Development of innovative and time and energy-efficient Direct Air Capture (DAC) technologies to directly capture carbon dioxide (CO2) from the atmosphere is crucial for minimization of unabated CO2 emissions contributing to climate change. In this study, we investigated for the first time the dynamic behavior of CO2 and water/humidity (H2O) desorption in a spent vacuum DAC bed unit packed with zeolite 13X particles to identify strategies to decrease its regeneration time and energy requirements, known as two major barriers to large-scale deployment of DAC systems. This research addresses a knowledge gap by studying the dynamic desorption of CO2 and H2O from a vacuum DAC unit, aiming at evaluating its effectiveness for capturing CO2 from humid air. We developed a comprehensive modeling framework, including a two-dimensional dynamic, non-isothermal, and two-scale heterogeneous model, to simulate the dynamic behavior of concomitant CO2 and H2O desorption during the regeneration phase of the DAC process. We highlighted the effects of ambient temperature (cold and hot climate), magnitude and time evolution of a volumetric power source heating the packed bed, vacuum conditions, CO2 and H2O uptake by the adsorbent, wall heat transfer, and desorption kinetics on the performance of a packed bed DAC regenerator. The results indicated that applying a high volumetric energy input for a shorter time resulted in a significant decrease (35 %) in regeneration time and improved H2O desorption efficiency (2 %). At CO2 uptakes greater than 2.0 mol/kg, the energy requirement for the entire desorption process (CO2 + H2O) is lower than the energy requirement for the CO2 desorption process alone at low CO2 content (<1.0 mol/kg). A moderate vacuum (70-90 %) produces acceptable water desorption and energy consumption savings.

Marinized bubbling fluidized beds hold promise for reducing ship emissions, but face significant challenges due to sea-induced hydrodynamic instability. This study investigates the dynamics of single bubbles in fluidized beds under simulated marine conditions, using digital image analysis and particle image velocimetry to evaluate the effects of rolling amplitude and frequency, nozzle position, and static inclination on bubble behavior and bed stability. Comparative analyses of vertical, inclined, and rolling beds show that nozzle placement and wall interactions strongly influence bubble trajectories, shapes, and size evolution. Rolling bed oscillations tend to stabilize bubble shapes but introduce bifurcated growth patterns and enhance gas drift near walls, while inclined beds amplify bubble shrinkage through channeling effects. Granular temperature analysis shows that rolling motion mitigates oscillations, redistributes particle kinetic energy, and stabilizes void fraction and bubble behavior despite exacerbated wall channeling at higher rolling amplitudes. These findings provide valuable insights into overcoming hydrodynamic challenges, optimizing fluidized bed designs, and improving their stability and performance for sea-going applications.

Mixing remains a major limitation in microfluidic systems, where molecular diffusion under laminar flow conditions is inefficient for rapid homogenization. Magnetic actuation using magnetic nanoparticles provides a remote, contactless, and tunable active mixing strategy. Although numerous experiments demonstrate that magnetic fields induce secondary flows and enhance mixing, their interpretation has remained empirical as predictive models were lacking. Focusing on dilute, clusterless magnetocolloidal suspensions operating at low Reynolds number, we argue that these limitations were primarily conceptual rather than experimental. Recent advances in two-phase predictive modeling now provide a description without adjustable constitutive fitting parameters within the dilute, clusterless regime, enabling spin-up flow and Kelvin body force to be identified, quantified, and controlled as distinct transport mechanisms. The corresponding closure relations are derived in the single-particle limit. These frameworks further reveal magnetocaloric heating under high-frequency rotating magnetic fields, coupling flow generation, mixing enhancement, and localized thermal effects. We show how magnetic actuation can be exploited as a design variable to control mixing and heat.

Needle-free injection systems (NFISs) provide an alternative route for transdermal drug delivery by using high-speed liquid microjets to penetrate soft biological tissues without solid needles, offering reduced pain, lower contamination risk, and eliminating disposal challenges. The performance of NFISs relies on the fluid mechanics of the jet, which is influenced by nozzle characteristics (diameter, shape, and design), jet velocity, injection volume, the properties of the injected drug fluid, and the mechanical properties of the target tissue. Each of these parameters can directly affect jet penetration depth and dispersion shape in target tissues. In this review, we examine the main actuation mechanisms, including spring powered, gas powered, Lorentz force, piezoelectric, and laser-induced systems, and summarize how jet fluid mechanics controls jet stability, penetration depth, jet regimes, and in-tissue dispersion patterns. To generalize these findings, we identify the key dimensionless parameters that control jet behavior across NFIS technologies and highlight the limitations related to nozzle design, jet instabilities, imperfect volume delivery, and the large variability in skin mechanics.

Conversion of carbon dioxide (CO2) to cyclic carbonates is important for carbon capture and utilization and enables the production of valuable, non-toxic chemicals from a climate-relevant greenhouse gas. This paper reports a catalytic strategy for synthesizing cyclic carbonates using commercial solid mesoporous silica supports with controlled particle sizes. Tripropylammonium groups were grafted onto the silica surface to activate it for CO2 conversion. Batch reactor experiments confirmed that the functionalized silica catalyzes the reaction under milder temperature and pressure conditions than previously reported. Importantly, this strategy effectively suppresses polymer by-product formation, enabling selective cyclic carbonate production while offering potential applications for controlled polymer synthesis through reverse optimization. A subsequent gas-phase cycloaddition reaction was conducted in a micropacked bed reactor. The reactor performance was assessed using the chemical regime method to separate intrinsic kinetics from mass transfer effects. Compared to conventional fixed-bed reactors, the reaction times were significantly reduced, from several days in batch systems to similar to 1 minute in centimetric reactors and <1 second in microreactors. These findings support the potential for commercial-scale implementation.

Direct air capture (DAC) technologies offer a promising avenue for mitigating climate change by removing CO2 from the atmosphere. Innovations in energy-efficient DAC technologies are essential to increase their deployment and reduce costs, making them a more viable and accessible solution for carbon removal. Currently, DAC is an energy-intensive process, and reducing its energy consumption is vital for cost-effectiveness. This research focuses on enhancing the DAC process, specifically the regeneration phase, by utilizing structured packed beds coated with zeolite 13X. The goal is to achieve faster and more energy-efficient desorption of CO2 and H2O. We investigated the dynamic behavior of the co-desorption of CO2 and H2O during the solid-based DAC process that uses structured packed beds coated with zeolite 13X and heated by internal Joule heating via a two-dimensional unsteady-state, nonisothermal, two-scale heterogeneous model. The study examines how the magnitude and time evolution of the volumetric energy source heating the packed bed, along with CO2 and H2O uptake, coated zeolite layer thickness, and packed bed height affect the desorption process and energy consumption in DAC units, specifically comparing structured and random packing configurations. The results indicate that under similar starting regeneration conditions (same total mass of CO2 and H2O adsorbed in the unit, quantified in kilograms), the specific energy requirements associated with the CO2 desorption process are lower in a DAC unit with structured packing than in a unit with random-packing spherical zeolite particles. On the other side, at the same starting CO2 and H2O uptakes (quantified in mol/kg) and high CO2 uptake levels (>2.0 mol/kg), structured packing and packed beds with spherical particles exhibit similar specific energy requirements for CO2 and combined CO2 and H2O desorption processes. In DAC systems, using structured packing instead of randomly packed units for CO2 and H2O desorption can significantly reduce the duration of the desorption process and improve the H2O desorption efficiency.

Direct air capture (DAC) of CO2 via solid adsorbents is a promising and scalable technology, but its implementation is limited by high energy demands driven by a low atmospheric CO2 concentration and high desorption temperatures. Advancing this technology requires developing novel sorbents and process strategies that maximize the CO2 adsorption capacity while enabling low-temperature regeneration. Competitive H2O adsorption is another major hurdle in CO2 capture as H2O outcompetes CO2 for active sites, reducing CO2 adsorption capacity and increasing the energy penalty for regeneration due to the higher heat of H2O desorption. This work investigates how ambient humidity and temperature and their variability affect CO2 adsorption on packed beds of zeolites 13X for DAC, with the aim of optimizing conditions for maximum CO2 adsorption and helping to overcome the obstacles of low CO2 concentration and high energy barriers for large-scale deployment. To this end, the dynamic behavior of CO2 and H2O coadsorption in a DAC unit packed with zeolite 13X particles was studied via a two-dimensional, nonisothermal, two-scale heterogeneous dynamic model. Results indicate that while water competitively inhibits CO2 adsorption, solid-sorbent DAC efficiency is optimized at lower temperatures and lower humidity, which enhances CO2 adsorption while minimizing unnecessary energy-intensive water accumulation. A moderate and time-constant inlet relative humidity (around 30%) appears to be a potential optimal point for CO2 capture (CO2 reaches near-maximum adsorption capacity while minimizing unnecessary excess H2O accumulation) during summer night operation at 15 degrees C and moderate gas velocity. Higher gas velocities facilitate rapidly moving adsorption in packed beds, quickly maximizing CO2 capture even at 50% humidity, but they result in rapid and uniform H2O accumulation that significantly increases regeneration energy. Conversely, in winter conditions, lower temperatures reduce the absolute H2O content in the air despite high relative humidity (e.g., 88%), slowing the rate of H2O adsorption throughout the second half of the packed bed, thus preventing premature saturation of the entire packed bed with H2O, allowing it to function effectively without immediate moisture overload.

