Ultraviolet Absorption Spectroscopy Properties Of Inorganic Anions Such As Sulphate And Nitrate

The existence of electricity has improved people’s quality of life and changed the whole world.Electricity generating from Coal-fired power plants supply the whole world for life,accommodation,travel,and so on,making life colourful.However,coal burning will produce pollutants,especially emit a large amount of SO₃ through ultra-low emissions,which seriously threatens the living environment and life of human beings.Therefore,the monitoring of SO₃ content in coal-fired power plants is an urgent task.For the monitoring of SO₃ content,this paper proposes a method of ultraviolet absorption spectroscopy.Compared with other methods,UV absorption spectroscopy has a series of advantages suah as fast response,high sensitivity,no pollution,and potential for continuous on-line monitoring,so it is a environmentally friendly technology for SO₃ content monitoring.Combined with the conversion relationship between sulfuric acid and SO₃,the UV absorption spectrum detection method of sulfate has been studied in this paper.Meanwhile,the ultraviolet absorption spectrum properties of nitrate,carbonate,sulfite and chloride as well as the methods of sulphate concentration monitoring have been explored.The UV absorption spectrum detection method of sulfate was carried out.Firstly,the ultraviolet absorption spectrums of sulfuric acid in air and oxygen-free environment were measured.Then,the ultraviolet absorption spectra of sulfuric acid with sodium sulfate and potassium sulfate were compared in an oxygen-free environment.Finally,an optical parameter（OP）was defined to establish its relationship with the sulfate concentration.It was found that the ultraviolet absorption spectrum of sulfate in air is concave,and is almost identical with the ultraviolet absorption spectrum of sodium sulfate and potassium sulfate in an oxygen-free environment.Studies have shown that the UV absorption spectrum of sulfate is not interfered by cations,and the strong absorption of oxygen in the same band will affect its accurate measurement;the sulfate concentration and OP satisfy the quadratic function relationship which can be used to quantify sulfate.The UV absorption spectroscopy properties of inorganic anions such as nitrate were studied.Firstly,the UV absorption spectra of nitrate,sulfite,chloride and carbonate ions were measured.Then,another optical parameter（OP）was defined to establish its association with nitrate concentration.It has been found that the absorption cross section nitrate,sulfite,carbonate and chloride ions are one to two orders of magnitude larger than that of sulfate.The study indicated that nitrate,sulfite,chloride and carbonate interfere with the UV absorption spectrum of sulfate,and the nitrate concentration and OP satisfy a linear function which can be used to quantify nitrate.On-line monitoring of sulfate concentration was carried out.A flow on-line monitoring method and apparatus for sulfate concentration was created and the sulphate concentration were monitored using the apparatus.The study found that the device can effectively eliminate the influence of the heat from D₂ lamp source and ambient temperature on sulfate concentration monitoring,and obtained good sulphate concentration momonitoring results such asΔC_max=48.95μM,ΔC/C_max=1.64%,as well as DL_min=7.94μΜ.