Search Results (123)

Vegetable tannins (VTs) are natural polyphenolic compounds widely used in leather tanning as sustainable alternatives to chrome-based processes. Traditionally, only a limited number of commercially available tannins, such as mimosa, quebracho, and chestnut, are employed globally, often requiring long-distance transportation with associated environmental and economic costs. This review systematically explores recent advances (2015–2025) in the identification and evaluation of alternative VT sources derived from underutilized plant species in Africa and Asia. Chemical composition, extraction efficiency, and tanning performance, including hydrothermal stability, tensile strength (TS), elongation at break (EB%), and tear strength (Ts), are critically analyzed and compared with conventional agents. Particular focus is given to the tannin/non-tannin ratio (T/N), a key indicator of tanning potential. Promising results were found for extracts from Acacia xanthophloea, Cassia singueana, Solanum incanum, Pontederia crassipes, and Xylocarpus granatum. Preliminary environmental assessments (COD, BOD, TDS) also suggest comparable impacts to standard tannins. However, performance variability due to species, plant part, seasonality, and extraction conditions remains a challenge. This review underscores the potential of regionally sourced VTs to support proximity-based economies and reduce the environmental footprint of the leather industry, while highlighting the need for further studies to optimize extraction protocols and scale industrial application. Full article

As the global energy industry shifts away from fossil fuels, there is a growing need for sustainable and renewable hydrogen production methods. This research investigates the potential of using biochar derived from animal waste as a precursor for creating effective catalysts for the hydrogen evolution reaction (HER). By incorporating copper and nickel into the biochar through hydrothermal processing, the study examined the resulting catalysts’ structural, chemical, and catalytic properties. Techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR) confirmed the successful integration of metallic nanoparticles and revealed notable changes in surface morphology, elemental composition, and functional group distribution. The Cu–Ni co-doped biochar catalyst (Cu–Ni/BC) demonstrated a significant 45% increase in hydrogen evolution efficiency compared to the undoped biochar control sample. These results highlight the synergistic effects of copper and nickel in enhancing the catalyst’s electron transfer capabilities and active site availability. This study offers a sustainable, cost-effective, and environmentally friendly alternative to conventional hydrogen production catalysts, presenting considerable potential for waste valorization while promoting clean energy solutions. The research aligns with circular economy principles, contributing to the advancement of sustainable energy technologies. Full article

This study presents a social life cycle assessment (S-LCA) of the F-CUBED Production System (FPS), an innovative process that converts wet biogenic residues—specifically paper biosludge, virgin olive pomace, and fruit and vegetable residues—into intermediate bioenergy carriers via hydrothermal treatment (TORWASH^®), pelletization, and anaerobic digestion. The hydrothermal carbonization of these low-grade, moisture-rich biogenic residues enhances the flexibility and reliability of renewable energy systems while also offering the potential to reduce environmental burdens compared to conventional disposal methods. Through this S-LCA, the study aims to evaluate the cradle-to-gate socioeconomic impacts of the FPS in three European contexts—Sweden, Italy, and Spain—using the 2020 UNEP Guidelines and the Social Hotspots Database (SHDB) and applying quantitative modeling via SimaPro. The functional unit is defined as 1 kWh of electricity produced. The assessment combines SHDB-based modeling with primary data from stakeholder surveys conducted in the three countries. Impact categories are harmonized between SHDB and UNEP typologies, and the results are reported in medium-risk-hour equivalents (mrheq). The results show a heterogeneous social impact profile across case studies. In Sweden, the treatment of paper biosludge delivers substantial benefits with minimal risk. In Spain (orange peel), the introduction of the FPS demonstrated a strong social benefit, particularly in health and safety and labor rights, indicating high institutional performance and good integration with local industry. Conversely, in Italy (olive pomace), the FPS revealed significant social risks, especially in the biopellet production and electricity generation sectors, reflecting regional vulnerabilities in labor conditions and governance. This suggests that targeted mitigation strategies are recommended in contexts like Southern Italy. These findings highlight that the social sustainability of emerging bioenergy technologies is context-dependent and sensitive to sectoral and regional socioeconomic conditions. This S-LCA complements prior environmental assessments and emphasizes the importance of integrating social performance considerations in the deployment and scaling of innovative bioenergy systems. Full article

