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Title: Facilitated transport of copper with hydroxyapatite nanoparticles in saturated sand

Author
item WANG, DENGJUN - Chinese Academy Of Sciences
item Bradford, Scott
item PARADELO, MARCOS - Universidad De Vigo
item PEIJNENBURG, WILLIE - National Institute For Public Health And The Environment (RIVM)
item ZHOU, DONGMEI - Chinese Academy Of Sciences

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2011
Publication Date: 12/20/2011
Citation: Wang, D., Bradford, S.A., Paradelo, M., Peijnenburg, W., Zhou, D. 2011. Facilitated transport of copper with hydroxyapatite nanoparticles in saturated sand. Soil Science Society of America Journal. 76(2):375-388.

Interpretive Summary: The transport of many groundwater contaminants is known to be facilitated by the presence of mobile soil particles in water. The objective of this research was to better quantify the influence of water velocity, solution pH, and iron oxide grain coatings on the facilitated transport of copper. Results indicated that copper transport was facilitated by soil particles at higher solution pH and in the presence of iron oxide grain coatings. This information will be of interest to scientists and engineers concerned with predicting the facilitated transport of contaminants in soils and aquifers.

Technical Abstract: Saturated packed column experiments were conducted to investigate the facilitated transport of Cu with hydroxyapatite nanoparticles (nHAP) at different pore water velocities (0.22-2.2 cm min–1), solution pH (6.2-9.0), and fraction of Fe oxide coating on grain surfaces (', 0-0.36). The facilitated transport of Cu by nHAP (nHAP-F Cu) was found to increase with decreasing nHAP retention and decreasing transport of dissolved Cu. In particular, nHAP-F Cu transport increased with pH (8.0, 8.5, and 9.0) and especially ' (0.07-0.36) but was less significant than dissolved Cu transport at lower pH (6.2 and 7.0). The transport of dissolved Cu decreased with pH and ' because of increased Cu sorption or precipitation. The nHAP retention decreased with velocity, pH, and decreasing '. Scanning electron microscope images revealed that nHAP retention at pH 7.0 was controlled by surface roughness and nHAP aggregation, whereas measured zeta potentials indicate that attachment of the nHAP occurred on the Fe oxide coated grains. The retention profiles of nHAP exhibited a hyperexponential shape,with greater retention in the section adjacent to the column inlet and rapidly decreasing retention with depth for all of the considered pH and ' conditions, but tended to become more exponential in shape at a higher velocity. These observations suggest that hyperexponential profiles are a general phenomenon of unfavorable attachment conditions that is sensitive to the hydrodynamics at the column inlet.