ABSTRACT
Photo-induced processing has been widely applied in industries including automobile manufacturing, electronics, textiles, chemicals, medical treatment and wastes control[8]. High Frequency (HF) Discharge Electrodeless Lamp (HFDEL), a typical UV light source, has been invented over 100 years and started to apply into the photolysis of organic compounds in solution and the irradiation of gases since 1970s[9]. Unlike the conventional lamps energized by the electric field between the electrodes, the principle of HFDELs is that the gas or materials in the lamp are excited by HF electromagnetic field to form stable UV-emitting discharge plasma. Such unique discharge pattern endows the HFDELs with lots of advantages compared to the conventional UV lamps (i.e. low pressure mercury lamps), including long lifetime of UV output, high UV/Vacuum UV (VUV) radiant power, VUV-mediated generation of O3 in conjunction with UV to create Hydroxyl radicals (HO•) and adaptable lamp shapes. Com-
1 INTRODUCTION
Air pollution consists of a heterogeneous mixture of gasses and particles that include carbon monoxide (CO), nitrates (NOX), sulfur dioxide (SO2), ozone (O3) and Volatile Organic Compounds (VOCs)[1]. Exposure to VOCs might cause toxic effects on central nervous system and internal organs, and the related symptoms, such as headache, respiratory tract irritation, dizziness and nausea, are known as the Sick Building Syndrome (SBS)[2]. For high concentration (several hundred of ppm) of VOCs emission sources, catalytic incineration and combustion (200-900oC) have been well developed and successfully operated but are not cost-effective for low concentration of VOCs[3]. Sulfur compounds such as H2S, methanethiol (CH3SH), Dimethyl Sulfide (DMS), dimethyl disulfide, are mainly responsible for the nauseous odors emitted from these plants[4,5]. They are characterized by high toxicity, resulting in concentration-dependent toxicity in the respiratory, cardiovascular and nervous systems[6] and extremely low odor threshold values, e.g. 7.6 × 10−4
pared to Microwave Discharge Eletrodeless Lamps (MDELs), HFDELs possess higher energy conversion efficiency, have no need for resonant cavity and overcome the short lifetime of magnetron equipped on MDELs. However, little has been done on the photolysis of air pollution.
