Research On The Removal Of Pfoa From Water With Cd_xZn_1-xS And G-C₃N₄

Perfluorooctane acid（PFOA）is widely used in industrial production because of the properties of strong stability,hydrophobic and hydrophobic.But PFOA can be absorbed by the human body by ingesting,inhaling and skin contact,causing cancer,liver enlargement and other diseases,and it is difficult to degrade because of its stability and accumulation.Therefore,in this paper,in order to research the removal rate of PFOA in the water,two photocatalysts(Cd_xZn_1-xS and g-C₃N₄)are prepared in this paper.The concrete research contents are as follows:（1）A method was established for the determination of PFOA in the water using the liquidchromatograpycoupledtoquaderupole-timeofflight-massspectrum（LC-QTOF-MS）.The materials were separated in a chromatographic column which was called ZORBAX Eclipse Plus C₁₈,（2.1×100mm,3.5μm）with the methyl alcohol as the mobile phase.They were determined by negative electrospray ionization（ESI^-）mass spectrum and analyzed by selective ion monitor（SIM）.It could be applied to the qualitative and quantitative analysis to PFOA.The results proved that during the concentration from0.1ng.mL^-1to 10ng.m L^-1,the correlation coefficient（R²）of this method was 0.9980 which had a good linear correlation.The detection limit of the method was 0.025ng.mL^-1.The rate recovery of PFOA was 99.5%-110.7%,and the relative standard deviation（RSD）was1.23%-3.78%.（2）Different mass proportion of urea and melamine（0:10,2:8,4:6,6:4,8:2,10:0）were used as raw materials to synthesize the g-C₃N₄ by the calcination method.The microstructure and optical properties of g-C₃N₄ were characterized by scanning electron microscopy（SEM）、X-ray diffraction（XRD）and photo luminescence（PL）.Using methylene blue（MB）as the simulation object,photocatalytic performance of the preliminary experiment was carried out.The results proved that g-C₃N₄ whose raw material ratio was 2:8 was the best catalyst to MB among all the materials.On this basis,the influence of factors about different raw material ratio,initial concentration of catalyst and the conditions of pH on PFOA in water was investigated.The results proved that in the acidic condition（pH=3）,g-C₃N₄ whose raw material ratio was 2:8 was the best one among all the materials The removal rate was 28%after 6 hours in dark and 72%in light.（3）Different molecular proportion of Cd_xZn_1-xS（x=0,0.2,0.4,0.6,0.8,1）were synthesized by the sol-gel method.The optical properties and microstructure of Cd_xZn_1-xS were characterized by fourier transform infrared spectroscopy（FT-IR）、SEM and XRD.Using MB as the simulation object,photocatalytic performance of the preliminary experiment was carried out.The results proved that in the acid condition,Cd_0.2Zn_0.8S whose calcination temperature was 250℃was the best catalyst to MB among all the materials.On this basis,the influence of factors about different ratio of Cd/Zn,calcination temperature,initial concentration of catalyst and the conditions of pH on PFOA in water was investigated.The results proved that in the acidic condition（pH=3）,Cd_0.2Zn_0.8S whose calcination temperature was 450℃was the best catalyst among all the materials.The removal rate was 50%after 6 hours in dark and 75%in light.