiting period. The emission fluxes of CO₂ and N₂O increased with higher nitrogen application rates but decreased with a more severe water deficit. CH₄ acted as a sink, with its uptake decreasing as nitrogen application increased and the water deficit intensified. CO₂ was the dominant contributor to the global warming potential of the intercropping system of wolfberry and alfalfa, accounting for 85.3–94.6% of the total. The emission fluxes of CO₂ and N₂O were significantly positively correlated with the soil water content, while the CH₄ emission flux was significantly positively correlated with the soil temperature. The W0N2 treatment achieved the highest system yield and net profit, whereas the W1N2 treatment exhibited the highest return on investment. A comprehensive evaluation using the entropy weight–TOPSIS model identified W1N2 as the optimal treatment. An integrated water–nitrogen decision model determined that the optimal water and nitrogen combination for achieving a high yield, a high efficiency, and low emissions was an irrigation amount of 4245–4413 m³·ha⁻¹ and a nitrogen application rate of 290–323 kg·ha⁻¹. The findings of this study can provide a scientific basis for the sustainable water and nitrogen management of characteristic cash crop intercropping systems in arid regions. Full article

The development of sustainable electrode materials for supercapacitors requires a deeper understanding of the relationship between precursor structure, processing, and electrochemical performance. In this work, coconut-fiber-derived activated carbons were synthesized via KOH activation, and the influence of oxidative and hydrothermal pre-treatments was systematically investigated. The materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR), while electrochemical performance was evaluated using cyclic voltammetry and galvanostatic charge–discharge measurements in a three-electrode system with 1 M H₂SO₄ electrolyte. The results show that hydrothermal pre-treatment leads to improved electrochemical performance, with CF-HTC-AC exhibiting a specific capacitance of ~332 F g⁻¹ at 0.5 A g⁻¹ and enhanced rate capability. In contrast, the oxidatively treated sample (CF-OC-AC) presents a higher diffusion-controlled contribution, indicating a stronger pseudocapacitive behavior associated with oxygen-containing functional groups. These findings demonstrate that electrochemical performance is governed by a balance between capacitive and diffusion-controlled processes rather than by a single structural parameter. The hydrothermal pre-treatment provides an effective strategy to optimize this balance, highlighting precursor conditioning as a key factor in the design of biomass-derived carbon electrodes for supercapacitor applications. Full article

The high-value utilization of non-wood pulping black liquor is of great significance for the sustainable development of the pulp and paper industry. In this study, concentrated black liquor, obtained from the five-time recycling of KOH-pretreated wheat straw chemi-thermomechanical pulp (CTMP), was used as the feedstock for the preparation of humic-like acids (HLAs) through hydrothermal humification by utilizing the enriched organic components and residual alkalinity. Urea was further introduced to synthesize nitrogen-enriched humic-like acids (N-HLAs). The hydrothermal conditions and urea dosage were systematically optimized, and the products were characterized by elemental analysis (EA), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and particle size analysis (PSA). The results showed that the optimal hydrothermal condition was 180 °C for 4 h, under which the HLA yield reached 15.75%. With the addition of 1 mol/L urea, the yield of 1N-HLA further increased to 16.81%. Structural analyses demonstrated that hydrothermal treatment promoted the transformation of small molecular organics into highly aromatic and condensed macromolecular structures, while nitrogen-containing functional groups were successfully incorporated into the HLA molecular framework through urea modification. Bioactivity assay results showed that 1N-HLA exhibited a promoting effect on radish seed germination and seedling growth at a concentration of 100 mg/L. This study provides theoretical and technical support for the valorization of pulping black liquor and the green synthesis of functional humic-like materials. Full article

This study investigated carbonaceous materials prepared from Paulownia tomentosa leaves by hydrothermal carbonization, slow pyrolysis, and HCl post-treatment for the adsorption of metribuzin and tebuconazole from water. Hydrochars were prepared at 180–220 °C, pyrochars at 400–600 °C, and the pyrochar produced at 600 °C was further treated with HCl. The materials were characterized by yield, ash content, active and exchangeable pH, oxidizable organic carbon content, FTIR, SEM, and CO₂-derived surface and pore properties. Increasing processing temperature reduced the yield in both conversion routes. Hydrochars retained more oxygen-containing and oxidizable organic structures, whereas pyrochars showed stronger carbonization, higher ash content, and higher CO₂-derived surface area. HCl treatment decreased the ash residue, thereby resulting in improved CO₂-accessible surface and pore properties and more fragmented morphology. Metribuzin adsorption was better described by the pseudo-second-order kinetic model across all sorbents, with the highest fitted equilibrium adsorbed amount observed following HCl treatment. Tebuconazole showed higher initial uptake toward most untreated materials, but its kinetic profiles were non-monotonic, with a decrease in the adsorbed amount at longer contact times. Consequently, the conventional PFO and PSO models did not adequately describe its complete kinetic behavior. Nonlinear isotherm modeling showed predominantly Freundlich-type fitting for metribuzin, suggesting heterogeneous adsorption sites, whereas tebuconazole was formally better described by Langmuir-type fitting, although with poorer fit quality for several materials. The results show that Paulownia tomentosa leaves are a suitable precursor for carbonaceous sorbents and that HCl-treated pyrochar is the most promising material for metribuzin adsorption. Full article

