Journal of Hazardous Materials 176 (2010) 814–819 Contents lists available at ScienceDirect Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat Removal of insecticide carbofuran from aqueous solutions by banana stalks activated carbon J.M. Salman, B.H. Hameed ∗ School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia article info Article history: Received 9 August 2009 Received in revised form 7 October 2009 Accepted 20 November 2009 Available online 26 November 2009 Keywords: Carbofuran Adsorption Activated carbon Banana stalks Regeneration abstract In this work, activated carbon was prepared from banana stalks (BSAC) waste to remove the insecti- cide carbofuran from aqueous solutions. The effects of contact time, initial carbofuran concentration, solution pH and temperature (30, 40 and 50 ◦ C) were investigated. Adsorption isotherm, kinetics and thermodynamics of carbofuran on BSAC were studied. Equilibrium data were fitted to the Langmuir, Freundlich and Temkin isotherm models and the data best represented by the Langmuir isotherm. Ther- modynamic parameters such as standard enthalpy (H ◦ ), standard entropy (S ◦ ) and standard free energy (G ◦ ) were evaluated. Regeneration efficiency of spent BSAC was studied using ethanol as a sol- vent. The efficiency was found to be in the range of 96.97–97.35%. The results indicated that the BSAC has good regeneration and reusability characteristics and can be used as alternative to present commercial activated carbon. © 2009 Elsevier B.V. All rights reserved. 1. Introduction The increasing use of pesticides in agriculture and domestic activities for controlling pests is vastly polluting the environ- ment day by day [1]. Besides, toxicity of the parent pesticides and their degradation products is making these chemical substances a potential hazard. When these pesticides are introduced into the environment through spraying on crops, droplets of pesticides fall on soil, plant and water. While some part of these chemicals stays in the area where it is applied; and the major part gets transported to various environmental compartments [2]. Carbofuran is a carba- mate insecticide and nematocide used for the control of a variety of solid welling and foliar-feeding pests on many fruit and vegetable crops [3]. Carbofuran is degraded in water by hydrolysis, microbial decomposition and photolysis. In the soil, it is degraded by hydroly- sis, microbial action, and to a lesser extent, photodecomposition. Its persistence is dependent upon pH, soil type, temperature, moisture content and the microbial population [4]. The maximum acceptable concentration (MAC) for carbofuran in drinking water is 0.09 mg/L [5]. Carbofuran insecticides are widely used in agriculture. Their determination has become increasingly important in recent years because of the widespread use of these compounds, which is due to their wide-ranging biological activity and relatively low persistence compared to organochlorine pesticides [6]. ∗ Corresponding author. Tel.: +60 45996422; fax: +60 45941013. E-mail address: chbassim@eng.usm.my (B.H. Hameed). Several methods either independent or in conjunction have been used for the removal of these pesticides including chemical oxidation with ozone [7], photo degradation [8], combined ozone and UV irradiation [9], Fenton degradation [10], biological degrada- tion [11], ozonation [12], membrane filtration [13] and adsorption [14]. Adsorption on activated carbon is the most widespread tech- nology used to deal with purification of water contaminated by pesticides and other hazardous chemicals. However, due to the high cost of commercial activated carbon, its use in the field is some- times restricted on economic considerations. Moreover, the high cost associated with its regeneration led to exploring new inexpen- sive materials [15], and this has been the thrust of this work aiming at preparing renewable activated carbon from banana stalks (BS) for the removal of insecticide carbofuran from aqueous solutions. Banana (Musa sapientum) is native to Southeast Asia, where it was one of the first cultivated crops. In Malaysia, banana is grown in most of the states. It remains the second most important fruit crop (after durian). Most of the bananas produced are consumed locally and about 10% are exported [16]. Therefore, we attempt to use banana stalk, abundantly available lignocellulosic agricul- tural waste, as a cheap and renewable precursor for preparation of banana stalks activated carbon (BSAC) for carbofuran removal. 2. Materials and methods 2.1. Adsorbate Technical grade Carbofuran (C 12 H 15 NO 3 ) of 99.9% purity sup- plied by Sigma–Aldrich (M) Sdn Bhd, Malaysia was used as an 0304-3894/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2009.11.107