In situ anchor of multi-walled carbon nanotubes into iron-based metal-organic frameworks for enhanced adsorption of polycyclic aromatic hydrocarbons by magnetic solid-phase extraction

In this work, a magnetic MIL-101(γ-Fe2O3)/MWCNTs composite derived from iron-based metal-organic frameworks (MIL-101(Fe)) with multi-walled carbon nanotubes (MWCNTs) was successfully synthesized by low-temperature calcination process. The composite was used as adsorbent of magnetic solid-phase extraction (MSPE) for enhanced and rapid enrichment of trace polycyclic aromatic hydrocarbons (PAHs) based on its strong π-π stacking interactions, hydrophobic and cationic-π stacking interactions. The pseudo-second-order kinetic model and Langmuir isotherm model could be applied to better describe the adsorption process. The maximum adsorption capacity for PAHs reached 93.9 mg g-1. In addition, the conditions of MSPE process were optimized by orthogonal array design (OAD). A MSPE-HPLC-UV method was established for the sensitive detection of PAHs in real water samples and exhibited wide linear range (0.05-1000 µg L-1), low detection limits (0.02-0.41 µg L-1) and high enrichment factors (44-169) for PAHs. The relative standard deviations (RSD) ranged from 0.8 to 4.0% and 1.2-7.2% for single batch and batch-to-batch, respectively, and the spiked recoveries at two levels of 10 and 50 µg L-1 ranged from 79.6 to 112% with RSD of less than 5.81%. The unique MWCNTs in situ anchor MIL-101(γ-Fe2O3) composite with an outstanding PAHs adsorption performance provides a new opportunity and promising application in removal of toxic pollutants.