Preparation of activated carbons from rambutan (Nephelium lappaceum) peel by microwave-induced KOH activation for acid yellow 17 dye adsorption V.O. Njoku a,b , K.Y. Foo a,c , M. Asif d , B.H. Hameed a,⇑ a School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia b Department of Chemistry, Faculty of Science, Imo State University, P.M.B. 2000 Owerri, Nigeria c Environment and Occupational Health Programme, School of Health Sciences, Health Campus, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia d Chemical Engineering Department, College of Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia highlights  Highlight the renewable use of rambutan peel.  Evaluate the potential of microwave induced activation.  Short activation time of 12 min and low chemical impregnation ratio of 1.00.  High BET and Langmuir surface area of 971.54 and 1518.83 m 2 g 1 .  Monolayer adsorption capacity for acid yellow 17 dye of 215.05 mg g 1 . article info Article history: Received 15 January 2014 Received in revised form 29 March 2014 Accepted 31 March 2014 Available online 6 April 2014 Keywords: Activated carbon Adsorption Dye Isotherm Microwave Rambutan peel abstract A novel agricultural waste, rambutan (Nephelium lappaceum) peel was used as the precursor for prepara- tion of activated carbon by chemical assisted KOH activation. Microwave heating was employed for activation, and thereby considerably reduced the activation time. The prepared activated carbon was characterized by pore structural analysis, zero-point-of-charge (pH pzc ), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The adsorption performance for the removal of acid yellow 17 (AY 17) was investigated. The effects of contact time, initial dye concentration and pH on the adsorption process were studied. The equilibrium time was 4 h, and results indicated high adsorp- tion capacity, even at high initial dye concentrations. Kinetic studies showed that pseudo-second-order kinetic model better described the adsorption process. The experimental adsorption isotherms were modeled using the Langmuir, Freundlich and Temkin equations. The best fit was obtained with the Langmuir isotherm model, implying that the adsorption of AY 17 onto RPAC from the aqueous solutions proceeds by a monolayer formation. The maximum monolayer adsorption capacity of AY 17 was 215.05 mg g 1 . Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction Activated carbon adsorption is a highly effective method widely used for the removal of water pollutants [1,2]. A major challenge of adsorption process is the high production cost of activated carbons [2]. This has resulted to a growing research at reducing the produc- tion cost of activated carbons. A such effort is the identification of low cost alternative precursors [3–7]. Agricultural wastes have been proven to be the greatest interest due to their accessibility and abundantly availability. Rambutan (Nephelium lappaceum) is an attractive tropical fruit produced in large quantities in Malaysia. The sweet and juicy pulp is consumed for its exotic taste, while the peel is disposed to the sanitary landfills [8]. Research on the use of rambutan peel (RP) for the production of activated carbon is a welcome development as it would serve as a cheap alternative precursor as well as at reducing the cost of waste management [9]. The adsorptive properties of activated carbon depend on the surface area, good internal porous structure, high thermal stability, low acid/base reactivity and chemical structure of the surface [10]. These properties depend on the preparation method as well as the http://dx.doi.org/10.1016/j.cej.2014.03.115 1385-8947/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +60 45996422; fax: +60 45941013. E-mail address: chbassim@usm.my (B.H. Hameed). Chemical Engineering Journal 250 (2014) 198–204 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej