Abstract
Microplastics (MPs) have a great potential to adsorb heavy metal pollutants such as Pb2+ and the dissolved organic matter(DOM) in the aquatic environment will affect this adsorption behavior. In this study, batch experiments were performed to investigate the adsorption characteristics of Pb2+ onto polystyrene microplastics (PSMPs) in the presence and absence of HA(a kind of representative DOM). The adsorption kinetics of Pb2+ onto PSMPs conformed to the pseudo-second order model, and the adsorption isotherms were well fitted by the Langmuir model. With the increase of HA concentration, the Pb2+ adsorption onto PSMPs increased. Site energy distribution analysis showed that the presence of HA increased the adsorption site energy of PSMPs, thus enhancing the adsorption capacity for Pb2+. The fluorescence quenching analysis of HA further indicated that part of HA were adsorbed onto PSMPs, which increased additional binding sites on the surface of PSMPs. This was attributed to the abundant functional groups that could react with Pb2+ of HA. The pH and ionic strength of solution changed the structure of HA and the adsorption sites of PSMPs, which influenced the adsorption capacity of PSMPs for Pb2+. This study illustrated the effect of HA on the process and mechanism of Pb2+ adsorption onto PSMPs, and provided more information for the evaluation of environmental behavior and toxicological effects of microplastics in aquatic environments.
Humic Acid Promotes the Adsorption of Lead onto PSMPs: Site Energy Distribution Theory and Fluorescence Quenching Analysis
