Preparation Of Dichlorophen Molecularly Imprinted Polymer With Core-Shell Structures And Adsorption Characteristics Study

As a kind of chlorophenols materisal,dichlorophen?DCP?is widely used in the chemical,agricultural and pharmaceutical industries.The substance is a potential persistent organic pollutants,which has low residual concentrations in environmental waters,is highly toxic,is not easily degraded,and poses a hazard to aquatic organisms and the ecological.It is an economical,efficient and convenient method to adsorpt and separate of pollutants by adsorbent materials.The traditional adsorbent has a certain effect on the removal of pollutants,but the presence of natural organic matter reduces the adsorption efficiency.When the molecular weight of the pollutant is large,the adsorption becomes weak,and the adsorption cycle of the adsorbent becomes significantly shorter.At present,there are few reports on the adsorption of dichlorophen in water environments by adsorbent materials.Molecular imprinting technology has better properties than general natural recognition?enzyme and substrate?molecules.Therefore,to use of this technology prepare imprinted adsorbent for selective adsorption of dichlorophen has great potential.In this paper,a silica-imprinted polymer,a mesoporous silica imprinted polymer and a magnetic mesoporous silica imprinted polymer were prepared by using a cheap and simple synthetic silicon substrate as a carrier material for surface imprinting.The morphology and structure of the samples were analyzed by SEM,TEM,FT-IR,TGA and other characterization methods.Using the template molecule dichlorophen as the target pollutant,the adsorption performance was studied by equilibrium adsorption experiments and selectivity and regenerative experiments.The main research contents are as follows:?1?The silica was synthesized by alkaline catalyzed hydrolysis in an ethanol solution using tetraethyl orthosilicate as a silicon source.Using DCP as template molecule and silica as carrier material,the surface of silica material was chemically modified by surface grafting method.Silica imprinted polymers?MIPs?and non-imprinted polymers?NIPs?with a polymer layer of about 50 nm thick were successfully prepared on the surface of the modified material by two-step precipitation polymerization.Characterization was carried out by SEM,TEM,FT-IR and TGA.From the SEM and TEM images analysis,the synthesized imprinted polymer has uniform size and good dispersibility.The thermogravimetric analysis indicated that the synthesized MIPs have good thermal stability.The adsorption isotherms and kinetic analysis results showed that the adsorption processes of MIPs and NIPs were consistent with the Langmuir isotherm model,and the adsorption equilibrium can be achieved within 90 min.The adsorption process of MIPs and NIPs was in accordance with the pseudo-secondary kinetic model.The adsorption performance experiments showed that the maximum adsorption capacity of MIPs at318 K was Q_e=56.0 mg g^-1,and the adsorption capacity of MIPs for DCP was higher than that of NIPs.Selective adsorption experiments demonstrated that MIPs have significant selective recognition and adsorption properties for DCP.After six reuses,the adsorption capacity of MIPs decreased slightly compared with that of the first reuse,which indicated that MIPs had better recycling performance.?2?Mesoporous silica was prepared by using cetyltrimethylammonium bromide as a template.DCP and mesoporous silica was used as the template molecule,the support carrier,respectively.Then the surface of the mesoporous material was chemically modified by surface grafting method,and a polymer layer of about 20 nm thick was successfully imprinted on the surface of the modified material by two-step precipitation polymerization.Successfully prepared surface-imprinted mesoporous silica imprinted polymers?MSNs@MIPs?and non-imprinted mesoporous silica polymers?MSNs@NIPs?with high adsorption capacity for dichlorophen and fast reaching adsorption equilibrium.Characterization was carried out by SEM,TEM,FT-IR and TGA.From the SEM and TEM images analysis,the mesoporous silica pores have a good periodic distribution,and the polymer imprinted layer is thin and uniform,which is beneficial to the adsorption.The adsorption performance experiments showed that the maximum adsorption amount of MSNs@MIPs at 318 K was Q_e=91.1 mg g^-1,and the adsorption reached equilibrium quickly within 40 min.The presence of mesoporous structure significantly improves the adsorption performance of the imprinted adsorbent.The Freundlich isotherm model can better fit the experimental data,indicating that during the adsorption process,the adsorption of DCP by the polymer is multi-molecular layer adsorption,and the adsorption may be performed on a non-uniform surface.The pseudo-second-order kinetic equation also showed a higher degree of fit.Both selective and regenerative experiments have also demonstrated that MSNs@MIPs can be successfully applied to the selective adsorption process of DCP.?3?The ordered pores of the mesoporous matrix and a higher specific surface area were beneficial to the formation of magnetic nanoparticles in mesoporous channels.The surface of magnetic mesoporous materials was chemically modified by surface grafting with DCP as template molecule and magnetic mesoporous silica as carrier.A polymer layer about 40 nm thick was successfully imprinted on the surface of the modified material by two-step precipitation polymerization,and magnetic molecularly imprinted polymers?MMSNs@MIPs?and non-imprinted magnetic mesoporous polymers?MMSNs@NIPs?were obtained.The imprinted polymer not only has magnetic separation characteristics,but also has higher adsorption capacity and faster adsorption rate.The samples were characterized by SEM,TEM,FT-IR,TGA and VSM.Isothermal model analysis showed that the adsorption process of MMSNs@MIPs and MMSNs@NIPs conformed to Freundlich isotherm model,and the maximum adsorption capacity of MMSNs@MIPs at 318 K was Q_e=69.54 mg g^-1.Kinetic studies showed that the adsorption of DCP by MMSNs@MIPs and MMSNs@NIPs reached equilibrium within 60 minutes,and the adsorption process of both conformed to pseudo-second-order kinetics model.The Ms of MMSNs@MIPs was 1.02 emu/g,and the imprinted material can be separated by magnetic field more quickly.The regeneration experiment proved that the adsorbent can be used repeatedly and effectively reduce the economic cost in practical application.