The electrolytic process of diluted aqueous chloride solutions (0.07 M) was investigated at Ti/RuO2.2SnO2 and Ti/Pt electrodes, at different values of current density (250, 750 and 1500 A m-2), temperature (10, 25 and 65 °C) and electrolysis time (0 – 180 minutes). The time evolution of chlorine species (i.e. active chlorine, chlorite, chlorine dioxide, chlorate and perchlorate), as well as their faradic efficiency, were investigated to understand whether their formation and consumption was either chemical or electrochemical. Different current efficiency profiles were generally observed for the two explored electrode materials, when the applied current density and the temperature were varied in the above reported experimental intervals. At the Ti/RuO2.2SnO2 (especially at the lowest current density), similar current efficiencies for the synthesis of active chlorine and chlorate were estimated. On the contrary, rather low current efficiencies for active chlorine and high current efficiencies for chlorate and perchlorate were measured at the Ti/Pt electrode. The concentration trends of chlorate and perchlorate indicated that the electrochemical route was responsible for their presence in the bulk solution, instead of a chemical path. This insight was corroborate by the measured anodic potentials: high values for the anode potential were indeed related to high current efficiencies for chlorate and perchlorate. The low concentration levels (and thus low current efficiencies) assessed for chlorite and chlorine dioxide throughout the tests were not useful for discriminating between a chemical and an electrochemical depletion processes; however, further potentiodynamic tests suggested that chlorites are highly reactive towards both anodic and cathodic surfaces, thus suggesting that the electrochemical path of depletion could prevail over the chemical one. Conversely, due to a solution pH quite unfavourable to the stability of chlorine dioxide, its low concentration level was justified by a chemical depletion route.
Investigation on the active chlorine production from diluted chloride solutions and electrochemical reactivity of their side-products
NEODO, Stefano;ROSESTOLATO, Davide;FERRO, Sergio;DE BATTISTI, Achille
2012
Abstract
The electrolytic process of diluted aqueous chloride solutions (0.07 M) was investigated at Ti/RuO2.2SnO2 and Ti/Pt electrodes, at different values of current density (250, 750 and 1500 A m-2), temperature (10, 25 and 65 °C) and electrolysis time (0 – 180 minutes). The time evolution of chlorine species (i.e. active chlorine, chlorite, chlorine dioxide, chlorate and perchlorate), as well as their faradic efficiency, were investigated to understand whether their formation and consumption was either chemical or electrochemical. Different current efficiency profiles were generally observed for the two explored electrode materials, when the applied current density and the temperature were varied in the above reported experimental intervals. At the Ti/RuO2.2SnO2 (especially at the lowest current density), similar current efficiencies for the synthesis of active chlorine and chlorate were estimated. On the contrary, rather low current efficiencies for active chlorine and high current efficiencies for chlorate and perchlorate were measured at the Ti/Pt electrode. The concentration trends of chlorate and perchlorate indicated that the electrochemical route was responsible for their presence in the bulk solution, instead of a chemical path. This insight was corroborate by the measured anodic potentials: high values for the anode potential were indeed related to high current efficiencies for chlorate and perchlorate. The low concentration levels (and thus low current efficiencies) assessed for chlorite and chlorine dioxide throughout the tests were not useful for discriminating between a chemical and an electrochemical depletion processes; however, further potentiodynamic tests suggested that chlorites are highly reactive towards both anodic and cathodic surfaces, thus suggesting that the electrochemical path of depletion could prevail over the chemical one. Conversely, due to a solution pH quite unfavourable to the stability of chlorine dioxide, its low concentration level was justified by a chemical depletion route.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
