Preparation Of Polymer Microspheres Modified By Iron Ion/Zero-valent Iron And Their Application In Enhancing The Removal Of Water Pollutants

In recent years,with the continuous development of industry,the improper discharge of industrial wastewater leads to the deterioration of water environment.Non-degradable organic dyes,antibiotics,nitrobenzene,phosphate are common water pollutants in industrial wastewater.Among them,organic dyes with high chroma,complex molecular composition,difficult to degrade and high toxicity can bring health problems to aquatic organisms and human.Antibiotics can trigger some strains to produce very high resistance,which will threaten the ecological environment and social security.4-nitrophenol can damage DNA or inhibit DNA synthesis,resulting in adverse effects on blood,liver and central nervous system.Phosphorus can lead to eutrophication,causing phytoplankton and algae to bloom in the water,eventually killing or even exterminating other animals and plants in the water.Therefore,it is urgent to find suitable adsorbent to purify water pollutants.Polymer micro-and nanomaterials have great structural advantages in removing water pollutants due to their abundant functional groups,high specific surface area and strong permeability.Meanwhile,polymers with rich functional groups are also easy to modify.Therefore,this thesis focuses on the preparation of polymer-based micro/nano materials with various morphologies and structures,such as hard microspheres,hollow microcapsules and magnetic polymer composites.Meanwhile,the prepared polymer-based adsorbents were further modified with iron ion or zero-valent iron to enhance their removal ability towards water pollutants.The specific work is summarized as follows:（1）Firstly,polydopamine（PDA）microspheres were prepared by oxidative self-polymerization of dopamine in alkaline environment.Then,different transition metal ions were used to modify the PDA microspheres,and the adsorption capacity of the modified PDA microspheres towards methylene blue（MB）was investigated.The results showed that the PDA microspheres modified by Fe³⁺,Co²⁺,Ni²⁺and Mn²⁺had improved the adsorption capacity of methylene blue.Among them,the PDA microspheres modified by Fe³⁺(Fe³⁺-PDA)had the best adsorption performance,and the capture capacity of MB was twice that of pure PDA microspheres.The adsorption process of MB by Fe³⁺-PDA was analyzed by kinetic model and thermodynamic model.The adsorption mechanism of MB by Fe³⁺-PDA was systematically investigated by analyzing the influencing factors and carrying out a series of characterizations.（2）In order to enhance the adsorption performance of polymer micro-and nanomaterials,Fe₂O₃@polyphosphazene with core-shell structure was firstly prepared by a hard template route using Fe₂O₃cube as template,hexachlorocyclotriphosphazene（HCCP）and polyethylene imine（PEI）as comonomers.Subsequently,Fe₂O₃ was etched with acid and Fe³⁺was chelated in situ onto polyphosphazene matrix to obtain Fe³⁺modified hollow polyphosphazene microcapsule(HPCP-Fe³⁺).Then,we systematically studied the adsorption capacity of HPCP-Fe³⁺towards phosphate as the target pollutant.The experimental results show that the adsorption capacity of HPCP-Fe³⁺for phosphate can reach 84.23 mg g^-1 at 25℃,and the equilibrium time is only 40min.The kinetic study shows that the adsorption of phosphate by HPCP-Fe³⁺conforms to the quasi-second-order kinetic model.The mechanism analysis confirmed that the amino group and the chelated Fe³⁺on the surface of polyphosphazene played an important role.（3）To make use of the degradation ability of Fe⁰ to pollutants,the Fe³⁺ions on HPCP-Fe³⁺was directly reduced to Fe⁰ with sodium borohydride,and Fe⁰ modified hollow polyphosphazene microcapsules（HPCP-Fe⁰）was obtained directly.Then with chlortetracycline（CTC）as the research object,the degradation performance of HPCP-Fe⁰ to CTC was studied.The results showed that HPCP-Fe⁰ had a good degradation ability to CTC under acidic,neutral,and alkaline conditions.Finally,the degradation mechanism was studied in detail by FTIR and XPS,and the specific degradation path of CTC was studied by mass spectrometry.（4）In order to endow polyphosphazene adsorbent with magnetic separation function,we firstly prepared urchin-like Fe₃O₄ with high specific surface area,and then core-shell structure Fe₃O₄@polyphosphazene（Fe₃O₄@PCP）were obtained by coating polyphosphazene on urchin-like Fe₃O₄ with HCCP and PEI as comonomers.Subsequently,by loading Fe⁰ on the surface of Fe₃O₄@PCP,Fe⁰ modified magnetic nanomaterial Fe₃O₄@PCP-Fe⁰ was prepared.The dosage of HCCP and PEI was regulated,and SEM and BET analysis were used to optimize Fe₃O₄@PCP-Fe⁰ with the best morphology and high specific surface area.Finally,using 4-NP as the target pollutant,the removal performance of Fe₃O₄@PCP-Fe⁰ towards 4-NP was studied,and the removal mechanism was further explored by a series of characterization（FT-IR,XPS,MS）.In summary,we prepared a series of polymer-based adsorbents and further enhanced their removal ability of water pollutants by Fe³⁺/Fe⁰ modification.These studies will provide a theoretical basis for the construction of new adsorption materials.