Avaliação do uso do bagaço de cana como adsorvente para a remoção de contaminantes, derivados do petróleo, de efluentes

Abstract

Oil by-products, such as lubricating oils, gasoline, diesel and their constituting organic compounds, pollutants hard to degrade, are constantly released into the hydrographic basins as a result of different industrial processes, accounting for serious pollution problems to sea life. An increasing concern at the environment has intensified the study of techniques for the removal of these polluting charges from liquid effluents. In this respect, adsorption has drawn much attention because it presents itself as an effective, money-saving, highly selective method at molecular level besides having low energy consumption. Besides the concern at the efficacy of the removal of pollutants, the final destination of the adsorbing solid once its life-span is over, must also be taken into consideration. Thus, the research for low-cost adsorbing materials likely to be reused for other purposes has been intensified, having their aggregate value increased by the adsorption process. Once sugar-cane bagasse is abundant throughout Brazil, it has a high surface area and is highly hydrophobic, its use as a bioadsorbent for organic contaminants has aroused the interest of the academic community. Thus, the aim of the present work is to assess the adsorption ability of sugar-cane bagasse for the removal of oil by-products contaminating liquid effluents, with the aim of treating those and carrying out the concomitant energetic enrichment of bagasse for its later use as fuel in boilers. This way, adsorption experiments in agitated reactor were carried out to investigate the factors which influence and optimize the bioadsorption of oil by-product contaminants on sugar-cane bagasse and to understand the mechanisms of this process. Therefore, the assessment of the kinetic curves and of the adsorption isotherms of gasoline and of n-heptane in aqueous solutions at room temperature was carried out. The results show the promising trait of bagasse as an adsorbent, being able to adsorb up to 99 % of gasoline and 90 % of n-heptane contained in solution containing about 5 % of these contaminants. Furthermore, the adsorption kinetics of gasoline is very quick (with equilibrium times lower than 5 minutes) and adsorption is favourable and takes place in multi layers. When describing experimental isotherms the models of Langmuir, Freundlich, Langmuir-Freundlich, Jovanovic-Freundlich, Dual-Site Langmuir Model (DSL) and Multispace Adsorption Model (MSAM) were assessed. The DSL and MSAM models are the ones which better describe the isotherms for gasoline adsorption, however, they are still poor to describe the isotherms of n-heptane adsorption.