Mechanistic models of electrocoagulation kinetics of pollutant removal in vinasse waste: Effect of voltage

Abstract

Vinasse is bioethanol liquid waste with high Chemical Oxygen Demand (COD) content, which is harmful to the environment. It therefore requires treatment and one of the potential methods to treat is electrocoagulation (EC). This process involved some mechanisms such as electrode dissolution, adsorption, entrapment, sedimentation and flotation. Furthermore, the working volume during the process, in reality, was not constant as it reduced. Hence, mechanistic models of EC were employed to have the detailed COD removal process. In this study, four mechanistic models were proposed and applied to simulate the COD removal process at voltage of 7.5 and 12.5 V. The results showed that Model 2 gave better prediction than the others due to its low Sum of Squares Error (SSE) which was 0.1189-0.2289 while the others showed SSE of 0.1884-0.5792. The model assumed that settled sludge was formed from the adsorption and entrapment of COD on the coagulants, while the floated sludge was formed from flotation of the settled sludge. Furthermore the model recorded higher kinetic constant values such as adsorption rate (ka), entrapment rate (ke) and flotation rate (kf) at 12.5 V compared with those at 7.5 V. In conclusion, the proposed model successfully figured out the details of COD removal mechanisms during the EC of vinasse and the kinetic constant values increased with increase in voltage. It is expected that this model could be useful to predict the behavior of EC process with different conditions as well as to design EC system for industrial scales.