- Title
- Water transport properties and agglomeration efficacy of a high-internal-phase, water-in-oil emulsion binder
- Creator
- DeIuliis, Gabrielle
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2022
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- This thesis is concerned with investigating a water-in-oil emulsion binder used for the selective recovery of ultrafine hydrophobic particles. The emulsion binder is composed of a dispersed aqueous phase (containing NaCl) surrounded by oil, stabilized by an emulsifier (sorbitan monooleate). Ultrafine particles (0.1 – 100 µm) are recovered via agglomeration through hydrophobic interaction with the continuous organic films of the binder. Hydrophobic particles in the size range of 1 – 100 µm are traditionally recovered via froth flotation using air bubbles. However, given the efficiency of particle-air bubble attachment declines in the ultrafine size range (<20 µm), alternative recovery techniques are required. Particle agglomeration has long been a topic of scientific research due to the ability for recovering these ultrafine particles using a hydrophobic substrate such as pure oil. Due to the economic downfalls of using pure oil to agglomerate a large specific surface area of particles, alternate hydrophobic substrates such as a water-in-oil emulsion binder were developed. The emulsion binder is unique in that it possesses a hydrophobic physical exterior required for the particle agglomeration but is composed of up to 95% water. Hence, the novel agglomeration technique using this emulsion binder has seen a notable reduction in the organic liquid requirements (~20-fold) compared to using pure oil (van Netten et al., 2017). Another key feature of the emulsion binder is the ability for particle recovery to be achieved in a matter of seconds. Traditional techniques such as oil agglomeration require minutes of processing time while froth flotation often requires tens of minutes. Selective and ultrafast recovery of ultrafine particles is facilitated by the permeable organic films of the emulsion binder. Meaning that, hydrophobic particles can adhere to the surface of the binder and form agglomerates in the absence of hydrodynamic resistance. In this study, the permeability of the emulsion binder which allows this ultrafast hydrophobic particle recovery is extensively explored. In addition to the permeability, the osmotically driven water permeation (induced by NaCl) into the binder which occurs parallel to the agglomeration, further encourages particle attachment. This water permeation through the emulsion binder was formally investigated and initially quantified as a function of salt concentration driving force. The agglomeration efficacy and permeation flux of emulsion binders across a much broader range of compositions was also explored. Thin cylindrical structures of the emulsion (rivulets) were soaked in water and their growth was analysed to quantify the water uptake behaviour of various binders. A change in rivulet diameter scaled with the square root of time, consistent with a diffusion mechanism. The growth parameter, used to describe the water uptake mechanism, was found to weakly increase with internal salt concentration at a diminishing rate. The direct dependence on osmosis was confirmed. To study the effect of emulsion composition on the permeation flux, an expansive range of SMO:oil ratios (0.2 – 100) were used. The various emulsions exhibited consistent water transport properties at relatively high concentrations of SMO. This finding validated the assumption that at high concentrations of SMO, there will be a notable number of micellar structures within the system. These micellar structures appear to facilitate the transport of external water (containing no salt) at what appears to be a lower and more consistent rate. The agglomeration efficacy was investigated over the broad range of compositions defined by SMO:oil ratios in the binder. The agglomeration efficacy was analysed in terms of an oil dose (wt%) requirement for recovering ultrafine silica particles hydrophobized with cetyltrimethylammonium bromide (CTAB). The oil dose (wt%) decreased as the SMO:oil ratio in the binder increased. Using these extreme binder formulations, the oil dose requirements was reduced considerably, to as little as 0.07 wt% of the silica in the feed. The inferred oil film thickness surrounding and facilitating recovery of the hydrophobic silica scaled with (SMO:oil)-0.5, reaching a lower limit of 4.5 nm. A concise quantification of the water uptake flux and agglomeration efficacy under various expansive emulsion compositions is presented in this work. A comprehensive description of the functionality of the binder was determined.
- Subject
- chemical engineering; minerals processing; emulsion binder technology; emulsion binder agglomeration; ultrafine particle recovery; particle beneficiation; froth flotation
- Identifier
- http://hdl.handle.net/1959.13/1513434
- Identifier
- uon:56720
- Rights
- Copyright 2022 Gabrielle DeIuliis
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 11 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 540 KB | Adobe Acrobat PDF | View Details Download |