Surface Functionalization Of Polydopamine And Their Separation And Enrichment Performance Of PFOS In Water

Due to its biocompatibility and superparamagnetism,Fe₃O₄ has been favored by many scientific researchers.It is used as the core of the adsorbent to construct a functional organic shell on its surface.On the one hand,it can improve the stability of Fe₃O_4.On the other hand,it can solve the shortcomings such as time and labor consumption of solid-liquid separation,low adsorption capacity,slow mass transfer rate,insufficient adsorption selectivity and difficult recovery of adsorbent.In this paper,the preparation of adsorbent for core-shell structure was carried out with Fe₃O₄ as the core,and it was applied to the separation and enrichment of Perfluorooctane sulfonate?PFOS?.The main research results are as follows:Fe₃O₄ microspheres were prepared by solvothermal method using iron chloride hexahydrate as iron source,ethylene glycol as solvent and reducing agent,sodium acetate as precipitant and polyethylene glycol as surfactant.The uniformity,dispersibility and particle size of Fe₃O₄ microspheres were controlled by adjusting reaction temperature,reaction time and iron source concentration.The masses of ferric chloride,sodium acetate and polyethylene glycol in hexahydrate were 5.4,4.8 and 1.5 g,ethylene glycol was 60 mL,the reaction time was 8 h,and the reaction temperature was180?.Fe₃O₄ microspheres with uniformity,uniform dispersion and good morphology were complicated in this state.The self-polyoxidation reaction of dopamine in alkaline solution was used to coat the surface of Fe₃O₄ microspheres with polydopamine.The dopamine concentration and polymerization time were adjusted to control the dispersion of Fe₃O₄@PDA and the thickness of the coating.When the dopamine was added in an amount of 50 mg and the polymerization time was 12h,Fe₃O₄@PDA microspheres with a shell thickness of 20 nm,uniform dispersion and uniform particle size were successfully prepared.The prepared Fe₃O₄ and Fe₃O₄@PDA were characterized by transmission electron microscopy,infrared absorption spectroscopy,vibrating sample magnetometer and X-ray photoelectron spectroscopy.The preparation process of PFOS molecularly imprinted polymer is complicated,and the problem of toxic and harmful organic solvents is introduced.The core of Fe₃O₄,water as solvent,dopamine as cross-linking agent,and the amino and hydroxyl groups in dopamine are dual-function monomer,it was successfully polymerized in one step,prepared a superparamagnetic core-shell type Fe₃O₄@MIPDA microsphere.It was found by scanning electron microscopy and projection electron microscopy that the prepared Fe₃O₄@MIPDA has uniform particle size,good dispersion and uniform thickness of MIP layer.Through adsorption kinetics,adsorption isotherms and selectivity experiments,the adsorption properties were examined and showed specific adsorption capacity for PFOS.This selectivity is derived from the size and chargeability of the template molecules.It will be applied to the separation and enrichment of PFOS.On the one hand,it has the ability to extract and elute PFOS rapidly due to its thin MIP layer.On the other hand,due to the presence of Fe₃O₄,rapid solid-liquid separation can be achieved.Therefore,it takes only 40 minutes to complete the separation and enrichment of PFOS.It makes up for the shortcomings of the traditional SPE method,which is cumbersome and time-consuming.In view of the fact that the current core-shell magnetic carbon microspheres have poor dispersibility,uneven carbon layer thickness,small specific surface area and low adsorption capacity,Fe₃O₄@PDA is used as a base material,and hydroxyl groups and imino groups on polydopamine are used to adsorb glucose.The intermediate product produced in the hydrothermal process successfully prepared Fe₃O₄@PDA@C with uniform particle size,uniform dispersion and uniform shell thickness.Furthermore,the annealing and KOH activation were carried out to maintain its good core-shell morphology.At the same time,Fe₃O₄@PDA@C-K microspheres with high specific surface area and mesoporous structure were successfully prepared,and the specific surface area reached 266.672 m²·g^-1,and a partial hydroxyl group was introduced.The adsorption performance of Fe₃O₄@PDA@C-K on PFOS in water was investigated.The experimental results show that Fe₃O₄@PDA@C-K has high adsorption capacity and high mass transfer rate.The PFOS was enriched as a magnetic solid phase extraction?MSPE?adsorbent,and a high sensitivity,high precision and wide linear range PFOS analysis method was established,which was successfully applied to the analysis and detection of actual water samples.