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Title: Facilitated transport of Cu with hydroxyapatite nanoparticles in saturated sand: Effects of solution ionic strength and composition

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

Submitted to: Water Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2011
Publication Date: 9/16/2011
Citation: Wang, D., Paradelo, M., Bradford, S.A., Peijnenburg, W.J., Chu, L., Zhou, D. 2011. Facilitated transport of Cu with hydroxyapatite nanoparticles in saturated sand: Effects of solution ionic strength and composition. Water Research. 45:5905-5915.

Interpretive Summary: The transport and fate of many groundwater contaminants, including viruses, are known to be facilitated by the presence of soil particles in water. The objective of this research was to better quantify the influence of water chemistry on the facilitated transport of copper, an agricultural contaminant. Results indicated that the facilitated transport of copper was strongly dependent on the water chemistry because it influences the amount of copper on mobile soil particles. This information will be of interest to scientists and engineers concerned with predicting the facilitated transport of contaminants in soils and aquifers.

Technical Abstract: Column experiments were conducted to investigate the facilitated transport of Cu in association with hydroxyapatite nanoparticles (nHAP) in water-saturated quartz sand at different solution concentrations of NaCl (0 to 100 mM) or CaCl2 (0.1 to 1.0 mM). The experimental breakthrough curves and retention profiles of nHAP were well described using a mathematical model that accounted for two kinetic retention sites. The retention coefficients for both sites increased with the ionic strength (IS) of a particular salt. However, the amount of nHAP retention was more sensitive to increases in the concentration of divalent Ca2+ than monovalent Na+. The effluent concentration of Cu that was associated with nHAP decreased significantly from 2.62 to 0.17 mg L-1 when NaCl increased from 0 to 100 mM, and from 1.58 to 0.16 mg L-1 when CaCl2 increased from 0.1 to 1.0 mM. These trends were due to enhanced retention of nHAP with changes in IS and ionic composition (IC) due to compression of the double layer thickness and reduction of the magnitude of the zeta potentials. Results indicate that the IS and IC had a strong influence on the co-transport behavior of contaminants with nHAP nanoparticles.