Retention and release of black phosphorus nanoparticles in porous media under various physicochemical conditions

Authors: LIANG, YAN - GUANGXI UNIVERSITY; LIU, JINXING - GUANGXI UNIVERSITY; DONG, PENGCHENG - GUANGXI UNIVERSITY; QIN, YAN - GUANGXI UNIVERSITY; ZHANG, RUPIN - CHINESE ACADEMY OF SCIENCES; Bradford, Scott

Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2023
Publication Date: 7/21/2023
Citation: Liang, Y., Liu, J., Dong, P., Qin, Y., Zhang, R., Bradford, S.A. 2023. Retention and release of black phosphorus nanoparticles in porous media under various physicochemical conditions. Chemosphere. 339. Article 139604. https://doi.org/10.1016/j.chemosphere.2023.139604.
DOI: https://doi.org/10.1016/j.chemosphere.2023.139604

Interpretive Summary: Black phosphorus nanoparticles (BPNs) have a plate like structure with unique properties that are being exploited in many industrial processes and products. There is concern about potential adverse impacts of BPNs on ecosystem health, but the environmental fate of BPNs has not yet been reported in the literature. This study examines the fate of BPNs under various solution chemistry conditions and in sands of different size and surface roughness. Conditions and mechanisms that enhanced the mobility of BNPs were identified (e.g., lower ionic strength, higher pH, large sand sizes, and smoother sand). This information will be of interest to scientists, engineers, and government regulators that are concerned with the risks of BPNs in the environment, and industries that use them in manufacturing.

Technical Abstract: Black phosphorus nanosheets/nanoparticles (BPNs) are widely applied in many fields. However, the transport of BPNs in the subsurface still has not yet been reported and there is increasing concern about potential adverse impacts on ecosystems. Roles of median grain size and surface roughness, BPN concentration, and solution chemistries (pH, ionic strength, and cation types) on the retention and release of BPNs in column experiments were therefore investigated. The mobility of BPNs significantly increased with increasing grain size and decreasing surface roughness due to their influence on the mass transfer rate, number of deposition sites and retention capacity, and straining processes. Transport of BPNs was enhanced with an increase in pH and a decrease in ionic strength because of surface deprotonation and stronger repulsion that tends to reduce aggregation. The BPN transport was significantly sensitive to ionic strength, compared with other engineered nanoparticles. Additionally, charge heterogeneity and cation-bridging played a critical role in the retention of BPNs in the presence of divalent cations. Higher input concentrations increased the retention of BPNs, probably because collisions, aggregation at pore throat locations, and hydrodynamic bridging were more pronounced. Small fractions of BPNs can be released under decreasing IS and increasing pH due to the expansion of the electrical double layer and increased repulsion at convex roughness locations. A mathematical model that includes provisions for advective dispersive transport and time-dependent retention with blocking or ripening terms well described the retention and release of BPNs. These findings provide fundamental information that helps to understand the transport of BPNs in the subsurface environments.