Removal of elemental mercury in flue gas with PMS solution catalyzed by Co doped BiFeO3
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摘要: 采用酒石酸溶胶凝胶法制备了一系列的钴掺杂的铁酸铋催化剂（BiFe1-xCoxO3，x=5%-20%，x为Co/CoFe物质的量比），借助于X射线衍射（XRD）、扫描电子显微镜（SEM）、比表面积（BET）、磁强振动计（VSM）、X射线光电子能谱（XPS）等手段对催化剂进行表征。在自制鼓泡反应器内，利用钴掺杂铁酸铋活化过一硫酸氢钾（PMS），开展了模拟烟气中单质汞脱除实验，获得反应的最佳条件。当钴掺杂量为10%，催化剂用量为0.5 g/L，PMS浓度为3.9 mmol/L，溶液初始pH值为8，反应温度70 ℃时，反应100 min内Hg0的平均脱除效率达89.36%。以乙醇和叔丁醇为淬灭剂，证明了·OH和SO4·-为Hg0催化氧化的活性物种，且SO4·-起主要作用，并结合XPS分析结果推测了脱汞反应机理。Abstract: A aseries of Co-doped BiFeO3 magnetic catalysts(BiFe1-xCoxO3, x=5%-20%) were synthesized by the tartaric acid sol-gel method, and the prepared catalysts were characterized using X-ray powder diffraction (XRD), Brunauer Emmett Teller (BET) technique, vibration sample magnetometer (VSM) and X ray photoelectron spectroscopy(XPS). The catalytic activity of Co doped BiFeO3 to activate Peroxymonosulfate (PMS) was evaluated at a self-designed bubbling reactor. The effects of Co ration in catalyst, dosage of the catalyst, PMS concentration, and solution pH and reaction temperature on the removal of elemental mercury were investigated systematically, and the optimum conditions were obtained. The result indicates that the average removal efficiency of elemental mercury reaches 89.36% within 100 min under the following condition:70℃, 10% doping Co, 3.9 mmol/L PMS concentration, 0.5 g/L catalyst dosage and pH 8. Moreover, it is testified that SO4·- and·OH are the active species when Hg0 is oxidized to Hg2+, where the tert-butyl alcohol and ethyl alcohol are used as quenchers. Finally, the mechanisms of mercury removal with PMS solution catalyzed by BiFe0.9Co0.1O3 are speculated on the basis of XPS results.
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Key words:
- peroxymonosulfate /
- Co doped BiFeO3 /
- sulfate radical /
- mercury
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图 2 BiFeO3和BiFe0.9Co0.1O3晶体的XRD谱图，BiFe0.9Co0.1O3的XPS光谱
Figure 2 (a) XRD patterns of BiFeO3 and BiFe0.9Co0.1O3, (b) XPS spectra of BiFe0.9Co0.1O3
图 3 室温下BiFe0.9Co0.1O3和 BiFeO3 的磁性
Figure 3 Magnetic hysteresis of BiFe0.9Co0.1O3 and BiFeO3 at room temperature
图 5 BiFe0.9Co0.1O3氮吸附和解吸曲线
Figure 5 N2 absorption and desorption curves of BiFe0.9Co0.1O3
图 6 Co掺杂量对单质汞脱除效率的影响
(PMS: 3.9 mmol/L; pH: 8; catalyst, 0.5 g/L; temperature: 70 ℃; Hg0：101 μg/m3; reaction time：100 min)
Figure 6 Effect of Co ration in catalyst on Hg0 removal efficiency
图 7 催化剂的用量对单质汞脱除效率的影响
(PMS: 3.9 mmol/L; pH: 8; temperature: 70 ℃; Hg0：101 μg/m3; reaction time：100 min)
Figure 7 Effect of catalyst dosage on Hg0 removal efficiency
图 8 PMS的浓度对单质汞脱除效率的影响
(pH: 8; catalyst: 0.5 g/L; temperature: 70 ℃; Hg0: 101 μg/m3; reaction time: 100 min)
Figure 8 Effect of PMS concentration on Hg0 removal efficiency
图 9 溶液pH值对单质汞脱除效率的影响
(PMS: 3.9 mmol/L; catalyst: 0.5 g/L; temperature:70 ℃; Hg0: 101 μg/m3; reaction time: 100 min)
Figure 9 Effect of solution pH on Hg0 removal efficiency
图 10 反应温度对单质汞脱除效率的影响
(PMS: 3.9 mmol/L; pH: 8; catalyst: 0.5 g/L; Hg0: 101 μg/m3; reaction time: 100 min)
Figure 10 Effect of reaction temperature on Hg0 removal efficiency
图 11 烟气组分对单质汞脱除效率的影响
(a): CO2 and O2; (b): SO2; (c): NO (PMS: 3.9 mmol/L; pH: 8; temperature: 70 ℃; catalyst: 0.5 g/L; Hg0: 101 μg/m3; reaction time: 30 min)
Figure 11 Effects of flue gas components on Hg0 removal efficiency
图 12 淬灭剂对单质汞脱除效率的影响
(PMS: 3.9 mmol/L; pH: 8; temperature: 70 ℃; catalyst: 0.5 g/L; Hg0: 101 μg/m3)
Figure 12 Effect of quencher on elemental mercury removal efficiency
表 1 平行实验结果
Table 1 Results of parallel test
1 2 3 4 5 Average value Variance Removal efficiency /% 91.32 89.94 87.96 89.78 87.98 89.36 1.43 
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表 2 反应前后催化剂XPS分峰拟合分析
Table 2 Results of XPS peak-differentiation-imitating analysis before and after reaction
Element Before reaction After reaction binding energy E/eV valence state percentage/% binding energy E/eV valence state percentage/% Co 779.1 Co2+ 41.99 779.4 Co3+ 37.76 780.1 Co2+ 38.99 780.3 Co3+ 39.10 781.3 Co2+ 19.02 781.3 Co2+ 23.14 Fe 709.8 Fe2+ 60.26 709.8 Fe2+ 71.14 711.3 Fe3+ 15.28 711.3 Fe3+ 7.95 712.9 Fe3+ 24.46 712.9 Fe3+ 20.91 O 529.8 lattice oxygen 51.39 529.8 lattice oxygen 45.77 531.2 hydroxyl oxygen 48.61 531.2 hydroxyl oxygen 52.45 oxygen oxygen
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