Friction characteristics are critical mechanical properties of clay, playing a pivotal role in the structural stability of cohesive soils. In this study, molecular dynamics simulations were employed to investigate the shear behavior of undrained montmorillonite (MMT) nanopores with varying surface charges and interlayer cations (Na+, K+, Ca2+), subjected to different normal loads and sliding velocities. Consistent with previous findings, our results confirm that shear stress increases with normal load. However, the normal load-shear stress curves reveal two distinct linear regions, indicating segmented friction behavior. Remarkably, the friction coefficient declines sharply beyond a critical pressure point, ranging from 5 to 7.5 GPa, while cohesion follows an inverse trend. The elevated friction coefficient at lower pressures is attributed to the enhanced formation of hydrogen bonds and concomitant changes in density distribution. Furthermore, shear strength was observed to increase with sliding velocities, normal loads, and surface charges, with Na-MMT exhibiting superior shear strength compared to KMMT and Ca-MMT. Interestingly, the friction coefficient shows a slight decrease with increasing surface charge, while ion type exerts a minimal effect. In contrast, cohesion is predominantly influenced by surface charge and remains largely unaffected by ion type, except under extreme pressures and velocities.

Hazardous alkylphenol wastes (HAPW) are a class of organic semisolid waste characterized by large production, complex composition and difficulties associated with recycling. Their generation and disposal lead to significantly environmental issues, including water and soil pollution, and present a substantial industrial challenge. To address these issues, a sustainable, low-carbon strategy for the high-value utilization of HAPW has been proposed. We take HAPW as a compatibilizer in the production of epoxy asphalt for road construction materials. Experimental results show that the HAPW-based epoxy asphalt containing 19.5 wt% HAPW exhibited optimal mechanical properties (tensile strength: 4.16 MPa; elongation at break: 164.92 %), exceeding industrial standards and outperforming epoxy asphalt produced using commercial cardanol through conventional processes. With a detailed molecular dynamics simulation, it is found that the HAPW plays two key roles in enhancing the interactions between epoxy resins and asphalt: (i) HAPW generates numerous hydrogen bonds with both asphalt and epoxy resin phases, strengthening noncovalent interactions and improving interfacial miscibility between the two phases. (ii) HAPW could react with the epoxy resin through the phenolic hydroxyl group, which further improves the interactions between epoxy resin and asphalt. This approach facilitates the treatment of hazardous organic waste in an environmentally sustainable and low-carbon way, enabling the recovery and repurposing of organic waste into high-valued products. Consequently, it promotes the resource utilization of industrial wastes while simultaneously contributing to a reduction in carbon emissions.

The effect of several prevalent cations (including Na+, K+, Mg2+, Ca2+, Al3+, and Fe3+) on the adsorption of monochlorobenzene (MCB) onto bentonite was investigated at the coexistence of nonionic surfactant Tween 80 (T80) in surfactant-enhanced remediation (SER). They are all favorable for MCB and T80 adsorption, especially Mg2+ and Ca2+. Adsorption of MCB is strongly depended on T80 micelles. When its concentration exceeds the solubility, MCB is easier to bind with T80 micelles and be adsorbed by bentonite. Acidic environment can facilitate MCB and T80 adsorption, but the effect of cations on the adsorption is most significant under alkaline conditions. Adsorption capacity of MCB increases first followed by a slight decrease with increasing cations concentrations. The maximum adsorption rate of MCB determined is about 68.4% in a solution containing Mg2+ in the isothermal adsorption of MCB, while it is only 6.8% in a cation -free solution. Various characterizations showed that cations mainly changed the repulsion between bentonite particles and T80 micelles and the agglomeration and structure of bentonite, thus affecting the adsorption of MCB and T80 micelles. Our research demonstrated the nonnegligible promotion of MCB adsorption on bentonite by cations and acidic environment, which will adversely affect SER efficiency.