Adsorptive removal and enrichment of perfluorooctanoic acid and perfluoroundecanoic acid in water using polyethylene terephthalate bottle waste-derived magnetic mesoporous carbon

A multifunctional magnetic mesoporous carbon derived from polyethylene terephthalate (PET) waste plastic bottles and acid mine drainage (AMD-mag@PET-MPC) was employed for the adsorptive removal of perfluorooctanoic acid (PFOA) and perfluoroundecanoic acid (PFUnDA) in water systems. Under optimised conditions, the equilibrium data were best described by the Langmuir isotherm model with maximum adsorption capacities of 356 and 225 mg g −1 for PFOA and PFUnDA, respectively. The kinetic data best fit the pseudo-second-order kinetic model, suggesting that chemisorption is involved. The thermodynamic data suggested the feasibility of the random and spontaneous nature of the adsorption process. The adsorption mechanism involves hydrogen bonding, π–π interactions and electrostatic interactions. The AMD-mag@PET-MPC adsorbent was further applied as the extraction phase in the magnetic solid phase extraction (MSPE) of PFOA and PFUnDA in surface water and wastewater samples. Under optimised conditions, the analytical characteristics, such as linear range (1.7–5000 and 0.6–5000 ng/L), with a correlation coefficient (R 2 ) above 0.99, were attained for both analytes. The limit of detection (LOD = 0.19–0.5 ng/L) and limit of quantification (LOQ = 0.6–1.7 ng/L) were achieved. The relative standard deviations (%RSD) for intraday and interday values were below 5%. The feasibility of the developed MSPE/UHPLC-MS/MS method for the analysis of PFOA and PFUnDA was assessed in real surface water and wastewater samples. The relative extraction recoveries ranging from 80–99% and 87%–105% were attained in wastewater and surface water.