Controllable Preparation Of Magnetic Nano/microspheres For The Removal Of Pollutants In Water

Recently, as the over-speed development of economy, the sharp increase of population, environmental problems become increasingly serious, especially water pollution. Large numbers of industrial, agriculture and domestic pollutants were discharged into water. All of these pollutants threat to aquatic life and also human health. Water pollution has become one of the greatest threat to human survival and development. Besides, the kinds of water pollutants become more and more widely, complex in composition, a lot of hard biodegradable organic pollutant were discharged into water bodies, which caused severe and persistent contamination to surface and groundwater. How to remove contaminants in water becomes a hot topic at home and abroad.Magnetic nanoparticles have attracted numerous attentions because of their sensitive magnetic responsiveness, large specific surface area, and large amount of surface functional groups make it could be modified easily. Magnetic nanocomposite that combines the advantages of magnetic nanoparticles that mentioned above with other materials will improve their property and broaden application. Therefore, design and synthesis of the magnetic nanocomposite with shape-controlled, high reaction activity and high magnetic property become one of the focuses of this research. Then main contents for this paper carried out as follows:1. Magnetic responsive metal-organic frameworks nanospheres with core-shell structure for highly efficient removal of methylene blueMagnetic metal-organic frameworks（MOFs） nanospheres with high specific surface area and sensitive response were fabricated by a step-by-step assembly strategy. Fe₃O₄ nanospheres were firstly prepared by the traditional hydrothermal method. They were then modified by poly（acrylic acid）（PAA） through distillation–precipitation polymerization. The core-shell MOFs were prepared using Fe₃O₄@PAA nanoparticles as templates through a versatile step-by-step self-assembly strategy. The shell thickness of the MOFs could also be easily controlled by tuning the number of assembly cycles. The obtained materials were used as adsorbent to remove methylene blue from wastewater. Results demonstrated that the obtained hybrid materials had higher adsorption capacity and could be easily recycled from liquid media by an external magnetic field because of the presence of a magnetic core and could be reused after been washed by ethanol.2. Preparation and characterization of magnetic porous carbon microspheres for removal of methylene blue by heterogeneous Fenton reactionHigh specific surface area magnetic porous carbon microspheres（MPCMS） were fabricated by annealing Fe2+ treated porous polystyrene（PS） microspheres, which were prepared using two-steps seed emulsion polymerization process. The resulting porous microspheres were then sulfonated, and Fe2+ was loaded by ion exchange, followed by annealing at 250°C for 1 h under ambient atmosphere to obtain the PS-250 composite. The MPCMS-500 and MPCMS-800 composites were obtained by annealing the PS-250 at 500 and 800°C for 1 h, respectively. The iron oxide in MPCMS-500 was mainly existed in the form of Fe₃O₄ which was concluded by characterization. The MPCMS-500 carbon microspheres were used as catalysts in heterogeneous Fenton reactions to remove methylene blue（MB） from wastewater with the help of H2O₂ and NH2 OH. Results indicated this catalytic system has good performance in terms of removal MB, it could remove 40 mg L-1 MB within 40 min. After the reaction, the catalyst was conveniently separated from the media within several seconds using an external magnetic field, and catalytic activity was still viable even after 10 removal cycles. The good catalytic performance of the composites could be attributed to synergy between the functions of the porous carbon support and the Fe₃O₄ nanoparticles embedded in the carrier. This work indicates that porous carbon spheres provide good support for development of a highly efficient heterogeneous Fenton catalyst useful for environmental pollution cleanup.3. A facile approach to the fabrication of rattle-type magnetic carbon nanospheres for the removal of methylene blue in waterRattle-type magnetic carbon nanospheres were obtained easily by annealing core–shell–shell hybrid nanospheres. The nanospheres were fabricated by combining, in a single step, a tetraethyl orthosilicate sol–gel process and the condensation polymerization of resorcinol and formaldehyde in the presence of ammonia. Subsequent annealing and silicon dioxide removal in sodium hydroxide solution resulted in materials with a high specific surface area（250.3 m2 g-1） that could be separated easily from aqueous media using an external magnetic field. Methylene blue was selected as a typical organic pollutant to test adsorption and Fenton catalytic degradation performance. The results demonstrate the potential applicability of the rattle-type magnetic carbon nanospheres. The nanospheres could remove methylene blue rapidly with an adsorption capacity of 45.15 mg g-1. They can also effectively catalyze the degradation of methylene because of their special structure.4. Novel magnetic molecular imprinted polymers microspheres for selective and efficient determination of Tetrabromobisphenol AA well-defined molecularly imprinted polymer（MIP） microspheres with excellent specific recognition ability toward Tetrabromobisphenol A was prepared on Fe₃O₄ nanoparticles, which was modified by 4-vinylbenylchloride through distillation–precipitation polymerization, based on the combination of reversible addition-fragmentation chain transfer（RAFT） polymerization and click chemistry. It involves the first synthesis of Fe₃O₄ nanoparticles by hydrothermal method and then modified by 4-vinylbenylchloride, which makes azide groups was easily introduced due to the relatively large amount of benzyl chloride groups. The alkyne terminated RAFT chain transfer agent were then immobilized onto the surface of Fe₃O₄ with high efficiency via the Cu（I）-catalyzed azide–alkyne cycloaddition（Cu AAC） ‘click’ reaction. Finally, imprinted thin film was prepared in the presence of Tetrabromobisphenol A as the template. The binding results demonstrated that as prepared imprinted beads showed obvious molecular imprinting effects towards the template, fast template rebinding kinetics and an appreciable selectivity over structurally related compounds.