Contribution of air-water interface in removing PFAS from drinking water: Adsorption, stability, interaction and machine learning studies

Insights into PFAS environmental fate through computational chemistry: A review

Per- and polyfluoroalkyl substances (PFAS) are widely used chemicals that exhibit exceptional chemical and thermal stability. However, their resistance to degradation has led to their widespread environmental contamination. PFAS also negatively affect the environment and other organisms, highlighting the need for effective remediation methods to mitigate their presence and prevent further contamination. Computational chemistry methods, such as Density Functional Theory (DFT) and Molecular Dynamics (MD) offer valuable tools for studying PFAS and simulating their interactions with other molecules. This review explores how computational chemistry methods contribute to understanding and tackling PFAS in the environment. PFAS have been extensively studied using DFT and MD, each method offering unique advantages and computational limitations. MD simulates large macromolecules systems however it lacks the ability model chemical reactions, while DFT provides molecular insights however at a high computational cost. The integration of DFT with MD shows promise in predicting PFAS behavior in different environments. This work summarizes reported studies on PFAS compounds, focusing on adsorption, destruction, and bioaccumulation, highlighting contributions of computational methods while discussing the need for continued research. The findings emphasize the importance of computational chemistry in addressing PFAS contamination, guiding risk assessments, and informing future research and innovations in this field.

Molecular insights into the adsorption and penetration of oil droplets on hydrophobic membrane in membrane distillation

Membrane fouling induced by oily substances significantly constrains membrane distillation performance in treating hypersaline oily wastewater. Overcoming this challenge necessitates a heightened fundamental understanding of the oil fouling phenomenon. Herein, the adsorption and penetration mechanism of oil droplets on hydrophobic membranes in membrane distillation process was investigated at the molecular level. Our results demonstrated that the adsorption and penetration of oil droplets were divided into four stages, including the free stage, contact stage, spreading stage, and equilibrium stage. Due to the extensive non-polar surface distribution of the polytetrafluoroethylene (PTFE) membrane (comprising 95.41 %), the interaction between oil molecules and PTFE was primarily governed by van der Waals interaction. Continuous oil droplet membrane fouling model revealed that the new oil droplet molecules preferred to penetrate into membrane pores where oil droplets already existed. The penetration of resin (a component of medium-quality oil droplets) onto PTFE membrane pores required the "pre-paving" of light crude oil. Finally, the ΔE quantitative structure-activity relationships (QSAR) models were developed to evaluate the penetration mechanism of pollutant molecules on the PTFE membrane. This research provides new insights for improving sustainable membrane distillation technologies in treating saline oily wastewater.

Insights into the pH-dependent interactions of sulfadiazine antibiotic with soil particle models

Sulfonamide antibiotics (SAs) are widely used as a broad-spectrum antibiotic, leading to global concerns due to their potential soil accumulation and subsequent effects on ecosystems. SAs often exhibit remarkable environmental persistence, necessitating further investigation to uncover the ultimate destiny of these molecules. In this work, molecular dynamics simulations combined with complementary quantum chemistry calculations were employed to investigate the influence of pH on the behavior of sulfadiazine (SDZ, a typical SAs) in soil particle models (silica, one of the main components of soil). Meanwhile, the quantification of SDZ molecules aggregation potential onto silica was further extended. SDZ molecules tend to form a monolayer on the soil surface under acidic conditions while forming aggregated adsorption on the surface under neutral conditions. Due to the hydrophilicity of the silica, multiple hydration layers would form on its surface, hindering the further adsorption of SDZ molecules on its surface. The calculated soil-water partition coefficient (Psoil/water) of SDZ+ and SDZ were 9.01 and 7.02, respectively. The adsorption evaluation and mechanisms are useful in controlling the migration and transformation of SAs in the soil environment. These findings provide valuable insights into the interactions between SDZ and soil components, shedding light on its fate and transport in the environment.

Theoretical investigation of asphaltene molecules in crude oil viscoelasticity enhancement

Understanding the mechanisms of viscosity enhancement in crude oil phases is crucial for optimizing extraction and transportation processes. The enhanced viscosity mechanism of crude oil phase can be attributed to the intricate intermolecular interactions between asphaltene molecules. However, the molecular mechanism of the viscosification of asphaltene molecules in crude oil is not yet to be fully understood. In this work, molecular dynamics simulations were employed to investigate the dynamic behavior and viscosification mechanism of asphaltene molecules in complex oil phases. Research suggests that the neutral surface of asphaltenes features abundant positive and negative electrostatic potential regions, facilitating complementary pairing between these areas. This significantly augments electrostatic interactions among asphaltene molecules. Besides, the expansive nonpolar expanse on the normal asphaltene surface facilitates interactions between asphaltenes and crude oil molecules. This leads the crude oil viscosity of the system containing normal asphaltene is higher than that of the system containing acidic asphaltene under the same mass fraction (382 μ Pa·s for AAsp and 416 μ Pa·s for NAsp). This work provides insight into the viscosity enhancement mechanisms in crude oil phases and is helpful in improving the efficiency of crude oil extraction and transportation.