The biosorption capacity of different cortex fruit wastes including banana (Musa paradisiaca), lemon (Citrus limonum) and orange (Citrus sinesis)peel were evaluated. In order to perform these experiment, grinded dried cortexes were used package in 100 mm high, 10 mm i.d. columns. The grinded material was pawdered in a mortar and passed through a screen in order to get two different partirle sizes, 2 and 1 mm, for all powders. To estímate the biosorption capabilities of the tested materials, different heavy metals were passed througn the columns and elution filtrate reloaded different times to increase the retention of metals. The heavy metals used were prepared as synthetic samples at 10mg/L of Pb,Cd and Cu using primary standards. In preliminary experiments using banana cortex, it was found thet materials with 1 mm size showed higher retention capability (up to 12%) than the material with 2 mm of particle size. Considering these results, 1 mm particle size material was used in further experiments with the Other waste materials. It was found that for Pb and Cu removal,lemon and orange cortex showed better biosorption capability when compared with banana cortex (up to 15% less for Pb and 48% less for Cu). For Cd, banana cortex showed better biosorption capability 57%(67.2 mg/g of cortex) more than orange (28.8 mg/g of cortex) and more than lemon(12 mg/g of cortex). Reload of the column with the filtrate after passing through the column improved the removal capability of all the materials tested 10% to 50% depending on the cortex and metal tested.

l. Introduction.

Metals are ubiquitous constituents in the biosphere, vital to our industry, infrastructure and daily life. Since the industrial revolution, metals have increasingly been redistributed in the environment, with accumulation in terrestrial and aquatic habitats being associated with adverse effects on the biota and human health (Sparks. 2005). Common sources for these pollutants to the environment includes rocks and metalliferous minerals, but mainly anthropogenic inputs from agricultura, metallurgy, energy production, microelectronics, mining, sewage sludge and waste disposal (Landa. 2005; Giltmour and Riedel. 2009). Atmospheric deposition is the major mechanism for metal input to plants and soils. Volatile metaloids such as As, Hg, Se and Sb can be distributed as gases or enriched in particles, while Cu, Pb and Zn are transported as particulates (Adriano, 2001: Adriano et al., 2004). In terrestrial ecosystems, soils are the major sink for metals in aquatic systems. Metal contaminants can affect aquatic systems through runoff, leaching and transport via mobile colloids (Adriano, 2001; Adriano et al., 2004).

Once in the environment, metals represents a serious risk to the different ecosystems due to their well known toxicological effects and their ability to migrate to surface or underground water (Khaniki et al., 2005).Due to their persistence and potential to bioaccumulation and bioaugmentation, removal of metals from water has become an essential environmental task. However, conventional processes present several limitations in the removal of these contaminants from water and in many of the cases, are not effective neither economically viable for the treatment or low concentrations Of heavy metals (Popurl et al., 2007). Among the novel approaches developed for the removal Of metals in wáter, technologies based on biological methods for metal removal and/or recovery have emerged as cost-effective alternatives in recent years (Popuri et al., 2007). Biosorption is a physical-chemical process. Simply defined as the removal of substances from solution by biological

material. This a property of both living and dead organisms (and their components), and has been heralded as a promising biotechnology because of its simplicity, analogous operation to conventional ion-exchange technology, apparent efficiency and availability of biomass and waste bioproducts (Macaskie. 1991; Gadd , 2001. volesky, 1990; Garnham et al., 1992; Gadd and White, 1993; Wang and Cheri, 2009). Several biosorption studies have been carried out using microbial systems, mainly bacteria, microalgae and fungi (Bae et al.,