A new green technology: hydrothermal electrolysis for the treatment of biodiesel wastewater

Recently, biodiesel has become more attractive as an alternative diesel fuel because it is renewable, biodegradable, non-toxic, and environmentally friendly. In this study, we have developed a new green process called ??hydrothermal electrolysis??, by which industrial wastewater can be converted to more value-added chemicals under high-temperature and high-pressure aqueous conditions. We prepared model biodiesel wastewater and carried out hydrothermal electrolysis experiments by using both a continuous flow reactor and a batch autoclave. Current efficiencies and the effects of reaction time and reaction temperature on the decomposition of biodiesel wastewater and removal of total organic carbon (TOC) were investigated under various operating conditions. It was found that conversions of both TOC and glycerol inside the model biodiesel wastewater increased with increasing applied current. With the autoclave, the maximum glycerol conversion was recorded as 83% by applying 1 A current at 250 °C, whereas with the flow reactor, 75% of glycerol was converted into gas and liquid products under the effect of 1 A current for 60 min at a reaction temperature of 280 °C. In the case of TOC removal from the liquid product solution, under identical conditions, it was found that 23 and 15.9% TOC conversions were achieved by the batch and continuous flow reactors, respectively.