In this thesis, the surface properties of cassiterite due to the changes of two material properties, i.e. crystallographic orientation, and Fe as a minor element in the lattice, and their implication for selective separation are studied.
In the study of the crystallographic orientation of cassiterite, the physicochemical behaviors of the surfaces SnO2(110), SnO2(100), as well as SnO2(001) were investigated by using high-resolution direct force spectroscopy. The measurements were conducted between a silica sphere and sample surfaces in 10 mmol/L KCl between pH 3.1 and 6.2 using colloidal probe atomic force microscopy (cp-AFM-hydrophilic). Dissimilar interactions were detected on different-oriented surfaces. The pH values where the force switched from positive to negative can be clearly distinguished and be ordered as SnO2(100) < SnO2(001) ≈ SnO2(110). The most potent attractive force was found to be on the (110) cassiterite surface compared to the (100) and (001) cassiterite surfaces at lower pH. By fitting the force curves in the DLVO theory framework, anisotropic surface potentials were computed between the three sample surfaces following a similar trend as force interaction. This differential surface potential might be due to the difference in Sn cation density and electron affinity. To study the implication of crystallographic orientation to surfactant adsorption, we used Aerosol22 (sulfosuccinamate) as an anionic collector for cassiterite flotation to functionalize the different samples at pH 3. The contact angle measurements, the topography visualizations by AFM, and the force measurement using cp-AFM with hydrophobized spheres (cp-AFM-hydrophobized) have shown that Aerosol22 was adsorbed on the sample surfaces inhomogeneously. The adsorption followed the order of SnO2(110) > SnO2(100) > SnO2(001) in the concentration from 1 × 10−6 mol/L to 1 × 10−4 mol/L.
In the study of Fe as a minor element in the lattice of cassiterite, synthetic pure cassiterite, and cassiterite doped with two different Fe contents were successfully recrystallized by means of sintering. Their crystal structure and chemical compositions are characterized by X-ray powder diffraction (XRD) as well as scanning electron microscopy (SEM) combined with energy-dispersive X-ray (EDX) analysis. Their floatability was studied by microflotation with a diphosphonic acid surfactant named Lauraphos301 as a collector. Unlike the addition of ferric ions in solution, which strongly depressed the floatability of all the cassiterite samples, a much higher flotation efficiency of the Fe-doped cassiterite samples was found especially at lower collector concentrations. The cassiterite floatability is proportional to the Fe content in the cassiterite at a broad range of pH, and the recovery has the following order:
Cassiterite with 1417 ppm Fe > cassiterite with 1165 ppm Fe > pure cassiterite The electrokinetic behavior of the cassiterite samples with and without the collector was studied by electrophoretic measurements and revealed that the chemical interaction dominated the adsorption. With the help of the particle shape analysis, a more angular shape was found for the Fe-doped cassiterite samples. Moreover, without the influence of particle shape, abundant adsorption of Lauraphos301 was found on the Fe-doped cassiterite samples by AFM topography imaging. The minor amount of Fe in the cassiterite lattice and a more angular shape of the Fe-doped cassiterite samples were believed to enhance floatability collectively.
The study reveals that the influence of the chemical composition of the minerals on flotation was almost inextricably bound up with particle morphology and emphasizes the importance of considering both factors and investigating them individually for the flotation study.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:90821 |
| Date | 22 April 2024 |
| Creators | Wu, Haosheng |
| Contributors | Eckert, Kerstin, Gao, Zhiyong, Rudolph, Martin, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | 10.1021/acsomega.0c03980, 10.1021/acsomega.2c07230 |
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