球磨微米硫化零价铁活化双氧水降解有机污染物的研究

Mechanochemically Sulfidated Zero Valent Iron as an Efficient Fenton-like Catalyst for Degradation of Organic Contaminants

报道了机械球磨方法制备的微米硫化零价铁(S-ZVI)可以快速活化H_2O_2降解各类有机污染物.S-ZVI/H_2O_2降解苯酚的单位比表面积反应速率常数是ZVI/H_2O_2的5倍以上,且苯酚的降解不存在初始抑制阶段.探针化合物乙醇的淬灭反应结合电子顺磁共振(EPR)实验证明S-ZVI/H_2O_2体系产生的氧化活性物质为·OH.反应前后S-ZVI颗粒的扫描电子显微镜(SEM)和X射线衍射(XRD)表征结合电化学测试和苯酚降解结果表明S-ZVI中FeS取代ZVI表面的钝化膜(铁氧化物),加速了电子从Fe0传递到H_2O_2,更快地释放Fe^(2+),引发Fenton反应.在这过程中FeS主要作为电子的导体而非Fe^(2+)的释放源.

Mechanochemically sulfidated zero valent iron（S-ZVI）, prepared from ball milling of ZVI and sulfur powder, was used as a catalyst for heterogeneous Fenton oxidation of a variety of persistent organic compounds including phenol, chlorophenols, nitrobenzene, bisphenol A and tetracycline. The 100% removal of phenol was achieved within 1 min in S-ZVI/H_2O_2 system while it took 10 min in ZVI/H_2O_2 system. The initial surface area normalized phenol degradation rate by S-ZVI was 5 times of that of ZVI, suggesting the much higher efficiency of S-ZVI in catalyzing the decomposition of H_2O_2 for oxidative degradation of organic contaminants. In addition, an initial lag period of phenol degradation in ZVI/H_2O_2 system was absent in S-ZVI/H_2O_2 system. The removal efficiency of phenol was dependent on the initial H_2O_2 concentration, S-ZVI dosage, initial phenol concentration, and p H. The optimum p H and H_2O_2 concentration was 3.0 and 2 mmol·L^（-1）, respectively, when the initial phenol concentration was 0.2 mmol·L^（-1） and the S-ZVI dosage was 0.12 g·L^（-1）. The phenol degradation was effectively scavenged by a ·OH probe compound, ethanol and the electron paramagnetic resonance（EPR） studies successfully detected DMPO（5,5-dimethyl-1-pyrroline-N-oxide）-OH signals, which collectively suggests that the reactive species responsible for contaminant degradation in S-ZVI/H_2O_2 system was ·OH. S-ZVI particles before and after reaction were characterized by scanning electron microscopy/energy dispersive X-ray spectroscopy（SEM-EDS） and X-ray diffraction（XRD）. SEM-EDS results showed that the oxidation of S-ZVI by H_2O_2 resulted in the formation of iron hydroxide nanoparticles on the particle surface while FeS was not significantly consumed. Tafel analysis of S-ZVI and ZVI modified electrodes demonstrated that S-ZVI had a greater overall rate of electron transfer than ZVI. Therefore, FeS as a better electron conductor facilitated the electron transfer from Fe^0 to H_2O_2 resulting in faster Fe^（2＋） releasing and H_2O_2 activation, which enhanced contaminant degradation.