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 185 nm was measured in the presence of different ions. At 254 nm, only nitrate showed a measurable absorption coefficient of [Formula: see text] = 3.51 M[Formula: see text] cm[Formula: see text], and all other ions showed a molar absorption coefficient below the detection limit. However, at 185 nm, all the ions showed high absorption coefficients, with nitrate giving the highest absorption coefficient of [Formula: see text] = 5568 M[Formula: see text] cm[Formula: see text]. Second, the hydroxyl radical (HO[Formula: see text]) 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 185 nm UV to form HO[Formula: see text], 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.

Novel Collimated Beam Setup to Study the Kinetics of VUV-Induced Reactions.

Vacuum UV (VUV) process is an incipient advanced oxidation process, which can be used for water treatment. This process relies on the formation of hydroxyl radicals through the VUV-induced photolysis of water. In particular, the use of ozone-generating mercury vapor lamps, which emit 10% of the radiation at 185 nm and 90% at 254 nm, is showing very promising results for the degradation of micropollutants. The kinetics of VUV process has been studied in batch- and flow-through reactors, but the effect of 254 and 185 nm photons cannot be isolated, mass transfer resistances can take place and the interpretation of the results is complex. In this technical note, a new VUV collimated beam to conduct kinetic tests is presented, which offers several advantages: (1) it allows the irradiation of samples with 185, 254 nm photons, or both, (2) the concentration of reagents is uniform in the reaction volume and (3) it allows to change the fluence rate by changing the distance between the lamp and the photoreactor. Details of the geometry are presented, as well as an analysis of the collimation and uniformity of the radiation of the new VUV-collimated beam setup.

Photocatalytic metamaterials: TiO2 inverse opals.

The study of the photocatalytic activity of TiO(2) inverse opals showed that these structures behave as metamaterials: their properties arise principally from the 3D periodic structure of the material and marginally from porosity, reflectivity and scattering.