Study On The Transport Of Nanoparticles In Porous Media

Nanoparticles will inevitably be released into the natural environment throughout their life cycle.Once the nanoparticles enter the environment,they will directly or indirectly threaten ecological safety as well as human health.To assess the environmental risk of nanoparticles and facilitate the successful implementation of nanoparticles’ pollution management in the future,it is necessary to understand the transport of nanoparticles in porous media.In this study,a combination of laboratory column test and numerical simulation was used.Quartz sand media,limestone media,and dual-porosity media were taken as porous media used to simulate natural soil environment,and the transport of different nanoparticles in saturated porous media was investigated by considering factors such as media size,nanoparticle surface groups,ionic strength,flow velocity,and the presence of geotextiles.The main findings are as follows:(1)In saturated quartz sand media,the mass balance(MB)of nano-polystyrene plastics(PS)decreased from 99% to 91% as the average particle size of the media decreased from 0.15 cm to 0.03 cm;the modification of surface amino group made the mass balance of nanopolystyrene plastic decreased from 92% to 20%;the modification of surface carboxyl group made the mass balance of nano-polystyrene plastic increased from 92% to 96%;the mass balance of nano-polystyrene plastic decreased from 92% to 10% as the ionic strength increased;with the increase of flow rate,the mass balance of nano-polystyrene plastic increased;the presence of geotextile made the penetration curve of nano-polystyrene plastic wider and the maximum outflow concentration decreased.(2)In saturated limestone media,the modification of surface amino groups increased the mass balance of nano-polystyrene plastics from 6% to 24%;the modification of surface carboxyl groups increased the transport of nano-polystyrene plastics slightly;there was no significant difference in the transport of nano-polystyrene plastics in saturated limestone media with different ionic strengths;as the flow rate increased from 1.4 m L/min to 4.2 m L/min,the mass balance of nano-polystyrene plastics increased from 2% to 11%;the penetration curve of polystyrene nanoplastics in the presence of geotextile was wider and the maximum efflux concentration was lower;the transport ability of polystyrene nanoplastics in saturated limestone media was much lower than its transport ability in saturated quartz sand media.(3)In the saturated dual-porosity media,the modification of surface amino groups reduced the mass balance of nano-polystyrene plastic from 59%(with surface carboxyl modification)to 49%;with the increase of ionic strength,the mass balance of nanopolystyrene plastic decreased from 54% to 49%;with the increase of flow rate from 1.4m L/min to 4.2 m L/min,the mass balance of nano-polystyrene plastic increased from 42% to62%;the presence of geotextile reduced the transport of polystyrene nanoplastics in dualporosity media and led to a delay of polystyrene nanoplastics breakthrough.(4)In the saturated dual-porosity media,the mass balance of titanium dioxide nanoparticles decreased from 41% to 30% as the ionic strength increased from 0.1 mmol/L to25 mmol/L;the mass balance of titanium dioxide nanoparticles increased from 20% to 41%as the flow rate increased from 1.4 m L/min to 3.6 m L/min;And the presence of geotextile could increase titanium dioxide nanoparticles retention and lead to a delay of titanium dioxide nanoparticles breakthrough.