Electrochemical conversion of sulfur dioxide with a rotating cylinder electrode working as anode or cathode

Abstract

BACKGROUND: A batch electrochemical reactor with a rotating cylinder electrode is analysed for the transformation of sulfur dioxide into either sulfuric acid or colloidal sulfur. RESULTS: Potentiostatic experiments carried out at 30 °C and 500 rpm with 5 g L-1 SO2 in 0.5 mol L-1 H2SO4 conclude that -0.7 V, against SCE, represents an appropriate potential for the sulfur production at a 316 L stainless steel cathode. The figures of merit were: 0.15 kg m-3 h-1 space time yield and 39.7 kWh kg-1 for specific energy consumption. Galvanostatic experiments at 30 °C and 1000 rpm with three-dimensional electrodes identify graphite felt as a promising anodic material. Using a gas phase of 5% SO2 in nitrogen and 0.5 mol L-1 H2SO4 as supporting electrolyte, a macrokinetic current density of 100 mA cm-2 represents an appropriate value, being the space time yield 7.58 kg m-3 h-1 with 2.86 kWh kg-1 specific energy consumption. CONCLUSION: An electrochemical reactor with a rotating cylinder electrode showed a good performance for the production of colloidal sulfur. Sulfur dioxide was also converted into sulfuric acid including a separator in a reactor with a three-dimensional rotating cylinder anode and co-current gas and liquid flows.