Magnesium is a valuable industrial metal prized for its strength and reactivity. Traditionally, magnesium was extracted from seawater and brines. However, to meet the rising global demand, it is now primarily sourced from mineral deposits. This shift has sparked renewed interest in extracting magnesium from non-saline sources, including carbonates, silicates, halides, oxides, and hydroxides. This review examines the extraction technologies currently used for these mineral-based resources, including pyrometallurgical, hydrometallurgical, and electrometallurgical methods. Each method is assessed based on the reactions involved in the transformation, operational principles, efficiency, and energy requirements. The review emphasizes the importance of mineral pretreatment—thermal, mechanical, and chemical—in improving magnesium recovery, especially from refractory silicates. By summarizing recent advancements and process innovations, the review aims to inform future research and industrial practices, and support the development of sustainable, cost-effective, and scalable magnesium extraction strategies.

Primary and remedial cementing are critical in well construction to ensure zonal isolation and structural support. In horizontal or tilted wellbores, gravity-driven exchange flows, caused by density differences between drilling mud and cement slurry, can occur and result in stratified layers, weak spots, or voids, compromising cement quality. These challenges intensify during complex procedures such as rotating-while-cementing or operational pauses, where fluid redistribution occurs. Our study numerically examines immiscible exchange flows in near-horizontal pipes with axial rotation, modeling rotating-while-cementing conditions. A heavier displacing fluid occupies the upper pipe section, while a lighter fluid fills the lower section, creating a density-unstable configuration. Simulations assess the effects of rotational speed, density differences, and pipe inclination. Our results reveal predominantly counter-current stratified flows, with increased rotational speed amplifying interfacial instabilities and kinking waves but reducing displacing fluid frontal velocity. Conversely, greater density differences and inclinations away from horizontal affect exchange flows by increasing interfacial frontal velocities.

Pyrochlore, the primary mineral in niobium-bearing ores, generates diverse surface terminations during comminution, which can influence subsequent froth flotation. Using density functional theory (DFT) simulations, we evaluated the stability of all possible low-index pyrochlore surface terminations and analyzed their interactions with water and amine collectors. The simulations revealed that oxygen-terminated surfaces are more stable than metal-exposed ones. We also examined hydration behavior, which precedes collector interaction during flotation. Oxygen-terminated surfaces readily undergo hydroxylation, forming strong covalent bonds and dense hydration layers, while metal-terminated surfaces exhibit weaker hydrogen bonding and greater hydrophobicity. To simulate pH-dependent flotation conditions, we investigated the adsorption of neutral and protonated amines on hydroxylated (hydrophilic) and bare (hydrophobic) surfaces. Importantly, this study is the first to explicitly consider twin surfaces-the metastable counterparts of thermodynamically favored planes that are generated by mechanical breakage-and to reveal their distinct surface terminations and reactivity. Contrary to the prevailing assumption that Nb-N bonding dominates, our results revealed multiple adsorption mechanisms. Notably, hydrophilic surfaces exhibited enhanced adsorption, especially in the presence of protonated collectors. These results emphasize the importance of considering termination-specific adsorption pathways and collector speciation when designing effective pyrochlore reagents. Elucidating these surface-dependent interactions provides new insights for the development of selective reagents.

