Search Results (292)

This review is devoted to the occurrence, extraction, structural characterization and catalytic applications of vanadyl porphyrins present in heavy crude oils and petroleum residues. Vanadyl porphyrins represent the major vanadium-containing compounds in petroleum systems and play a dual role as both catalyst poisons during refining processes and valuable precursors for functional catalytic materials. Particular attention is devoted to recent advances in extraction technologies, including solvent extraction, ionic liquids, deep eutectic solvents, functionalized adsorbents and chelating agents. Process intensification approaches such as ultrasound- and microwave-assisted extraction, are also discussed as promising strategies for improving extraction efficiency and selectivity. Furthermore, recent developments in petroleum characterization using FTICR-MS, EPR, HYSCORE and LA-ICP-MS techniques are reviewed, providing insights into metalloporphyrin speciation, oxidation states, and distribution within complex petroleum matrices. Beyond their traditional role in catalyst deactivation, vanadyl porphyrins have emerged as attractive precursors for catalytic materials applied in oxidation reactions, photocatalysis, oxidative desulfurization, wastewater treatment and selective organic synthesis. The development of hybrid catalytic systems based on mesoporous silica, graphene oxide, carbon nanotubes, polymer matrices, and metal–organic frameworks has significantly improved catalyst stability, activity and recyclability. Current challenges related to the selective extraction, preservation of metalloporphyrin structure and catalytic performance evaluation are also discussed. Overall, this review provides an integrated perspective on the recovery, characterization and valorization of vanadyl porphyrins for sustainable petroleum upgrading and environmental applications. Full article

The fading of painted relics is a widespread deterioration phenomenon in ancient painted cultural relics, yet its underlying mechanism has long been attributed solely to pigment oxidation. Directed at colored drawings with complex surface microstructures, such as pottery paintings, wall murals and architectural paintings, here we challenge this view by demonstrating that light scattering induced by sub-micron pores within the paint layer plays a dominant role, especially Mie scattering when pore sizes approach visible light wavelengths (400–700 nm). In order to minimize the damage to the genuine painted relics, a large number of simulated experiments were conducted first. Using porous polyacrylamide (PAM) membranes and nylon 6 filter membranes as model systems, we show that pore-induced scattering reduces the optical path length for light absorption, leading to a significant decrease in color saturation and brightness. By filling the pores with non-volatile colorless ionic liquids ([BMIM]PF₆) (n = 1.41) or glycerol (n = 1.47)—both possessing refractive indices close to those of the pigments—the scattering is effectively suppressed, and the original color is restored. The filling treatment reduces the color difference (ΔE*ab) by 30%–50% and the surface reflectivity by 20%–40%. Mercury intrusion porosimetry and fluorescence spectroscopy confirm that pore elimination and optical path lengthening are responsible for the color recovery. The proposed mechanism and restoration strategy were successfully validated on authentic painted brick fragments from the Western Qing Tombs (Hebei, China), where severely faded green and red patterns reappeared after ionic liquid treatment. This study provides a new interface-regulation paradigm for the conservation of painted cultural heritage, shifting the focus from irreversible chemical remediation to reversible physical restoration and offers a generalizable platform for controlling light scattering in porous optical materials. Full article

Radix Paeoniae Alba, the dried root of Paeonia lactiflora Pall., contains characteristic monoterpene glycosides, but efficient recovery of these polar constituents remains challenging. This study developed an ionic liquid-assisted sequential ultrasound–microwave extraction method and evaluated paeoniflorin, oxypaeoniflorin and albiflorin by HPLC as multi-marker responses. Among the ionic liquids tested, 1-propyl-3-methylimidazolium dihydrogen phosphate showed the best extraction response. Box–Behnken response surface optimization gave practical extraction conditions of a solid-to-liquid ratio of 1:26 g/mL, ionic liquid concentration of 0.12 mol/L and ultrasound time of 22 min. Under these conditions, paeoniflorin and total marker glycosides reached 29.12 and 34.98 mg/g dry material, respectively, representing increases of 32.4% and 34.5% compared with conventional reflux extraction. UPLC-QTOF-MS profiling provided complementary chemical profile information for the optimized extract and tentatively annotated Paeonia-related monoterpene glycoside derivatives, galloylated glucose derivatives and polyphenolic constituents. Electrostatic potential, SAPT and non-covalent interaction analyses, supported by ¹H NMR chemical shift perturbation, suggested possible hydrogen bonding, electrostatic and dispersion interactions between paeoniflorin and the selected ionic liquid. These results support the optimized process as an efficient extraction approach and provide molecular interaction insights into ionic liquid-assisted recovery of monoterpene glycosides. Full article

There has been a rising trend for recovering waste heat, especially after the invention of new types of semiconductors. Among all available utilization options, thermoelectric generation (TEG) systems are promising for recovering waste heat. Thermoelectric devices are environment-friendly, operate silently, and are suitable for low- to high-power applications. This review paper presents a comprehensive study of TEGs, starting with the current problem, state of the art, advantages, disadvantages, generation and related principles, and applications, and covers different arrangements (individual and combined) and working fluids. Furthermore, this article systematically covered various experimental and numerical studies, including optimization, offering insights into heat exchanger configurations, working fluids, and performance parameters. Here, an effort is made to describe the contributions of individual/coupled TEG systems. As a coupled system, the individual TEG system is used with other systems like solar, distillation, solar pond, etc., for cogeneration and enhanced efficiency. The thermal/system parameters of individual/coupled systems are thoroughly discussed, and their impact on efficiency and power generation is illustrated. It was found that the design of the heat exchanger configuration varies from plate type to an efficient liquid-based electricity generation system in these TEG systems. The working fluid inside the fluid loop of a thermoelectric generation system varies from simple fluids to nanofluids. The current state of thermoelectric generation technology is facing challenges in module materials, equipment cost optimization, and commercialization. The progressive TEG generation capabilities have improved with recent advancements in these areas. The power densities are increasing from 0.5 to 1.2 W/cm² in earlier standalone TEGs to 2.5–4.8 W/cm² in recent optimized hybrid configurations, and overall system efficiencies are rising from an average of 5.2% (standalone) to 18.7% in coupled solar-TEG or waste heat recovery systems. The reported maximum ZT values are also improved from ~1.2 to 2.1–2.8 in next-generation materials. Liquid-based heat exchangers in conjunction with nanofluids are the most efficient way to maximize temperature gradient coefficient (0.75–0.92) and minimize parasitic losses. While flexible, ionic, and hybrid next-generation material platforms are still in the early phases of development (TRL 3–5), liquid-based heat exchanger systems improved with nanofluids are closest to commercialization (Technology Readiness Level, TRL 6–8). Therefore, further research in these areas is required to mitigate these challenges. Finally, the recent developments in the thermoelectric generation field and future research direction are briefly discussed. Full article

The genus Cynara is native to the Mediterranean region and is widely used in food and traditional medicine worldwide. Cynara is characterized by its diverse phytochemical composition, with sesquiterpene lactones, a subclass of terpenoids, being particularly distinctive. These compounds are naturally synthesized as defense mechanisms against herbivores and pathogens while acting as allelochemicals. The sesquiterpene lactones found in Cynara exhibit potential anticancer, anti-inflammatory, and antimicrobial activities. They also possess significant phytotoxic activity, making them promising natural bioherbicides for agricultural applications. The effective exploitation of these compounds requires the use of appropriate extraction solvents and techniques. Compared with conventional solvents and extraction methods, green solvents, including ionic liquids and deep eutectic solvents, together with modern extraction techniques, particularly ultrasound-assisted extraction, supercritical fluid extraction, and Naviglio extraction, have proven highly effective for their recovery. In addition, the application of elicitation strategies, such as salt stress, shading, hormones, and microbial biostimulants, has emerged as a promising approach for enhancing the production of these compounds during cultivation. Therefore, this review highlights Cynara as a valuable source of sesquiterpene lactones with broad applications in medicine and agriculture and provides guidance on technical approaches relevant to their extraction and the enhancement of their production. Full article

To address prevalent industrial challenges, including the high cost of fabricating microstructures via photolithography and 3D printing, impurity residues easily generated by conventional physical/chemical pore-forming techniques, and the limited sensitivity of regular capacitive sensors, this paper innovatively proposes an integrated low-temperature in situ gas foaming strategy using ammonium bicarbonate for the fabrication of porous TPU-based ionic gels. Relying on the complete gaseous decomposition property of ammonium bicarbonate upon heating, a three-dimensionally interconnected continuous porous network is spontaneously constructed inside the polymer matrix. Thermoplastic polyurethane (TPU) is selected as the continuous polymer phase, and [EMIM][TFSI] imidazolium ionic liquid is blended as the ion source to synthesize composite ionic gel substrates. A PDMS composite slurry filled with graphene is employed to prepare flexible substrates, followed by low-temperature oxygen plasma surface modification to introduce polar functional groups such as hydroxyl and carboxyl onto electrode surfaces. A standard sandwich-structured ionic pressure sensor with the configuration of “top modified electrode—porous ionic gel dielectric layer—bottom modified electrode” is finally assembled. The porous framework and modified electrodes constitute a dual synergistic enhancement system: the porous structure markedly reduces the equivalent elastic modulus of the gel and improves its compressive deformation capacity; polar-modified electrodes optimize the interfacial compatibility between electrodes and gels, shorten ion migration paths and lower interfacial contact resistance. Systematic calibration of multiple batches of parallel samples reveals that the as-fabricated sensor achieves a high sensitivity of 25.3 kPa⁻¹ across the full measuring range from 0 to 1000 kPa with a linear fitting coefficient R² = 0.992. The loading response time and unloading recovery time of the device are 60 ms and 80 ms respectively, with a performance degradation of less than 3% after 1000 consecutive loading–unloading cycles, featuring low hysteresis error and excellent signal repeatability. Multi-scenario in vivo wearable tests on human subjects verify that the device can precisely capture subtle fluctuations of radial artery pulse and periodic laryngeal deformation during swallowing, distinguish characteristic waveform patterns of various English words according to differences in vocal cord vibration, and accurately detect bending motions when attached to finger joints. The entire fabrication process adopts common chemical raw materials and standard laboratory equipment without expensive micro-nano processing facilities, featuring convenient raw material procurement and high process fault tolerance, which enables large-area coating-based mass production. This work delivers a novel technical route for the low-cost large-scale production of high-performance ionic flexible sensors and bears significant industrialization reference value for applications in wearable medical monitoring, bionic robotic electronic skin, flexible human–machine interactive touch panels and other related fields. Full article

Ionic liquid-assisted extraction can improve the recovery of monoterpene glycosides from Radix Paeoniae Alba, whereas post-extraction purification and ionic-liquid-associated marker-level quality control remain necessary before further bioactivity evaluation. In this study, a macroporous resin-based purification process was developed for monoterpene glycoside-enriched extracts obtained by conventional reflux extraction and ionic liquid-assisted microwave–ultrasound extraction. Among the five tested resins, AB-8 resin showed the best adsorption performance and was selected for further process optimization. The optimized purification conditions were a loading concentration of 13 mg/mL, loading pH of 7, elution with 70% ethanol, loading volume of 6 BV and elution volume of 9 BV. After purification, the total quantified monoterpene glycoside content increased from 6.59% to 51.68% in the conventional extract and from 15.30% to 75.30% in the ionic liquid-assisted extract. The ionic-liquid-associated elemental marker content in the ionic liquid-assisted extract decreased from 5.593% to 0.072% after purification, corresponding to an approximately 98.7% reduction at the elemental-marker level. Stability evaluation indicated that Na₂SO₃, Fe³⁺, ascorbic acid, sucrose and light exposure affected the detected monoterpene glycoside content to different extents, whereas short-term heating within 20–80 °C caused only slight fluctuations. The purified extracts showed stronger DPPH and ABTS radical scavenging activities and reducing power than the crude extracts. In LPS-stimulated RAW264.7 cells, the purified extracts reduced NO production and downregulated the mRNA expression of IL-6, IL-1β, TNF-α, iNOS and COX-2, suggesting anti-inflammatory potential at the NO and gene-expression levels. AB-8 resin purification enriched the monitored monoterpene glycosides, reduced the selected ionic-liquid-associated elemental marker, and generated purified fractions suitable for subsequent stability and bioactivity evaluation. Full article

