| Mercury is a global pollutant,and even at very low concentrations,it is quite toxic and can cause harm to the environment and the human body.However,zero-valent mercury(Hg0)in coal-fired flue gas is difficult to be removed by existing desulfurization,denitrification,and other devices,so the effective removal of Hg0 has gradually become a research hotspot.In this paper,a self-made septum-free plexiglass reactor was used,and direct oxidation of the anode allows the Hg0 in the simulated flue gas to be oxidized to Hg2+/Hg2+ for removal.The effects of different conditions on the removal efficiency of Hg0 were studied,and the ability of three different electrodes to oxidize Hg0 was compared.The removal mechanism of Hg0 was also explored.First of all,the application of foamed titanium as an anode to the electrochemical catalytic oxidation of Hg0 in simulated flue gas shows that the electrode performance is stable and the effect is very good.The effects of different factors such as electrolytic voltage,reaction temperature and gas concentration on the removal of Hg0 were investigated.The results show that when the voltage is increased from 1 V to 6 V,the removal efficiency of Hg0 increases first and then decreases,and the effect is best at 4 V,which can reach 90%;the effect of gas flow rate on the removal efficiency of Hg0 is not obvious,but the reaction is improved.Rate;electrolyte concentration increased from 0.05 M to 0.8 M,Hg0 concentration first rose and then decreased,the best effect at 0.5 M;reaction temperature and pH have little effect on the removal of Hg0.In the optimal conditions:electrolysis voltage 3 V,gas flow rate 100 mL/min,pH value 11,Na2SO4 solution concentration 0.5 M,reaction temperature 60 ℃,without any catalyst,Hg0 removal efficiency of up to 90%At the same time,it was found that foamed titanium anodes can achieve good removal effects at higher initial concentrations of Hg0,which is beneficial to industrial applications.Secondly,PbO2 was prepared by hydrothermal method,and the pure β-PbO2 was prepared by XRD analysis.The cyclic voltammogram test shows that the foamed titanium electrode,Ti/Sb-SnO2/PbO2 electrode and carbon paper anode all have good electrochemical performance.The electric double layer capacitance of the Ti/Sb-SnO2/PbO2 electrode is 11.7 times that of the foamed titanium electrode.The addition of PbO2 makes the electrochemical performance of the foamed titanium electrode to be enhanced.When the Ti/Sb-SnO2/PbO2 electrode was used as the anode,it was found that the gas flow rate had a great influence on the removal efficiency of Hg0.When the flow rate was too small,the gas propulsion rate was too slow,and the reaction was not timely leading to a decrease in the removal efficiency,the flow rate was too large,and the impact on the electrodes.Larger,will also affect the removal effect;except under the condition of 1 V voltage removal is poor,under the other voltage conditions,Hg0 has a good removal effect,indicating that the voltage has little effect on the removal efficiency of Hg0;Hg0 initial The higher the concentration,the higher the removal efficiency of Hg0.When the initial mercury concentration increases from 300 μg/m3 to 1000 μg/m3,the removal efficiency of Hgo increases from 23%to83%.This indicates that if the concentration of Hg0 in the actual gas is too low,enrichment is required and the treatment can be performed by this method.To achieve a better treatment effect.Once again,when the carbon paper was an anode,it was found that the reaction temperature was the most important factor for the removal efficiency of carbon paper for anodizing and removing Hg0.The removal efficiency of Hg0 can reach 90%at room temperature.However,as the temperature increases,the removal efficiency gradually decreases,and the removal efficiency of Hg0 is only 33%at 80℃;the initial concentration of Hg0 has almost no effect on the removal efficiency of Hg0;at the same time,the concentration of electrolyte solution is opposite to Hg0 when carbon paper is used as an anode.The effect of the removal efficiency is also relatively small;since the carbon paper used in the experiment is relatively thin,when the flow rate is too large,the carbon paper may be broken to generate cracks,which will reduce the removal efficiency of Hg0.Finally,through the comparative study of three types of electrode,such as foam titanium electrode,Ti/Sb-SnO2/PbO2 electrode and carbon paper electrode,it is found that these three materials can achieve a good removal efficiency of Hg0.However,there will be subtle differences under different conditions,which also helps to select the most suitable electrode under different flue gas conditions.Although the Sb-SnO2/PbO2 film enhances the electrochemical performance of the foamed titanium electrode,this enhancement does not increase the removal efflciency of Hg0 under any conditions.The reaction system can be found when the Ti/Sb-SnO2/PbO2 electrode is used.The current increases significantly and the current increase does not necessarily favor the conversion of Hg0. |
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