Table 2.
Migration characteristics of NPs in porous media.
| NPs (size, nm) | Diameter of NPs (nm) | Solid phase | Aqueous phase | Key findings | Reference |
|---|---|---|---|---|---|
| Polystyrene with fullerene (C60) | 200 | Natural sea sand (average diameter 0.45 mm, porosity 44.88 %) | Artificial seawater (salinity 35 PSU) | NPs facilitated C60 transport through increased colloidal ζ-potential | (Dong et al., 2019b) |
| Functionalized polystyrene (carboxyl, sulfonic, amino) | 200 | Natural sea sand (average diameter 0.45 mm, porosity 44.88 %) | Artificial seawater (salinity 35 PSU) | Addition of humic acid significantly promoted the migration of NPs through enhanced steric repulsion | (Dong et al., 2019a) |
| Polystyrene with E. coli | 20, 200 | Quartz sand (diameter ranging from 0.3 to 0.425 mm, porosity 0.42) | NaCl (10, 50 mmol/L) and CaCl2 (1, 5 mmol/L) solutions | NPs increased bacterial transport at high ionic strength conditions. The adsorption of NPs on bacteria induced the repel effect that facilitated the migration of E. coli | (He et al., 2018) |
| Polystyrene with naphthalene | 121.9 | Quartz sand (average diameter 0.6 mm, porosity 0.44) | NaCl solution (0.5 5, 50 mmol/L) | Naphthalene decreased the mobility of NPs through charge-shielding | (Hu et al., 2020) |
| Polystyrene with sewage sludge | 187 | Soil | Water | NPs were detached jointly with organic matter from the sludge during the artificial rainfall | (Keller et al., 2020) |
| Aged polystyrene (UV or O3) | 487.3 | Loamy sand soil | Water | Greater mobility of aged NPs was the result of the surface oxidation, which increased surface charge negativity and hydrophilicity | (Liu et al., 2019c) |
| Polystyrene | 100 | Soil (45 % sand, 36 % silt, and 19 % clay) | Water | NPs enhanced the migration of non-polar and weakly-polar molecules (e.g., pyrene, 2,2’,4,4’-tetrabromodiphenyl ether) in soil, while did not affect the transport of polar molecules (e.g., bisphenol A) | (Liu et al., 2018) |
| Functionalized polystyrene (carboxyl, amino) | 50, 200 | Agriculture-impacted shallow sandy aquifer | Natural groundwater | The suspended organic matter increased both the particle stability and mobility, while the dissolved organic matter reduced both | (Song et al., 2019) |
| Carboxylate-modified polystyrene | 20, 200 | Quartz sand (with 0.5 % biochar/magnetic biochar addition) | NaCl solution (0.1 mmol/L) | Biochar/magnetic biochar amendment decreased the mobility of NPs | (Tong et al., 2020a) |
| Carboxylate-modified polystyrene | 20, 200 | Quartz sand (diameter ranging from 0.3 to 0.425 mm) | NaCl solution (5, 25 mmol/L) | Biochar decreased the mobility of NPs through the formation of heteroaggregates | (Tong et al., 2020b) |
| Polystyrene | 100 | Desert soil, red soil and black soil | NaCl (1, 5, 10, 20 mmol/L) and CaCl2 (1, 2, 5 mmol/L) solutions | Retention of NPs was positively correlated with Fe/Al oxides contents, and negatively correlated with soil pH | (Wu et al., 2020a) |