Utilização do carvão produzido a partir do capim Andropogon (Andropogon Gayanus Kunt cv. Planaltina) para o pós-tratamento de efluente de indústria de tinta por filtração

Abstract

The objective of this study was to evaluate the biomass potential of andropogon grass (Andropogon gayanus Kunt cv. Planaltina) in the production of coal by the pyrolysis process for use in filtration systems for the post-treatment of paint industry effluent. The andropogon grass presents rapid growth and natural occurrence in the state of Tocantins, making this proposal a sustainable alternative for the production of charcoal. The effluent generated by the paint industry is difficult to degrade and presents high solids concentration, organic matter and metals, such as aluminum, cadmium, cobalt, zinc, chromium and copper salts. In this research the produced coal was evaluated in laboratory scale as a filter medium for the post-treatment of the final effluent of a medium-sized paint industry, which presents a treatment system composed of coagulation, followed by decantation. The biomass under study was collected around the city of Palmas-TO, and, characterized by immediate analysis (moisture content, ashes, fixed, volatile mass, carbon and apparent density), elemental analysis (CHSN-O), determination of specific compounds (cellulose, hemicellulose, lignin), pH, Fourier-transform infrared spectroscopy (FTIR) and Scanning Electron Microscope (MEV). The charcoal produced was characterized by immediate analysis, elementary, microscopic analysis, thermogravimetric (TG), particle size analysis and surface area determination (BET/N2). For the filtration process with the coal, three descending filters were used, being of these, two filters of sand and one of the coal. The efficiency of the filters was evaluated by the following parameters: color, turbidity, removal of total solids, suspended and settleable, Chemical Oxygen Demand and heavy metals. According to the parameters presented by Resolution CONAMA nº 357/05, it can be seen that only the concentration of copper exceeded the maximum permitted by the legislation. The metals with greater toxicity to the environment: Al, Cd and Cr, were removed with 99.99%, 99,77% and 99,58% efficiency, respectively. The removals of COD and solids reached very close levels of totality, and turbidity and color parameters were reduced with an efficiency greater than 90%. The results obtained in this work show that the coal produced by the pyrolysis of Andropogon grass biomass, presents characteristics favorable to the retention of metals, removal of organic matter and effluent solids, which are mainly justified by the porosity and surface area of the biomaterial.