Chemical Engineering Journal 173 (2011) 385–390 Contents lists available at ScienceDirect Chemical Engineering Journal j ourna l ho mepage: www.elsevier.com/locate/cej Microwave assisted preparation of activated carbon from pomelo skin for the removal of anionic and cationic dyes K.Y. Foo, B.H. Hameed ∗ School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia a r t i c l e i n f o Article history: Received 20 April 2011 Received in revised form 26 July 2011 Accepted 28 July 2011 Keywords: Acid blue Activated carbon Adsorption Methylene blue Microwave Pomelo skin a b s t r a c t In this work, pomelo skin, an industrial effluent abundantly available from the fruit juice processing plants, was utilized as a feedstock for preparation of activated carbon (PSAC) via microwave induced NaOH activation. The activation process was performed at the input power of 800 W and irradiation time of 5 min. The porosity, functional and surface chemistry were featured by means of low temperature nitrogen adsorption, elemental analysis, scanning electron microscopy, Fourier transform infrared spec- troscopy and evaluation of surface acidity/basicity. The adsorptive property of PSAC was tested using methylene blue and acid blue 15 dyes as the model adsorbates. Equilibrium data was examined using a comparison of linear and non-linear isotherm models. The adsorption behavior was well described by the non-linear Langmuir isotherm model, showing a monolayer adsorption capacity for methylene blue and acid blue 15 of 501.10 mg/g and 444.45 mg/g, respectively. The findings revealed the potential use of pomelo skin derived activated carbon for removal of cationic and anionic dyes. © 2011 Elsevier B.V. All rights reserved. 1. Introduction For the past few decades, the persisting color and the non- biodegradable nature of the spent dye baths remain an aesthetic concern among the environmentalists [1]. Adsorption technique, particularly by carbon adsorbents has emerged to be the best efficient technology, which finds diverse applications in several disciplines of purification and decontamination processes [2–5]. Nevertheless, its wide scale implementation is deteriorated by the high prices of commercial activated carbons, which are tra- ditionally produced from charcoal, woods, and coconut shells. Accordingly, research has been devoted towards the utilization of the biomass waste available from fields or generated from the industrial manufacturing plants [6–10]. In Malaysia, approximately 1895 ha of pomelo (Citrus grandis) trees are grown commercially, with an estimated annual produc- tion of 8830 metric tons of pomelo fruits. Pomelo fruit is primarily eaten fresh and available as food complements in desserts, salads, fruit cocktail, jam, juice combinations or food processing industries [11]. The thick peels of pomelo are candied or used as flavorings and marmalade. However, the enveloping membranous skin around the segments is bitter and usually discarded as waste. To the best of our knowledge, not much study has been reported on the benefi- cial use of pomelo skin. Therefore, this research was undertaken to ∗ Corresponding author. Tel.: +60 45996422; fax: +60 45941013. E-mail address: chbassim@eng.usm.my (B.H. Hameed). examine the feasibility of pomelo skin, a lignocellulosic biomass emitted from the fruit juice manufacturing plants, as the feed- stock for preparation of activated carbon via microwave assisted NaOH activation. Structural, functional and elemental character- ization of the prepared adsorbent was performed. Moreover, the surface chemistry, adsorption equilibrium of both cationic (methy- lene blue) and anionic (acid blue 15) dyes, and a comparison of both linear and non-linear isotherms were elucidated. 2. Materials and methods 2.1. Adsorbate Methylene blue (MB), a cationic dye with the molecular struc- ture C 16 H 18 N 3 SCl (molecular weight 319.85) and acid blue 15 (AB), an anionic dye with the molecular structure C 42 H 46 N 3 NaO 6 S 2 (molecular weight 775.95), supplied by Merck (M) Sdn. Bhd, Malaysia, were chosen as the targeted adsorbates in this study. The dye stock solution was prepared by dissolving accurately weighed dye in distilled water to a concentration of 500 mg/L. The experi- mental solution was obtained by diluting the dye stock solution in accurate proportions to different initial concentrations. 2.2. Preparation of PSAC Pomelo skin (PS) used in the present study was collected from a local fruit juice manufacturing plant. The collected sam- ple was thoroughly washed, air-dried, cut and sieved to obtain the 1385-8947/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2011.07.073