Contaminants of emerging concern (CECs), including pharmaceuticals and perfluorinated compounds, pose a growing threat to water quality due to their persistence and resistance to conventional treatment methods. In this context, photocatalytic processes capable of promoting both oxidative and reductive transformations have attracted increasing attention. This study explores the synthesis and performance of a SnS₂-TiO₂ heterojunction photocatalyst, designed to facilitate such reactions under solar and UV-A light. The composite was synthesized via the hydrothermal method and thoroughly characterized for its morphological, structural, surface, and semiconducting properties. The results confirmed the formation of a type-II heterojunction with improved visible-light absorption and suppressed charge recombination. Photoelectrochemical measurements indicated enhanced charge separation and favorable band-edge alignment for reductive processes. Photocatalytic experiments with amoxicillin (AMX) and perfluorooctanoic acid (PFOA) revealed distinct degradation behaviors: AMX was predominantly degraded via superoxide-mediated reductive pathways, whereas PFOA exhibited limited transformation, likely proceeding via a combination of oxidative and reductive mechanisms. While overall removal efficiencies were moderate, this study highlights the role of band structure engineering and heterojunction design in tailoring photocatalytic behavior. The SnS₂-TiO₂ system serves as a promising platform for further development of composite materials to address the challenge of CECs in water treatment. Full article

Nut by-products, particularly shells, are a globally abundant agricultural residue. Their widespread accumulation poses a serious environmental challenge. However, nut shells are of great interest due to their inherent lignocellulosic composition. For instance, they are rich in cellulose, a high-value biopolymer widely used in the production of bio-based materials. Therefore, this review critically analyses conventional and novel pre-treatment strategies for the extraction of cellulose from nut shells, emphasising the importance of optimising valorisation routes to minimise ecological impact. Various techniques—ranging from alkaline treatments to emerging approaches such as deep eutectic solvents and hydrothermal methods—have been examined and compared. The findings in cellulose purification through different strategies reveal that, while some methods are promising, others remain underexplored. Emphasis is placed on the necessity of comprehending the specific structural and chemical characteristics of each type of nut shell; as such, knowledge is fundamental to understanding the efficiency of the applied methods. This review highlights the growing interest in the valorisation of nut shell by-products as promising lignocellulosic resources of significant utility. Therefore, it also reveals the need for further research, focusing on process scalability, cost-efficiency, and environmental impact. Advancing in these areas is essential to enable the transition of nut shells from waste to a highly valuable resource. Full article

Chicken manure (CM) is a nutrient-rich but environmentally problematic biomass that requires sustainable management. This study applied a three-step process consisting of hydrothermal activation (ZnCl₂ or H₃PO₄), catalytic hydrothermal carbonization (HCl or FeCl₃), and low-temperature pyrolysis (250 °C) to develop an energy-efficient method for producing biochar. The resulting biochars were systematically analyzed for their physicochemical properties, heavy metal content, and carbon sequestration potential, and compared with conventional pyrolysis-based biochars. Among the tested samples, the biochar produced via H₃PO₄ activation and HCl-catalyzed HTC [P-HTC(HCl)] exhibited the most favorable characteristics, including the highest carbon content (59.5 wt.%) and the lowest H/C ratio (0.65). As a result, it achieved the highest total potential carbon (TPC, 158.8 g_carbon/kg_biochar) and CO₂ reduction potential (CRP, 465.9 g_CO2-eq/kg_biochar), attributed to the strong dehydration and decarboxylation reactions and effective inorganic removal induced by Brønsted acid action. In contrast, conventional pyrolysis biochars showed significantly higher concentrations of heavy metals—up to 633 mg/kg of Cu and 2331 mg/kg of Zn—due to thermal concentration effects, whereas P-HTC(HCl) biochar presented a more balanced and environmentally acceptable heavy metal profile. In conclusion, the proposed low-temperature hydrothermal-assisted process demonstrates great potential for producing high-performance biochar from chicken manure with enhanced environmental safety and carbon storage efficiency. Full article

