title: Deposition and transport of functionalized carbon nanotubes in water-saturated sand columns.
abstract: Knowledge of the fate and transport of functionalized carbon nanotubes (CNTs) in porous media is crucial to understand their environmental impacts. In this study, laboratory column and modeling experiments were conducted to mechanistically compare the retention and transport of two types of functionalized CNTs (i.e., single-walled nanotubes and multi-walled nanotubes) in acid-cleaned, baked, and natural sand under unfavorable conditions. The CNTs were highly mobile in the acid-cleaned sand columns but showed little transport in the both natural and baked sand columns. In addition, the retention of the CNTs in the both baked and natural sand was strong and almost irreversible even after reverse, high-velocity, or surfactant flow flushing. Both experimental and modeling results showed that pH is one of the factors dominating CNT retention and transport in natural and baked sand. Retention of the functionalized CNTs in the natural and baked sand columns reduced dramatically when the system pH increased. Our results suggest that the retention and transport of the functionalized CNTs in natural sand porous media were mainly controlled by strong surface deposition through the electrostatic and/or hydrogen-bonding attractions between surface function groups of the CNTs and metal oxyhydroxide impurities on the sand surfaces.
authors.affiliation: Department of Agricultural and Biological Engineering, University of Florida, Gainesville, FL 32611-0570, USA.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Tian
authors.forename: Bin
authors.initials: B
authors.lastname: Gao
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.forename: Verónica L
authors.initials: VL
authors.lastname: Morales
authors.forename: Rafael Muñoz
authors.initials: RM
authors.lastname: Carpena
authors.forename: Qingguo
authors.initials: Q
authors.lastname: Huang
authors.forename: Liuyan
authors.initials: L
authors.lastname: Yang
mesh_terms: D000143:Acids; D000465:Algorithms; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D037742:Nanotubes, Carbon / Q000737:chemistry*; D016062:Porosity; D012822:Silicon Dioxide; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry; D014867:Water
chemical_list: D000143:Acids; D037742:Nanotubes, Carbon; D013501:Surface-Active Agents; D014867:Water; D012822:Silicon Dioxide