智能聚合物包覆型纳米氧化铁的催化性能

Catalytic Property of Smart Polymer Coated Nano-Fe_3O_4

针对非均相Fenton反应效率偏低及pH值适应范围窄的问题，设计以智能聚合物调节纳米铁氧化物表面性能．通过原位共沉淀法合成纳米四氧化三铁，并将其表面健合的羧甲基纤维素钠与单体丙烯酸接枝共聚生成具有pH值响应性能的环境敏感聚合物来包覆氧化铁，形成复合纳米颗粒（PAA—CO—CMCNa／Fe3O4），研究了复合材料的催化性能．结果表明：pH值在3～7的宽范围内，该复合纳米材料均可在30min内将210mg／L的苯酚完全去除，催化降解苯酚的矿化率高达75％，并显示良好的稳定性和重复使用性能，这是由于聚合物层在该范围内的选择性溶胀既有助于纳米磁性材料的分散稳定，又能改善界面传质，从而促进非均相催化反应．

To solve the problems that heterogeneous Fenton reaction efficiency is low and an efficient reaction rate only occurs in a narrow pH range, smart polymer was designed to adjust the surface performance of magnetite （Fe3O4） nanoparticles.Fe3O4 nanopaticles were first synthesized through in situ co-precipitation. Sodium carboxymethyl cellulose （CMCNa） was bonded on the surface of generated Fe3O4 nanoparticles. Then, the acrylic acid （AA） monomers were grafted onto the chains of CMCNa and copolymerized to form a pH-responsive polymer. By this insltu encapsulation method, the poly （acrylic acid）-co-sodium carboxymethyl cellulose/magnetite （PAA-co- CMCNa/Fe3O4） nanocomposites were synthesized in this work. The catalytic activity of nanocomposites was investigated. Results show that the composite catalyst exhibites excellent catalytic property, stability and reusability. In the wide pH range of 3--7, phenol （210 mg/L） is almost completely removed after 30 min and 75% of phenol is mineralized. The superior catalytic performance of PAA-co-CMCNa/Fe3O4 nanocomposites could be associated with the pH- sensitive characteristic of the polymer coating in aqueous solutions. In the proper pH range, the hydrophilic polymer chain is highly swollen, which promotes the dispersion of Fe3O4 nanopaticles and solid-liquid interface mass transfer. Accordingly, the heterogeneous catalytic reaction is accelerated.