Integrated ⁴⁰Ar/³⁹Ar and U-Pb geochronology, combined with microstructural analysis of Early Cretaceous volcanics from eastern China, challenge conventional interpretations of flat ⁴⁰Ar/³⁹Ar age spectra. K-feldspar sample JD-1K (122.12 ± 0.81 Ma) preserves magmatic sanidine characteristics (homogeneous composition, disordered monoclinic structure), while hydrothermally altered perthite JD-2K yields a flat plateau age of 99.83 ± 0.73 Ma (~20 Ma younger than coeval K-feldspar, biotite, and zircon samples). Microstructural analyses using energy dispersive spectroscopy (SEM−EDS), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM) methods unequivocally demonstrate that the concordant ⁴⁰Ar/³⁹Ar age spectrum of sample JD-2K is a result of isotopic resetting during fluid-mediated recrystallization processes, rather than primary post-crystallization thermal stability. In step-heating experiments, contrasting argon release patterns correlate with microstructural heterogeneities. This study challenges the paradigm that flat ⁴⁰Ar/³⁹Ar spectra uniquely signify post-crystallization thermal histories, demonstrating that hydrothermal alteration can fully reset argon systems to produce misleadingly concordant ages. This study highlights the complexity of interpreting isotopic data in hydrothermally altered rocks, emphasizing the necessity of integrated petrological-geochemical analyses to differentiate primary magmatic signals from secondary overprints. Full article

This study developed a hydrothermal-crystallization coupling strategy for selective titanium extraction from low-grade titanium-bearing blast furnace slag. Systematic parametric optimization revealed that an optimum titanium extraction efficiency of 92.3% was achieved under mild hydrothermal conditions. Phase evolution analysis demonstrated that the leaching residues comprised commercially valuable calcium oxalate hydrate and amorphous silica aggregates, while titanium primarily existed as stable Ti(OH)₂(C₂O₄)₂²⁻ complexes in the leachate. Subsequently, 99.4% of titanium in the leachate was precipitated through the hydrothermal decomposition method, and mixed-phase titanium oxides with a grade of 90.5% were obtained through alkaline washing. Comparative analysis highlights three notable advantages over conventional metallurgical processes: (1) selective extraction specificity for low-concentration titanium minerals, (2) process intensification through integrated hydrothermal-crystallization operations, and (3) environmental benignancy via reagent recyclability. Full article

This review discusses the potential of emerging technologies, as well as their integration with conventional methods, to optimize the extraction of lignocellulosic compounds from cocoa pod hull (CPH), an agro-industrial residue that represents approximately 76% of the total weight of the fruit. CPH is primarily composed of cellulose, hemicellulose, lignin, and pectin. Emerging technologies such as microwave-assisted extraction, hydrothermal treatment, subcritical water, ionic liquids, deep eutectic solvents, and ultrasound treatment have proven effective in recovering value-added compounds, especially when combined with conventional techniques to improve process efficiency. Furthermore, the use of technologies such as high-voltage electric discharge (HVED) is proposed to reduce inorganic contaminants, such as cadmium, ensuring the safety of by-products. The CPH compounds’ applications include use in the food, pharmaceutical, cosmetics, agricultural, biopolymer, and environmental industries. The conversion of CPH to biochar and biofuels via pyrolysis and supercritical extraction is also discussed. The integration of technologies presents an opportunity to valorize CPH and optimize by-product development; however, as research continues, process scalability and economic viability must be assessed. Full article

This study assessed the changes in the mechanical and surface properties of the transition zone in multilayered translucent monolithic zirconia subjected to long-term hydrothermal aging. A total of 360 disk-shaped specimens (diameter: 15.0 mm; thickness: 1.2 mm) were prepared using conventional (3Y-TZP in LT; ZL, 4Y-TZP in MT; ZM) and multilayered translucent zirconia (5Y-TZP in MT Multi; ZT, 3Y/5Y-TZP in Prime; ZP) among IPS e.max ZirCAD blocks. Specimens were divided into three groups (n = 30) and aged in the autoclave at 134 °C under 0.2 MPa for 0 h (control group), 5 h (first aged group), and 10 h (second aged group). The mechanical and surface properties of the transition zone in the multilayered translucent zirconia were investigated, followed by statistical analysis (α = 0.05). Before and after aging, ZL (1102.64 ± 41.37 MPa) and ZP (1014.71 ± 139.86 MPa) showed the highest biaxial flexural strength (BFS); ZL showed the highest Weibull modulus (31.46) and characteristic strength (1121.63 MPa); and ZT exhibited the highest nanoindentation hardness (20.40 ± 1.80 GPa) and Young’s modulus (284.90 ± 20.07 GPa). After aging, ZL (116.75 ± 9.80 nm) exhibited the highest surface roughness (Ra); the monoclinic phase contents in ZL and ZP increased; and surface uplifts, microcracks, and irregular defects caused by phase transformation appeared on ZL and ZP surfaces. The 3Y/5Y-TZP transition zone exhibited flexural strength, Vickers hardness, phase distribution changes, and surface microstructure changes similar to those of 3Y-TZP before and after aging; however, the surface roughness was lower than that of 3Y-TZP and higher than those of 4Y-TZP and 5Y-TZP after aging. The mechanical and surface characteristics, excluding BFS and Vickers hardness, were influenced by the yttrium oxide content in each zone and the aging process. Full article

