Study On The Selective Degradation Of Salicylic Acid By Molecular Imprinted TiO₂

PPCPs are a kind of organic pollutants with high molecular weight,difficult biodegradability and complex structure.They have the characteristics of low concentration and high toxicity.Salicylic acid?SA?is one of them,which can pollute the water body and detect its residues in urban sewage for many times.Because of its non-toxic,harmless,high catalytic efficiency and low cost,titanium dioxide has become the most commonly used semiconductor photocatalyst nowadays.However,because of the photocatalytic reaction mechanism of titanium dioxide,it has no selective degradation ability when used to degrade the mixed pollutant system,and can not meet the needs of actual sewage treatment.In this paper,molecularly imprinted titanium dioxide photocatalyst was prepared by combining molecularly imprinted technology with photocatalytic technology,using SA as a simulated pollutant,which enhanced the selective degradation ability of titanium dioxide to SA.Firstly,molecularly imprinted titanium dioxide?MIP-TiO₂?was synthesized by surface molecular imprinting with SA as template molecule and o-phenylenediamine?OPD?as functional monomer.When the ratio of template molecule,titanium dioxide and functional monomer is 1:2.5:3,reaction pH is 2,and illumination is 60 min,the photocatalytic activity of MIP-TiO₂ is the highest.When SA mono-component solution was degraded,the degradation rate of SA at 10 mg/L reached 86.65%after photocatalytic degradation for 180 minutes,which was 1.7 times higher than that of unmodified TiO₂?50.54%?.For mixed component solution system,MIP-titania can correctly identify and selectively photocatalytic degradation of target molecule pollutants.Compared with unmodified titanium dioxide,MIP-TiO₂ has good selective degradation ability for target molecule SA,and the selective factor alpha reaches 2.52.Secondly,in order to further improve the photocatalytic efficiency of molecularly imprinted titanium dioxide,a graphene-doped molecularly imprinted titanium dioxide composite catalyst?MIP-TiO₂/GO?was prepared by adding appropriate amount of graphene?GO?as a good conductor of electrons in the preparation of molecularly imprinted titanium dioxide.The photocatalytic degradation experiments of SA were carried out.The experimental results show that MIP-TiO₂/GO is more effective than MIP-TiO₂.Molecular pollutants have higher photocatalytic efficiency.After photocatalytic degradation for 180 minutes,the degradation rate of SA at 10 mg/L reached 96.46%,which is 1.1 times higher than that of MIP-TiO₂.MIP-TiO₂/GO has good selective degradation ability to target molecule SA in mixed component solution,and the selective factor alpha reaches 2.60.The experimental results show that the modification of TiO₂ by molecular imprinting technology can enhance the selective photocatalytic degradation ability of TiO₂,which can selectively adsorb and degrade the target pollutants with low concentration and high toxicity.The addition of graphene will improve the photocatalytic activity of MIP-TiO₂ and will not reduce its photocatalytic selectivity.