Mobility of Multi-Walled Carbon Nanotubes in Unsaturated Porous Media
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Carbon nanotubes (CNTs) are engineered nanoparticles with unique properties. As a result, CNTs have been used in a wide range of commercial products including electronics, optical devices and for drug delivery leading to their disposal in the natural environment, but their transport mechanisms are poorly understood, so an improved understanding of CNT mobility is necessary to develop appropriate CNT disposal systems. In this study, a sand packed column was used to investigate the mobility of multi-walled carbon nanotubes (MWCNTs) in unsaturated porous media under unfavorable conditions for deposition. Experiments were designed to assess water content, flow rate and grain size effect on the mobility of MWCNTs. It was found that variation in water content had no effect on mobility of MWCNTs until 16% effective saturation. Thick water film, high flow rate and repulsive force between MWCNTs and porous media made MWCNTs highly mobile. At high flow rate MWCNTs were highly mobile and their mobility decreased with decreasing flow rate. At low flow rate, slow exchange between immobile and mobile water zones made MWCNTs less mobile and increased their deposition. In both sands (D50=300-150 µm) used in this study, MWCNTs were mobile and their mobility slightly decreased in finer sands due to increase in surface area and the number of depositional sites, as well as decrease in pore water velocity. In finer sands, effects of physical straining were not observed. A comparison of different aspect ratios for MWCNTs suggested that, the aspect ratio has low impact on mobility. An increase in size due to aggregation enhances physical straining and made hydrophobic MWCNTs less mobile in an unsaturated porous media.
Place, publisher, year, edition, pages
2012. , 45 p.
MWCNTs, Mobility, Porous media, Unsaturated, Water content, Flow rate.
Oceanography, Hydrology, Water Resources
IdentifiersURN: urn:nbn:se:uu:diva-179452OAI: oai:DiVA.org:uu-179452DiVA: diva2:544753
Master Programme in Earth Science
2012-06-14, Norrlands I, Geo-centrum, Uppsala, 20:47 (English)
UppsokLife Earth Science
Sharma, Prabhakar, Assitant Professor
Halldin, Sven, Professor