Mineral resources, particularly copper, are crucial for the sustained economic growth of developing countries like Kazakhstan. Over the past four decades, the diversity and importance of critical minerals for high technology and environmental applications have increased dramatically. Today, copper is a critical metal due to its importance in electrification. Porphyry deposits are important sources of copper and other critical metals. Conventional exploration methods for mapping alteration zones as indicators of high-potential zones in porphyry deposits are often associated with increased cost, time and environmental concerns. Remote sensing imagery is a cutting-edge technology for the exploration of minerals at low cost and in short timeframes and without environmental damage. Kazakhstan hosts several large porphyry copper deposits, such as Aktogay, Aidarly, Bozshakol and Koksai, and has great potential for the discovery of new resources. However, the potential of these porphyry deposits has not yet been fully discovered using remote sensing technology. In this study, a remote sensing-based mineral exploration approach was developed to delineate hydrothermal alteration zones associated with Aktogay porphyry copper mineralization in eastern Kazakhstan using Landsat-8 and ASTER satellite sensors. A comprehensive suite of image processing techniques was used to analyze the two remote sensing datasets, including specialized band ratios (BRs), principal component analysis (PCA) and the Crosta method. The remote sensing results were validated against field data, including the spatial distribution of geological lineaments and petrographic analysis of the collected rock samples of alteration zones and ore mineralization. The results show that the ASTER data, especially when analyzed with specialized BRs and the Crosta method, effectively identified the main hydrothermal alteration zones, including potassic, propylitic, argillic and iron oxide zones, as indicators of potential zones of ore mineralization. The spatial orientation of these alteration zones with high lineament density supports their association with underlying mineralized zones and the spatial location of high-potential zones. This study highlights the high applicability of the remote sensing-based mineral exploration approach compared to traditional techniques and provides a rapid, cost-effective tool for early-stage exploration of porphyry copper systems in Kazakhstan. The results provide a solid framework for future detailed geological, geochemical and geophysical studies aimed at resource development of the Aktogay porphyry copper mineralization in eastern Kazakhstan. The results of this study underpin the effectiveness of remote sensing data for mineral exploration in geologically complex regions where limited geological information is available and provide a scalable approach for other developing countries worldwide. Full article

Nanoparticles (NPs) have generated significant interest in various fields due to the unique properties that materials exhibit at the nanoscale. This study presents a comparative analysis of copper nanoparticles (Cu-NPs) and cobalt nanoparticles (Co-NPs) synthesized via conventional solvothermal and green hydrothermal synthesis using ethylene glycol and Medicago sativa extract, respectively. The conventional solvothermal synthesis showed higher efficiency for both Cu-NPs and Co-NPs with yields of 32.5% and 26.7%, respectively. Characterization through UV–visible spectroscopy (UV–vis), Fourier-transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) revealed that while solvothermal synthesis produced larger particles (76.5 nm for Cu-NPs, 86.8 nm for Co-NPs), the green hydrothermal method yielded smaller particles (53.8 nm for Cu-NPs, 67.7 nm for Co-NPs) with better control over particle size distribution and spherical morphology, showing minimal agglomeration. UV–vis confirmed metal oxide formation, while FTIR showed complex patterns in NPs (green hydrothermal), indicating plant extract compounds. Antifungal evaluation against Pseudocercospora fijiensis showed complete inhibition at 2000 ppm for both NP types, with no mycelial growth after 30 days. When integrated into chitosan, solvothermal NPs produced rougher surfaces, and scanning electron microscope (SEM) confirmed the presence of copper and cobalt in the nanocomposites. This study provides insights into the synthesis of nanoparticles using an environmentally friendly process and their microbiological applications for future use in organic agriculture. Full article

