Wednesday, 19 February 2014

New Insight into the Effect of the Formation Environment of Fh on Its Structure and Property

Hui Liu,   Xiuling Li,   Yan Wang,   Xin Yang,   Zhen Zhen,   Rufen Chen,   Denglu Hou and    Yu Wei  


Ferrihydrite(Fh) is a naturally occurring nanoscale iron oxyhydroxide mineral. It is of great interest in soil science and environmental science due to its extremely high surface area and reactivity. In this work, Fh samples were prepared by three procedures (named Fh-1, Fh-2, and Fh-3). The formation of Fh-1 went through a pH change from acidic to neutral, and the formation of Fh-2 went through a pH change from alkaline to neutral, while Fh-3 was formed at a constant neutral pH. The three Fhs were characterized by high-resolution transmission electron microscopy (HRTEM), terahertz (THz) spectroscopy, nitrogen adsorption isotherms, and low-temperature magnetic techniques. All these techniques indicate that the microstructure and formation process of Fh are strongly coupled. More importantly, the differences of the three Fhs in microstructure are reflected not only in their bulk structure but also in their surface properties. The adsorption and degradation of azo dye Mordant Yellow 10 (MY10) on the three Fhs were investigated. On the one hand, comparing with Fh-1 and Fh-2, Fh-3 exhibits a high density of active site per area, which leads to a large adsorption capacity. On the other hand, a strong affinity between Fh-3 and MY10 results in a more irreversible adsorption and a low degradation rate. The results from current study shed new light on synergetic effects of porosity and the variations of local structure on photocatalysis by iron oxide particles.

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