Avaliação da eficiência de biossorventes agroindustriais e de biomassa microbiana para remoção de chumbo

Abstract

In the last decades society has undergone several transformations, among which the advancement of technology and the increased use of natural resources were the pillars of most of them. This fact has made the growth of the transformation industries and the products obtained from them fundamental to modern society. In this sense, the contamination generated by these industries has increased, especially contamination by heavy metals, which can cause severe damage to the environment. There are metals, such as iron (Fe) and copper (Cu), which are important for the functioning of organisms, in appropriate proportions. However, some metals, such as lead (Pb), are especially harmful and have the characteristic of bioaccumulation, which makes them even more dangerous. Effluent treatment regulations related to lead are strict, and thus industries need to adapt to them. Currently, the main ways to remove heavy metals from wastewater are chemical precipitation, electrolysis, and reverse osmosis. However, these methods have some inefficiencies and are generally expensive. As an alternative to these methods comes adsorption, which is a process characterized by mass transfer, in which a substance in a liquid stream is selectively transferred to a surface of a porous solid. One way to perform the adsorption process is through the use of plant or microbial biomass to remove substances in liquid streams, giving rise to the term biosorption. This method is characterized mainly by being more economically feasible than traditional adsorption methods. In this context, this work aimed to study the efficiency of biosorbents used in the removal of lead in effluents. Biosorbents of agroindustrial and microbial origin were analyzed. The aspects analyzed were the kinetics, thermodynamics and adsorption isotherms of each process. Through the research of scientific articles it was possible to collect data of biosorbents used for the removal of lead (II). From these data, which were summarized in the initial concentration of lead, the dosage of biosorbent used, temperature at which the process was performed and the results of kinetic and thermodynamic analysis and adsorption isotherms, it was possible to verify which of the biosorbents are good alternatives for the removal of lead. At the end of the analyses, it was possible to verify that there was a greater number of experiments performed with materials of agroindustrial origin, due to the greater availability and abundance of these materials. In this sense, it was also verified a wide variety of products that can be used as biosorbents. In relation to the kinetics of the processes, a tendency towards a pseudo-second order model was observed. In relation to the isotherms, a better fit in the Langmuir model was almost totally observed and, finally, the process showed a greater tendency to be endothermic and have an increase in entropy over time. In general, biosorption for the metal lead (II) is a good economical alternative without loss of efficiency.