Search Results (135)

Oxygen carriers (OCs) are essential materials in chemical looping technologies for low-carbon hydrogen production; however, the environmental implications of their synthesis remain insufficiently explored. This study presents a gate-to-gate life cycle assessment (LCA) of a chamotte–nickel OC produced via wet impregnation, following ISO 14040/44 guidelines. The functional unit was defined as 1 kg of oxygen carrier (OC), with input material requirements including chamotte, nickel nitrate, and water, as part of the synthesis process. Environmental impacts were modelled using ReCiPe 2016 Midpoint (H). Environmental hotspots varied across impact categories, with wet impregnation and energy-intensive thermal processes showing substantial contributions, while transportation-related burdens were relevant in selected toxicity and resource-related categories. Wet impregnation contributed 38.93% to climate change, approximately 55.6% to ozone depletion, and approximately 95.6% to terrestrial acidification in the modelled inventory. Thermal treatments also contributed substantially to several impact categories, primarily because of their high electricity requirements. Hotspot analysis identified precursor selection, energy supply, and logistics as key drivers of environmental burdens. Qualitative mitigation options include precursor substitution, renewable-energy integration, energy-efficiency improvements, and industrial symbiosis; however, these alternatives were not quantitatively evaluated in the present LCA. These results offer actionable guidance for sustainable OC design and highlight the importance of integrating LCA into early-stage oxygen-carrier design to reduce the environmental burdens associated with material synthesis. Further assessment incorporating OC performance, lifetime, regeneration, and hydrogen yield would be required to determine the implications of these material-level improvements for the environmental performance of hydrogen production. Full article

Cobalt–nickel–copper alloys were electrodeposited over a range of current density and with three different aqueous electrolytes having variable metal ion ratios, in order to examine changes in the deposit composition and to use them as cathodes for nitrate electrolysis. The alloys were electrodeposited galvanostatically from a citrate electrolyte onto rotating cylindrical steel substrates. The electrodeposition process exhibited anomalous codeposition behavior, favoring Co reduction over Ni and Cu. These electrodeposits were then used to examine their ability to reduce nitrate in simulated wastewater with 50 mg-N/L of NO₃⁻, sodium chloride, and sodium sulfate. Nitrate conversion and selectivity were characterized after electrolysis in a single-compartment cell with the alloys serving as the working electrode. Despite co-evolving hydrogen, the electrodeposited alloys were effective at generating both N₂ at high electrolysis current densities and ammonia species at lower values, with the deposit composition also affecting the conversion and products. It is the first demonstration of using Co-Ni-Cu ternary alloys for nitrate reduction. Full article

Cu-Ni co-deposit electrodes were prepared and tested in an undivided cell for the electrochemical removal of nitrate from aqueous solutions. Pulsed electrodeposition (PED) under a dynamic hydrogen bubble template and direct electrodeposition (DE) techniques were used for synthetizing porous nickel- and copper-based cathodes. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analyses showed dendritic and cauliflower-like deposits with a uniform distribution of nickel and copper on the electrode surface, both using flat and foam nickel supports. The PED technique on nickel foam generated highly porous Cu-Ni coatings, with the largest electrochemical active surface area (ECSA) among all the investigated electrodes. Electrolysis in alkaline solutions containing nitrates was performed in an undivided cell in potentiostatic mode. The selectivity towards N₂ was strongly dependent on both copper loading and applied potential; in particular, the foam electrode containing about 23% Cu showed very low ammonia production even at the highest cathodic overpotential, evidencing its marked preference for nitrogen formation. The process performed in the undivided cell using foam-supported Cu-Ni cathodes enabled 100% of conversion of nitrate to molecular nitrogen within approximately 7 h, allowing the complete denitrification of the water. Full article

Mining can significantly affect the spatial distribution and temporal evolution of groundwater chemistry. From July to August 2024, the research team collected 26 surface water and groundwater samples in the Shengli Coal Mine area of the Mongolian Plateau, conducting comprehensive hydrogeochemical analyses on surface water flowing through the mining area, groundwater within the mining area, seepage water, and groundwater outside the mining area. The results indicate that groundwater in this region is notably affected by human activities such as mining operations. Specifically, in surface water flowing through the mining area, concentrations of total dissolved solids (TDS), sulfates, nitrates, and nickel showed significant increases. Compared to groundwater systems in other areas of the Mongolian Plateau, nickel levels in the mining area’s groundwater were significantly higher, while nitrate levels exhibited the opposite trend. A significant positive correlation was observed between metal element concentrations in surface water and groundwater. The study found that abnormal distributions of heavy metals such as beryllium (Be), thallium (Tl), and tin (Sn) may originate from point-source pollution caused by mining activities. Furthermore, concentrations of manganese (Mn), arsenic (As), and antimony (Sb) in the groundwater of this area exceeded relevant regulatory limits, with arsenic being particularly prominent. The levels of arsenic in both surface water and groundwater may pose carcinogenic risks to human health. This study shows that nearly half of the sampled water bodies in the area require purification treatment to meet drinking water standards, highlighting the urgent need for further attention to water quality safety issues. The conclusions derived from this research provide theoretical support for understanding the long-term evolutionary mechanisms of groundwater in mining areas, while also offering important insights for improving groundwater environmental management and ensuring water resource security in mining regions. Full article

