Impedance spectra of anodic dissolution of iron in distillery vinasse

Electrocoagulation technique has a great application potential to treat distillery vinasse, a liquid effluent generated from alcohol distilleries. The anodic dissolution of carbon steel in this effluent in the potential range of -750 mV to -100 mV was investigated by potentiodynamic polarization; likewise, the electrochemical impedance spectroscopy spectra were registered over anodic potentials of -560 mV, -500 mV and -400 mV (overpotentials of 20 mV, 80 mV and 180 mV) corresponding to the active dissolution region in order to propose a mechanism for describing the behavior of the carbon steel electrodissolution. Were explored the effects of the flow regime (Reynolds number of 5,500 and 11,500) and the temperature (60 °C and 80 °C) over the behavior of the spectra. At low current densities the impedance behavior can be satisfactorily described by the combination of the catalytic and non-catalytic mechanism of iron dissolution. It was also found that the dissolution must be carry out at current densities closely to 1 mA cm−2 to prevent the possible formation of iron oxide layers on the anode. The anodic dissolution was favored by increasing the flow regime and temperature as well.