Aggregation and transport of rutile titanium dioxide nanoparticles with montmorillonite and diatomite in the presence of phosphate in porous sand

Cotransport of titanium dioxide nanoparticles and formaldehyde in saturated and unsaturated columns packed with quartz sand

“…Also, TiO 2 nanoparticles may facilitate the transport of coexisting pollutants and colloidal and biocolloidal particles through porous media (Cai et al, 2013(Cai et al, , 2014(Cai et al, , 2019G. Chen et al, 2012;Chowdhury et al, 2012;Fang et al, 2016;Guo et al, 2018;Xia et al, 2019). However, the cotransport of TiO 2 nanoparticles and FA in saturated and unsaturated porous media, to our knowledge, has not been investigated previously.…”

Sensitivity of the Transport of Plastic Nanoparticles to Typical Phosphates Associated with Ionic Strength and Solution pH

“…Generally, the d p was in the order of pH 10 < pH 7 with phosphate alone < pH 7 with both phosphate and NaCl. These results indicate that the charge screening under a higher IS and deprotonation of the surface hydroxyl groups under a higher pH [ 42 ] play important roles in the charge of the PNP surface.…”

“…Previous studies demonstrated the enhanced transport of colloids (e.g., graphene oxide, TiO 2 , and ZnO NPs) in the presence of abundant NaH 2 PO 4 or K 2 HPO 4 under a broad concentration range (e.g., 0.1–10 mM) [ 38 , 41 , 42 , 49 ]. In contrast, it was also evident that the transport of TiO 2 NPs would be reduced by increasing NaH 2 PO 4 when the phosphate was higher than 1 mM because of the compressed electrical double layer [ 50 ].…”

“…The zeta potentials of porous media became slightly more negative as phosphate concentration increased at low levels ( Tables S1 and S2 ). The enhanced transport that occurred in the presence of 0.25 mM NaH 2 PO 4 can be explained by the competition for retention sites and the increased electrostatic repulsion attributed to the absorption of the phosphates, which can function as proton donors for hydrogen bonding on the collector surface [ 38 , 41 , 42 ]. However, the charge screening and the compression of the electrical double layer under a higher IS became more significant, as demonstrated by the less negatively charged PNPs and the greater retention with increasing Na 2 HPO 4 and 1 mM NaH 2 PO 4 .…”

“…The presence of phosphates in the environment inevitably alters the composition of solution chemistry and the properties of the natural collector surface (i.e., soil grain surface), thus influencing colloid transport [ 40 ]. It has been demonstrated that phosphates can facilitate the transport of graphene oxide, nTiO 2 , and ZnO-NPs by increased electrostatic repulsion and the competition for retention sites between colloids and phosphates [ 38 , 41 , 42 ]. However, the influence of phosphates on the interaction of plastic particles and collector surfaces is still rarely studied and poorly understood.…”