AFM of Iron Oxide Particles Attachment on Mica

Abstract

The attachment of iron oxide colloidal particles on a mica surface in the presence of humic acid (HA) and/or aluminum ions (Al³⁺) was investigated with atomic force microscopy (AFM). In the absence of both HA and Al³⁺, adhesion of some individual colloidal particles onto the solid substrate increased with time as clusters formed and grew. HA substances present in the colloidal suspension considerably reduced the attachment of iron oxide colloidal particles onto the mica surface. In addition, most attached colloidal particles tended to aggregate following long immersion times forming big clusters on specific areas of the mica sheet, thus displaying a selective way of attaching to the mica surface. The presence of Al³⁺ greatly increased the attachment of iron oxide colloidal particles whether in the absence or in the presence of HA. These observations carry significance in the colloid‐facilitated transport and mobilization of contaminants in subsurface environments, where humic substances have previously been known to enhance transport, while polyvalent metal ions are noted as promoters of particle aggregation in suspensions and slurries.

Keywords:

• Humic acid
• Colloidal particles
• Mica
• Mobilization