Kaolin is a common mineral resource that is used commercially. However, when processed, it generates a large amount of waste, usually rich in kaolinite, mica and quartz, which gives rise to the need to manage and reuse these mineral residues, in agreement with the SDG 12/UN (ensuring sustainable consumption and production) requirements. Therefore, this work aims to explore how to add value to this residue via its use as a photocatalytic support for TiO₂, while also meeting the SDG 6 (clean water and sanitization) requirements. After determination of its chemical and mineralogical composition, the residue underwent mineralogical separation, by mechanical stirring and sieving of its aqueous suspension. After separation, TiO₂ was deposited on the quartz fraction of the residue by the modified-Pechini method, using different quartz proportions and at different calcination temperatures. For the deposition of TiO₂ on the mica fraction, the conventional hydrothermal synthesis was used, with 20% of the mica. Each material was tested in a photohydroxilation of terephthalic acid under UV-C irradiation to evaluate the formation of hydroxyl radicals. The results of the photocatalytic tests demonstrated that quartz and mica are inert to photocatalysis but provide an interesting support for TiO₂. The highest photocatalytic efficiency was obtained for the material synthesized at 600 °C with 20% of the quartz. Full article

Electrocatalytic water splitting is a critical approach for achieving carbon neutrality, playing an essential role in clean energy conversion. However, the slow kinetics of the oxygen evolution reaction (OER) remains a major bottleneck hindering energy conversion efficiency. Although noble metal catalysts (e.g., IrO₂ and RuO₂) show excellent catalytic activity, their high cost and scarcity limit their applicability in large-scale industrial processes. In this study, we introduce a novel electrocatalyst based on selenized NiFe-layered double hydroxides (NiFe-LDHs), synthesized via a simple hydrothermal method. Its key innovation lies in the selenization process, during which Ni atoms lose electrons to form selenides, while selenium (Se) gains electrons. This leads to a significant increase in the concentration of high-valent metal ions, enhances electronic mobility, and improves the structural stability of the catalyst through the formation of Ni-Se bonds. Experimental results show that selenized NiFe-LDHs exhibit excellent electrocatalytic performance in 1 M KOH alkaline solution. In the oxygen evolution reaction (OER), the catalyst achieved an ultra-low overpotential of 286 mV at a current density of 10 mA cm⁻², with a Tafel slope of 63.6 mV dec⁻¹. After 60 h of continuous testing, the catalyst showed almost no degradation, far outperforming conventional catalysts. These results highlight the potential of NiFe-LDH@selenized catalysts in large-scale industrial water electrolysis applications, providing an effective solution for efficient and sustainable clean energy production. Full article

Hydrothermal carbonization (HTC) is a promising thermochemical process to convert residues into hydrochar. While conventional HTC utilizes one type of residue as raw material only, Co-HTC generally combines two. By mixing dry and wet wastes, Co-HTC can advantageously avoid water addition. Therefore, this work investigated the potential of hydrochar derived from the Co-HTC of sawdust and non-dewatered sewage sludge as a dye (methylene blue) adsorbent and evaluated the toxicity of the resulting Co-HTC process water (PW) on Daphnia magna. Three hydrochars were produced by Co-HTC at 180, 215, and 250 °C and named H-180, H-215, and H-250, respectively. For methylene blue adsorption, H-180 and H-215 had a better performance than H-250. Both H-180 and H-215 presented a maximum adsorption capacity of approximately 70 mg·g⁻¹, which was superior compared with the adsorption of methylene blue by other hydrochars in the literature. Moreover, the removal percentage obtained with H-180 remained satisfactory even after five cycles. Regarding the toxicological assays of the PWs, raising the Co-HTC temperature increased the variety of substances in the PW composition, resulting in higher toxicity to D. magna. The EC₅₀ values of PW-180, PW-215, and PW-250 were 1.13%, 0.97%, and 0.51%, respectively. This highlights the importance of searching for the treatment and valorization of the PW. Instead of viewing this by-product as an effluent to be treated and disposed of, it is imperative to assess the potential of PWs for obtaining other higher added-value products. Full article