Cotransport of titanium dioxide nanoparticles and formaldehyde in saturated and unsaturated columns packed with quartz sandCotransport of titanium dioxide nanoparticles and formaldehyde in saturated and unsaturated columns packed with quartz sand Peer-Reviewed Journal Publication Δημοσίευση σε Περιοδικό με Κριτές 2024-02-082023enLaboratory-scale experiments were conducted to investigate the simultaneous transport of titanium dioxide (TiO2) nanoparticles and formaldehyde (FA) in columns packed with quartz sand under water saturated and unsaturated flow conditions. The effects of interstitial velocity and solution ionic strength on the TiO2 and FA cotransport were examined. The experimental results indicated that substantial retention of TiO2 nanoparticles occurs in both saturated and unsaturated porous media. The solution ionic strength was found to have a noticeable effect on the retention of TiO2 nanoparticles in the packed columns. Moreover, the results from the TiO2 nanoparticle transport experiments in water-saturated packed columns suggested that the TiO2 nanoparticle mass recoveries increased with increasing flow rate. The results from the TiO2 nanoparticles and FA cotransport experiments in both water saturated and unsaturated packed columns did not reveal a distinct relationship between mass recoveries and flow rate. The transport of FA in both saturated and unsaturated packed columns was hindered in the presence of TiO2 nanoparticles, especially at high ionic strength. This work provides useful insights into fate and transport of TiO2 nanoparticles and FA in saturated and unsaturated porous media.C.V.C. received funding from the Partnership for Research and Innovation in the Mediterranean Area (PRIMA), under Grant Agreement no. 1923-InTheMED.http://creativecommons.org/licenses/by/4.0/Vadose Zone Journal221Chrysikopoulos_et_al_Vadose Zone J._22(1)_2023.pdfChania [Greece]Library of TUC2024-02-08application/pdf1.3 MBfree Chrysikopoulos Constantinos Χρυσικοπουλος Κωνσταντινος Fountouli Theodosia Φουντουλη Θεοδοσια Wiley TiO2 rutile nanoparticles Porous-media Ionic-strength Colloid transport Humic-acid