Journal of Hazardous Materials 146 (2007) 237–242 Adsorption of benzene and toluene from aqueous solutions onto activated carbon and its acid and heat treated forms: Inﬂuence of surface chemistry on adsorption N. Wibowo, L. Setyadhi, D. Wibowo, J. Setiawan, S. Ismadji ∗ Department of Chemical Engineering, Widya Mandala Surabaya Catholic University, Kalijudan 37, Surabaya 60114, Indonesia Received 26 October 2006; received in revised form 5 December 2006; accepted 5 December 2006 Available online 10 December 2006 Abstract The inﬂuence of surface chemistry and solution pH on the adsorption of benzene and toluene on activated carbon and its acid and heat treated forms were studied. A commercial coal-based activated carbon F-400 was chosen as carbon parent. The carbon samples were obtained by modiﬁcation of F-400 by means of chemical treatment with HNO 3 and thermal treatment under nitrogen ﬂow. The treatment with nitric acid caused the introduction of a signiﬁcant number of oxygenated acidic surface groups onto the carbon surface, while the heat treatment increases the basicity of carbon. The pore characteristics were not signiﬁcantly changed after these modiﬁcations. The dispersive interactions are the most important factor in this adsorption process. Activated carbon with low oxygenated acidic surface groups (F-400Tox) has the best adsorption capacity. © 2006 Elsevier B.V. All rights reserved. Keywords: Activated carbon; Adsorption; Surface chemistry; Benzene; Toluene 1. Introduction Aromatic organic compounds such as benzene and toluene are important materials in the chemical process industries. These materials are usually used as raw materials in numerous chem- ical productions and also often as solvent in a wide variety of manufacturing processes [1]. Since these organic compounds are classiﬁed as ﬂammable, toxic, carcinogenic, and/or mutagenic agents, their presence in water stream even at low concentrations is of major environmental concern [2,3]. Hence, the removal of these organic pollutants from the water stream is critical to ensure the safety of water supplies. A considerable effort has been dedicated in the past years concerning the removal of these compounds from wastewa- ter, several methods have been proposed and developed, and the most extensively used is adsorption process [4–8]. For this purpose, various types of adsorbent have been used for removal of these organic compounds and adsorption onto acti- vated carbons is a proven, reliable technology for removal of ∗ Corresponding author. Tel.: +62 31 3891264; fax: +62 31 3891267. E-mail address: suryadi@mail.wima.ac.id (S. Ismadji). small quantities of soluble organic compounds from water or wastewater. To the present, activated carbon remains to be one of the most important microporous adsorbent from an industrial view of point. This adsorbent has very complex surface characteris- tics (porosity and surface chemistry), with pore size ranging from micropores (less than 2 nm) to macropores (more than 50 nm), and has a variety of surface groups, impurities and irregularities. The surface characteristics of activated carbon depend on the raw material used and the method of activation [9,10]. The surface chemistry of activated carbons determines their moisture content, catalytic properties, acid-base character, and adsorption capacity [11]. The surface chemistry of activated carbon is related to the presence of heteroatoms (oxygen, hydro- gen, and nitrogen) other than carbon atom within the carbon matrix [10,11]. For adsorption of organic compounds in aque- ous phase, the surface chemistry and the pH of the solution are the most important factors in controlling the adsorption process. The nature of surface groups in activated carbon can be modi- ﬁed through physical, chemical, and electrochemical treatments, and the most common is liquid phase treatment (chemical) using nitric acid and hydrogen peroxide. The treatment using oxidiz- 0304-3894/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2006.12.011