The exponential increase in photovoltaic panel (PV) waste highlights the urgent need to develop efficient and sustainable recycling processes. It is estimated that by 2030, 8 million tons of PV modules will reach their end-of-life stage, posing a significant environmental challenge and requiring the development of green technologies for resource recovery. This study assessed the performance of imidazolium-based ionic liquids (ILs) as “designer solvents” for the selective leaching of copper and silver from disused PV panels. Specifically, four quaternary imidazolium salts were evaluated: [Bmim]HSO₄, [Emim]HSO₄, [Bmim]Cl, and [Emim]Cl. Leaching tests were conducted on silicon wafers containing 0.28% Ag and 0.19% Cu under varying temperatures (25, 50, and 80 °C), IL concentrations (20% and 60% v/v), and hydrogen peroxide (H₂O₂) dosages (0% and 3% v/v) as an oxidizing agent. The results identified [Bmim]HSO₄ as the most effective leaching agent. The system achieved a maximum copper extraction of 96.70% at 60% v/v concentration and 80 °C. For silver, the highest extraction of 45.13% was obtained using [Bmim]HSO₄ at 20% v/v and 80 °C. The addition of H₂O₂ was crucial, demonstrating a clear synergistic effect with the imidazolium-based ILs by promoting oxidative dissolution. These findings confirm that imidazolium-based ionic liquids represent a promising and environmentally friendly alternative for the recovery of high-value metals in the circular economy of photovoltaic recycling. Full article

The agrifood industry generates substantial amounts of waste to meet the increasing global food demand, raising environmental concerns. Valorization of these residues through the recovery of high-added-value compounds and renewable energy production, such as biogas via Anaerobic Digestion (AD), offers a sustainable solution. In this study, the potential of Olive Pomace (OP), Brewers’ Spent Grain (BSG), and Cereal Wheat Bran (BR) as substrates for AD was investigated. Lignin was removed from these biomasses using an Ionic Liquid (IL) composed of triethylamine and sulphuric acid ([Et₃N][HSO₄]), and the delignified residues, called Olive Pomace Pulp (OPP), Brewers’ Spent Grain Pulp (BSGP), and Cereal Wheat Bran Pulp (BRP), were evaluated for their biogas and biomethane production potential through the volumetric method, coupled with an alkaline trap for biogas upgrading. An analysis was performed, considering biogas and biomethane yields, AD duration, and energy requirements. Raw biomasses provided different biomethane concentrations, with OP reaching 53.73%, BSG 76.59%, and BR 77.36%. After IL treatment, the methane content was 55.6% for OPP, 60.0% for BSGP, and 54.6% for BRP. Owing to their similar composition, BSG and BR displayed comparable biomethane production profiles. The analysis highlighted BSG and BR as the most efficient substrates for AD following lignin removal. Overall, this approach demonstrates the potential of agro-industrial waste valorization to produce bioenergy and support the transition toward a circular economy. Full article

Phycobiliproteins (PBPs) are a family of pigment-proteins renowned for their exceptional light-harvesting, fluorescent, and antioxidant properties. Among cyanobacteria, Spirulina stands out as one of the richest natural sources of PBPs, particularly phycocyanin (PC) and allophycocyanin (APC), yet the large-scale production of analytical-grade PBPs remains hampered by an inherently complex downstream process that relies on multiple purification steps, compromising both yield and scalability. This work presents a streamlined strategy to obtain analytical-grade PC, combining ultrasound-assisted extraction (UAE) with an aqueous ionic liquid (IL) solution and a single hydrophobic interaction chromatography (HIC) step, integrated within a biorefinery framework. The proposed approach yielded analytical-grade PC with a recovery of up to 50.44% and enhanced APC purity up to 10.57-fold. Furthermore, the IL was successfully reused in both extraction and purification steps without compromising yield or purity. The environmental performance of the proposed process was assessed through a cradle-to-gate life cycle assessment (LCA), with system boundaries encompassing the following biorefinery stages: cultivation, harvesting and drying, PC extraction and purification, post-processing, and spent biomass valorization via anaerobic digestion. The LCA identified the main environmental hotspots and guided the proposal of targeted process improvements—particularly HIC salt substitution and increased IL recovery—which reduced environmental impacts by 65.9–89.8% across most categories. The proposed strategy was further benchmarked against two model scenarios for analytical-grade PC production, one conventional and one innovative, revealing its relative advantages and limitations. Overall, this work demonstrates a viable pathway for producing high-purity PC that balances process efficiency with environmental sustainability, supporting the development of greener microalgae-based bioprocesses. Full article

