Efficient removal and trace determination of chlorophenols from water using mixed hemi-/ad-micelle ionic liquid-coated magnetic graphene oxide and the adsorption mechanism

Mixed hemi-micelle magnetic solid phase extraction (MHMSPE) based on magnetic graphene oxide nanoparticles (MGONPs) and 1-hexadecyl-3-methylimidazolium bromide (C16mimBr) was developed for the efficient removal and trace determination of chlorophenols (CPs) in water. The adsorption mechanism of three kinds of CP was studied by applying computer simulation and zeta-potential studies. The large surface area and excellent adsorption capacity of the MGONPs after being coated with C16mimBr were exploited adequately in the MHMSPE process. Comparative studies showed that MGONPs were superior to Fe3O4 NPs as an adsorbent for the extraction of more CPs in MHMSPE. Zeta-potential data indicated that mixed hemi-micelles were formed when the amount of C16mimBr was adjusted from 1.8 to 12 mg (MGONPs = 30 mg). Different carbon chain lengths of IL-coated MGONPs were used in a further comparative study. Response surface methodology (RSM) based on Central Composite Design (CCD) was successfully applied to optimize the extraction parameters. Under optimum conditions, good linearity was obtained for the two target analytes, with correlation coefficients (R2) ranging from 0.9945 to 0.9975. The limits of detection (LODs) were in the range of 0.10–0.13 μg L−1. Finally, MGONPs-C16mimBr were successfully applied for both removal and trace determination of two CPs in environmental and tap water samples and the extraction recoveries for 1.00 μg of 2,4-DCP and 2,4,6-TCP were in the range of 78–82% and 87–90%, with high preconcentration factors (PFs) of 410 and 456, respectively.