Uso de energia fotovoltaica no tratamento de águas residuárias da produção de biodiesel por eletrocoagulação

Abstract

This study aimed to apply the electrocoagulation technique in the treatment of wastewater from the biodiesel purification process. The individual and combined influence of the inert parameters (current density and electrolysis time) were analyzed. As response variables of the EC process, the parameters color, turbidity, COD, TOG and residual Al were considered, whose maximum removals will be considered as criterion of optimal condition of the EC process. In the first stage of the study a DCCR was applied to obtain the model or response surface, applying the EC technique to the biodiesel effluent in a batch bench reactor, which included a pair of aluminum electrodes, fed by a source of direct current. The electrochemical treatment proved to be very efficient for variable responses in the range of values studied for current density and reaction time factors, reaching removal of up to 52%, 90%, 99% and 98% for COD, TOG, turbidity and respectively, applying 27.93 mA.cm- 2 for 64'49 ". However, it was not possible to fit a predictive model for these variables. For the second step, the conditions that obtained the best removal efficiency of the response variables were used, considering the minimum generation of residual aluminum after the electrolysis. The treatment time was set to 5 minutes and current density of 4 mA.cm-2 was adjusted, and the power supply was replaced by a non-battery photovoltaic system, applying the direct current to the effluent treatment by electrocoagulation to evaluate the energy efficiency involved in the treatment process. The use of the energy supplied directly by the photovoltaic panel was effective in the removal of impurities from the effluent, reaching removal of up to 44%, 90%, 90% and 80% for COD, TOG, turbidity and color, respectively. It was verified that the amount of energy supplied by the panel could be applied to a larger volume and even in a continuous flow of effluent, either on days with higher solar incidence or lower incidence (partly cloudy days), it would still be sufficient for maintain the treatment system.