The removal of chromium(VI) from aqueous solutions by Fagus orientalis L. F.N. Acar * , E. Malkoc Department of Environmental Engineering, Faculty of Engineering, Atat€ urk University, 25240 Erzurum, Turkey Received 3 October 2003; received in revised form 9 November 2003; accepted 19 November 2003 Abstract The removal of chromium(VI) from aqueous solution under different conditions using an adsorbent was investigated. This adsorbent is Beech (Fagus orientalis L.) sawdust studied by using batch techniques. Batch studies indicated that the percent adsorption decreased with increasing initial concentration of chromium(VI). A contact time of 80 min was found to be optimum. Maximum chromium(VI) removal was observed near a pH of 1.0. Adsorption conformed to the Freundlich and Langmuir iso- therms. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Chromium(VI); Adsorption; Sawdust; Adsorption isotherms 1. Introduction The pollution of water resources due to the disposal of heavy metals has been an increasing worldwide concern for the last few decades. It is well known that some metals can have poisonous or otherwise harmful effects on many forms of life (Yu et al., 2000). The metals (Zn, Cu, Pb, Cd, etc.) have a harmful effect on human physiology and other biological systems when they are found above the tolerance levels (Budinavo et al., 1994). The presence of trivalent and hexavalent chromium in the environment is the cause of many well documented toxic effects. The maximum levels permitted in wastewater are 5 mg/l for trivalent and 0.05 mg/l for hexavalent chro- mium. When low levels are present in the environment, trivalent chromium apparently plays an essential role in plant and animal metabolism, while hexavalent chro- mium is directly toxic to bacteria, plants and animals (Richard and Bourg, 1991). The main sources of chro- mium pollution are mining, leather tanning and cement industries, use in dyes, electroplating, production of steel and other metal alloys, photographic material and corrosive paints (Ramos et al., 1994). Numerous tech- niques are available for water purification and metal recovery operations from wastewater. Many of these are established methods, while others are still in the exper- imental stage. Often, only a combination of various treatment processes can provide the effluent quality de- sired. Inorganic heavy metals are usually removed from aqueous waste streams by chemical precipitation, electro deposition and cementation. Other methods, including activated carbon, ion exchange, and reverse osmosis, can be used concentrate waste streams and remove the heavy metals. Activated carbon is effective in reducing hexavalent chromium, mercury and many metals com- plexed by organic ligands (Yu et al., 2000). The high cost of activated carbon has inspired a search for suitable low-cost adsorbents. Some of the low-cost adsorbents are already reported for the removal of Hg(II) are fly ash (Sen and De, 1987), coal (Pandey and Chaudhri, 1982; Cullen and Siviour, 1982), rice–husk ash (Tiwari et al., 1995), removal of Cu(II) are maple sawdust (Yu et al., 2000), soil and clay (Atanassova, 1995), removal of Cr(VI) are dried activated sludge (Aksu et al., 2002), clinoptilolite (Toprak and Girgin, 2000), fly ash–wol- lastonite (Panday et al., 1984), sphagnum moss peat (Sharma and Forster, 1993). 2. Methods Beech sawdust (Fagus orientalis L.) was obtained from Erzurum Forest Products Management, Turkey. It * Corresponding author. Fax: +90-442-231-4782. E-mail address: facar@atauni.edu.tr (F.N. Acar). 0960-8524/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2003.10.032 Bioresource Technology 94 (2004) 13–15