Toward Sustainable Non-Emitting Asphalts: Understanding Diffusion–Adsorption Mechanisms of Hazardous Organic Compounds

Abstract

Advancing sustainable materials requires addressing their environmental impacts, particularly emissions. This study contributes to the development of sustainable, non-emitting asphalt by providing a detailed understanding of the diffusion and adsorption behaviors of hazardous organic compounds (HOCs) emitted from asphalt. Using molecular simulations and quantum analysis, it is investigated how the diffusion and adsorption characteristics of sulfur- and oxygen-containing HOCs change as aging progresses in asphalt. The results show that oxidation reduces the diffusion rate of HOCs and increases their adsorption energy. Dispersion forces and electrostatic attractions are key mechanisms stabilizing HOCs within the asphalt matrix. As oxidation progresses, hydrogen bonding and polar interactions between asphaltenes and highly polar HOCs become dominant. Among the asphalt components, asphaltenes, followed by resins, have the most significant impact on HOC binding. Additionally, non-aromatic HOCs exhibit higher diffusion rates than aromatic HOCs. These findings provide crucial insights into the emission mechanisms of asphalt over its service life and offer guidance for designing future, sustainable, emission-free asphalts. By reducing harmful emissions, this research contributes to pollution control, improved air quality, and the broader goal of sustainable pavement development.