The marine sector is under increasing pressure to reduce greenhouse gas (GHG) emissions while maintaining fuel operability in cold climates. This study presents a new sensing technique to overcome the limitations of conventional cloud point (CP) measurements by combining fast monodirectional cooling (FMC) with digital image analysis, providing improved accuracy and reproducibility for marine biofuel blends. To support the freeze-tolerant integration of renewable fuels into fossil-based matrices, two blending strategies were tested with this newly developed cell. The first involves blending Arctic diesel and marine gas oil (MGO) with renewable components such as hydrotreated vegetable oil (HVO) and fatty acid methyl ester (FAME)-based biodiesel. While HVO effectively lowers CP and improves cold flow, biodiesel tends to increase CP due to early crystallization of saturated FAMEs. Notably, MGO-HVO blends exhibited a nonmonotonic CP trend, with some blends unexpectedly reducing the CP below that of either of the individual fuels, suggesting synergistic molecular interactions. The second strategy addresses the cold flow limitations of biodiesel by blending it with Jet A-1, a drop-in fuel known for its favorable low-temperature properties. However, even at high Jet A-1 concentrations, CP levels remained high due to persistent FAME crystallization. These findings highlight the importance of tailored blending strategies to address decarbonization goals with reliable cold weather performance, and provide practical guidance for formulating winter-grade marine fuels that meet both environmental and operational requirements.

Asbestos tailings represent a historical liability in many countries. Canada aims at transforming this industrial legacy into an opportunity to both mitigate the environmental footprint and recover critical (such as magnesium, nickel, chromium, and cobalt) and strategic metals, which represent significant economic development potential. This study aimed to investigate the recovery of critical and strategic metals (CSMs) from asbestos tailings using hydrochloric (HCl) acid leaching, with acid concentration (2–12 mol/L), leaching temperature (20–90 °C), and solid–liquid ratio (10–40%) as key process parameters. The tailing samples studied is composed mostly of chrysotile and lizardite. It contains about 40% magnesium (as its oxide MgO) and nickel and chromium showing contents 52 and 60 times higher than their respective average crustal abundances (Clarke values). Iron content is 8.7% (expressed as its ferric oxide Fe2O3). To optimize key factors influencing the leaching process, a statistical experimental design was employed. The designed leaching experiments were subsequently performed, and results were used to define leaching conditions aiming at maximizing Mg and Ni recoveries while minimizing iron contamination using response surface methodology (RSM) based on the central composite design (CCD). A quadratic polynomial model was developed to describe the relationship between the process parameters and metal recoveries. Among the tested effects of acid concentration, temperature, and pulp density on magnesium recovery, the modeling indicated that both hydrochloric acid concentration and leaching temperature significantly enhanced metal recovery, whereas increasing pulp density had a negative effect at low temperature. The empirical mathematical model derived from the experimental data, accounting for the uncertainties on chemical data, indicated that high magnesium recovery was achieved at 90 °C, with 10–12 N hydrochloric acid and a solid-to-liquid ratio of 33.6–40%. These findings reveal the potential for the recovery of critical and strategic metals, both in terms of efficiency and economic viability.

Jet penetration into soft gels is essential for optimising fluid delivery in medical therapies, biomedical engineering, and soft robotics. In this work, we visualise the jet flow of a Newtonian fluid into a soft viscoplastic gel using camera imaging and time-resolved tomographic particle image velocimetry (PIV) systems. The flow is primarily governed by the Reynolds number ( $Re = 350-5000$ ) and the effective viscosity ratio ( $m$ up to 22). We observe three flow regimes – mixing, jellyfish, and fingering – with transitions between them quantified in the $Re-m$ plane. An experimentally informed, systematic, practical, semi-analytical modelling framework is developed to estimate jet penetration depth over time, incorporating PIV results and an approximate functional decomposition approach to describe the velocity distribution and Reynolds stress contributions. The model provides reasonable estimations across all three regimes.

This study investigates the underlying mechanisms of active transverse mixing in dilute magnetic colloidal suspensions in microchannels, focusing on the interplay between the Kelvin Body Force (KBF) and spin-up flow under a rotating magnetic field (RMF). By studying the effects of KBF-induced flow on mixing, we identify the KBF as the dominant force that generates strong transverse motion, which significantly enhances the transverse mixing of scalar and nanoparticles. Using a Y-shaped microchannel model with one-sided injection of magnetic nanoparticles (MNPs), we show how the KBF disrupts the axial flow pattern, thereby promoting rapid mixing and reducing scalar field segregation. In comparison, the spin-up flow shows limited influence, suggesting the clear advantage of the KBF in optimizing mixing efficiency. These results highlight the potential of tuning RMF parameters to maximize KBF-driven mixing in microfluidic applications. On the other hand, further investigation of spin-up flow in the cluster regime could improve our understanding of the dynamics of KBF-driven mixing and provide new insights for microfluidic reactor design.

