Extraction of three nitrophenols using polypyrrole-coated magnetic nanoparticles based on anion exchange process

• Fe3O4@polypyrole (PPy) NPs were synthesized via oxidative polymerization of pyrrole.
• The size, morphology and surface coating of synthesized NPs were characterized.
• The Fe3O4@ PPy NPs were used as the magnetic adsorbent for extraction nitrophenols.
• Anionic forms of nitrophenols were extracted with an anion exchange process.
• The developed method was applied for determination of nitrophenols in water samples.

In this research, the applicability of polypyrrole-coated Fe3O4 nanoparticles (Fe3O4@PPy NPs) as an anion exchange magnetic nanosorbent is demonstrated. For this purpose, three nitrophenols were selected as models which are acidic compounds with low log P values and their extraction in neutral form (only based on hydrophobic interactions) is difficult. The extracted nitrophenols were separated and determined by high-performance liquid chromatography-UV detection. The size, morphology and surface coating of synthesized Fe3O4@PPy NPs have been characterized via different techniques such as Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy and thermo-gravimetric analysis. The important parameters influencing the extraction efficiency were studied and optimized. Under the optimum extraction conditions (300 mL sample solution with pH 10, extraction and desorption times of 10 and 2 min, respectively, 500 μL of 0.1 M HNO3 in acetonitrile as eluent, and 40 mg of adsorbent), a linear range between 0.75 and 100 μg L−1 (R2 > 0.997), and limits of detection ranging from 0.3 to 0.4 μg L−1 were obtained. Preconcentration factors in the range of 125–180 were achieved and relative standard deviations (RSDs%) were less than 4.9 (n = 4) for the three nitrophenols. The analytical method was successfully applied for environmental water samples such as tap water, rain water and river water. The recoveries varied within the range of 84–109% confirming good performance of the method in various waters samples. The results showed that the proposed method is a rapid, convenient and feasible technique for determination of nitrophenols in aqueous samples.