In order to select the optimum sorbent, six different kinds of
fatty acids (C6–C11) coated MNPs (including hexanoic acid, heptanoic
acid, octanoic acid, nonanoic acid, decanoic acid and undecanoic
acid) were used to investigate the adsorption ability.
Contrast test was also carried out with bare MNPs to determine
whether coatings can improve the adsorption efficiency. As can
be seen from Fig. 4, the adsorption efficiency was only about 36%
obtained with bare Fe3O4, the adsorption efficiency was improved
obviously when fatty acids coated MNPs were used as sorbents.
The result suggested that prepared MNPs were coated with fatty
acids successfully, the adsorption efficiency improved remarkably
with the increase of the chain length of coatings, no significant
improvement was obtained with alkyl chains of more than 10