Ozonation of Phenol-Containing Wastewater Using O3/Ca(OH)2 System in a Micro Bubble Gas-Liquid Reactor

The degradation of phenol in aqueous solution was investigated in an integrated process consisting of O3/Ca(OH)2 system and a newly developed micro bubble gas-liquid reactor. The effects of operating parameters such as Ca(OH)2 dosage, reactor pressure, liquid phase temperature, initial phenol concentration and inlet ozone concentration on degradation and mineralization (TOC removal) were studied in order to know the ozonation performance of this new integrated process. It is demonstrated that the degradation and TOC removal efficiency increased with increasing inlet ozone concentration and increasing Ca(OH)2 dosage before 2 g/L, as well as decreasing initial phenol concentration. The optimum Ca(OH)2 dosage should exceed Ca(OH)2 solubility in liquid phase. The reactor pressure and liquid phase temperature have little effects on the removal and TOC removal efficiency. When Ca(OH)2 dosage exceeded 3 g/L, the degradation and TOC removal of phenol almost reached 100% at 30 and 55 min, respectively. The intensification mechanism of Ca(OH)2 assisted ozonation was explored through analysis of the precipitated substances. The mechanism for Ca(OH)2 intensified mineralization of phenol solution is the simultaneous removal of CO32- ions, as hydroxyl radical scavengers, due to the presence of Ca2+ ions. Results indicated that the proposed new integrated process is a highly efficient ozonation process for persistent organic wastewater treatment.