Preparation,Properties And Application Of Nitrophenol Double Template Magnetic Molecularly Imprinted Polymers

As an important chemical raw material,4-NP and 2,4-DNP are widely used in dyes,insecticides and rubber.The content of these two substances is high in the water environment because of the unreasonable discharge of industrial and agricultural wastewater.4-NP and 2,4-DNP have the characteristics of high toxicity,strong carcinogenicity and difficult biodegradation.They can be ingested and accumulated in the human body through the food chain and drinking water,posing a serious threat to human health.The US Environmental Protection Agency(USEPA)and the European Union have listed them as priority pollutants in water.Therefore,finding a method that can efficiently remove it has critical research significance and application value in human health and environmental protection.Molecular imprinted technology is a technology developed in recent years to efficiently remove trace pollutants from water.It has the advantages of strong pertinence and high removal rate.However,conventional imprinted methods can only remove a single substance efficiently.This thesis improves the conventional single template imprinted method and introduces the concept of double template.By changing the ratio of the two template molecules in the imprinted polymers,double-template imprinted polymers with high adsorption capacity and specific recognition ability for two or more pollutants was prepared.At the same time,adsorption performance of the molecularly imprinted polymers(MIPs)to a single target molecule is improved,which shows the advantages of the dual-template imprinted polymers in the removal and separation of a certain type of pollutants.In this thesis,in order to efficiently remove 4-nitrophenol(4-NP)and 2,4-dinitrophenol(2,4-DNP),4-NP and 2,4-DNP were selected as the template molecule,among which 4-NP:2,4-DNP=0.8:0.2.Using OPDA as functional monomer,Fe₃O₄@Si O₂ as carrier,ethylene glycol dimethacrylate(EGDMA)as cross-linker and AIBN as initiator,double template magnetic molecularly imprinted polymers(D3-MIPs)was prepared using surface molecular imprinted technology.The thesis optimizes the preparation conditions that affect the adsorption performance of MIPs,including the type and amount of functional monomers,the dosage of cross-linking agent,the choice of solvent system and the ratio of two template molecules.Under the best conditions,the isothermal adsorption and kinetic processes of single template,double template and non-imprinted polymers were investigated.The results demonstrate that when the initial concentration of the solution is 5?500 mg/L,the adsorption capacities of 4-NP-MIPs,2,4-DNP-MIPs and D3-MIPs can reach 82.42mg/g,57.33 mg/g and 97.35 mg/g,respectively,which is 5-8 times the adsorption capacity of NIPs.The adsorption can reach equilibrium within 60 min and the adsorption rate of double template imprinted polymers is higher than that of single template imprinted polymers.The better fit model of MIPs is the Freundlich adsorption model and the pseudo-second-order kinetic model,indicating that the adsorption process of MIPs is a chemical adsorption process.Scatchard analysis shows that when MIPs bind pollutants,there are many adsorption sites with different adsorption energies.The theoretical adsorption capacities of 4-NP-MIPs,2,4-DNP-MIPs and D3-MIPs for target molecules are 103.97 mg/g,73.14 mg/g and 123.99 mg/g,respectively.And double template polymers have better adsorption performance.The FT-IR and SEM characterization results and the adsorption experiments mutually verify that D3-MIPs have a good polymerization effect,and have specific recognition sites and good imprinting performance.Competitive adsorption experiments were conducted with bisphenol A(BPA)?4-NP and 2,4-DNP as the interfering substance.The results showed that both single and double template imprinted polymers had higher imprinting factors and selection factors.The selection factor of 4-NP-MIPs and 2,4-DNP-MIPs were respectively 12.99 and 6.92,and the relative adsorption coefficients of 4-NP-MIPs and 2,4-DNP-MIPs were 0.99 and 0.97in two mixture systems.It shows that MIPs have a high selective adsorption capacity.The application of D3-MIPs in actual water still shows excellent specific adsorption capacity.After 8 regenerations,the adsorption capacity of D3-MIPs decreased by 7.51%,confirming that MIPs cycle regeneration is good.