The reduction of waste lubricant oil distillate through the enhancement of organics degradation by ozonation with elevated temperature and stable pH for the zero discharge

Evaporation has been widely applied to deal with the hazardous waste of waste lubricant oil, and around 90% distillate obtained should be further treated for the final discharge or reuse as recycled water. Waste lubricant oil distillate contained amounts of pollutants of alkanes, aliphatic amines, etc., with chemical oxygen demand of 2042–2153 mg/L. To improve the ozonation efficiency, microbubble-ozonation with elevated temperature and stable pH was employed to deal with waste lubricant oil distillate in this work. The removal rates of chemical oxygen demand and total organic carbon increased from 53.07% and 25.08% to 87.45% and 72.75%, respectively, under the condition of 45 °C and stable pH 11. Active-ozone concentration increased from 26.41 to 41.76 mg/L, and the corresponding hydroxyl radical concentration increased from 29.78 to 49.28 μg/L with and without temperature and pH control. Ozone reaction rate (k) increased by 0.019 min⁻¹. The reduced molecular weight after treatment also increased the biodegradability of the waste lubricant oil distillate due to the enhanced degradation of alkanes, aromatics and many other organic compounds. With the elevated temperature and stable pH, microbubble ozonation efficiency increase greatly, and it could be the promising processes for the further treatment of waste lubricant oil distillate in an efficiency way.