Monday, April 30, 2007

Use of agricultural residues for the production of oxidized lignins in acidic medium aiming heavy metals removal from effluents

Gisele Aparecida Amaral Labat, Biotechnology, Escola de Engenharia de Lorena, Universidade de São Paulo, Estrada Municipal do Campinho, s/n, Lorena, 12600-970, Brazil and Adilson Roberto Gonçalves, Biotechnology, Escola de Engenharia de Lorena EEL/USP, Estrada Municipal do Campinho, s/n, Lorena, 12600-970, Brazil.

Sugarcane bagasse and straw are burned in boilers for generation of energy in sugar and alcohol industries. However, excess of those by-products could be used to obtain products with higher value. Beyond cellulosic pulps lignin is also removed from vegetable fibers. The lignin could be oxidized and applied in effluents treatments for heavy metals removal. Oxidized lignins presents very strong chelating properties. The use of pulps and lignin allowing the integral use of the vegetable biomass. Lignins were obtained by ethanol-water pulping of sugarcane bagasse and straw. The oxidation of lignins were performed using acetic acid and Co/Mn/Br catalytical system at 50, 80 and 115°C for 5h. Activation energy (Ea) was calculated for lignins from sugarcane bagasse and straw and presented Ea of 34.4 kJ.mol-1 and 23.3 kJ.mol-1, respectively. The first value indicates higher crosslinked formation. A kinetic study of the oxidation was evaluated by UV/Visible. FTIR spectra of various samples of oxidized lignins were submitted to Principal Component Analysis (PCA). The results showed slight structure modifications in lignins after oxidation reaction.

[Aknowledgements: Fapesp, CNPq, Lignocarg-ALFAProgram]