Synergistic effects of microplastic stability and adsorption rate on co-transport of microplastics and Pb under surfactant

Abstract

The emergence of microplastics (MPs) and their coexistence with heavy metal contaminants pose potential risks to the safety of the subsurface environment and public health. Therefore, it is crucial to explore the co-transport of MPs (polypropylene (PP), polyethylene (PE), polystyrene (PS), polymethyl methacrylate (PMMA) and polytetrafluoroethylene (PTFE)) with the heavy metal Pb(II) under the surfactant (sodium dodecyl benzene sulfonate (SDBS) and cetyltrimethylammonium bromide (CTAB)). In this study, column experiments were performed to investigate the co-transport of MPs and Pb(II) under surfactants. The co-transport mechanism of MPs with Pb(II) under surfactant was revealed by MPs stability and batch adsorption experiments. Experimental results showed that the presence of Pb(II) did not influence the mobility of MPs under CTAB and SDBS; however, MPs can affect the mobility of Pb(II). Specifically, under CTAB, the MPs increased the recovery rate of Pb(II) from 86% to 87.55%–97.55%. However, under SDBS, the high mobility of PS, PE, and PP inhibited the transport of Pb(II), and the recoveries of Pb(II) decreased from 79% to 57.53%–70.96%. The low mobility of PTFE and PMMA slightly promoted the transport of Pb(II). This could be attributed to two reasons. One aspect is the adsorption rate of Pb(II) by MPs, which plays a pivotal role in influencing the transport tendency of Pb(II) with MPs. Another aspect is the MPs stability, as greater stability enhances their dispersity and accelerates the adsorption rate of Pb(II), thereby facilitating the co-transport of Pb(II) with MPs. This study could provide valuable insights for assessing the transport and environmental impact of MPs and heavy metals in the presence of surfactants.