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a b s t r a c tFe 3 O 4 magnetic nanoparticles (MNPs) with diameters about 10 nm were synthesized successfully and used to remove phenol and aniline from aqueous solution. The results showed that phenol and aniline could be eliminated easily from solution under acidic and neutral conditions in the presence of MNPs and H 2 O 2 . When the concentrations of Fe 3 O 4 MNPs and H 2 O 2 were 5 g L −1 and 1.2 M, respectively, phenol and aniline could be removed completely after 6 h of reaction at 308 K, and the total organic carbon (TOC) abatement efficiency for phenol and aniline were 42.79% and 40.38%. Some intermediates such as formic acid, acetic acid, fumaric acid and hydroquinone were detected during reaction. Fe 3 O 4 MNPs exhibited good stability and reusability, also showed excellent catalysis ability to eliminate some substituted phenolic and aniline compounds from solution. Fe 3 O 4 MNPs had good superparamagnetism and was readily separated from solution by applying an external magnetic field. Finally we proposed that phenol and aniline might be degraded by the hydroxyl free radicals (·OH) released from H 2 O 2 in the presence of Fe 3 O 4 MNPs as catalysts.

The research presented in this paper investigates the adsorption of cation surfactantsscetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC)sonto magnetic nanoparticles and the application of this mixed hemimicelles solidphase extraction (SPE) method for the preconcentration of several typical phenolic compoundssbisphenol A (BPA), 4-tertoctylphenol (4-OP), and 4-n-nonylphenol (4-NP)sfrom environmental water samples. In this novel SPE method, the charged surfactants CTAB and CPC form mixed hemimicelles on Fe 3 O 4 nanoparticles (Fe 3 O 4 NPs), which causes retention of analytes by strong hydrophobic and electrostatic interactions. The SPE method combines the advantages of mixed hemimicelles and magnetic nanoparticles. In order to provide guidelines for the mixed hemimicelles SPE method development, surfactant adsorption isotherms and -potential isotherms were also investigated. The main factors affecting the adsolubilization of analytes, such as the amount of Fe 3 O 4 NPs and surfactants, the type of surfactants, the solution pH, the sample loading volume, and the desorption conditions, were investigated and optimized. A concentration factor of 800 was achieved by the extraction of 800 mL of several environmental water samples using this SPE method. Under the selected conditions, detection limits obtained for BPA, 4-OP, and 4-NP were 12, 29, 34 ng/L, respectively. The accuracy of the method was evaluated by recovery measurements on spiked samples, and good recoveries (68-104%) with low relative standard deviations from 2 to 7% were achieved. The advantages of this new SPE method include high extraction yields, high breakthrough volumes, short analysis times, and easy preparation of sorbents. To the best of our knowledge, this is the first time that a mixed hemimicelles SPE method based on magnetic separation and nanoparticles has been used for the pretreatment of environmental water samples.