Derivatização química e caracterização de uma lignina do bagaço da cana de açúcar

Abstract

Lignin obtained hydrolyzing sugar cane bagasse using DHR treatment (Dedini s Rapid Hydrolysis) was chemically modified with the aim to produce new materials. The reaction performed with sodium monochloroacetate results in an anionic polyelectrolyte (CML-Na) soluble in water at pH > 5.5. The degree of substitution measured by compleximetric titration ranged from 0.42 to 0.49 based on the lignin p-hydroxyphenyl unit. Doped with neodymium ion, from aqueous solution of Nd(NO3)3, generates the complex water insoluble CML -Nd. UV/Visible, IR and fluorescence spectroscopic investigation of these materials proved the incorporation of the rare earth metal as well as properties which support the possibilities of its use in photonic devices. The existence of a band at 880nm due to Neodymium electronic transition 4I9/2 → 4F3/2 permits the selective lignin metal complex excitation. The polyelectrolyte properties were investigated determining the Critical Aggregation Concentration (CAC) using pyrene as a probe. The value 14 x10-3 g dm-3, corresponding to a CMC of approximately 22 atoms of carbon in a linear polyelectrolyte, was obtained. Use of this material such as stabilizing aqueous alumina suspension in ceramic industries and to complex heavy metal ions to clean water is some important applications. Differential Scanning Calorimetry (DSC) showed a decrease from 395o C to 330o C when lignin reacts to produce the sodium polyelectrolyte, and to 270o C when doped with the Nd3+. The heat liberate doesn t change significantly comparing the degradation of pure lignin and sodium polyelectrolyte. However, an intense increase occurs when one changes to neodymium containing form.