Polyphenols from Sugarcane Vinasses, Quantification, and Removal Using Activated Carbon After Biochemical Treatment in Laboratory-Scale Thermophilic Upflow Anaerobic Sludge Blanket Reactors

Studies on the removal of polyphenols from sugarcane vinasses using three upflow anaerobic sludge blanket (UASB) reactors operating isothermally at temperatures of 45, 55, and 65 °C are presented. The procedure started evaluating the stability of the reactors through the quantification of four important parameters of the process: temperature, pH, alkalinity factor, and acetic acid production. The physical and chemical characterizations of the vinasses were made to evaluate the applied treatment. Total polyphenols were quantified before and after the biochemical treatment using the Folin-Ciocalteu’s method. The obtained results showed that this biochemical treatment was not enough by itself to remove the phenolic compounds present in the vinasses feed. The use of complementary treatment for the removal of polyphenols with activated carbon was proposed and evaluated. The effectiveness of the adsorption process was analyzed and compared through the models of Langmuir, Freundlich, and Dubinin-Radushkevich, using the obtained experimental data. The model that provided the best fit of the experimental data was the Langmuir model with a correlation coefficient of 0.991. The adsorption process achieved to reduce the concentration of polyphenols in the vinasses from 3600 mg of gallic acid equivalent (GAE)/L to 1072 mg GAE/L by single-step adsorption. That is equivalent to an overall reduction of 70.2%.