Adsorption of hydrogen sulphide (H 2 S) by activated carbons derived from oil-palm shell Jia Guo a, * , Ye Luo b , Aik Chong Lua c , Ru-an Chi a , Yan-lin Chen a , Xiu-ting Bao a , Shou-xin Xiang a a Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, School of Chemical and Pharmaceutical Engineering, Wuhan Institute of Technology, Wuhan 430073, PR China b School of Physical Science, Wuhan Institute of Technology, Wuhan 430073, PR China c School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore Received 17 January 2006; accepted 14 September 2006 Available online 28 November 2006 Abstract Adsorption of hydrogen sulphide (H 2 S) onto activated carbons derived from oil palm shell, an abundant solid waste from palm oil processing mills, by thermal or chemical activation method was investigated in this paper. Dynamic adsorption in a fixed bed configu- ration showed that the palm-shell activated carbons prepared by chemical activation (KOH or H 2 SO 4 impregnation) performed better than the palm-shell activated carbon by thermal activation and a coconut-shell-based commercial activated carbon. Static equilibrium adsorption studies confirmed this experimental result. An intra-particle Knudsen diffusion model based on a Freundlich isotherm was developed for predicting the amount of H 2 S adsorbed. Desorption tests at the same temperature as adsorption (298 K) and at an elevated temperature (473 K) were carried out to confirm the occurrence of chemisorption and oxidation of H 2 S on the activated carbon. Surface chemistries of the palm-shell activated carbons were characterized by Fourier transform infrared spectroscopy and Boehm titration. It was found that uptaking H 2 S onto the palm-shell activated carbons was due to different mechanisms, e.g. physisorption, chemisorption and/or H 2 S oxidation, depending on the activation agent and activation method. Ó 2006 Elsevier Ltd. All rights reserved. 1. Introduction Hydrogen sulphide (H 2 S), a ‘‘rotten-egg’’ smell gas pro- duced by anaerobic digestion in acid condition from organic and inorganic compounds containing sulphur, pre- sents dual problems of its toxicity and foul odour. H 2 S can be detected by most people as low as 0.0047 ppm [1]. Although no significant physical harm may be caused in such a low concentration, the exposure to this nuisance can lead to nausea, loss of appetite, and other negative effects. From the point of view of engineering design of a purification system, the odour threshold of H 2 S is 0.18 ppm [2]. Various measures can be applied to reduce or eliminate H 2 S emissions from different sources, particu- larly sewage treatment facilities. Among these measures, the use of activated carbon is most successful and wide- spread due to its safety and effectiveness of the operation process [3]. Usually, activated carbons used for H 2 S adsorption are those activated carbons modified with caus- tic chemicals such as KOH and NaOH [4] or oxidative agents KI and KMnO 4 [5] which promote oxidation of H 2 S to elemental sulphur. All of these carbon modifica- tions, however, create the hazard of fixed-bed self-ignition owing to the high heat released by the reactions [6]. More- over, the adsorptive capacity of the activated carbon may be significantly decreased by the modification process since the micropores are not accessible due to the blockage of pore entrances [7]. For these reasons the use of activated 0008-6223/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbon.2006.09.016 * Corresponding author. Tel.: +86 27 87194980; fax: +86 27 87194465. E-mail address: guojia@mail.wit.edu.cn (J. Guo). www.elsevier.com/locate/carbon Carbon 45 (2007) 330–336