作为一种高级氧化技术(AOPs),芬顿氧化法(Fenton)因其操作简单、绿色高效而备受关注.其基本原理是Fe^2+催化H2O2产生的羟基自由基(·OH)进攻有机物使之降解为无机小分子或盐.电芬顿法(Electro-Fenton,E-Fenton)是利用电化学方法原位生成H2O2的Fenton衍生法,其优点在于不需要从外界加入H2O2、高效节能、无选择性、并且易于和其他处理技术耦合,是一种非常有价值和应用前景的新型水处理技术.电芬顿技术的理论探究和工艺优化,是当今高级氧化技术的理论和实践研究的重要内容.E-Fenton过程的关键步骤是阴极材料上氧还原反应(Oxygen reduction reaction,ORR)持续生成H2O2.由于析氢过电位高、稳定性好、性能优异,碳材料成为ORR反应最常用的电催化阴极材料.石墨毡作为一种三维多孔立体材料,具有电化学活性面积大、传质好、导电性强、价格低等优点,是ORR的理想阴极材料.聚苯胺材料作为一种导电高分子材料,价格便宜、加工性好、且含有丰富的N原子,在基础研究和实际应用领域都十分活跃.我们创新性地采用电聚合的方法合成了聚苯胺@石墨毡(PANI@GF)复合电极,并通过降解邻苯二甲酸二甲酯(dimethyl phthalate,DMP)研究了其在电芬顿过程中的电催化性能.通过扫描电镜、X射线光电子能谱分析对电极表面结构和杂原子掺杂性进行了物化表征.结果显示PANI@GF复合电极同时具有宏观和微观的三维多孔结构,这种结构蓬松的多孔结构为氧气提供了合适的传递通道和足够的反应面积.所制备复合电极中N原子含量约为1.9%,且吡啶N和吡咯N的含量相对较高.这些N原子来自聚苯胺分子中含有的大量N原子,并能够促进ORR反应.石墨毡和聚苯胺两种材料的在结构和组分上的特点,使得PANI@GF复合电极具有优异的电芬顿降解DMP的性能.在DMP浓度为50 mg/L、电位0.5 V(vs.SCE)、氧气流速?
An energy-effective polyaniline coated graphite felt (PANI@GF) composite cathode for the elec- tro-Fenton (E-Fenton) process was synthesized through an electro-polymerization method. The electrocatalytic activity of the cathode for the 2e- ORR process was investigated and dimethyl phthalate (DMP) was used as a model substrate to evaluate its performance in the E-Fenton process. The as-prepared PANI@GF composite possessed a three-dimensional porous structure, which is favorable for 02 diffusion, while the large amount of N atoms in the conductive polyaniline (PANI) enhanced 2e- ORR reactivity. The DMP degradation of the E-Fenton system using PANI@GF was significantly enhanced owing to the improvement in ORR performance. The apparent kinetic con- stant for DMP degradation was 0.0753 min-1, five times larger than that of GF. The optimal carboni- zation temperature and polymerization time for the preparation of the PANI@GF composite cath- ode was found to be 900 ℃ and 1 h, respectively. Measurement conditions are a crucial factor for proper evaluation of cathode electrocatalytic performance. Accordingly, the 02 flow rate, Fe^2+ con- centration, and pH for DMP degradation were optimized at 0.4 L/min, 1.0 mmol/L, and 3.0, respec- tively. These results indicate that the present PANI@GF composite cathode is energy-effective and promising for potential use as an E-Fenton system cathode for the removal of organic pollutants in wastewater.