A binder-free Co₃O₄ nanoneedle electrode grown directly on nickel foam (Co₃O₄@NF) was fabricated by hydrothermal synthesis followed by calcination and evaluated for electrocatalytic nitrate reduction to ammonium. The integrated three-dimensional architecture combines the catalytic activity of Co₃O₄ with the high conductivity and open porosity of nickel foam, thus exposing abundant active sites, shortening electron-transfer pathways, and facilitating mass transport. Among the electrodes prepared at different calcination temperatures, Co₃O₄@NF calcined at 400 °C delivered the best performance. Under the optimal conditions of −1.4 V vs. Ag/AgCl, pH 7, and an initial NO₃⁻-N concentration of 50 mg L⁻¹, the electrode achieved 83.4% nitrate removal within 480 min together with 98.7% ammonium selectivity. Electrochemical measurements revealed a markedly enlarged electrochemically active surface area and reduced charge-transfer resistance after Co₃O₄ loading. Mechanistic analyses via TBA quenching experiments and DFT calculations revealed that both the direct pathway and the hydrogen-assisted indirect pathway were operative, with the indirect pathway being dominant due to its lower free energy barrier while maintaining negligible nitrite accumulation. The electrode also showed good cycling stability and retained high ammonium selectivity in real water matrices. These results demonstrate that binder-free Co₃O₄ nanoneedles supported on nickel foam constitute a promising cathode architecture for coupling nitrate removal with ammonia recovery. Full article

Fine particulate matter (PM_2.5) composition, rather than mass alone, plays a critical role in determining toxicity and health impact. This study examined short-term associations between daily PM_2.5 constituents—black carbon (BC), nitrate (NO₃⁻), ammonium (NH₄⁺), and trace elements—and cardiopulmonary hospital admissions in Makkah, Saudi Arabia. Twelve months of constituent data from the Alharam monitoring site were linked to Herra hospital admissions for cardiovascular (CVD) and pulmonary diseases, stratified by visit type, age, and sex. Negative-binomial generalized linear models estimated adjusted relative risks (aRRs) per interquartile range increase in each constituent, controlling for meteorology, seasonality, and temporal trends. Mean PM_2.5 was 113.6 µg/m³; BC, sulfur, NO₃⁻, and NH₄⁺ dominated the fine fraction. Crustal elements were strongly intercorrelated (r > 0.9), while BC, lead (Pb), and nickel (Ni) showed moderate correlations (r ≈ 0.4–0.6), suggesting shared anthropogenic origins. BC increased CVD emergency/outpatient visits by 18% (aRR = 1.18; 95% CI: 1.08–1.29) and inpatient admissions by 25% (aRR = 1.25; 95% CI: 1.07–1.46). Ni and sulfur were also significant predictors; crustal elements were not. Multi-pollutant models confirmed BC and Pb as independent predictors (aRR = 1.19; 95% CI: 1.02–1.38). Effects were strongest among older adults aged 45–65 at lag 0–2 days. These findings highlight the need for emission controls targeting traffic and industrial combustion sources. Full article

Catalytic hydrodeoxygenation (HDO) of aromatic aldehydes represents a core research direction in the efficient utilization of lignin. In this study, a cost-effective catalyst was constructed by incorporating rich lattice defects into Ni nanoparticles. The catalyst was synthesized via a uniform precipitation method, employing urea as the precipitant. By introducing aluminum nitrate during the precipitation process, nickel was effectively segregated to inhibit its growth and the generation of well-crystallized, defect-free Ni nanoparticles, thereby generating a substantial quantity of defective Ni nanoparticles with abundant lattice defects. The catalyst was characterized using XRD, TEM, HRTEM, EDS line and mapping scanning, XPS and H₂-TPD, confirming the formation of Ni nanoparticles with a narrow size distribution of ~5 nm with numerous lattice defects. The hydrodeoxygenation of vanillin was employed to evaluate the catalyst’s activity, with investigations into the effects of Al content, solvents, temperature, H₂ pressure, and reaction time. The reaction was successfully conducted at 363 K in water. The catalyst demonstrated excellent hydrodeoxygenation activity across a series of other aromatic aldehyde compounds. Cycle experiments confirmed the catalyst’s stability, maintaining its activity over at least five consecutive uses. Full article

