超顺磁性氧化石墨烯复合材料固定辣根过氧化物酶催化去除氯酚

采用超声辅助共沉淀法成功地将磁性Fe3O4纳米颗粒沉积在氧化石墨烯表面,利用透射电镜、磁滞回归曲线和X射线光电子能谱对材料进行了表征。将该材料作为载体固定辣根过氧化物酶,考察了固定化酶催化2-氯酚、4-氯酚和2,4-二氯酚降解反应,研究了溶液pH值、反应温度、反应时间、H2O2和氯酚浓度以及固定化酶用量对酚类物质去除率的影响。基于取代基数量和位置不同,去除率排序为2-氯酚<4-氯酚<2,4-二氯酚。另外,采用GC-MS研究了降解过程中的氧化产物。固定化酶的生化性质研究表明,固定化酶比游离酶具有更好的储存稳定性、pH稳定性和热稳定性。经过4次循环利用,固定化酶仍保留66%的活性,说明磁性纳米材料可以分离回收并重复利用,在污水处理领域具有应用前景。

Enzymatic removal of chlorophenols using horseradish peroxidase immobilized on superparamagnetic Fe3O4/graphene oxide nanocomposite

Magnetic Fe3O4nanoparticles were successfully deposited on graphene oxide sheets by ultra-sound-assisted coprecipitation. The nanoparticles were characterized using transmission electron microscopy, vibrating sample magnetometry, and X-ray photoelectron spectroscopy. The synthe-sized material was used as a support for the immobilization of horseradish peroxidase (HRP). The removals of 2-chlorophenol, 4-chlorophenol, and 2,4-dichlorophenol using the immobilized HRP were investigated. Batch degradation studies were used to determine the effects of the initial solu-tion pH values, reaction temperature, reaction time,H2O2and chlorophenol concentrations, and immobilized enzyme dosage on the removal of chlorophenols. The different numbers and positions of electron-withdrawing substituents affected the chlorophenol removal efficiency; the order of the removal efficiencies was 2-chlorophenol< 4-chlorophenol< 2,4-dichlorophenol. The oxidation products formed during chlorophenol degradation were identified using gas chromatography-mass spectrometry. The biochemical properties of the immobilized HRP were investigated; the results indicated that the storage stability and tolerance to changes in pH and temperature of the immobi-lized HRP were better than those of free HRP. The nanoparticles were recovered using an external magnetic field, and the immobilized HRP retained 66% of its initial activity for the first four cycles, showing that the immobilized HRP had moderate stability. These results suggest that the immobi-lized enzyme has potential application in wastewater treatment.