硫化零价铁的制备及去除头孢噻肟机理研究

The preparation of sulfide-modified nano zero-valent iron for cefotaxime removal

采用后置硫化法制备了硫化纳米零价铁(S-nZVI),并采用X射线光电子能谱(XPS)、X射线衍射(XRD)和透射电镜(TEM)等方法表征了材料表面形貌及元素化学形态等特性.同时,以头孢噻肟为目标污染物,考察了S-nZVI对其去除效率及去除机理等.结果表明,S-nZVI颗粒呈球形,平均粒径为56 nm,材料表面形成一层不连续的低密度FeS/FeSn.硫化率、Fe^(2+)和溶液p H均能影响S-nZVI对头孢噻肟的去除.S/Fe=1/4(质量比),S-nZVI投加量为0.5 g·L^(-1),溶液pH为8时,120 min内头孢噻肟的去除率为82.2%,远大于nZVI的去除率(23.4%).最后,采用液相色谱-电喷雾质谱分析了头孢噻肟的降解产物,发现头孢噻肟的降解主要是由酯基取代反应和内酰胺键的开环反应引起的.

Sulfide-modified nano zero-valent iron（ S-nZVI） was prepared by post sulfurized method and was characterized with X-ray diffraction,transmission electron microscopy and X-ray photoelectron spectroscopy for the surface morphology and valence electronic information. The results show that the S-nZVI nanoparticles were nearly spherical with an even diameter of 56 nm. Moreover,low density FeS/FeS nformed a discontinuous layer on the surface of nZVI. Cefotaxime（ CFX） was selected for investigating the removal efficiency and removal mechanism.Sulfur content,Fe2＋content and solution pH could affect the removal efficiency of CFX and 82.2% of CFX was removed by S-nZVI1/4 in 120 min（ dose 0.5 g·L-1,CFX initial concentration 20 mg·L-1,pH= 8）,which was much higher than that of nZVI（23.4%）. The degradation products of CFX were analyzed by using HPLC-ESI-MS to elucidate the degradation pathway. The degradation of CFX was mainly caused by the ester substitution reaction and the opening and cleavage of theβ-lactam ring.