2nd CUTSE International Conference 2009 EE_09 Red Mud as Sorbent for SO 2 Gas Cleaning Nabilah Aminah Lutpi School of Environmental Engineering Universiti Malaysia Perlis 02600 Perlis, Malaysia nabilah@unimap.edu.my Leon Munro, John Zhu School of Chemical Engineering University of Queensland 4027 Brisbane, Australia Abstract— The main purpose of this study was to investigate for SO 2 removal using red mud as sorbent in laboratory for the sake of gas cleaning. The study was carried out by using a laboratory- scale reactor to examine the batch absorption study of SO 2 gas with slurry and liquor of red mud samples from Worsley Alumina Pty. Ltd., Western Australia. The intention of the batch absorption study is not only constrain for gas cleaning of SO 2 using red mud, but this study also revealed how effective the sulfur dioxide in neutralizing the red mud which are verified as hazardous and caustic due to the high pH of 10-13. Prior to the absorption study, the red mud needs to undergo for alkalinity test to determine the intensity of carbonate and hydroxide ions presence in the red mud. From the experiment, the hydroxide and carbonate ions are assumed to be consumed at specific pH of the sample’s alkalinity, taking into consideration the fact that hydroxide is commonly present at pH levels greater than 8.3, while carbonate is present at pH between 4.5 and 8.3. In other hand, analysis from the batch absorption studies exhibited good performance of red mud as sorbent with respect to sulfur capacity. Keywords-Red Mud; Gas Cleaning; SO 2 I. INTRODUCTION Flue gas generally consists of H 2 O, O 2 , CO 2 , CO, NO x , SO x and a variety of particulates [1]. However, regulation requires that industries comply with the imposed emission limits of SO 2 as this is the major problematic constituent in the flue gas due to the detrimental impact on both the environment and health [2]. Sulphur dioxide (SO 2 ) is a toxic and hazardous gas that is generated by industrial activities such as coal-burning and electric power generation [3]. The development of technology for the removal of SO 2 from flue gas has progressed through several distinct stages [4]. These includes the replacement of fuels with high sulphur content with those containing a much smaller amount [2], conducting a specific combustion processes which result in the generation of SO 2 such as fluidized bed combustion (FBC) and sorbent injection, and finally the advent of flue gas desulphurization (FGD) technology [5]. In other efforts, a variety of sorbents were modified and applied to the present technology for a higher efficiency of SO 2 removal. Examples of such modified- sorbent processes include the magnesia spray absorption process [6], and those which make use of aluminum organometallic [7], CuO/γ-Al 2 O 3 [8] and Bayer red mud [1,9]. However, not much research has been conducted in waste gas cleaning using red mud. This is because the application of red mud is focusing more on the water treatment such as coagulant production and adsorption of anion, heavy metals, dye, organics and bacteria/virus removal [10]. In 1977, a desulphurisation plant was built by a Japanese company, Sumitomo Chemical Co. Ltd, which discovered the chemical properties of red mud and its use as an agent to remove SO 2 from flue gas [1]. The process, referred to as the Sumitomo Bauxite Residue Desulphurisation System (BRDS), has the capacity to effectively remove up to 96% of the SO 2 in flue gas [1]. However, a detailed description of the BRDS process from authentic sources is still unfounded; hence most information about the plant is uncertain. On the other hand, red mud is alkaline bauxite residue that has a high pH value, in the range of 10-13, as a result of the presence of hydroxide [11]. The alkaline characteristics of red mud are the main cause of numerous environmental problems such as groundwater contamination, damage to dykes and corrode the pipelines for pumping [12, 13, 14]. As a result, red mud is categorized as hazardous, corrosive and toxic substance due to the presence of high levels of calcium, oxalate and sodium hydroxide [11, 15, 16]. In addition, the capability of sodalite to exchange Na + ions may result in a serious impact to the environment [13]. Therefore, the project will focus on waste remediation technologies whereby red mud is used as economical adsorbent for the removal of SO 2 emission. These studies will not only solve the problems to comply with the stringent environmental regulation of SO 2 emissions limits and gas cleaning, but also neutralize the caustic and hazardous red mud in economical ways.