Green construction of self-floating polysaccharide-based hydrogels with catalytic activity for efficient organic pollutants reduction.

This study employed an anionic heteropolysaccharide extracted from overgrown Enteromorpha and homopolysaccharide pullulan to fabricate a self-floating hydrogel by introducing bubble templates. Subsequently, green in-situ reduction and immobilization of silver nanoparticles (Ag NPs) in the hydrogel were successfully achieved without additional reducing agents. The heteropolysaccharide from Enteromorpha provides carboxyl and sulfate groups for Ag+ ions complexation, which is beneficial for the in-situ reduction of Ag NPs and inhibits their aggregation. The incorporation of bubble templates facilitates the creation of a hierarchical pore structure in the hydrogel, giving it self-floating properties for easy recycling, while the hierarchical network with rich anchor sites ensuring adequate traction for Ag NPs dispersion and stabilization. By adjusting polysaccharide content and using bubble templates, Ag NPs smaller than 10 nm can be obtained. The composite hydrogel exhibits tunable catalytic activity and excellent degradation towards Rhodamine B, Methyl Orange, and 4-Nitrophenol, with the normalized rate constant (knor) of 78.89, 59.08, and 30.42 min-1 g-1, respectively. Notably, the reduction efficiency remained above 98 % after 6 recycles with little leaching of Ag NPs, benefiting from its self-floating ability for easy recovery in practical applications.

Microscopic Understanding of Interfacial Performance and Antifoaming Mechanism of REP Type Block Polyether Nonionic Surfactants.

In many practical applications involving surfactants, achieving defoaming without affecting interfacial activity is a challenge. In this study, the antifoaming performance of REP-type block polymer nonionic surfactant C12EOmPOn was determined, and molecular dynamics simulation method was employed to investigate the molecular behaviors of surfactants at a gas/water interface, the detailed arrangement information of the different structural segments of the surfactant molecules and the inter-/intra-interactions between all the structural motifs in the interfacial layer were analyzed systematically, by which the antifoaming mechanisms of the surfactants were revealed. The results show that the EO and PO groups of REP-type polyether molecules are located in the aqueous phase near the interface, and the hydrophobic tails distribute separately, lying almost flat on the gas/water interface. The interaction between the same groups of EOs and POs is significantly stronger than with water. REP block polyethers with high polymerization degrees of EO and PO are more inclined to overlap into dense layers, resulting in the formation of aggregates resembling "oil lenses" spreading on the gas/water interface, which exerts a stronger antifoaming effect. This study provides a smart approach to obtaining efficient antifoaming performance at room temperature without adding other antifoam ingredients.

Adsorption Behaviors of Different Components of Shale Oil in Quartz Slits Studied by Molecular Simulation.

Understanding the adsorption state and molecular behavior of the diverse components of shale oil in shale slits is of critical importance for exploring novel enhanced shale oil recovery techniques, but it is hard to be achieved by experimental measurements. In this paper, molecular dynamics (MD) simulations are performed to quantitatively describe the microbehavior of shale oil mixtures containing different kinds of hydrocarbon components, including asphaltene, in quartz slits. The spatial distributions of all the presenting components are given, the interaction energy between the components and quartz is analyzed, and the diffusion coefficients of all the components are calculated. It was found that asphaltene molecules play a vitally important role in restricting the detachment and diffusion movement of all hydrocarbon components, which is actually a key problem limiting the recovery efficiency of shale oil. The effects of temperature, slit aperture, and the appearance of CO2 on the adsorption behavior of the different shale oil components are examined; the results suggest that the light and medium components are the fractions with the most potential in thermal exploitation, while injection of CO2 is beneficial for the extraction of all the components, especially the medium components. This work gives insights into the effect of asphaltene on shale oil recovery in quartz slits and might provide guidance on the utilization of thermal and CO2-enhanced enhanced oil recovery (EOR) techniques in shale oil production.

The construction of bio-inspired hierarchically porous graphene aerogel for efficiently organic pollutants absorption.

Three-dimensional graphene aerogel shows a wide application in many frontier domains, which have attracted extensive research interest owing to its large specific surface area and high porosity. However, it is still a great challenge to construct the ideal hierarchical pore structure while guaranteeing excellent absorption and mechanical performance. In this paper, inspired by the bio-based porous material, a hierarchical graphene aerogel with inter-connected micro-/nano-scale pore structure was constructed. The micro and nano-scale pores are generated by the bubble and nanoparticles (NPs) template, respectively. The resulting graphene aerogel (GA) presents low density, increased interfacial areas, high mechanical performance, and excellent absorption performance towards a mass of organic solvents. In combination with its high compressibility, a diverse organic solvent can be absorbed efficiently and recycled by extrusion conveniently. Besides, owing to the scattered hydrophilic sites of functional groups and NPs on the surface of GA-b/NP, it shows high adhesion properties for water droplets, thus presents great potential in high-efficiency fog collecting materials. In a word, the proposed approach presents a novel strategy for the construction of the hierarchical aerogel with light-weight and elasticity, as well as the achievement of efficient functionalization, which has great potential for the preparation of diverse functional composites.