The surface state of hematite and its wetting characteristics

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• 作者：Kaustubh Shrimali ^{kaustubh.shrimali@gmail.com" class="auth_mail" title="E-mail the corresponding author} ; Jiaqi Jin ^{jiaqi.jin90@gmail.com" class="auth_mail" title="E-mail the corresponding author} ; Behzad Vaziri Hassas ^{behzadvaziri@hotmail.com" class="auth_mail" title="E-mail the corresponding author} ; Xuming Wang ^{X.Wang@utah.edu" class="auth_mail" title="E-mail the corresponding author} ; Jan D. Miller ; ^{Jan.Miller@utah.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Hematite ; Goethite ; Atomic force microscopy ; Molecular dynamics simulation ; Hydroxylation ; Zeta potential
• 刊名：Journal of Colloid and Interface Science
• 出版年：2016
• 出版时间：1 September 2016
• 年：2016
• 卷：477
• 期：Complete
• 页码：16-24
• 全文大小：1646 K

文摘

Apart from being a resource for iron/steel production, the iron oxide minerals, goethite and hematite, are used in the paint, cosmetics, and other industries as pigments. Surface characteristics of these minerals have been studied extensively both in resource recovery by flotation and in the preparation of colloidal dispersions. In this current research, the wetting characteristics of goethite (FeOOH) and hematite (Fe₂O₃) have been analyzed by means of contact angle, bubble attachment time, and Atomic Force Microscopy (AFM) measurements as well as by Molecular Dynamics Simulation (MDS). Goethite is naturally hydroxylated and wetted by water at all pH values. In contrast, the anhydrous hematite surface (001) was found to be slightly hydrophobic at natural pH values with a contact angle of about 50°. At alkaline pH hydroxylation of the hematite surface occurs rapidly and the hematite becomes hydrophilic. The wetting characteristics of the hematite surface then vary between the hydrophobic anhydrous hematite and the completely hydrophilic hydroxylated hematite, similar to goethite. The hydrophobicity can be restored by heating of the hydroxylated hematite surface at 60 °C. The hydrophobic character of the anhydrous hematite (001) surface is confirmed by MDS which also reveals that after hydrolysis the hematite (001) surface can be wetted by water, similar to the goethite (001) surface.