The schematic diagram of the experimental system Cilengitide shown in Fig. 1. The system consisted of simulated flue gas, a photocatalytic reactor and a mercury analyzer. The N2 was divided into two branches, whose flow rates were controlled by two mass flow meters (MFC, CS200 type) separately. The total flow of the two branches was 1.2 L/min. One gas stream with a flow rate of 0.2 L/min passed through the Hg0 permeation tube to introduce Hg0 vapor into the system. The Hg0 inlet concentration was around 65 μg/m3. The mercury permeation tube was placed in a U-shape glass tube which was immersed in a constant 55 °C water bath to ensure a constant Hg0 permeation rate. The other stream of N2 had a flow rate of 1 L/min. An on-line mercury analyzer (VM3000 mercury vapor monitor, Mercury Instruments, Germany) based on atomic absorption spectrometry was used to measure the gas phase concentration of Hg0. The gas flowed through two silica gel columns before entering the mercury analyzer to remove water vapor. Finally, the gas got through the active carbon bottle and vented out of the system.