Quantitative analysis on removal path of emulsified oil in the reactor of EC

Abstract

Abstract Electrocoagulation (EC) technology using aluminum as sacrificial electrode has been successfully applied to remove the emulsified oil with micron size. This study aimed to employ mass balance measurements to quantify the oil separation between flotation and sedimentation for studying pollutant removal mechanism and then research into deciphering EC, which is novel to emulsified oil demulsification using EC. The effects of current density, stirring speed and surfactant type on oil removal path were investigated. The percentage mass floated was found to increase with current density increase. After electrolysis, the maximum current density, 150 A m−2, produced the largest pollutant recovery at the surface (approximately 90% of the total mass). In contrast, the mass fraction of oil floated was observed to increase and then decrease with increasing stirring intensity by magnetic stir. Under the same condition, the dramatic mixing, 1000 rpm, transported the less pollutant by floated (only about 63% of the total mass); and yet the gentle mixing of 500 rpm, created the maximum mass floated (approximately 90% of the total mass). For a given current density and stirring intensity, the dominant removal path of emulsified oil is always flotation. Experiments were conducted to determine the optimum operating conditions as current density of 75 A/m2 and stirring speed of 300 r/min, for maximum removal efficiency of emulsified diesel in bulk solution, approximately 97.3%. Type of surfactant is identified as the key operational parameter influencing which pollutant removal mechanism dominates. Through comparing SDBS, Tween 80, and the mix surfactant with both SDBS and Tween 80, the pollutant fates were found to be various due to different foaming characteristic of these reagent. Ultimately, the emulsified oil in the bulk solution was more difficult to be removed with the more types of surfactant.