45 Journal of Science and Technology in the Tropics (2007) 3: 45-50 Changes in physicochemical characteristics of oil palm frond after NaOH treatment towards improved heavy metal sorption A. Z. Abdullah*, B. Salamatinia, N. Razali and A. H. Kamaruddin School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang, Malaysia (*Email: chzuhairi@eng.usm.my) Received 12.10.2006; accepted 25.01.2007 Abstract NaOH treatment on oil palm frond (OPF) was investigated for improvement in copper (Cu) and zinc (Zn) sorption from aqueous solution. The OPF was chemically modified by soaking it in 0.6 M NaOH solution for 45 min, followed by washing and drying. The sorption process of Cu and Zn was carried out in an orbital shaker and shaken at 150 rpm using metal solutions at 100 ppm. Increased heavy metal sorption capacity of the OPF resulted after NaOH treatment. Changes in surface morphology and elemental composition analysis suggested the solubilization of hemicellulose or pectin from OPF, detected by material shrinkage and reduced –CH 3 amount. Na was the counter ion in the treated biomass for exchange with heavy metals as suggested by thermogravimetry analysis (TGA). The higher nitrogen-containing groups in NaOH-treated OPF as detected through elemental analysis acted as the positively charged functional groups that bound Na to be subsequently exchanged with heavy metal during the sorption process. Other functional groups that could play the same role, but of less importance, were the sulphur-containing groups. Keywords Oil palm frond – NaOH – heavy metal – sorption – physicochemical characteristics INTRODUCTION Heavy metals are among the most common pollutants found in industrial wastewater and conventional methods for heavy metal removal are often ineffective, uneconomical or technically complicated [1]. Current research on heavy metal removal is moving towards the use of low-cost sorbent materials [2, 3]. Being a tropical country, Malaysia has an enormous supply of biomass resources generated mainly from agricultural activities. Currently, Malaysia is the leading producer of palm oil in the world and this industry also generates about 50 million tonnes of biomasses in 2005 [4]. These biomasses are mainly in the form of palm press fibre (PPF), empty fruit bunch (EFB), shell and oil palm frond (OPF). Therefore, the utilization of those biomasses for value-added applications such as in the sorption of heavy metals needs to be explored and investigated. Interest has risen in removing heavy metals by sorption on agricultural materials such as waste wool, nut wastes, tree barks, modified cotton and sawdust [5]. These agricultural wastes, which are biopolymers in nature, possess a variety of functional groups such as hydroxyl groups to which other moieties can be reacted for possible enhancement in the efficiency of metal ion sorption [1, 6]. The sorption properties of the biomass can be improved or modified by several methods [5-7]. NaOH pretreatment has been reported in the literature to potentially improve the heavy metal sorption of various biomasses [8]. However, there is little report on the use of NaOH treated OPF for this application. The chemical composition of this oil palm biomass could be significantly different from those reported and treatment with NaOH could result in heavy