Liquid-state thermocells (LTCs) are emerging electrochemical heat engines for harvesting low-grade thermal energy across small temperature differences. Their practical performance is jointly limited by internal dissipation associated with ionic and electrochemical transport, as well as by external irreversibility arising from finite thermal coupling to the heat source and sink. In this work, a finite-rate thermodynamic framework is developed for LTCs subject to coupled internal and external irreversibilities. The model combines effective thermoelectrochemical transport, a phenomenological asymmetric Joule-heat partition parameter motivated by electrode and interfacial heat effects, and non-ideal thermal contacts, thereby enabling analytical optimization of power output in four representative configurations. Closed-form expressions are derived for the maximum power and the efficiency at maximum power (EMP), together with the admissible operating domain and an equivalent-circuit interpretation. The results show that the thermal impedance ratio governs a transition between externally limited and internally limited regimes. In the externally dominated limit, all configurations recover the Curzon–Ahlborn efficiency, whereas in the internally dominated limit, the asymptotic EMP depends on the side receiving irreversible heat release. When both dominant irreversibilities are located on the hot side, the highest EMP is achieved, while the opposite configuration yields the lowest EMP. These findings provide a thermodynamic benchmark for the LTC architecture and clarify how thermal contact asymmetry and internal heat release pathways should be coordinated to enhance performance in low-grade heat recovery. Full article

Imidazole-based ionic liquids hold immense potential in the field of mineral flotation due to their tunable properties. In this study, three imidazole-based ionic liquids with varying carbon chain lengths (OMB, DMB, and HMB) were selected as collectors for quartz flotation to systematically investigate the microscopic mechanisms by which carbon chain length influences the agglomeration and flotation behavior of quartz. Flotation tests and online particle-bubble monitoring (PBM) results indicate that the elongation of the collector’s carbon chain significantly enhances its collecting ability and reduces the required reagent dosage. To achieve the complete recovery of quartz in a neutral system, a dosage of 35 mg/L is required for OMB, whereas HMB requires only 8 mg/L. As the carbon chain lengthens, the optimal pH range for highly efficient flotation shifts from alkaline to neutral-acidic. Interfacial measurements and mechanistic analyses (Zeta potential and FTIR spectroscopy) confirm that the imidazole ring of the collector physically adsorbs onto the quartz surface through the synergistic action of electrostatic forces and hydrogen bonding, thereby inducing the hydrophobic agglomeration of particles. Notably, in a strongly alkaline system (pH = 11), the long-chain HMB promotes the formation of oversized quartz agglomerates. This leads to a depletion of free reagents in the liquid phase and destabilizes the bubble liquid film, ultimately triggering a sharp decline in recovery. Density functional theory (DFT) calculations further corroborate the structure–activity relationship at the molecular level: the extension of the carbon chain increases the highest occupied molecular orbital (HOMO) energy and electron-donating ability. The adsorption energy of HMB on the quartz (001) surface reached −350.2 kJ/mol, exhibiting the strongest solid–liquid interfacial affinity. This study elucidates the competitive mechanism of carbon chain length in regulating electrostatic adsorption, hydrophobic agglomeration, and froth stability, providing a solid theoretical foundation for the molecular design of novel green flotation reagents for quartz. Full article

