Production of biosorbents from waste olive cake

Chapter 1 - Introduction The presence of heavy metals in the environment is an important issue because of their toxicity and threat to human life and environment itself. Heavy metal contamination exists in aqueous waste streams of many industries, such as metal plating facilities, mining operations, and tanneries. Chromium is one of the metals associated with these activities. Chromium, one of the prior heavy metal pollutants, occurs in two stable oxidation states in aqueous solutions, Cr (VI) and Cr (III), and their properties are very different. Cr (VI) species, having mobile and strongly oxidant characters, are known as mutagen and potential carcinogen. In contrast, Cr (III), having a limited hydroxide solubility and toxicity is generally regarded as non-pollutant. Because of these dramatic differences in physical and chemical properties of two chromium types and benign character of Cr (III), detoxification and immobilization process of Cr (VI) is based on its reduction to Cr (III). Many different processes have been investigated for removing chromium from aqueous solutions. Treatment processes include chemical precipitation, membrane filtration, ion exchange, carbon adsorption, and co precipitation/adsorption. For Cr (VI) removal, the reduction-precipitation technique is abundantly practiced. In this technique, Cr (VI) is first reduced to Cr (III) and precipitation of insoluble chromium hydroxide is a final step in removal process. But these traditional techniques are incapable of reducing concentration to the levels required by law or are prohibitively expensive. In recent years the most promising alternative method for removal of these metal ions uses the sorption by waste materials, from industrial or agricultural operations, which are low cost and abundant. Biosorption is known as the removal of heavy metals by the passive binding to non-living biomass from an aqueous solution. Recently, olive oil wastes have been tested as biosorbents of heavy metals with promising results. At present, this agricultural waste material obtained from the olive oil industry is used principally as a solid fuel and is available in abundance in the Mediterranean Region. The total production of olive oil reaches 1.75 million tons in the European Union, being the worldwide production around 2.3 million tons. Spain is leader in this field, with a 30% 1