Applied Catalysis A: General 469 (2014) 33–44 Contents lists available at ScienceDirect Applied Catalysis A: General j ourna l h om epage: www.elsevier.com/locate/apcata Synthesis of reverse micelle -FeOOH nanoparticles in ionic liquid as an only electrolyte: Inhibition of electron–hole pair recombination for efficient photoactivity R. Jusoh a , A.A. Jalil a,∗ , S. Triwahyono b , A. Idris c , S. Haron a , N. Sapawe a , N.F. Jaafar b , N.W.C. Jusoh a a Institute of Hydrogen Economy, Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia b Ibnu Sina Institute for Fundamental Science Studies, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia c Institute of Bioproduct Development, Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia a r t i c l e i n f o Article history: Received 27 April 2013 Received in revised form 30 August 2013 Accepted 28 September 2013 Available online xxx Keywords: -FeOOH nanoparticles Ionic liquid Reverse micelle Photo-Fenton-like 2-Chlorophenol a b s t r a c t Discrete -FeOOH nanoparticles (5–10 nm) were synthesized by a simple electrochemical method using an ionic liquid (IL), dodecyltrimethylammonium bromide (IL - FeOOH). IL that acts as an only electrolyte is capable of producing IL - FeOOH nanoparticles without any agglomeration. Its crystallinity, morphology, functional characteristics, and surface area were analyzed using an X-ray diffractometer, a transmis- sion electron microscope, a Fourier-transform infrared spectrometer, and the Brunnauer–Emmett–Teller (BET) method, respectively. The characterization results verified that reverse micelle formation of IL plays an important role in the stabilization and miniaturization of the -FeOOH nanoparticles. The activity of IL-FeOOH was tested on a photo-Fenton-like degradation of 2-chlorophenol (2-CP). Results showed that a nearly neutral condition of pH 5 was able to completely degrade 2-CP within 180 min of reaction at 50 ◦ C, using 0.03 g L -1 of catalyst dosage and 50 mg L -1 of 2-CP initial concentration, with only a small amount of H 2 O 2 (0.156 mM). It was found that the reverse micelle formed around the catalyst surface could trap the photogenerated electron to inhibit the recombination of photo-induced electron–hole pairs thus enhancing its catalytic activity. Kinetic studies using the Langmuir–Hinshelwood model illus- trated that a surface reaction was the controlling step of the process. A reusability study showed that the catalyst was still stable after four subsequent reactions as shown by infrared spectroscopy. The results provide strong evidence to support the potential use of using IL as an alternative electrolyte to synthesize photo-Fenton-like nanocatalyst that can be used to treat organic pollutants such as 2-CP. © 2013 Elsevier B.V. All rights reserved. 1. Introduction In the huge array of organic pollutants generated by man- made activities, a sizable fraction belongs to various chlorinated phenol compounds. Among them, 2-chlorophenol (2-CP) is used in various chemical processes such as in agriculture, paper, cosmetic, biocide, and public health industries. They belong to the large group of hazardous pollutants presenting seri- ous threats to the surrounding ecosystem [1] and the lethal dosage values (LD 50 ) determined in mice indicate that 2-CP is considerably more toxic than dichlorophenols [2]. When released into the environment, they can cause negative effects to aquatic organisms, while in higher concentrations they present a ∗ Corresponding author. Tel.: +60 7 5535581, fax: +60 7 5536165. E-mail address: aishah@cheme.utm.my (A.A. Jalil). serious threat to humans as well since chlorinated compounds are known to be the starting material for dioxins and furans [3,4]. Thus, an efficient treatment is required to avoid the envi- ronmental impact caused by these harmful and recalcitrant pollutants. The ability of biological and physical methods in the treat- ment of chlorophenols can be successfully applied, but demand for secondary treatment should be taken into account as well [5]. Chlorophenols do not undergo direct sunlight photolysis in the natural environment since they only absorb light below 290 nm [2]. Therefore, advanced oxidation technologies (AOTs) present a promising alternative to common treatment methods. AOTs are based on the generation of hydroxyl radicals ( • OH), a reactive species capable of degrading or mineralizing the majority of organ- ics [6,7]. The integration of two different AOTs (photocatalytic and Fenton-like) often offers synergistic reaction routes for the pro- duction of • OH [8], and has been shown to be suitable for the 0926-860X/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.apcata.2013.09.046