Impedance spectra of anodic dissolution of iron in distillery vinasse

Abstract

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 -750mV to -100mV was investigated by potentiodynamic polarization; likewise, the electrochemical impedance spectroscopy spectra were registered over anodic potentials of -560mV, -500mV and -400mV (overpotentials of 20mV, 80mV and 180mV) 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 1mAcm−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.