VUV/TiO_2/O_3去除水中微量硝基苯的研究

Removal of Trace Nitrobenzene in Water by VUV/TiO_2/O_3

采用负载在钛片上的二氧化钛(TiO2)薄膜光催化剂,以能发射185 nm真空紫外线(VUV)的紫外灯为光源,研究臭氧强化的真空紫外光催化方法(VUV/TiO2/O3)对水中微量硝基苯的去除效果.结果表明,VUV/TiO2/O3是一种有效地去除水中微量硝基苯的方法,VUV/TiO2/O3的表观一级反应速率常数比UV/TiO2/O3和VUV/O3分别高102.8%和30.8%,去离子水中50μg/L的硝基苯反应60 s后就降低到检测限以下.VUV/TiO2/O3对硝基苯的降解速率随臭氧投加量的增加而显著增大,臭氧投加量1.52 mg/L时的反应速率比不加臭氧时提高了134.4%;虽然表观一级反应速率常数随初始浓度增加而稍有下降,但初始浓度170μg/L的硝基苯反应2 min后也无法检出.水中常见的重碳酸盐和腐殖酸对硝基苯降解有显著的抑制作用,两者浓度分别为2 mmol/L和3.2 mg/L时,VUV/TiO2/O3对硝基苯的表观反应速率常数分别下降82.9%和71.6%,反应速率常数的倒数与重碳酸氢根浓度线性相关.VUV/TiO2/O3能快速有效地去除地表水(含碳酸盐和天然有机物)中的微量硝基苯,4 min内初始浓度为90μg/L的硝基苯去除率达到96%,UV254降低了80%.

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 μg/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 μg/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 μg/L is removed within 4 min and the UV absorbanee at 254 nm is also reduced 80%.