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Influence Of Carboxymethyl Cellulose For The Transport Of Titanium Dioxide Nanoparticles In Clean Silica And Mineral-Coated Sands
Joo, S., S. R. AL-ABED, AND T. LUXTON. Influence Of Carboxymethyl Cellulose For The Transport Of Titanium Dioxide Nanoparticles In Clean Silica And Mineral-Coated Sands. J. Schnoor (ed.), ENVIRONMENTAL SCIENCE AND TECHNOLOGY. John Wiley & Sons, Ltd., Indianapolis, IN, 43(13):4954-4959, (2009).
The objectives of the current study are to: 1) determine changes in the transport properties of anatase TiO2 nanoparticles (ANTNPs) as solution chemistry changes, 2) understand the transport behavior of ANTNPs in systems that mimic natural environments, and 3) evaluate the mobility of ANTNPs in porous media (non-reactive and reactive).
The transport properties of titanium dioxide (anatase polymorph) nanoparticles encapsulated by carboxymethyl cellulose (CMC) were evaluated as a function of changes in the solute chemical properties in clean quartz, amorphous aluminum and iron hydroxide-coated sands. While pristine anatase TiO2 nanoparticles (ANTNPs) were completely immobile, the presence of CMC significantly enhanced their mobility. The magnitude of the surface charge exhibited by the CMC-coated anatase TiO2 nanoparticles (CMC-ANTNPs) significantly exceeded that of the uncoated ANTNPs, thereby leading to a negative surface charge over the pH range investigated (2-10). The mobility of CMC-ANTNPs was retarded by the presence of amorphous Fe and Al hydroxide, Na+ (30 mM), and Ca2+ (30 mM). Removal of CMC-ANTNPs was more significant in the presence of either Ca2+ or Fe-hydroxide. More retardation and incomplete breakthrough of the CMC-ANTNPs was observed in the mineral-coated sands. This is possibly due to an order of magnitude increase in the surface area of mineral- coated sands compared with the clean quartz sand grains and the potential for chelation between CMC bound to ANTNPs and Fe and Al hydroxides. Chemical-colloidal interactions such as chemicomplexation and ligand exchange were the most important factor controlling mobility of CMC-ANTNPs in mineral-coated sands.