Mitigation of asphalt volatile organic compounds emissions and health hazards using a TiO2-doped biochar composite: Microscopic and physiological insights

Abstract

This study developed a novel TiO₂-biochar composite as a modifier for functional asphalt coatings, achieving dual objectives of reducing VOCs emissions and mitigating cytotoxicity. The composite enhanced the softening point of the asphalt by approximately 6℃, reduced penetration and increased viscosity, thereby improving thermal stability and deformation resistance. Headspace-gas chromatography/mass spectrometry analysis confirmed an over 80 % reduction in VOC emissions, significantly reducing the release of harmful compounds like alkanes, cycloalkanes, and aromatic hydrocarbons, with the TiO₂-biochar modified and UV-exposed (TUBC) demonstrating the most pronounced effect. In vitro assays with human bronchial epithelial (BEAS-2B) cells showed the composite's cytotoxicity mitigation, with TUBC maintaining higher cell viability. The composite reduced ROS levels and the expression of cytotoxicity-associated biomarkers, suggesting a decrease in oxidative stress and inflammation. The high adsorption capacity of the composite and its photocatalytic degradation under UV light were identified as the key mechanisms for VOCs reduction. These findings collectively establish the TiO₂-biochar composite as a promising solution for asphalt for greener and safer asphalt applications, with potential for global environmental and health benefits. Future work will focus on further optimization and field validation to facilitate the adoption of this technology in infrastructure development worldwide.