Effects of inorganics on the degradation of micropollutants with vacuum UV (VUV) advanced oxidation

This research focused on the effects of inorganic water constituents on the efficiency of vacuum UV (VUV) for the degradation of micropollutants in surface water supplies. Atrazine was used as a model miropollutant, and bicarbonate, sulphate, and nitrate were used as the most common inorganic constituents in the water matrix. First, the absorbance of radiation at 254 and 185nm was measured in the presence of different ions. At 254 nm, only nitrate showed a measurable absorption coefficient of epsilon = 3.51 M-1 cm(-1) and all other ions showed a molar absorption coefficient below the detection limit. However, at 185nm, all the ions showed high absorption coefficients, with nitrate giving the highest absorption coefficient of epsilon = 5568 M-1 cm(-1). Second, the hydroxyl radical (HO center dot) scavenging effects of the same inorganic ions were evaluated; nitrate and bicarbonate showed a negative effect during the UV/H2O2 and VUV advanced oxidation processes. Sulfate was photolyzed with 185nm UV to form HO center dot, and for this reason, it assisted the degradation of the target micropollutant, as demonstrated by increases in the degradation rate constant. An additional component of this work involved developing a method for measuring the quantum yield of atrazine at 185 nm. This made it possible to distinguish the contribution of OH radical attach from that of direct photolysis towards the degradation of atrazine.