title: Suspending multi-walled carbon nanotubes by humic acids from a peat soil.
abstract: Suspension of the pristine and COOH-substituted multi-walled carbon nanotubes (P- and C-MWCNTs) with different outer diameters (ODs) by humic acids (HAs) from a peat soil was examined. Under shaking condition, MWCNTs were not suspended within 5 d. Without HAs, C-MWCNTs were slightly suspended by sonication within 16 h, but no suspension was observed for the pristine ones (P-MWCNTs). HAs greatly enhanced suspension of both P- and C-MWCNTs. The suspension enhancement was attributed to HA sorption, which increased electrostatic repulsion and steric hindrance between individual MWCNTs. Introduction of O-containing hydrophilic moieties to MWCNTs via HA sorption enhanced the interactions of their surfaces with water through H-bonding. Suspending capability of various MWCNTs on suspended mass concentration basis by four HAs showed inconsistent orders with the increasing or decreasing trend of their ODs. However, the suspended surface area concentrations of both P- and C-MWCNTs by individual HAs consistently followed an order of P8 > P30 > P50, and C8 > C30 > C50 (P and C, respectively, refer to P- and C-MWCNTs, and the numbers represent their ODs). These data implied that MWCNTs with smaller OD could be more strongly suspended by a given HA relative to those with larger OD under sonication condition.
authors.affiliation: Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, People's Republic of China.
authors.forename: Xinzhe
authors.initials: X
authors.lastname: Zhou
authors.forename: Liang
authors.initials: L
authors.lastname: Shu
authors.forename: Huibin
authors.initials: H
authors.lastname: Zhao
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Guo
authors.forename: Xilong
authors.initials: X
authors.lastname: Wang
authors.forename: Shu
authors.initials: S
authors.lastname: Tao
authors.forename: Baoshan
authors.initials: B
authors.lastname: Xing
mesh_terms: D006812:Humic Substances / Q000032:analysis*; D007700:Kinetics; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D016062:Porosity; D012987:Soil / Q000737:chemistry*; D055672:Static Electricity; D013499:Surface Properties; D013535:Suspensions
chemical_list: D006812:Humic Substances; D037742:Nanotubes, Carbon; D012987:Soil; D013535:Suspensions; D010100:Oxygen