This study evaluates the performance of Ni-La₂O₃/Beta catalysts for the dry reforming of methane, focusing on the effects of nickel loading, catalyst pretreatment, reaction temperature, and gas composition and flow rate. Catalysts with nickel contents ranging from 3 to 20 percent by weight were prepared via wet impregnation and characterized by gas adsorption, X-ray diffraction, temperature-programmed reduction with hydrogen, thermogravimetric analysis, and transmission electron microscopy. The results indicate that nickel gradually incorporates into the zeolitic support, preferentially occupying the most stable sites. Direct reduction of the impregnated catalyst precursors—omitting the calcination step—yielded materials with slightly higher methane conversion (ca. 3.5%) and enhanced stability. This improved performance is attributed to the reduction occurring during the thermal decomposition of supported nickel nitrate, which promotes finer nickel dispersion and stronger interaction with the La₂O₃-modified Beta zeolite. Full article

During the refining processes, when catalyst activity falls below acceptable levels and it is not possible to regenerate it for its reuse, the catalyst is disposed of as solid waste; however, the spent catalysts could be a promising source of metals for manufacturing new products due to their high content of heavy metals, such as nickel. In this research, nickel recovered from a spent hydrodesulfurization catalyst by ultrasonication-assisted leaching was used as a metal source for the synthesis of Ni-MOF-74 material (Ni-MOF-74E), and its properties and CO₂ adsorption capture capacity were compared with a Ni-MOF-74 prepared with commercial salt nickel nitrate (Ni-MOF-74C). The MOF-74 structure was confirmed by analytical techniques such as FT-IR and powder X-ray diffraction. By SEM and EDX, the fusiform morphology and the elemental composition were found. The CO₂ capture capacity, evaluated at 298 K, 288 K and 273 K, showed that the Ni-MOF-74E material presented an adsorption capacity higher than 2.2 mmol g⁻¹ and a heat adsorption of 44 kJ mol⁻¹. Full article

Porous NiCo₂O₄ nanomaterials were synthesized using in situ-generated polyacrylamide as a template, with cobalt nitrate, nickel nitrate, and urea serving as raw materials. XRD and FESEM analyses confirm the successful formation of spinel-structured NiCo₂O₄ electrode materials featuring a 3D macroporous/mesoporous architecture and an average crystalline size of approximately 8.1 nm, obtained through calcination of the amorphous precursor. Electrochemical evaluation of the as-prepared NiCo₂O₄ reveals that the specific capacitance retained at 10 A g⁻¹ reaches 88.9% of the value measured at 1 A g⁻¹, demonstrating excellent rate capability. Furthermore, the material exhibits a gradual increase in specific capacity over 3000 charge–discharge cycles, achieving a capacitance retention of up to 246.5%, which indicates good cycling stability and superior capacity retention. Full article

Copper-based electrocatalytic materials with high surface area are essential for various processes, such as water splitting and the electroreduction of carbon dioxide and nitrates. Three-dimensional nanostructured electrodes offer distinct advantages in these applications due to their expansive surface area, which enhances charge transfer and mass transport. For bimetallic systems, however, the phase state, whether a solid solution or a mechanical mixture of metals, is critically important for catalytic performance. This study explores the formation of Cu-Ni solid solutions via electrodeposition using the dynamic hydrogen bubble template method. Two types of electrolyte were employed: sulfate-based and citrate-based. Through characterization by X-ray diffraction, scanning electron microscopy, elemental mapping, and X-ray fluorescence spectroscopy, we demonstrate that metallic foams deposited from sulfate solutions are heterogeneous, with poor control over nickel content. In contrast, the use of citrate-based solutions allows the nickel content in the deposits to be effectively controlled by varying the solution composition, thereby enabling the formation of a solid solution. Full article

Efficient biological nitrogen fixation (BNF) is crucial for sustainable soybean productivity. Current strategies involve the use of Bradyrhizobium diazoefficiens and co-inoculation with plant growth-promoting bacteria like Azospirillum brasilense. To further optimize BNF and plant performance, we investigated the effect of co-inoculation with A. brasilense and B. diazoefficiens combined with the strategic application of the micronutrients Molybdenum (Mo), Cobalt (Co), and Nickel (Ni) on soybean grown under greenhouse conditions. We evaluated plant growth, photosynthetic parameters, accumulation of N, nitrate reductase activity, and nifH gene expression at the R1 reproductive stage. Our main finding was that the co-inoculation combined with the simultaneous application of Mo, Co, and Ni significantly maximized vegetative growth, photochemical efficiency, and BNF. Specifically, this triple supplementation increased nifH gene expression (0.22) compared to the inoculated control (0.003), leading to a substantial enhancement of photosynthetic parameters, including photosystem II (PSII) efficiency and net carbon assimilation (A). For example, the total dry mass was 14.36 g in the Mo + Co + Ni + AZO + BRADY combination and 6.50 g in the non-inoculated and non-micronutrient-treated plants. The total N content was also higher in the plants treated with Mo + Co + Ni + AZO + BRADY (73.20 g kg⁻¹). Crucially, the data also demonstrated that excessive levels of Co impaired the symbiosis, underscoring the necessity of precise dose management. These results confirm the strong synergistic potential of combining microbial co-inoculation with targeted mineral nutrition as a high-impact, sustainable strategy for boosting soybean productivity. Full article

