环己烷辅助水热法简易合成改性δ-MnO_2及其类Fenton催化性能

Facile Cyclohexane-mediated Hydrothermal Synthesis of Modified δ-MnO_2 with Enhanced Fenton-like Catalytic Activity

以KMnO_4为锰源,少量的环己烷为改性剂,采用简易的水热法制备了对照样品(CHM-0)和3种环己烷改性的δ-MnO_2(CHM-2,CHM-5和CHM-10).以亚甲基蓝(MB)溶液为模拟染料废水,比较了材料的吸附性能和类Fenton催化性能.采用X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)和N_2吸附-脱附等技术对材料进行了表征.利用GC-MS技术对水热反应过程中环己烷的中间氧化产物进行了分析;通过自由基捕获剂实验初步分析了改性δ-MnO_2的催化机理,并评价了其稳定性.结果表明,改性δ-MnO_2对亚甲基蓝(MB)的吸附性能和催化活性显著提高,且MB的吸附量随着环己烷添加量的增加而增大,而CHM-5的催化活性最高;在水热制备δ-MnO_2过程中,环己烷的中间氧化产物有丙酮、环己醇和环己酮;添加环己烷可改变δ-MnO_2的形貌与结晶度,CHM-0和CHM-5的比表面积分别为15.9及148.7m^2/g,比表面积的增大提高了δ-MnO_2的吸附性能和催化活性;环己烷改性δ-MnO_2具有良好的稳定性,其催化H_2O_2分解主要生成羟基自由基.

Unmodified δ-MnO2（ CHM-0） and modified δ-MnO2（ CHM-2,CHM-5 and CHM-10） were prepared via a hydrothermal method employing the reaction between KMnO4 and different amounts（ 0,2,5 or10 m L） of cyclohexane. The products were characterized by X-ray diffraction（ XRD）,field emission scanning electron microscope（ FESEM）,transmission electron microscopy（ TEM） and nitrogen adsorption-desorption measurements. The oxidation products of cyclohexane in the hydrothermal process were identified by gas chromatography-mass spectrometry（ GC-MS）. Their Fenton-like activity and adsorption capacity for methylene blue（ MB） were investigated. The effect of radical scavengers on the degradation of MB was also studied. The results indicate that the adsorption capacity of the modified samples increased with increasing the amount of cyclohexane,and CHM-5 exhibited the highest catalytic activity. The addition of cyclohexane could modify the morphology and crystallinity of δ-MnO2,and its oxidation products consisted of acetone,cyclohexanol and cyclohexanone. The surface area of CHM-5 was 148. 7 m2/g,much larger than 15. 9 m2/g of CHM-0.Hydroxyl radicals were the main active species.