Treatment of an aqueous solution of lignin by means of advanced oxidation processes

Abstract

The lignin is a macromolecule of vegetable origin, formed by units of phenilpropane. The pulp process for the production of paper modifies the lignin structure generating different types of pollutant residues. Some technologies and methodologies have been used for avoiding formation or to eliminate, but without good results, this work proposed the use of Advanced Oxidation Processes (PAO). Different conditions of oxidation were used as: UV/H2O2, UV/O3 and UV/H2O2/O3, to modify the lignin using a photoreactor type batch with capacity of a liter and equipped with a lamp UV of 1000 W. Used two concentrations of lignin (0.025 % and 0.05 %). Analized the value of the chemical oxygen demand (DQO), before and after the treatment. For the system light UV/H2O2 with lignin to 0.025 %, the DQO diminished of 323 mg l-1 to 144 mg/l during the hour of treatment and with lignin to 0.05 % the DQO diminished 870 mg l-1 to 175 mg l-1 in three hours of treatment. For the system light UV/H2O2/O3 with lignin to 0.025 %, the DQO diminished of 323 mg l-1 to 127 mg l-1 in an hour. For the concentration of 0.05 % the DQO diminished from 870 mg l-1 to 52 mg l-1 in three hours. For the system light UV/O3 with lignin to 0.025 %, the DQO diminished of 323 mg l-1 163 mg l-1 in two hours. With these results we conclude that the system of oxidation used modified the lignin in all the experiments. For that, the best conditions to transform the lignin was that of the system UV/H2O2/O3 followed of UV/H2O2 and the system light UV/O3 had less efficiency, for this needing more time to obtain approximately the same quantity of transformation of this compound. These results open the possibility of using this system to eliminate lignin or by-products in the paper industry.