Comparison on mineralization of 2,4,6-tribromophenol by UV-based advanced oxidation processes: UV/Na2S2O8 and UV/H2O2

Abstract

Mineralization of 2,4,6-tribromophenol (TBP) in water by UV-based oxidation processes (AOPs) including UV/H2O2 and UV/Na2S2O8 (UV/PS) was explored in this work. There was firstly systematically and comparatively an investigation of these two AOPs on the mineralization of TBP for toxicity change, mineralization efficiency and economic cost. The effects of oxidant concentration, initial TBP concentration and pH on TOC removal were investigated. The results indicated both UV-based oxidation systems had optimum oxidant concentration when the [oxidant]/[TBP] molar ratio reached 15/1. As TBP can absorb UV-254 nm, the initial TBP concentration can influence oxidant decomposition, and their mutual effects decide TOC removal efficiency. Raising pH from 3 to 11 inhibited the mineralization of TBP slightly in the UV/PS process while the mineralization rate reach its highest at pH 9 and decreased dramatically at pH 11. The effect of three inorganic ions on the efficiency of these UV-based AOPs was investigated, and the results were in the order NO 3 − > HCO 3 − > Cl−. Toxicity tests with activated sludge showed that oxidation processes can effectively reduce the toxicity of TBP. BOD measurements also revealed that biodegradability improved with both oxidation processes while UV/PS performed better. According to the calculation of the two UV-based AOPs, UV/PS is the much more effective and economic way. However, the formation of BrO 3 − in the UV/PS system will limit its application in treating wastewater containing brominated organic pollutants.