[Removal of trace nitrobenzene in water by VUV/TiO2/O3]

The removal of trace nitrobenzene in water by the ozone-enhanced VUV photocatalysis process (VUV/TiO2/O3) was investigated, in which low-pressure mercury lamp emitting 185 nm vacuum ultraviolet and titanium dioxide film coated on the titanium plate were used as light source and photocatalyst respectively. The results show that, VUV/TiO2/O3 is an effective method to remove trace nitrobenzene in water, and the pseudo-first-order rate constant of nitrobenzene in the VUV/TiO2/O3 process is 102.8% and 30.8% higher than that in the UV/TiO2/O3 and VUV/O3 respectively. And 50 microg/L nitrobenzene in deionized water is totally removed within 60 s by the VUV/TiO2/O3 process. Higher ozone dosage is beneficial to accelerate nitrobenzene degradation, and the apparent rate constant at ozone dosage of 1.52 mg/L is 134.4% higher than that without ozone addition. Though the rate constant is slightly decreased with increase of nitrobenzene concentration, 170 microg/L nitrobenzene is removed to below the detection limit within 2 min. Common species such bicarbonate and humic acid in water significantly inhibit the removal of nitrobenzene, and the apparent rate constant is reduced 82.9% and 71.6% respectively when 2 mmol/L bicarbonate and 3.2 mg/L humic acid are added into the water. The inverse of the apparent rate constant is linear with the bicarbonate concentration. Trace nitrobenzene in surface water containing bicarbonate and natural organic matter can be removed fast and effectively by the VUV/TiO2/O3 process, and 96% nitrobenzene with initial concentration of 90 microg/L is removed within 4 min and the UV absorbance at 254 nm is also reduced 80%.