Degradation Of Ammonia Nitrogen Wastewater By Modified Nano-TiO2/Non-Based Basalt Fiber Composite Photocatalyst

In the current study,mechanisms such as metal atoms deposition and ion doping were coupled for the modification of TiO2,and got Ag0-Ce4+-La³⁺/TiO2 powder photocatalyst at the same time.Nonwoven basalt fiber was chosen as the carrier of modified TiO2 photocatalyst for its great water resistance,excellent resistance to chemical erosion,good performance after the impact from load and fire.Ag0-Ce4+-La³⁺co-modified TiO2 coated basalt fiber photocatalyst were prepared via sol-gel method.The properties of the photocatalysts were characterized in detail by using transmission electron microscopy?TEM?,field-emission scanning electron microscopy?FESEM?,UV-visible absorption spectra,X-ray powder diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?.Based on the ammonia nitrogen degradation experiment,the effects of preparation technical parameters and the reaction conditions on the photocatalytic activity of modified TiO2 were evaluated systematically.According to the orthogonal experiments,the best proportion of AgNO3,Ce?NO3?3 · 6H2O and La?NO3?3 · 6H2O was tested.When Ag:Ce:La is 3:2:3,the modified TiO2 photocatalyst showed its best photocatalytic property.Inside the photocatalyst,the element Ag,Ce and La existed in the form of Ag0,Ce4+,and La³⁺respectively.During the modification process,Ag0 was deposited onto the surface of TiO2 photocatalyst,and Ce4+ or La³⁺ ions entered into TiO2 lattice,simultaneously,generated Ti?1-x-y?CexLayO2 solid solution,which caused the decrease of band gap energy from 3.2eV to 2.13eV.Ag/Ce4+/La³⁺ modifiers intensively restrain the growth of crystalline grain and the transformation of crystalline phase from anatase to rutile.The coupling effect of Ce4+-La³⁺ and Ag0 made the band gap energy of Ag0-Ce4+-La³⁺/TiO2 smaller than either Ce4+-La³⁺/TiO2 or Ag0-TiO2,and the spectral response range of 3%Ag0-Ce4+-La³⁺/TiO2 broader than 3%Ce4+-La³⁺/TiO2 or 3%Ag0-TiO2.As shown in the ammonia nitrogen removel experiment,after 6h degradation reaction,the degradation efficiency of ammonia nitrogen with 3%Ag0-Ce4+-La³⁺/TiO2 powder reached 93.9%.The result of nonwoven basalt fiber pretreatment experiment showed that samples etched with 3mol/L H2SO4 for 14h gained the largest loading capacity of modified TiO2?42.9%?.After heat treatment,the thickness of modified TiO2 photocatalyst coating sintered at 600? was about 100nm,which was loaded onto the surface of basalt fiber,the average size of modified TiO2 nanoparticles were about 30nm.After 6h degradation reaction,the degradation efficiency of ammonia nitrogen with 3%Ag0-Ce4+-La³⁺/TiO2/BF reached 95.3%,and the concentration of ammonia nitrogen decreased from 60.4mg/L to 2.8mg/L,the concentration of NO3--N and NO2--N increased from 1.3mg/L,0mg/Lto 8.8mg/L,4.3mg/L respectively.In the condition of low concentration of reactants and constant light,the degradation efficiency of ammonia nitrogen with 3%Ag0-Ce4+-La³⁺/TiO2/BF turned to be higher with the increase of pH value in wastewater,and turned to be up and then down with the increase of heat treatment temperature.The highest ammonia nitrogen degradation efficiency experiment conditions are as followed:pH value of ammonia nitrogen wastewater 11,heat-treated temperature 600?,Ag:Ce:La ratio 3:2:3.As the kinetic research shows,the photocatalytic oxidation of ammonia nitrogen under different conditions of modifier content,heat treatment temperature and pH value followed the Langmuir-Hinshewood first order reaction kinetics model.