Study On Treatment Of Organic Phosphorus Wastewater By Photocatalytic And Homogeneous Precipitation Technology

Organic phosphorus wastewater with high COD concentration,high salinity,great toxicity,has always been a difficult problem in the wastewater treatment.As an advanced technology,photocatalytic oxidation technology has the advantages of strong oxidation capacity,low secondary pollution,and it can selectively mineralized various pollutants into inorganic ions.In recent years,it has been widely concerned in the treatment of organic pollutants.However,photocatalytic technology can not break the phosphorus and carbon bonds,and can not completely eliminate the problem of organic phosphorus,resulting in excessive total phosphorus.Photocatalytic oxidation technology in combination with homogeneous precipitation,can perfectly solve the problem,thus controlling the total phosphorus of high concentration wastewater within 1 mg/L,and the COD within 300 mg/L to achieve the safety emission standard.This paper introduces the principle of photocatalytic oxidation technology and physicochemical properties of different photocatalyst.The effects of photocatalyst type and organic waste type on photocatalytic efficiency were studied,and these factors are optimized.Sharp titanium type TiO2(P25)was selected as the photocatalyst by catalytic test.Taking organophosphorus pesticides as an example,the decomposition mechanism and degradation path of organophosphorus pesticides were discussed.Combined with the reaction mechanism,the oxidation conditions were optimized,and the best oxidation conditions were determined.Under UV irradiation,TiO2 was used as catalyst,pH value was 6,reaction time was 2 hours,under this condition,the mineralization rate of sodium biethyl hypophosphite reached over 75%.By photocatalytic oxidation experiments,the degradation of organophosphorous flame retardants wastewater and organophosphorus pesticides wastewater was studied.On the basis of the microstructure of the catalyst,the role of organophosphorus pesticide structure in photocatalysis and the degradation pathway of organophosphorus were analyzed.Then the degradation efficiency of organophosphorus was analyzed by the related oxidation technology.Through a single factor comparison test on the factors affecting photocatalytic degradation,the best experimental conditions for the catalytic reaction were studied with the COD removal rate as the standard.Taking a concentration of 400 mg/L diethylsodium hypophosphite as an example,the best experimental conditions are:the catalyst concentration is 1.2g/L,the pH value is 4.5,H2O2 is 50 mM,and the removal rate of COD is 66%.Photocatalytic degradation of high concentration organophosphorous flame retardants wastewater was carried out.The effects of ferric salts,precipitants,pH value,reaction temperature and precipitation time on the size and morphology of homogeneous precipitation crystals were investigated,and the relationship between these factors and phosphorus removal was verified.In order to completely remove phosphorus from phosphorus containing wastewater,the best experimental conditions are discussed by combining photocatalytic technology with homogeneous precipitation.The best experimental conditions are as follows:TiO2 as catalyst,FeSo4 as iron source,reaction concentration of 0.5 mM,the best ratio of ferric salt and oxidant is n(Fe2+):n(H2O2)= 1:1,H2O2 is aneffective oxidant,reaction time is 1 h,and water cooling mode is selected.For photocatalytic technology combined with homogeneous precipitation,total phosphorus removal rate was 99.99%,COD removal rate was 98.88%,which was significantly higher than that of photocatalytic technologyor homogeneous precipitation alone.This is because photocatalytic oxidation technology not only reduces phosphorus content but also makes large molecules degrade into small molecules.In reducing COD,it is more beneficial to the homogeneous precipitation.Homogeneous precipitation method can make small molecules accelerate sedimentation,and enhance the phosphorus removal efficiency.The combination of photocatalytic oxidation and homogeneous precipitation can effectively remove phosphorus and reduce the COD value.