Rhodium is a high-value strategic platinum-group metal extensively applied in automotive exhaust purification, fine chemicals, glass production and high-temperature materials. Restricted by uneven primary resource distribution and volatile market prices, recovering rhodium from secondary resources has become increasingly critical. Solvent extraction is regarded as a promising technology for continuous and selective separation of rhodium, yet direct extraction of Rh(III) from chloride media faces severe industrial limitations. These bottlenecks are mainly attributed to diversified chloro-aqua complexes, kinetic inertness of low-spin Rh(III), strong hydration capacity and polynuclear species generation, while solution aging and inconsistent thermodynamic-experimental results further complicate extraction behaviors. This review systematically summarizes recent advances in rhodium solvent extraction from chloride media, correlating aqueous speciation regulation, activation chemistry, extractant molecular structure and extraction-stripping mechanisms. Special emphasis is placed on SnCl₂-, ascorbic acid-, trichloroacetic acid- and malonate-assisted activation systems, as well as amine-, phosphorus-, sulfur-based, synergistic, ionic-liquid and deep-eutectic-solvent extractants. Key factors affecting extraction efficiency, distribution ratio, selectivity and stripping performance are clarified, and current challenges are outlined. Future research should focus on quantitative speciation analysis, in situ mechanistic characterization, targeted extractant design, and integrated evaluation of extraction, stripping, recyclability, cost and real-feed adaptability, so as to provide theoretical support for efficient and clean rhodium recovery. Full article

Replacing artificial dyes with natural pigments in foods, especially carotenoids, has proven to be technologically feasible. This study developed a high-performance pitanga carotenoid extraction process using ionic liquids (ILs) and a factorial design to identify a potential substitute for artificial azo dyes, specifically Allura Red AC and Sunset Yellow FCF. 1-Hexyl-3-methyl-imidazolium chloride [C6mim]Cl was the most efficient IL. The optimized process conditions included a solid–liquid ratio R(S/L) of 1:10 m/m, an IL to ethanol co-solvent ratio R(IL/E) of 1:1 m/m, ultrasound power of 350 W, and six extraction cycles of 7 min each. These conditions yielded a total carotenoid content of 100.40 ± 3.71 μg/g (dry matter), demonstrating effective pigment recovery and a concentration suitable for practical use as a natural colorant alternative to synthetic azo dyes. The reuse of ILs and carotenoid purification were achieved through solid-phase extraction (SPE) using XAD-7HXP adsorbent, resulting in recovery rates of 89.2–76.2% for [C6mim]Cl and 108.9–23.2% for carotenoids. The major carotenoids identified were all-trans-β-cryptoxanthin, all-trans-rubixanthin, and all-trans-lycopene, whose combined presence contributed to a yellowish-orange hue similar to that of Sunset Yellow FCF, as confirmed by CIELAB parameters. Additionally, the [C6mim]Cl carotenoid extract exhibited high antioxidant activity, with an antioxidant capacity of 23.54 µmol of α-tocopherol equivalent. Full article

This study presents an innovative approach for the selective extraction of Co(II) and its separation from Ni(II) using ethyl ester glycine–betaine derivatives, specifically tri(n-pentyl)[2-ethoxy-2-oxoethyl]ammonium dicyanamide, as extractants in combination with continuous-mode liquid–liquid contact. Semi-pilot-scale implementation requires non-equilibrium conditions, characterized by short contact times between effluent and extractant phases. To address this, we propose dissolving analog of glycine–betaine ionic liquid (AGB-IL) in low-viscosity MIBK solvents to enhance mass transfer while reducing dependence on fossil-based solvents. Liquid–liquid extraction and continuous-flow stripping experiments were designed based on prior batch results and conducted in a saline environment, employing a chaotropic electrolyte for extraction and a kosmotropic electrolyte for stripping. Both open and closed systems were tested to compare extractive performance with batch conditions and with scenarios representative of industrial operations. Results indicate that continuous-flow systems achieve performance comparable to batch systems in terms of extraction efficiency, Co/Ni separation coefficients, and recyclability. These findings provide proof of concept for the development of semi-pilot and pilot-scale processes for efficient cobalt recovery. Full article