砷在金属氧化物/水界面上的吸附机制Ⅰ.金属表面羟基的表征和作用

Adsorption mechanism of arsenic on metal oxide adsorbent 1. Characterization and the role of metal surface hydroxyl groups

利用红外光谱对铁铈氧化物(Fe-Ce)吸附材料中的金属表面羟基(M—OH)进行了表征,并探讨了金属羟基在砷吸附中的作用.透射和原位温度漫反射-傅立叶变换红外光谱(FTIR)表征结果表明,Fe-Ce表面存在丰富的M—OH,但M—OH含量随制备温度升高而逐渐减少;Fe-Ce上的M—OH与一般金属氧化物的表面羟基特性存在显著不同,可能是一种特殊类型的结构性羟基.对砷吸附前后的Fe-Ce材料进行透射FTIR表征,发现砷饱和吸附后M—OH的摇摆振动消失,同时生成了新的As—O振动峰,表明M—OH在砷的去除中起着重要的作用;初始吸附pH由9.0降至5.0只引起了吸附剂上As—O键的伸缩振动向高频略微偏移;综合FTIR结果可以推测,M—OH和砷阴离子发生了直接的表面络合,在不同的pH条件下均与砷形成了内层络和物.

Characterization and the role of metal surface hydroxyl groups （M--OH） on an Fe-Ce oxide adsorbent were studied with transmission and in situ diffuse reflectance - infrared Fourier transform spectroscopy （FTIR）. The Fe-Ce oxide contained rich M--OH, which was apparently different from the conventional M--OH groups. The disappearance of the novel M--OH bending vibration band in FTIR spectra with the adsorption of As （V） demonstrated that the M--OH played an important role in the adsorption of As by the Fe-Ce adsorbent. The FTIR analysis results also suggest that direct surface eomplexation between M--OH and As（ V ） occurred in a wide pH range.