Utilization of sky fruit husk agricultural waste to produce high quality activated carbon for the herbicide bentazon adsorption V.O. Njoku a,b , Md. Azharul Islam 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 Forestry and Wood Technology Discipline, Khulna University, Khulna 9208, Bangladesh d Chemical Engineering Department, College of Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia highlights  Sky fruit husk as low-cost agricultural waste to produce activated carbon (SFHAC).  The BET surface area of the produced SFHAC is 1211.57 m 2 /g.  The monolayer maximum adsorption capacity of the SFHAC for herbicide bentazon was 166.67 mg/g. article info Article history: Received 9 February 2014 Received in revised form 3 April 2014 Accepted 4 April 2014 Available online 18 April 2014 Keywords: Adsorption Bentazon Isotherm Kinetic Sky fruit husk abstract The present study utilized an agricultural low cost biomass sky fruit husk for the preparation of activated carbon by chemical activation with orthophosphoric acid (H 3 PO 4 ) and later characterized by N 2 adsorp- tion–desorption isotherms, scanning electron microscopy (SEM) and Fourier transform infrared spectros- copy (FTIR). Batch adsorption process was followed in order to evaluate the potentiality of the prepared activated carbon having BET surface area of 1211.57 m 2 /g for the removal of anionic herbicide bentazon from aqueous solution. The effects of initial concentration, contact time and pH has been studied. The adsorption study indicates that the adsorption data followed the Freundlich model better than the Lang- muir which suggested the heterogeneous nature of the activated carbon surface. The monolayer maxi- mum adsorption capacity of the sky fruit husk activated carbon (SFHAC) was found to be 166.67 mg/g. Kinetic data fitted better to the pseudo-second order model and intraparticle diffusion phenomenon indi- cated more than one process is regulating the adsorption process. The thermodynamic parameters asso- ciated with the adsorption process, standard free energy change (DG°), enthalpy change (DH°) and entropy change (DS°) were also determined at different temperatures and adsorption process was found to be endothermic in nature. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction The pesticide usage has increased dramatically during the last two decades, concurrently with huge population pressure, changes in farming practices and the increasingly intensive agri- culture [1]. This widespread use of pesticides for agricultural and non-agricultural purposes has promoted the presence of their res- idues in various environmental matrices beyond their maximum limits. The agricultural direct runoff, leaching, percolation and careless disposal of empty containers are some major routes for the contamination of water bodies. This contaminated water may be responsible for various waterborne diseases with acute and long-term health effects ranging from diarrhea to death [2]. Pesti- cide contamination of surface and ground water has been well doc- umented globally and constitutes a major issue that gives rise to concerns at local, regional, national and global scales [3]. Bentazon is a post-emergence contact diazinone herbicide used to control annual weeds in a variety of crops especially in rice [4]. Bentazon soil–water distribution coefficient (K d ) is 0.72 that indi- cate it does not bind to, or adsorb, to soil particles and it is highly soluble in water. These characteristics usually suggest a strong mobility and potential for groundwater contamination. Bentazon, however, is so rapidly degraded in upper soil layers by sunlight and soil microbes that it does not tend to move (leach) below the surface layer of the soil. Its rapid degradation is expected to prevent the contamination of groundwater [5,6]. Bentazon is mod- erately toxic by ingestion and slightly toxic by dermal absorption http://dx.doi.org/10.1016/j.cej.2014.04.015 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 251 (2014) 183–191 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej