| Nitric oxide(NO),as a neurotransmitter and an important messenger molecule,is widely existed in various tissues and organs of the human body.It has a strong biological activity and plays an important role in many aspects of pathophysiology.However,it is also one of the indoor air pollutants,even at low concentration,which will still endanger human health.Based on this,it is very important to determine NO concentration accurately and control the concentration in a suitable range.The chemiluminescence detection method based on the reaction of NO and ozone is high sensitive,fast responsive,with wide linear detection range.What's more,it can be real-time,on-line monitoring,and the detection limit is as low as 0.5 ppb.So it is widely used in the analysis of NO detection.However,it has been found that when applying chemiluminescence method detecting NO,other impurity gas has a disturbing effect,and the interference directly affects the accuracy of the NO test results.Therefore,the study of other impurity gas interference and elimination it play a key role in the precise determination of trace NO.At the same time,NO as one of the indoor air quality evaluation standards,the accumulation of NO will cause methemoglobinemia and central nervous system damage in the human body.NO2 generated from NO and oxygen has a more significant effect on the lungs,so it is also necessary and important to explore the suitable catalyst,which is useful in the elimination of NO in the room.Based on the above problems,the main contents include the following aspects:Firstly,the effect of other volatile gases on the NO detection and the eliminating method of the interference were studied by chemiluminescence method when the low concentration of NO was measured.First of all,we studied the interference effects and the eliminating method of exogenous volatile gases on the trace NO detection through the chemiluminescence method.In this work,interference effects from volatile gases,such as ammonia,styrene,ethanol,ether,hexane and toluene were studied.And these organic compounds could impose serious interference to NO determination,when their concentrations were greater than 0.063 mg/m3,0.19 mg/m3,0.66 mg/m3,2.29 mg/m3,3.78 mg/m3 and 5.62 mg/m3,respectively.In order to improve the accuracy of NO analysis,different adsorbents were used to eliminate these volatile gases.Although volatile gases can be removed fully by zeolite molecular sieve,activated carbon and NaA molecular sieve membrane,part of NO is also absorbed simultaneously.In contrast,hydrophilic modified molecular sieve can effectively eliminate impurity gases and had little influence on NO determination.Therefore,hydrophilic modified zeolite can be used as the pretreatment material,and the content of NO can be detected by chemiluminescence after treatment.Therefore,the hydrophilic modified molecular sieve can be used as the pretreatment material to treat the sample gas,then improve the accurate determination of NO by chemiluminescence method.Secondly,the chemiluminescence method was used to detect the accumulation of NO in the room.The effects of different per capita space on the NO content in the room were investigated by simulating the indoor e nvironment of 3 m3,30 m3 and 70 m3,respectively.The experimental results showed that the content of NO in the environment increased in 1.9 times after 55 min in 3 m3 space.With the increase of residence time,the NO content was 3.3 times than the original concentration after 210 min.Then,the cumulative change of NO in the room can be detected by chemiluminescence under the condition that the per capita space is 6 m3,10 m3,23 m3 and the ventilation system normally open conditions in 12 m3,respectively.At last,the effect of smoking on NO content was studied,too.It was found that smoking could lead to a sharp increase in NO.It can be seen that the indoor body and its activities will cause the accumulation of NO,and the smoking will produce more N O,so in order to improve the indoor air quality we should pay attention to indoor ventilation and reduce the flue gas emissions.While the inquiry is also a personnel-intensive air quality assessment providing the basis for further protection of human health.NO as one of the indoor air pollutants and low concentration is also prone to accumulation,which is harmful to human health.Based on this,in order to improve the indoor air quality,we have studied the methods for indoor catalytic elimination of NO.The catalytic activity of the copper-manganese oxide synthesized through different methods on NO was investigated.Among them,the catalyst prepared by the precipitation method has higher catalytic activity,but the product of NO2 could cause environmental pollution.However,potassium-doped copper-manganese oxide prepared by potassium hydroxide impregnation treatment can eliminate indoor NO effectively and the product is nitrate,which belongs to an environment-friendly catalyst.The optimum synthesis co nditions were as follows: the molar ratio of copper and manganese precursors was 1:2 and the pH adjusting agent was tetramethylammonium hydroxide(TMAH),and the doping amount of potassium atom was 7.03%(7.4 mg/g).Potassium-doped copper-manganese oxide not only greatly improved the adsorption performance of NO,but also promoted the formation of nitrate,thereby further improving the NO elimination rate.The process does not produce harmful gas NO2 and no reducing agents(NH3,H2,alkane or urea)is required.In the low temperature conditions(265 °C),the elimination rate of NO is as high as 99.9% and it is also suitable in high oxygen concentration atmosphere.Therefore,potassium-doped copper-manganese oxide is a high-performance catalyst for low-concentration NO elimination,which has great potential in the purification of indoor air. |
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