Preparation Of Fe-MIP And TiO₂-SMIP And Selective Catalytic Degradation Of PNP

P-Nitrophenol?PNP?is an important raw material for fine chemical products.However,it is easy to cause serious river pollution in the later raw material waste disposal and discharge,which in turn affects human health.In the traditional physical,chemical?Fenton reaction and photocatalysis?and biological methods,PNP cannot be selectively treated in water,hence,it is important to choose a suitable method for the selective treatment of PNP in sewage.The imprinted material prepared by molecular imprinting technology has a cavity structure matching the imprinted molecules,and there are recognition sites matching the imprinted molecules in the cavity structure,which can selectively adsorb or degrade the imprinted molecules.Based on molecular imprinting technology,PNP was used as a template to prepare nano-iron molecularly imprinted catalyst?Fe-MIP?for Fenton reaction and TiO₂ surface molecular imprinted photocatalyst?TiO₂-SMIP?,and the selective adsorption and catalytic degradation of PNP were achieved.The nano-iron molecularly imprinted catalyst?Fe-MIP?catalyzes the PNP on the basis of adsorption.The strength of the adsorption capacity directly affects the later catalytic effect.Therefore,molecular imprinting technology was first used to prepare molecularly imprinted polymers?MIP?with PNP as template,and non-molecular imprinted polymers?NIP?without PNP were also prepared to study the adsorption performance.The BET characterization results show that the specific surface areas of MIP and NIP are 130.02 m²/g and 40.49 m²/g,respectively.The specific surface area of MIP is increased from 68.81 m²/g to 130.02 m²/g after releasing the template,and the surface of MIP is rougher than that of NIP.The isothermal adsorption studies on MIP and NIP with Langmuir model and Freundlich model show that the adsorption capacities on MIP of PNP at 298 K is 5.6306 mg/g,which is higher than that of NIP with 2.7033 mg/g).The selection coefficient of MIP for PNP is 1.807,which is higher than those of o-nitrophenol?1.228?and m-nitrophenol?1.285?.After using for 6times,the recovery rate of MIP is 86.45%,and the recovery rate of NIP is 91.13%.The complex formed by FeCl₃ and PNP was used as the template molecule for preparing Fe-MIP,and Fe-NIP and NIP were simultaneously prepared as the control group of Fe-MIP.BET characterizations show that the specific surface areas of Fe-MIP and Fe-NIP are 164.08 m²/g and 80.32 m²/g,respectively,which are higher than those of MIP and NIP.TEM test illuminates that the particle sizes of Fe-MIP and Fe-NIP metal particles range from 5 nm to 10 nm.Under the condition of pH value of3,the catalytic efficiency of Fe-MIP for PNP is 74.56%,which is higher than that of34.67%under neutral condition.The catalytic efficiency of Fe-MIP to PNP is increased with latter decreasing when the initial concentration of PNP is increased.The catalytic efficiency of Fe-MIP for PNP is 74.56%,which is higher than those of Fe-NIP?41.74%?and NIP?20.60%?.After recycling 5 times,the catalytic efficiency of Fe-MIP is 64.03% with catalytic efficiency loss of 10%,indicating that Fe-MIP has good recycling performance.Using titanium dioxide microspheres prepared by hydrothermal method as the carrier of TiO₂-SMIP and with PNP as the template molecule,TiO₂-SMIP was prepared by surface molecular imprinting technology.According to SEM test,TiO₂,TiO₂-APTES and TiO₂-SMIP have good dispersion performance,and the particle size is in the range of 600 nm to 850 nm.Thermogravimetric analyses of the synthesized TiO₂,the TiO₂-APTES and the grafted TiO₂-MIP reveal that TiO₂-SMIP has high grafting rate.In the absence of light,by Langmuir model and Freundlich model,the static adsorption simulations on the prepared TiO₂-SMIP and TiO₂-SMIP show that the adsorption capacity of TiO₂-SMIP at 298K is 6.9812 mg/g,which is higher than that of TiO₂-SNIP?4.5793 mg/g?,and the Langmuir model is more suitable for static adsorption simulations of TiO₂-SMIP and TiO₂-SNIP.The TiO₂-SMIP kinetics under no light by the pseudo-second-order kinetic model illuminates that the dynamic adsorption equilibrium is almost reached at 80 min.The catalytic tests show that the catalytic efficiency of TiO₂-SMIP for PNP is 72.79%,which is higher than 43.28% of TiO₂-SNIP.Using the first-order reaction kinetic equation to calculate the catalytic rate,the reaction kinetic constant of TiO₂-SMIP is 0.0081 min^-1,which is higher than0.00343 min^-1 of TiO₂-SNIP.The selection factor of TiO₂-SMIP for PNP reaches as high as 2.316.After recycling 5 times,the catalytic efficiency of TiO₂-SMIP is 64.09% with catalytic efficiency loss of only 8%,indicating that TiO₂-SMIP has good photocatalytic recycling performance.