title: Sorption of humic acid to functionalized multi-walled carbon nanotubes.
abstract: The environmental behavior of carbon nanotubes (CNTs) and humic acid (HA) is a prominent concern, but effect of functionalities on their sorption is not clear yet. Functionalized multi-walled CNTs (MCNT15) and HA were used to study their sorption behavior. Sorption rate of HA to MCNTs was dominantly controlled by its diffusion from liquid-MCNT boundary to MCNT surfaces. The sorption is in the sequence of MCNT15 > MCNT15-NH2 > MCNT15-OH > MCNT15-COOH > MCNT15-Ni, which was dependent on their surface area and meso- and macro-pore volume. The functionalities of MCNTs regulated the sorption by affecting their interaction mechanisms (i.e., H-bonding, π-π, and hydrophobic interaction). Additionally, the amount of these functionalities on the MCNT surface reduced indirectly the sorption sites due to the steric hindrance. Electrostatic repulsion deceased the sorption of HA by MCNTs with increasing pH. This study demonstrated the importance of functionalities on the MCNTs for the sorption of HA.
authors.affiliation: School of Civil & Environmental Engineering, National International Cooperation Base on Environment and Energy, University of Science and Technology Beijing, 30 Xueyuan Road, 100083 Beijing, PR China.
authors.forename: Fei
authors.initials: F
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Yao
authors.forename: Huilun
authors.initials: H
authors.lastname: Chen
authors.forename: Zhengji
authors.initials: Z
authors.lastname: Yi
authors.forename: Baoshan
authors.initials: B
authors.lastname: Xing
mesh_terms: D000327:Adsorption; D006812:Humic Substances; D057927:Hydrophobic and Hydrophilic Interactions; D008956:Models, Chemical; D037742:Nanotubes, Carbon / Q000737:chemistry*; D055672:Static Electricity
chemical_list: D006812:Humic Substances; D037742:Nanotubes, Carbon
keywords: Functionalized multi-walled carbon nanotube; Humic acid; Sorption; pH