The co-transport behavior of polyacrylonitrile microplastics and aniline compounds in porous media

Aniline compounds (ACs) and microplastics (MPs) are emerging contaminants that frequently co-occur in industrial wastewater and soil-groundwater systems. However, their co-transport mechanisms and in particular the role of MPs as carriers to enhance ACs transport remain unclear. This study employs adsorption and column experiments to systematically analyze the adsorption characteristics and mechanisms of polyacrylonitrile microplastics (PANMPs) for aniline and p-chloroaniline. It also examines the effects of key parameters, such as flow rates, pH, and IS, on the transport behavior of ACs in the presence of MPs, thereby offering new insights into their environmental fate. The adsorption experiments revealed that the adsorption of MPs onto ACs follows a multilayer physical adsorption mechanism, with enhanced adsorption capacity observed at lower pH and higher ionic strength (IS). Column transport experiments demonstrated that PANMPs significantly promote ACs migration. Notably, pH and IS modulated the co-transport behavior by altering the adsorption affinity between MPs and ACs, thereby enhancing the disparity in their transport behavior. Furthermore, the greater mobility of PANMPs with increasing flow rates led to a greater extent of ACs transport in the sand column. These findings are of great significance for understanding the transport behavior and fate of MPs and ACs in soil-groundwater.