Recently, aqueous asymmetric supercapacitors (ASCs) have attracted considerable attention as safe and high-power energy storage devices. However, achieving high energy density while maintaining long-term cycling stability remains a significant challenge. Herein, an aqueous ASC employing a Mo_1.33CT_x/CNT negative electrode and a hydrated V₂O₅·nH₂O/CNT positive electrode in a 5 M LiCl electrolyte is reported. The Mo_1.33CT_x i-MXene was synthesized via hydrothermal selective etching of an i-MAX precursor, whereas hydrated V₂O₅·nH₂O nanoflakes were prepared with peroxide-assisted hydrothermal treatment. The ordered-vacancy Mo_1.33CT_x i-MXene provides a stable negative potential window, redox-active sites, and favorable conditions for reversible Li⁺ intercalation/deintercalation, thereby contributing to pseudocapacitive charge storage. The assembled ASC delivered a stable operating voltage of 1.7 V, a specific capacitance of 61 F·g⁻¹ at 1 A·g⁻¹, an energy density of 25.2 Wh·kg⁻¹ at 883 W·kg⁻¹ and 86% capacitance retention after 10,000 cycles. Electrochemical impedance spectroscopy revealed relatively low internal resistance and efficient ion transport within the layered electrode architectures. These results highlight the strong potential of ordered-vacancy MXene/vanadium oxide systems for advanced aqueous energy storage applications. Full article

The increasing occurrence of pharmaceutical contaminants in aquatic environments has intensified the demand for sustainable and cost-effective water treatment technologies. This study investigated the conversion of potato peel waste into carbonaceous adsorbents through hydrothermal carbonization (HTC) and conventional pyrolysis (PRYR) for the removal of carbamazepine (CBZ) from synthetic wastewater. Hydrochars and biochars were synthesized under varying processing conditions and characterized using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), elemental analysis, and Brunauer–Emmett–Teller (BET) surface area analysis. Adsorption experiments were conducted using a 50 mg/L CBZ solution at pH 6, room temperature, and an adsorbent dosage of 1 g/L. The adsorption performance was evaluated after short contact times to assess rapid-removal capability. HTC-derived hydrochars exhibited significantly superior performance compared with pyrolysis-derived biochars, achieving up to 97% CBZ removal and adsorption capacities approaching 50 mg g⁻¹ within 1 min of contact. In contrast, pyrolysis-derived biochars achieved removal efficiencies between approximately 7 and 55% under similar conditions. Correlation analysis between adsorption behaviour and physicochemical properties revealed that adsorption performance was more strongly influenced by surface chemistry, aromaticity, and mesoporosity than by BET surface area alone. FTIR analysis suggested that hydrogen bonding, π–π electron donor–acceptor interactions, and pore filling contributed to CBZ adsorption. HTC hydrochars retained abundant oxygen-containing functional groups that promoted rapid and stable adsorption, whereas pyrolysis-derived biochars exhibited weaker adsorption interactions despite possessing higher surface areas. The findings demonstrate that hydrothermal carbonization provides an effective low-temperature route for valorising potato peel waste into efficient adsorbents for rapid pharmaceutical removal from water and highlight the critical role of adsorbent surface chemistry in determining adsorption performance. Full article

Nanostructured catalysts have become a core component of energy conversion in electrocatalysis and photocatalysis; however, successfully translating their performance from laboratory scale to industrial applications remains a long-standing challenge. This paper provides a critical assessment of the field, systematically tracing the entire development trajectory from catalyst design to practical application. We focus on five major classes of catalysts—monometallic catalysts, bimetallic/multimetallic alloy catalysts, metal compound catalysts, carbon-based composite catalysts, and single-atom catalysts—and explore synthetic strategies for achieving precise structural control, including hydrothermal/solvothermal methods, electrodeposition, template-assisted and MOF-derived syntheses, high-temperature pyrolysis, and post-treatment defect engineering. This paper delves into the mechanisms and performance descriptors governing the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), urea oxidation, photocatalytic water splitting, and CO₂ reduction. Based on the above analysis, this paper lays the mechanistic foundation for five core strategies to improve catalyst performance: morphology control, elemental doping, heterostructure and interface engineering, defect and vacancy engineering, and support modification. Furthermore, this paper provides an in-depth evaluation of the applications of these catalysts in water splitting, CO₂ valorization, fuel cells, metal–air batteries, and energy-saving electrolysis, with a particular focus on earth-abundant alternatives to precious metals. We argue that in many well-studied reactions, intrinsic activity may no longer be the primary bottleneck restricting their development; instead, the core challenge now lies in maintaining excellent catalytic performance under harsh and industrially relevant conditions, especially under high-current densities, impurity-containing feed systems, and long-term operating conditions. In response to this shift in research focus, this paper clearly identifies the key obstacles hindering the industrial application of catalysts and proposes practical directions for future research. Full article