Sandwich packings are innovative separating column internals based on a periodic arrangement of two conventional structured packings with different geometrical surface areas. They are operated with partially flooded layers to intensify phase interactions and enhance mass transfer. The application of sandwich packings in absorption and distillation processes requires detailed understanding of the gas-liquid mass transfer phenomena in the individual layers. For this reason, we carried out an experimental investigation of CO2 desorption and developed an additive approach to process the measured data. On this basis, liquid-side mass transfer correlations for the flow patterns in the flooded packings sections were derived. The novel additive approach together with the developed correlations allows accurate prediction of the liquid-side mass transfer in sandwich packings.

Marinized bubbling fluidized beds show potential for reducing ship exhaust emissions, but their performance is hampered by the unstable marine environment, which affects their hydrodynamic stability. This study addresses the challenge of roll-induced maldistribution by testing different geometric strategies of bed internals to improve operational resilience. Direct visualization techniques (including digital image analysis and particle image velocimetry) were used to investigate the hydrodynamics and stability of bubbling fluidized beds under various configurations in pseudo-2D vertical, inclined, and rolling conditions. Internal designs, such as rhombic and herringbone patterns, and vertical baffle arrays, significantly shield the beds from gas maldistribution and provide stable fluidization comparable to conventional aboveground setups. The rhombic internals achieved up to 93 % of the stability of classical vertical configurations without internals, while the herringbone reached 60 % and the vertical baffles reached 55 %. These configurations mitigate hydrodynamic fluctuations due to oscillations, improving operational reliability to effectively reduce emissions in marine environments.

Adsorption of carbon dioxide and other gases on a novel acetate functionalized silica adsorbent under various conditions is investigated experimentally and theoretically by grand-canonical Monte Carlo (GCMC) simulations. The acetate functional group has the capability to interact with the carbon atoms in CO2 molecules due to the electron-donating properties of the carbonyl and ether groups. However, the acetate functional group has not yet been examined for CO2 adsorption on silica. Adsorption of CO2, CH4, N2, and H2 was measured experimentally in the temperature range of 253-373 K and pressure range of 0-100 kPa. CO2 showed significantly higher adsorption compared to other gases with maximum adsorption of ca. 32 cc/gr at standard condition (STP) at a pressure of 100 kPa and a temperature of 253 K. The recorded adsorption data could be fitted by Freundlich isotherms, indicating heterogeneous adsorption sites. To better understand the heterogeneous adsorption sites, GCMC simulations were used to examine the effects of pore size, temperature, pressure, concentration of functional groups in the silica matrix, and competitive adsorption. The GCMC data was in good agreement with the experimental data and suggested the oxygen-containing moieties (i.e., carbonyl and ether groups) on the acetate group as the adsorption sites. These sites displayed high Lewis acid-base interaction with the CO2 molecules. The GCMC data indicated selective adsorption of CO2 over N2 and a CO2/N2 binary gas mixture selectivity of 20 for a 10/90 CO2/N2 feed. To the best of our knowledge, this is the first report on the experimental adsorption of CO2 over acetate functionalized silica adsorbent coupled with an investigation of the adsorption sites through GCMC simulations.

Understanding and tuning the electrochemical stability window (ECW) of ionic liquids (ILs) are essential for advancing energy storage technologies. In this study, density functional theory combined with the thermodynamic cycle method is employed to systematically investigate the ECWs of imidazolium-based cations paired with a range of fluorinated and chlorinated anions with potentials referenced to an aluminum electrode. A broad set of cation structures, including alkyl, methoxy-ethoxy, vinyl, and alkyl-bridged derivatives, is explored alongside common and hydrogen fluoride-containing anions, [F(HF)n]- (n = 0 - 3). The results show that while simple alkyl substitution has minimal redox impact, electron-donating and π-conjugated groups lower oxidation potentials via HOMO delocalization. Fluorinated anions confer high redox stability, whereas HF-containing anions limit both the oxidative and reductive boundaries. Notably, [im+-C3-im]+[BF4]- presents the widest ECW (5.813 V), while HF-containing anions yield narrower ECWs due to the coexistence of [F]- and [F(HF)]- entities. Accurate ECW estimation further requires proper consideration of anion redox pathways as the choice of reaction mechanisms strongly influences predicted stability limits. Comparative analysis with the HOMO-LUMO and adiabatic AIE-AEA methods confirms that the thermodynamic cycle approach delivers superior accuracy while remaining computationally efficient, making it well-suited for high-throughput screening. Furthermore, the solvent dielectric constant is found to significantly modulate redox boundaries, emphasizing the importance of solvation effects in predictive modeling. These insights provide a robust foundation for the design of ILs with tailored electrochemical performance in high-voltage rechargeable batteries.