Improved sorption of perfluorooctanoic acid on carbon nanotubes
hybridized by metal oxide nanoparticles
Received: 18 December 2017 /Accepted: 12 March 2018 /Published online: 22 March 2018
Springer-Verlag GmbH Germany, part of Springer Nature 2018
Multi-walled carbon nanotubes (MWCNTs) are often used as adsorbent because of their strong adsorption capacity. However,
due to the nature of MWCNTs, their ability to adsorb perfluorooctanoic acid (PFOA), a highly hydrophobic pollutant, is low. In
this study, MWCNTs were modified by three nano metal oxides (nano iron oxide, copper oxide, and zinc oxide). The pristine (as
the control) and modified MWCNTs were characterized by BET-N
, TEM, FTIR, XPS, and XRD, which showed that nano metal
oxides were well hybridized on the surface of MWCNTs. Radioactive-labeled PFOA (
C-PFOA) was used to quantify it at trace
level. Adsorption kinetics showed that intra-particle diffusion was the control step of PFOA adsorbing on metal oxides hybrid-
ized MWCNTs (MOHCNTs). Adsorption capacity of PFOA on the MOHCNTs was higher than that on the control due to
electrostatic and hydrophobic interactions. In addition, PFOA formed inner-sphere complexes with metal oxide nanoparticles via
ligand exchange. The alteration of PFOA adsorption capacity by increasing ionic strength was attributed to the aggregation
degree of MWCNTs, electrostatic shielding, and/or salting out effect. The presence of Ca
increased the adsorption, owing to not
only its higher electrostatic shielding ability than Na
but also its formation of bridge between PFOA and MOHCNTs. PFOA
adsorption on MOHCNTs strongly depended on medium pH value. These results provide an innovative approach for removing
trace PFOA from liquid medium.
Keywords Metal oxide nanoparticles
Carbon nanotubes have attracted much attention due to their
unique physical and chemical properties. Since their discovery
in the last century, a great deal of carbon nanotubes have been
applied in industries, especially in sensor, super battery, super
capacitor, and other fields (Liu et al. 2017a, b;Xuetal.2017).
Multi-walled carbon nanotubes (MWCNTs) are the represen-
tative material of excellent adsorbents because of their abun-
dant pore structure, large specific surface area, and ultra large
number of effective adsorption sites (Wang et al. 2009a, b).
Compared with that of other frequently used adsorbents,
the adsorption capacity of MWCNTs to many pollutants is
much better (Hosseini et al. 2011; Ghaedi et al. 2011a, b).
Previous studies have shown that the mechanisms of organic
compounds adsorption on carbon nanotubes are hydrophobic
interaction, π-π electron coupling stacking, π-π electron do-
nor acceptor (EDA), and so on (Arasteh et al. 2010;Chenetal.
2007, 2008). However, in practical production process, the
nozzle of MWCNTs is closed, which reduces the effective
surface area of MWCNTs. At the same time, the Van der
Waals force among MWCNTs causes them to reunite or twist
together (Yu et al. 2000). Moreover, MWCNTs also carry
some metal catalysts and amorphous carbon, which would
seriously weaken their adsorption properties (Yang et al.
2011). Therefore, MWCNTs should be treated by strong acid
Responsible editor: Guilherme L. Dotto
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s11356-018-1728-5) contains supplementary
material, which is available to authorized users.
* Chengliang Li
* Rong Ji
National Engineering Laboratory for Efficient Utilization of Soil and
Fertilizer Resources, College of Resources and Environment,
Shandong Agricultural University, Tai’an 271018, China
State Key Laboratory of Pollution Control and Resource Reuse,
School of the Environment, Nanjing University, Nanjing 210046,
Environmental Science and Pollution Research (2018) 25:15507–15517