Preparation Of Magnetic Nanocomposites And Its Removal For Organic Pollutants In Water

With the rapid development of the economy,environmental issues have become increasingly prominent,and the economic growth at the expense of the environment is unsustainable.The development of the economy and the improvement of material life have also made people pay more and more attention to the quality of life,and environmental health also accounts for a considerable proportion.The safety of the water environment is closely related to public safety and human health.However,the rapid development of industrialization leads to the discharge of wastewater containing a large number of intermediates,products,by-products and wastes,which has brought enormous challenges to the water environment,far exceeding the self-purification capacity of water bodies.The discharge of printing and dyeing wastewater makes the water environment problem severe.Therefore,environmental pollution remediation is particularly important.This article focus on water pollution prevention and restoration,based on the classical adsorption technology to remove organic pollutants in water.Adsorption is a method that can separate the target contaminants by transferring the target contaminants from water environment to the surface of the adsorbent.The adsorption method has unique advantages such as easy operation,simple equipment,low cost and no secondary pollution.The adsorbent is the most critical part of the adsorption method.The adsorption properties determine the removal efficiency and operating cost of the adsorption method to some extent.The three factors of adsorption technology are the saturated adsorption capacity,the adsorption selectivity,and the separation performance of the adsorbent.Based on the structure and properties of the target contaminants,design and synthesis of new adsorbents for the removal of organic pollutants in water were explored.For the newly synthesized adsorbent,a series of techniques were used to characterize the morphology,structure,surface functional groups and so on.And,batch experiments were conducted to study the adsorption performances and potential application of the novel adsorbents for the removal of organic pollutants in wastewater.This paper had the following conclusions:1 A magnetic nanomaterial CoFe₂O₄@vacancy@mSiO₂ with core-shell structure was prepared by solvothermal method and template method.The newly synthesized composites were characterized by various techniques such as BET surface area、SEM、TEM、EDX、XRD、FTIR and VSM.The results showed that CoFe₂O₄@vacancy@mSiO₂ had a core-shell structure and a mesoporous structure,and the BET surface area was 712.49 cm²/g.The experimental study on the removal of Rhodamine B（RhB）showed that the maximum adsorption capacity of CoFe₂O₄@vacancy@mSiO₂ for RhB was calculated to be 149.36 mg/g.The adsorptionprocessofRhBbyCoFe₂O₄@vacancy@mSiO₂magnetic nanocomposites accorded with the Freundlich isotherm,indicating that the adsorption of RhB on CoFe₂O₄@vacancy@mSiO₂ magnetic nanocomposites was a multi-molecular layer adsorption.The adsorption kinetics process conformed to the pseudo-second reaction kinetic model,and the adsorption process of RhB was spontaneous and exothermic in nature.2 A novel magnetic molecularly imprinted polymer using TBBPA as a template wasprepared.CoFe₂O₄@CNTswasusedasthesupport,and N-aminopropyl-r-aminoethyltrimethoxysilane was used for surface modification.The hydroxyethyl methacrylate was used as the functional monomer,and ethylene glycol dimethacrylate was used as the cross-linker.The template molecule was reacted with the functional monomer by non-covalent bond,and the template molecule was extracted by solvent to obtain the TBBPA-imprinted composite material CoFe₂O₄@CNTs@PHEMA-MIP.The imprinted molecular layer covered the surface of the support,which was beneficial to the mass transfer process of TBBPA,thus a fast dynamic process was obtained.CoFe₂O₄@CNTs@PHEMA-MIP exhibited the enhanced adsorption performances for TBBPA with the maximum adsorption capacity of 142.3 mg/g,which was significantly higher than that of non-imprinted adsorbent（45.6 mg/g）.The selectivity experiments of CoFe₂O₄@CNTs@PHEMA-MIP for TBBPA,BPA and 4-NP showed that CoFe₂O₄@CNTs@PHEMA-MIP had good selectivity for TBBPA.3 The cobalt ferrite was synthesized by a solvothermal method to endow the carbon nanotubes with magnetic properties.Then FeCl₃ was used as a catalyst to oxidize pyrrole in situ to form a polypyrrole polymer film coating on magnetic CNTs.The prepared CNTs-CoFe₂O₄@PPy was used as an adsorbent to remove organic synthetic dyes in water.Compared with cationic dyes,CNTs-CoFe₂O₄@PPy had a stronger adsorption capacity for anionic dyes such as methyl blue（MB）,methyl orange（MO）and acid fuchsin（AF）.CNTs-CoFe₂O₄@PPy effectively removed three organic dyes over a wide pH range（3.0-9.0）.The maximum adsorption capacity of CNTs-CoFe₂O₄@PPy for MB,MO and AF could reach137.00,116.06 and 132.15 mg/g,respectively.The Langmuir isotherm and pseudo-second kinetic models could well describe the adsorption equilibrium and kinetics of three dyes on CNTs-CoFe₂O₄@PPy.In addition,CoFe₂O₄ on CNTs-CoFe₂O₄@PPy was not only used as a magnetic response medium,but also could be used as an effective heterogeneous catalyst to catalyze PMS to generate active free radicals.Therefore,the catalytic performance of CNTs-CoFe₂O₄@PPy for the degradation of cationic dye methylene blue（MEB）by PMS was studied.