# Elemental Mercury Removal over CeO\({}_{2}\)/TiO\({}_{2}\) Catalyst Prepared by Sol-Gel Method
## 2 Materials and Methods
### Catalyst Performance Test and Characterization  
A laboratory-scale elemental mercury removal system was used in this study. The schematic of the setup is shown in Figure 2. The removal efficiency of Hg\({}^{0}\) (\(\eta\)) and NO (\(\eta^{\prime}\)) could be calculated from the following equations:  
\[\eta=\frac{C_{0}-C}{C_{0}}\times 100,\% \tag{1}\]  
\[\eta^{\prime}=\frac{C^{\prime}{}_{0}-C^{\prime}}{C^{\prime}{}_{0}}\times 100,\% \tag{2}\]  
where \(C_{0}\) represents the inlet Hg\({}^{0}\) concentration (\(\mu\)g\(\cdot\)m\({}^{-3}\)), \(C\) represents the outlet Hg\({}^{0}\) concentration (\(\mu\)g\(\cdot\)m\({}^{-3}\)), \(C^{\prime}{}_{0}\) represents the inlet NO concentration (\(\mu\)L\(\cdot\)L\({}^{-1}\)), and \(C^{\prime}\) represents the outlet NO concentration (\(\mu\)L\(\cdot\)L\({}^{-1}\)). It is noteworthy that both adsorption and oxidation of Hg\({}^{0}\) may happen over the catalyst. Therefore, reducing agents and a conversion system before Hg\({}^{0}\) analyzer would be needed for calculating the oxidation efficiency and adsorption efficiency of the catalysts. However, neither the adsorbed Hg nor the gaseous Hg\({}^{2+}\) could emit into the atmosphere, since the gaseous Hg\({}^{2+}\) would be removed later (for example, in WFGD). In other words, only the Hg\({}^{0}\) downstream of the catalyst should be considered as the mercury emission from the power plant in a practical situation. As a result, the removal efficiency of Hg\({}^{0}\) defined by Equation (1) is used in this paper. From Section 3.1 to Section 3.3, the effects of reaction temperature and flue gas components on the Hg\({}^{0}\) removal efficiency are investigated. In Section 3.4, the simultaneous removal performance of Hg\({}^{0}\) and NO is studied at various reaction temperatures; 0.500 g catalyst was placed into the quartz reactor whose the diameter was 8 mm. The total flow rate of the simulated flue gas was 1.0 L-min\({}^{-1}\). The space velocity during the experiments was about 120,000 h\({}^{-1}\), which has the same order of magnitude as many other studies [14; 17]. All the experimental conditions are presented in Table 2. \begin{table}
\begin{tabular}{c c c c} \hline
**Catalyst** & **C\({}_{\text{16}}\)H\({}_{\text{36}}\)O\({}_{\text{4}}\)Ti/mL** & **Ce(NO\({}_{\text{3}}\))\({}_{\text{3}}\)**-6H\({}_{\text{2}}\)O/g** & **C\({}_{\text{9}}\)H\({}_{\text{21}}\)O\({}_{\text{4}}\)V/g** \\ \hline pure TiO\({}_{\text{2}}\) & 44.00 & - & - \\ Ce0.1 Ti & 40.00 & 2.29 & - \\ Ce0.2 Ti & 36.67 & 4.21 & - \\ Ce0.5 Ti & 29.33 & 8.41 & - \\ Ce1.0 Ti & 22.00 & 12.62 & - \\ Ce0.5 Ti-V & 29.18 & 8.37 & 1.34 \\ \hline \end{tabular}
\end{table} 
Table 1: The amounts of the precursors used in the preparation process. \begin{table}
\begin{tabular}{c c c} \hline
**Variable** & **Temperature/\({}^{\circ}\)C** & **Fine Gas Components** \\ \hline Temperature & 150, 200, 250, 300, 350, 400, 450 & BG \({}^{\star}\) + 6\% O\({}_{\text{2}}\) + 45 \(\mu\)L\(\cdot\)L\({}^{-1}\) HCl + 200 \(\mu\)L\(\cdot\)L\({}^{-1}\) NO \\  & & + 200 \(\mu\)L\(\cdot\)L\({}^{-1}\) NH\({}_{\text{3}}\) + 500 \(\mu\)L\(\cdot\)L\({}^{-1}\) SO\({}_{\text{2}}\) \\ O\({}_{\text{2}}\) & 350 & BG + 45 \(\mu\)L\(\cdot\)L\({}^{-1}\) HCl + O\({}_{\text{2}}\) (0, 3%, 6%, 9%) \\ HCl & 350 & BG + 6\% O\({}_{\text{2}}\) + HCl (0, 15, 30, 45 \(\mu\)L\(\cdot\)L\({}^{-1}\)) \\ NO and NH\({}_{\text{3}}\) & 350 & BG + 45 \(\mu\)L\(\cdot\)L\({}^{-1}\) HCl + 6\% O\({}_{\text{2}}\) + \\  & & (NO + NH\({}_{\text{3}}\)) (0, 200, 400, 600 \(\mu\)L\(\cdot\)L\({}^{-1}\)) \\ NH\({}_{\text{3}}\)/NO & 350 & BG + 45 \(\mu\)L\(\cdot\)L\({}^{-1}\) HCl + 6\% O\({}_{\text{2}}\) +200 \(\mu\)L\(\cdot\)L\({}^{-1}\) NO + \\  & & NH\({}_{\text{3}}\) (0, 160, 180, 200, 220, 240 \(\mu\)L\(\cdot\)L\({}^{-1}\)) \\ SO\({}_{\text{2}}\) & 350 & BG + 45 \(\mu\)L\(\cdot\)L\({}^{-1}\) HCl + 6\% O\({}_{\text{2}}\) + \\  & & \(\text{SO}_{\text{2}}\) (0, 250, 500, 750 \(\mu\)L\(\cdot\)L\({}^{-1}\)) \\ \hline \end{tabular}
\end{table} 
Table 2: Experimental conditions.