On the hysteresis loop and equilibrium transition in slit-shaped ink-bottle pores

Reclaiming Selenium from Water Using Aluminum-Modified Biochar: Adsorption Behaviors, Mechanisms, and Effects on Growth of Wheat Seedlings

Although selenium is an essential nutrient, its contamination in water poses serious risks to human health and ecosystems. In this study, aluminum-modified bamboo biochar (Al-BC) was developed to reclaim Se(VI) from water. Compared to pristine biochar (BC), Al-BC had a larger specific surface area (176 m2/g) and pore volume (0.180 cm³/g). The modification, achieved by loading AlOOH and Al2O3 particles onto the surface, enabled Al-BC to achieve a maximum adsorption capacity of 37.6 mg/g for Se(VI) within 2 hours and remove 99.6% of Se(VI) across a pH range of 3-10. The main adsorption mechanism of Se(VI) involved electrostatic attraction, forming outer-sphere complexes between Se(VI) and AlOOH sites on the biochar. The bioavailability of Se sorbed on the spent biochar (Al-BC-Se) was thus evaluated. It was discovered that Al-BC-Se successfully released Se(VI), which impacted the growth of wheat seedlings. The Se content reached 134 μg/g dry weight (DW) in wheat shoots and 638 μg/g DW in roots, significantly exceeding normal selenium content (<40 μg/g DW). By successfully applying the modified biochar to capture selenium from water through adsorption and then reusing it as an essential nutrient in soil, this study suggests the promising feasibility of the "removal-collection-reuse" approach for the circular economy of selenium in wastewater.

Sequential N2 Adsorption by the Nanopore Entrance Filling Scheme in Nanopores of Carbon Nanotubes

The adsorption dynamics and mechanism of nitrogen molecules in 1-7 nm carbon nanotubes (CNTs) at 77 K were investigated by experiments and molecular dynamics simulations. The adsorbed nitrogen amount rapidly increased in 7 nm CNTs, while it gradually increased in 1 and 3 nm CNTs. The gradual increase in 3 nm CNTs was unexpected because of the presence of sufficient adsorption sites and the weak adsorption potential of nitrogen. The molecular dynamics simulations indicated that molecules were condensed in the entrance of nanopores after monolayer adsorption in 3 nm CNTs and monolayer and bilayer adsorption in 5 nm CNTs, called nanopore entrance filling. The proposed adsorption mechanism of nitrogen molecules in CNT nanopores is as follows: first, layer-by-layer adsorption occurs on monolayer sites, followed by preferential adsorption at the nanopore entrance. Consequently, preadsorbed molecules form a fluidic pore neck similar to an ink-bottle pore. Then, newly adsorbed molecules are condensed on the fluidic pore neck, and condensed molecules in the nanopore entrance finally move into the inner part of the nanopore. The proposed sequential adsorption mechanism via nanopore entrance filling without pore blocking starkly differs from micropore filling in micropores and layer-by-layer adsorption associated with capillary condensation in mesopores.

The characteristics of coalbed water and coal in a coal seam situated in the Red River Basin, Vietnam

An in-depth understanding of the hydrogeochemical characteristics of coal mines is helpful in establishing an effective and successful exploration program of coalbed methane (CBM). This study provides a comprehensive analysis of hydrogeological characteristics, characteristics of coalbed water, and characteristics of the coal sample from a coal seam located in the Red River Basin (RRB). These physicochemical characteristics along with the microbial composition of coalbed water were critically analyzed. A high concentration of chloride and sodium was found in the coalbed water, presumably due to the coal mine's stratigraphic association with marine or marine-transitional beds. A correlation between the occurrence of microbes and the chemical components in the coalbed water was established. The characteristics of the coal were systematically analyzed, including proximate, ultimate, and petrographic analyses. Based on the coal macerals, coal rank is classified as low-rank (sub-bituminous) with a vitrinite reflectance (R_{o, max}) of 0.36%, suggesting that this type of low-rank coal is favorable for biogenic methane generation. Pore structures and pore types were characterized using different methods, including low-temperature nitrogen adsorption/desorption (LTNA), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM). Coal from the study area has microporous and macroporous features. Pore types of the coal were also characterized using SEM. The primary genetic pore types of the Red River coal include plant tissue holes and blowholes.

Unexpected sorption-induced deformation of nanoporous glass: evidence for spatial rearrangement of adsorbed argon

Sorption of substances in pores generally results in a deformation of the porous matrix. The clarification of this effect is of particular importance for the recovery of methane and the geological storage of CO2. As a model system, we study the macroscopic deformation of nanoporous Vycor glass during the sorption of argon using capacitative measurements of the length change of the sample. Upon desorption we observe an unpredicted sharp contraction and re-expansion peak, which contains information on the draining mechanism of the porous sample. We have modified the theoretical model by Gor and Neimark1 to predict the sorption-induced deformation of (partly) filled porous samples. In this analysis, the contraction is attributed to a metastable or nonequilibrium configuration where a thin surface layer on the pore walls coexists with capillary bridges. Alternatively, pore blocking and cavitation during the draining of the polydisperse pore network can be at the origin of the deformation peak. The results are a substantial step toward a correlation between the spatial configuration of adsorbate, its interaction with the host material, and the resulting deformation.

Synthesis of aspirin-loaded polymer-silica composites and their release characteristics

This study describes a novel approach to the synthesis of polymer-drug-silica nanocomposites via encapsulation/isolation of drug molecules, introduced into the polymer matrix by the silica gel. For the first time, tetraethoxysilane (TEOS) gelation in the vapor phase of the acidic catalyst is presented as an efficient method to enter the silica gel nanoparticles into the polymer-aspirin conjugate. The conducted studies reveal that the internal structure of the polymer carrier is significantly reorganized after the embedding of aspirin molecules and the silica gel. The total porosity of the polymer-drug-silica nanocomposites and the molecular structure of the silica gel embedded in the system strongly depend on the conditions of the silica source transformation. Additionally, the release of the drug was fine-tuned by adapting the conditions of hydrolysis and condensation of the silica gel precursor. Finally, to prove the usefulness of the proposed synthesis, the controlled release of aspirin from the polymer-drug-silica nanocomposites is demonstrated.