α-Fe2O3砂芯微球制备及紫外辅助下活化PMS降解AO7

以FeCl₃为原料,尿素为沉淀剂,抗坏血酸为还原剂,聚乙烯吡咯烷酮为结构导向剂,纳米碳粉为模板,水热法制备了一种新型α-Fe₂O₃砂芯微球.通过透射电镜（TEM）、扫描电镜（SEM）、X射线衍射（XRD）和比表面积及孔径分析（BET/BJH）等手段对其结构和性能进行表征.结果表明新型α-Fe₂O₃砂芯微球尺寸均匀,直径为50μm左右,是由直径40nm"米粒状"纯相α-Fe₂O₃自聚而成,S_BET为25.45~32.46m²/g.在紫外（UV,高压汞灯）辐射下能够活化过硫酸盐（PMS）产生强氧化性的硫酸根自由基（SO₄^-·）.40min内AO7的降解率可达98.6%,采用电子自旋共振（ESR）技术鉴定了主要的活性氧自由基（ROS）为SO₄^-·.此外发现PMS作为一种电子捕获剂,能有效抑制光生电子（e_CB^-）和空穴（h_VB⁺）的复合,AO7能直接和h_VB⁺、SO₄^-·和羟基自由基（OH·）反应而迅速被氧化降解;α-Fe₂O₃回收重复使用10次,仍可以达到80%以上的去除率.通过考察α-Fe₂O₃投加量、PMS浓度、初始pH值、阴离子和初始AO7浓度等不同条件对AO7降解率的影响,发现在初始pH值为7.0,α-Fe₂O₃的投加量为1.0g/L,PMS浓度为0.3g/L时,40min内对AO7的降解率可以达到99%以上;阴离子CO₃^2-、NO₃^-以及Cl^-对该体系均有不同程度的促进作用.

Preparation of α-Fe2O3 sand core microspheres for the activation of UV-assisted peroxymonosulfate on the degradation of AO7

In this study, a novel type of α-Fe₂O₃ core microspheres were prepared hydrothermally by using FeCl₃, urea, and ascorbic acid, polyvinylpyrrolidone and nano-carbon powder as precursors. The microspheres were characterized by transmission electron microscope (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and BET/BJH methods. The results revealed that the core microsphere was self-assembled with the 40nm sized rice-grain shaped α-Fe₂O₃, the size of microsphere was uniform and the diameter was~50μm, the specific surface area of BET was between 25.45~32.46m²/g. This microsphere could activate peroxymonosulfate (PMS) to produce strong oxidative radical under ultraviolet (UV, mercury lamp) irradiation, which was confirmed as sulfate radical (SO₄^-·) with ESR (electron spin resonance) method. 98.6% of AO7 could be removed in 40 min in this system. It was found that PMS could effectively inhibit the recombination of photogenerated electrons (e_CB^-) and valence holes (h_VB⁺) as an electron capture agent, and AO7 can be oxidized by h_VB⁺, SO₄^-·and hydroxyl radical (OH·). After 10 cycles of application of α-Fe₂O₃, 80% of AO7 could be still removed in system. The effects of different dosage of α-Fe₂O₃, PMS, initial pH and initial concentration of AO7 on the degradation rate of AO7 were investigated. The results suggested that 99% of AO7 was eliminated within 40min under the optimum conditions:the initial pH was 7.0, the concentration of α-Fe₂O₃ and the PMS were 1.0g/L and 0.3g/L, respectively. The study of anion effect indicated that CO₃^2-, NO₃^- and Cl^- could promote AO7 degradation, which needed a further investigation in future works.