Determining the mobility of polystyrene nano-plastic in saturated quartz Sand-Limestone porous media

To investigate the transport of microplastics in mixed porous media, column experiments are conducted to investigate polystyrene nanoparticles (PSNPs) transport in saturated quartz sand (QS)-limestone (LT) porous media under different physicochemical conditions. The two-dimensional (2D) surface of DLVO interaction energy is calculated to quantify the continuous change of the DLVO energy barrier with ionic strength and predict the critical ionic strengths (CIS). Experimental results suggest the mobility of PSNPs is inhibited as the mass fraction of LT and grain size of PSNPs increases. However, PSNPs mobility is enhanced with initial concentration and flow velocity. Compared with monovalent cation (Na+), divalent cation (Ca2+) has a stronger charge shielding effect. Significantly, there is a significant correlation between the transport kinetic parameters of PSNPs and the DLVO energy barrier, which suggests 2D surface of DLVO interaction energy has a great applied potential in the prediction of nano-plastics behaviors in the natural subsurface environment. (C) 2022 Elsevier Ltd. All rights reserved.