Transmission X-ray Microscopy—A New Tool in Clay Mineral Floccules Characterization

Abstract

Abstract:Effective flocculation and dewatering of mineral processing streams containing clays are microstructure dependent in clay-water systems. Initial clay flocculation is crucial in the design and for the development of a new methodology of gas exploitation. Microstructural engineering of clay aggregates using covalent cations and Keggin macromolecules have been monitored using the new state of the art Transmission X-ray Microscope (TXM) with 60 nm tomography resolution installed in a Taiwanese synchrotron. The 3-D reconstructions from TXM images show complex aggregation structures in montmorillonite aqueous suspensions after treatment with Na + , Ca 2+ and Al 13 Keggin macromolecules. Na-montmorillonite displays elongated, parallel, well-orientated and closed-void cellular networks, 0.5-3 µm in diameter. After treatment by covalent cations, the coagulated structure displays much smaller, randomly orientated and openly connected cells, 300-600 nm in diameter. The average distances measured between montmorillonite sheets was around 450 nm, which is less than half of the cell dimension measured in Na-montmorillonite. The most dramatic structural changes were observed after treatment by Al 13 Keggin; aggregates then became arranged in compacted domains of a 300 nm average diameter composed of thick face-to-face oriented sheets, which forms porous aggregates with larger intra-aggregate open and connected voids.

How the hydro-gel flocculation microstructure changes

“…The formation of structured networks within the gelled or flocculated suspension of clay particles usually hinders the settling of particles and encapsulates water within the cellular structure. This is the cause of a suspension's resistance to settling, and it causes significant problems relating to clay mineral-rich slurry dewatering [14][15][16][17]. This paper presents microstructural investigations of a smectite suspension in order to better understand aggregate-forming behaviour.…”

The formation of a structural framework in gelled Wyoming bentonite: Direct observation in aqueous solutions

“…The most likely cause of these difference in performance is formation of structured networks within gelled or flocculated suspension of clay platelets may hinder particles, preventing their movement when settling in gravity force. Microstructural patterns within clay-rich suspension and sediments may not only cause settling difficulties but also in some way encapsulate water, which causes a major problem in clay-rich sludge dewatering [17,18,19,20]. The present study investigated smectite suspension microstructure in water and a medium salty aqueous environment to better understand this floccule-building phenomenon.…”