ADSORPTION AND TRANSPORT PROPERTIES OF OXIDIZED MULTI-WALLED CARBON NANOTUBES

Carbon Nanotubes;transport;adsorption;clean bed filtration theory;Langmuir isotherm;Environmental Engineering

Yang, JinBall, William P. ;

Johns Hopkins University

关键词: Carbon Nanotubes;    transport;    adsorption;    clean bed filtration theory;    Langmuir isotherm;    Environmental Engineering;   

Others  :  https://jscholarship.library.jhu.edu/bitstream/handle/1774.2/37202/YANG-DISSERTATION-2014.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: JOHNS HOPKINS DSpace Repository

【 摘 要 】

ABSTRACTThis work established quantitative relationships between the surface composition of oxidized multi-walled carbon nanotubes (O-MWCNTs) and their adsorption and transport properties under varying aquatic chemical conditions.The effects of aquatic and surface chemistry on adsorption properties of O-MWCNTs for Zn2+ and Ni2+ were found consistent with expectations based on prior study, and were similar to aggregated and dispersed O-MWCNTs. New studies revealed, however, a significant effect of O-MWCNT solid-to-liquid ratio on measured adsorption isotherms. Although causes of such effects remain poorly understood, these results have important environmental implications.Transport of various O-MWCNTs through silica glass bead media was studied in columns under conditions of steady flow and pulse inputs. These studies revealed that O-MWCNT transport was affected by aquatic and surface chemistry in ways generally consistent with theories of electrostatic interactions between surfaces. Dissolved Ca2+ destabilized O-MWCNTs more than Na+ and diminished the impact of O-MWCNT surface chemistry on transport. NOM at low concentrations (<4 mg-C/L) significantly stabilized O-MWCNTs under most conditions, including high ionic strength (IS) (10 mM Ca2+ or 100 mM Na+).For experiments when clean-bed filtration (CBF) dominated removal (i.e., pulse-input injections), the mathematical relationship between kd and approach velocity followed expectations of interception theory and suggested that CNT length is the relevant length scale for prediction of collisions. For step-input conditions and considering both breakthrough curves and in-situ concentrations of O-MWCNTs, models based on CBF and incorporating additional mechanisms of straining, site-blocking, and multilayer deposition (ripening) were developed. Model sensitivity studies revealed that at IS < 40 mM, site-blocking and straining were more important to model than other mechanisms. At higher IS (≥ 60 mM), CBF and ripening were the only important mechanisms to consider. At IS = 40 mM, site-blocking, straining and ripening were all important to consider. Thus, IS is a key variable controlling which mechanisms must be considered when modeling O-MWCNT interactions with silica-based porous media.Overall, findings from this study have furthered the understanding of O-MWCNTs in terms of their transport and adsorption properties. The results and associated model development can improve interpretation and simulation of O-MWCNTs behavior in aquatic systems.