The temporal dynamics and statistical properties of air nanobubbles (NBs) in ultrapure water were investigated using nanoparticle tracking analysis (NTA). Statistical analysis of NB lifetimes reveals a strong correlation between bubble size and persistence. The mean bubble diameter increases rapidly from ~100 nm for short-lived detections to a characteristic size of about 500 nm for bubbles surviving longer than 40 frames, after which the size remains approximately constant. The population of detected NBs decreases monotonically with increasing lifetime, approximately following an exponential decay. Temporal analysis of the cumulative population yields a scaling exponent of ~0.6, indicating correlated fluctuations rather than independent stochastic events. Spatial observations confirm that NBs are separated by micrometer-scale distances, excluding direct bubble–bubble interactions. The combined statistical and imaging results support a picture in which NBs behave as dynamically coupled gas domains embedded within localized dissolved-gas microenvironments. The observed non-monotonic population dynamics cannot be explained by irreversible dissolution alone. Instead, the data indicate that NBs undergo continuous cycles of dissolution and replenishment. Within this framework, localized gas micro-domains, potentially exhibiting non-extensive behaviour, evolve dynamically and act as transient reservoirs. Upon bubble disappearance, these regions persist and diffuse, while their interaction may locally restore conditions for nucleation. This mechanism provides a physically consistent explanation for the observed cyclic behaviour and the apparent persistence of NBs beyond classical predictions.

The effect of high-gravity fields, generated by rapid rotation, on CO₂ adsorption in activated carbon beds is examined. Adsorption-desorption kinetics is monitored before, during, and after short rotation periods at up to 5000 rpm. Rotation induced a reproducible transient bump in headspace pressure, quantitatively attributed to a centrifugal free energy shift (~12.2 J/mol) that overfilled weak adsorption sites beyond their static equilibrium. The bump mechanism is described by fold catastrophe theory, with a critical angular velocity (ω_c = 3500 rpm) triggering a sudden transition to a high-occupancy branch. Post-rotation, constant-rate zero-order desorption from shallow sites overlapped with a slower pseudo-first-order adsorption process as deep, previously inaccessible pores became available, increasing CO₂ capacity by 2.5%. Kinetic modeling produced an apparent diffusivity of 1.2 × 10⁻⁵ m²/s and a structural accessibility time constant of ~25 h. Thermodynamic analysis showed that rotation improved the overall free energy of adsorption and altered entropy in a manner consistent with the observed adsorption-desorption sequence. These results demonstrate that rotational fields can enhance CO₂ uptake, modify kinetic pathways, and trigger threshold phenomena in porous adsorbents.

The temporal dynamics and statistical properties of air nanobubbles (NBs) in ultrapure water were investigated using nanoparticle tracking analysis (NTA). Statistical analysis of NB lifetimes reveals a strong correlation between bubble size and persistence. The mean bubble diameter increases rapidly from ~100 nm for short-lived detections to a characteristic size of about 500 nm for bubbles surviving longer than 40 frames, after which the size remains approximately constant. The population of detected NBs decreases monotonically with increasing lifetime, approximately following an exponential decay. Spatial observations show that NBs are separated by micrometer-scale distances, excluding direct bubble–bubble interactions. Temporal analysis of the cumulative population yields a scaling exponent of ~0.6, suggesting correlated activation of localized gas micro-domains rather than independent stochastic events. These findings support a physical picture in which NBs behave as long-lived gas domains embedded in a gas–solution continuum, undergoing continuous molecular exchange with their surrounding environment. The results are consistent with non-extensive thermodynamic descriptions, where NBs are treated as diffuse interfacial entities rather than classical gas phases with sharp boundaries. Within this framework, bubble stability arises from coupling between bubble volume and local dissolved gas concentration, enabling persistence far beyond classical predictions.

In situ and operando small-angle X-ray and neutron scattering (SAXS and SANS) have become powerful techniques for studying adsorption processes because they provide real-time information that traditional ex situ methods cannot capture. This review examines the use of these techniques in four major material groups: soft matter and polymers, carbon-based materials, biological systems and ceramics. Unlike conventional before-and-after characterization, in situ methods allow researchers to follow structural changes during adsorption as they happen, revealing adsorption kinetics, intermediate states and pore-filling mechanisms. Operando approaches further connect nanoscale structural evolution with overall adsorption performance, leading to deeper mechanistic understanding. Important developments include monitoring structural rearrangements in polymers during adsorption, studying sodium storage mechanisms in hard carbon anodes using combined small- and wide-angle neutron scattering, observing protein conformational changes at hydrated interfaces, and identifying organic functional groups in mesoporous ceramics in real time. SANS contrast variation, especially through hydrogen/deuterium substitution, allows selective visualization of different components in complex systems, while synchrotron SAXS enables kinetic studies with millisecond time resolution. Despite these advantages, several challenges remain, including model-dependent interpretation of scattering data, difficulties in separating real structural changes from contrast-related artifacts, limitations in accessible timescales and the technical complexity of isotopic labeling. Future research is expected to focus on improved contrast methods, machine learning-assisted data analysis, multimodal approaches combining scattering with spectroscopy or microscopy and the application of these techniques to more complex and disordered adsorbents such as activated carbons, coals and bio-based materials. Overall, this review summarizes current methodologies, compares adsorption-related structural changes across different materials and highlights both current limitations and future opportunities for in situ and operando SAS studies in adsorption research.

A novel method for quantifying tortuosity by analyzing the pressure distribution of gas within a rotating porous bed is presented. The method utilizes a custom-designed disc-shaped cell packed with activated carbon particles and subjected to a high-speed rotation of 5000 rpm under an equilibrium initial pressure of 5045 mbar CO₂. The theory related to this method is outlined. From the radial pressure distribution, the apparent tortuosity is estimated to be ~2.3. This value is independently validated using an extracted apparent diffusion coefficient of D_app = (9.7 ± 0.3) × 10⁻⁷ m²/s and a corresponding tortuosity of τ_app = 2.2 ± 0.8. The findings establish a new route for probing the interplay between pore geometry, gas transport, and adsorption phenomena under centrifugal forces.