Effects of experimental parameters on Hg0 removal over magnetic AgI-BiOI/CoFe2O4 photocatalysts using wet process
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摘要: 采用水热-共沉淀法制备了一种新型的磁性AgI-BiOI/CoFe2O4复合材料光催化剂，考察了荧光灯辐照下光催化剂脱除模拟烟气中单质汞（Hg0）的性能，研究了实验参数对脱汞性能的影响及反应产物。结果表明，AgI-BiOI/CoFe2O4光催化剂的热稳定性较差，当煅烧温度超过400 ℃时该光催化剂的化学成分会发生变化；随着催化剂用量、反应溶液pH值、反应溶液温度和烟气中O2浓度的增加，脱汞效率先增加后不变或下降；反应溶液中存在的CO32-和SO42-对脱汞效率有一定的抑制作用；当通入SO2时，脱汞效率急剧下降；而NO对脱汞效率的抑制作用相对较小。反应产物分析表明，SO2、NO和Hg0的最终氧化产物分别是SO42-、NO3-和Hg2+。
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关键词:
- 磁分离 /
- AgI-BiOI/CoFe2O4 /
- 脱汞 /
- 荧光灯照射 /
- 实验参数
Abstract: A novel magnetic AgI-BiOI/CoFe2O4 hybrid composites were prepared via a solvothermal and subsequent coprecipitation method, and utilized to remove Hg0 from coal-fired flue gas under fluorescent light irradiation. The experimental parameters and main products presented in solution after reaction were investigated in detail. The experimental results showed that the AgI-BiOI/CoFe2O4 composites showing a poor thermal stability would transform into other compounds when the calcinated temperature was above 400℃. With the increases of photocatalyst dosage, reaction solution pH, temperature of reaction solution in reactor and O2 concentration, the Hg0 removal efficiencies were first increased and then unchanged or decreased. The presences of inorganic anions such as CO32- and SO42- in solution exhibited some inhibitory effects on Hg0 removal. Furthermore, the presence of SO2 had a dramatic inhibition on Hg0 removal, while the inhibitory effect of NO on Hg0 removal was relatively small. SO42-, NO3- and Hg2+ species were the final oxidation products of SO2, NO and Hg0 by reactive species. -
Figure 4 Effect of calcination temperature on Hg0 removal efficiency
conditions: baseline flue gas, t=35 ℃, initial pH=7, solution volume=1 L, FSL radiation intensity=11 W/L, catalyst dosage=200 mg/L
Figure 5 Effect of reaction solution temperature on Hg0 removal efficiency
conditions: baseline flue gas, initial pH=7, solution volume=1 L, FSL radiation intensity=11 W/L, catalyst dosage=200 mg/L
Figure 6 Effect of solution pH on Hg0 removal efficiency
conditions: baseline flue gas, t=35 ℃, solution volume=1 L, FSL radiation intensity=11 W/L, catalyst dosage=200 mg/L
Figure 7 Effect of anions in solution on Hg0 removal efficiency
conditions: baseline flue gas, t=35 ℃, initial pH=7, solution volume=1 L, FSL radiation intensity=11 W/L, catalyst dosage=200 mg/L
Figure 8 Effect of O2, SO2 and NO on Hg0 removal efficiency
error bars represent standard deviation of means (n=4) conditions: Hg0=55.0 μ g/m3, t=35 ℃, initial pH=7, solution volume=1 L, FSL radiation intensity=11 W/L, catalyst dosage=200 mg/L
Figure 9 Effect of catalyst dosage on Hg0 removal efficiency
conditions: Hg0=55.0 μ g/m3, t=35 ℃, initial pH=7, FSL radiation intensity=11 W/L
Figure 10 (a) Cycling runs for photocatalytic oxidation of Hg0 over AgI-BiOI/CoFe2O4 and (b) magnetic hysteresis loops for AgI-BiOI/CoFe2O4 after four consecutive runs
error bars represent standard deviation of means (n=3) conditions: Hg0=55.0 μ g/m3, t=35 ℃, initial pH=7, solution volume=1 L, FSL radiation intensity=11 W/L, catalyst dosage=200 mg/L
Table 1 Physical features of AgI-BiOI/CoFe2O4 hybrids calcinated at different temperatures
Sample BET surface area A/(m2·g-1) Total pore volume v/(cm3·g-1) Without calcination 20.7 0.066 200 ℃ calcination 33.9 0.114 400 ℃ calcination 15.1 0.056 600 ℃ calcination 1.5 0.002 
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Table 2 Reaction products of SO2 and NO by AgI-BiOI/CoFe2O4
Ion category SO32- SO42- NO2- NO3- Measured concentration 0 40.32 mg/L 0 15.50 mg/L
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