| Salicylic acid(SA)wastewater has potential biohazardous effects,and it is difficult to degrade such wastewater by traditional biological methods,which can be effectively solved by using the abundant titanium and bismuth mineral resources in China to develop into photocatalysts.In this paper,TiO2(TO),SA molecularly imprinted TiO2(STO),Bi2Ti2O7-TiO2(BTTO),SA/α-Bi2O3-Bi2Ti2O7-TiO2(SBBTTO)and other photocatalysts were prepared based on molecularly imprinted sol gel technology,and the mechanism of SA wastewater degradation was studied,which could achieve selective removal and efficient degradation of SA.The innovation of this research work and the research results achieved were mainly reflected in the following aspects:(1)A series of molecularly imprinted Ti-Bi based composite nano photocatalysts were prepared.Using 20 g tetrabutyl titanate as Ti source,adding 1.5 g of SA,calcining temperature 550℃,STO photocatalysis for 30 min,the degradation rate of SA was 53.11%.When the mass fraction of Bi:Ti was 20%and the calcination temperature was 550℃,the degradation rate of SA by BTTO photocatalysis for 30 min was 86.45%.When the content of SA was 1.5 g,the mass fraction of Bi:Ti was 20%,and the calcination temperature was 550℃,the degradation rate of SA by SBBTTO photocatalysis for 30 min was 92.54%,which was 1.97 times higher than that of TO.The BET specific surface areas of TO,STO,BTTO and SBBTTO were 3.65,5.83,14.53 and 32.78 m2/g respectively.Through characterization tests such as SEM,it was found that the synthesized SBBTTO had a pearl shell morphology,due to the fact that SA imprinted molecules played a certain role in regulating the morphology of BO before calcination of the catalyst,making SBBTTO add a BO ultra-thin nano sheet relative to BTTO,serving as a multi-directional transport platform for electrons at the surface and interface of interlayer heterostructures,enabling effective operation of surface electrons to participate in photocatalytic degradation reactions.(2)The influence mechanism of different factors in the photocatalytic degradation of SA was investigated.It mainly includes the effects of direct sunlight,different catalysts,pH value,and the amount of H2O2 added.The results showed that when no catalyst was added,the degradation rate of pollutants by only UV irradiation for 30 min was about 19%.After the catalyst was added,the UV light cannot completely irradiate the pollutants with equal intensity,hence the effect of direct light decomposition would have a decay of 63.3%～71.8%.SBBTTO could photocatalytic remove 75.21%of Fe(Ⅲ)-SA(Fe3+complexed SA solution)within 30 min,reflecting well photocatalytic performance.When the amount of catalyst added was 1.0 g/L,the reaction pH was 6.06,and the amount of 3%H2O2 added was 0.1 mL,the optimal degradation rate of SA by SBBTTO photocatalysis for 30 min was 96.25%.(3)The reaction mechanism of SA degradation by molecularly imprinted Ti-Bi-based composite photocatalyst was revealed.In the quenching experiment of SBBTTO,the maximum effective residual rate after adding EDTA was 73.4%,indicating that h+is the main active species in the photocatalytic reaction of SBBTTO.In ESR characterization,SBBTTO could produce stable h+,·OH,and ·O2-.The selectivity factor of SBBTTO to SA was 2.109>2,indicating that SBBTTO had obvious selectivity to SA.Compared to TO,the selectivity coefficient of SBBTTO increased by 2.10 times.When SA was degraded,dihydroxybenzoic acid was generated first,then phenol.Phenol was further oxidized to generate hydroquinone,catechol,etc.After the oxidation of dihydroxybenzene to benzoquinone,the ring-opening reaction occured until the single-chain organic compounds were gradually decomposed into CO2 and H2O.In summary,molecular imprinting morphology regulation could form Ti-Bi based photocatalysts with special morphology to achieve more efficient and selective removal of SA.The study of relevant reaction mechanisms provided new ideas for environmental remediation and new energy utilization. |
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