The fabrication of highly loaded and uniformly dispersed metal oxide nanoparticles (NPs) is much desired but still remains a great challenge. Herein, the NiO NPs exclusively confined in mesoporous silica SBA-15 were obtained by using nickel nitrate hydrate as a precursor through a facile solvent-free preparation method, which comprised manual grinding of Ni(NO₃)₂·6H₂O with SBA-15 and subsequent air calcination. Characterization results from X-ray diffraction (XRD) and transmission electron microscope (TEM) revealed that aggregation-free NiO nanoparticles with sizes of 3–5 nm were obtained at loading as high as 20 wt.% (weight%). Further increasing the NiO loading to 30 wt.% led to partial agglomeration of discrete nanoparticles to rod-like particles, while no external particles were observed. By comparing the sample derived from nickel acetate with exclusively external NiO particles, it was established that the pore confinement provided NiO nanoparticles with high thermal stability. Lastly, the catalytic performance of the prepared sample was evaluated in the model reaction of ammonia decomposition to CO_x-free H₂, and the stable NH₃ conversion of 93.7% was achieved at the weight hourly space velocity (WHSV) value of 30,000 mL·g⁻¹·h⁻¹ and at high temperature of 650 °C for 60 h, demonstrating the great potential of the solvent-free method in preparing thermally stable and robust supported catalysts. Full article

This review provides a critical and technically grounded assessment of continuous electrocoagulation processes (CEPs) for the treatment of industrial inorganic pollutants, emphasizing recent innovations, methodological developments, and practical outcomes. A comprehensive literature survey indicates that 53 studies published over the past 25 years have investigated CEPs for inorganic contaminant removal, with 36 focusing on standalone electrocoagulation systems and 17 exploring integrated CEPs approaches. Recent advancements in reactor design, such as enhanced internal mixing, optimized electrode geometry, and modular configurations, have significantly improved treatment efficiency, scalability, and operational stability. Evidence indicates that CEPs can achieve high removal efficiencies for a wide range of inorganic contaminants, including fluoride, arsenic, heavy metals (e.g., chromium, lead, nickel, iron), nitrates, and phosphates, particularly under optimized operating conditions. Compared to conventional treatment methods, CEPs offer several advantages, such as simplified operation, reduced chemical consumption, lower sludge generation, and compatibility with renewable energy sources and complementary processes like membrane filtration, flotation, and advanced oxidation. Despite these promising outcomes, industrial-scale implementation remains constrained by non-standardized reactor designs, variable operational parameters, electrode passivation, high energy requirements, and limited long-term field data. Furthermore, few studies have addressed the modeling and optimization of integrated CEPs systems, highlighting critical research gaps for process enhancement and reliable scale-up. In conclusion, CEPs emerge as a novel, adaptable, and potentially sustainable approach to industrial inorganic wastewater treatment. Its future deployment will rely on continued technological refinement, standardization, validation under real-world conditions, and alignment with regulatory and economic frameworks. Full article

The study employed a green, template-free ball milling method to construct a series of Ni-Al mixed oxide catalysts modulated by different nickel precursors (nitrate, acetate, carbonate, sulfate, and chlorate). Through multiscale characterization techniques (XRD, TEM, XPS, H₂-TPR, etc.) and catalytic performance evaluations, we systematically elucidated the regulatory mechanism of precursor types on the structure-performance relationship. The NiAlO_x-CO₃²⁻ catalyst derived from nickel carbonate exhibited a unique structure, an optimal Ni/Al ratio, and well-tuned active oxygen species, thereby demonstrating exceptional catalytic performance in the oxidative dehydrogenation of ethane (ODHE) at 475 °C with 53.2% ethane conversion, 72.6% ethylene selectivity, and maintained stability over 40 h of continuous operation. Beyond developing high-performance ODHE catalysts, this work establishes a “precursor chemistry–material structure–catalytic performance” relationship model, offering new insights for the rational design of efficient catalysts for light alkane conversion. Full article