Abstract:

In order to effectively improve the catalytic activity and separation of activated carbon in microwave field, magnetic Fe₃O₄/activated carbon(Fe₃O₄/AC) catalyst was prepared by chemical coprecipitation method, which was then used for the catalytic oxidation degradation of dimethyl phthalate(DMP) in aqueous solution under microwave radiation. The microstructures, morphology and magnetic properties of the catalysts were characterized by BET, SEM/EDS, XRD, XPS, FTIR and VSM. The effects of different reaction systems on the rate and kinetics of DMP degradation were studied. The effects of the amount of catalyst, the power of microwave radiation and the initial pH of the solution on the microwave-induced oxidation degradation of DMP with Fe₃O₄/AC were discussed. The reusability of Fe₃O₄/AC was also investigated. The results showed that Fe₃O₄ was the main iron oxide in the prepared catalysts, and was successfully loaded on the activated carbon. The saturation magnetization of superparamagnetic Fe₃O₄/AC could reach 21.2emu/g, and it could be quickly separated from the solution by external magnetic field. The degradation rates of DMP in the microwave-induced catalytic oxidation systems were higher than those with adsorption alone and microwave irradiation alone, and the degradation processes all followed the first-order reaction kinetics. The degradation rates of DMP could be enhanced with the increase of the dosage of Fe₃O₄/AC, the power of microwave radiation, and the initial pH of the solution. Repeated experiments showed that Fe₃O₄/AC had an excellent catalytic stability and reusability, and the degradation rate of DMP remained at 83.5% after 5cycles. It is concluded by GC-MS analysis that the degradation of DMP could be achieved by 5 pathways: hydrolysis, isomerization, hydroxylation, benzene ring trisubstitution and ring opening mineralization.

Key words: microwave-induced catalytic oxidation process, catalysis, catalyst, Fe₃O₄/AC, DMP, degradation

摘要：

为了有效地提高活性炭在微波场中的催化活性和分离性，采用化学共沉淀法制备了磁性四氧化三铁/活性炭（Fe₃O₄/AC）催化剂，并结合微波辐射技术用于催化氧化降解水中邻苯二甲酸二甲酯（DMP）。利用BET、扫描电镜/能谱（SEM/EDS）、X射线衍射（XRD）、X射线光电子能谱（XPS）、红外光谱（FTIR）和振动样品磁强计（VSM）等手段对催化剂的微观结构、形貌和磁性能进行了表征。研究了不同反应体系对DMP的降解率及反应动力学的影响，探讨了催化剂用量、微波辐射功率和溶液初始pH等因素对微波诱导Fe₃O₄/AC催化氧化降解DMP的影响，考察了催化剂的重复使用性能。结果表明，所制备的铁氧化物主要以Fe₃O₄为主，并已成功负载于活性炭上。Fe₃O₄/AC具有超顺磁性，饱和磁化强度为21.2emu/g，可通过外加磁场作用快速地从溶液中分离出来。微波诱导催化反应体系对DMP的降解率大于单独吸附或单纯微波辐射反应体系，且反应速率均符合一级反应动力学。催化剂用量越多，降解率越高；微波辐射功率的增加可以提高降解效率；溶液初始pH对DMP的降解率影响非常显著，随着pH的增大，降解率明显提高。Fe₃O₄/AC具备良好的催化活性及稳定性，循环使用5次后DMP的降解率仍保持在83.5%。通过气相色谱-质谱联用仪（GC-MS）分析，推断DMP在微波诱导Fe₃O₄/AC催化体系中的降解主要包括水解、异构化、羟基化、甲酸甲酯基的脱落和苯环三取代及苯环开环等5个途径。

关键词: 微波诱导催化氧化技术, 催化, 催化剂, Fe₃O₄/活性炭, 邻苯二甲酸二甲酯, 降解