Journal of Chromatography & Separation Techniques
Open Access
ISSN: 2157-7064
ISSN: 2157-7064
Marek S Zbik
The University of Queensland, Australia
Posters & Accepted Abstracts: J Chromatogr Sep Tech
Clay minerals were formed as result of the weathering of volcanic glass, lavas and igneous rocks like granites and basalts. Clays are useful for dam bed impregnation, to improve water retention properties and as drilling mud, to seal the cut, thus preventing fluid loss. They are also popular stabilizing additives in engine oils, cosmetics, pharmaceutical and chemical industries. Their water retention phenomenon prevents aggregates of clay-water suspension from settling under gravity force which cause difficulties in clay rich sludge dewatering. Dewatering of sludge by physical and chemical treatment becomes increasingly urgent in the view of growing demand for sites for the disposal of mining slurries, tailing and other mineral waste. Mine tailings are often disposed of as high water content slurries into tailing dams which will harm the natural environment and is very costly. Primary dewatering processes include aggregate formation, bridging flocculation, settling rate and bed height (density) before compression. This can be achieved by physico-chemical processes like aggregation, coagulation and flocculation which were clarified recently. Aggregation is usually understood as a process of formation larger and stable structural elements by primary particles connecting in face to face phase contacts and becoming unstable. Coagulation is connected mostly with interaction between primary particles within dense suspensions (gels) resulting in face to edge (FE) and edge to edge (EE) coagulating type contacts. Flocculation also is seen as a process of building larger structural elements and some authors relate this with coagulation. Others present flocculation as a separate type of coagulation to be achieved by flocculation using long chain polymers; however, this process is still not well understood. To understand micro structural behaviour of clay gelled suspen¬sion, the microstructure investigation was conducted using a transmission x-ray microscope (TXM) and cryo-SEM. The application of a high resolution TXM has increased with the availability of synchrotron photon sources. In the soft x-ray range (100 eV-1 keV), a zone plate based TXM, has achieved a spatial resolution of 60 nm. In this article, we are using the microscope constructed in the National Synchrotron Radiation Research Canter (NSRRC). All our results advocate, the structure building phenomenon within entire suspension may be blame for poor settling and de¬watering. All these may result of high water dielectric constant which polarizing clay particles and generating electrostatic charge. This charge leads to structure building phenomenon within the aqueous suspensions. It becomes clear that further technologies have to eliminate using water in mineral processing and develop new approach involving close loop processing environment in low dielectric constant liquids.
E-mail: marek.zbik@uw.edu.pl