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A Fundamental study on the effects of cation substitution on the molecular chemistry and surface reactivity of sphalerite

dc.contributor.advisorVon der Heyden, Bjornen_ZA
dc.contributor.advisorTadie, Margrethen_ZA
dc.contributor.authorBabedi, Lebogangen_ZA
dc.contributor.otherStellenbosch University. Faculty of Science. Dept. of Earth Sciences.en_ZA
dc.date.accessioned2018-11-23T12:46:19Z
dc.date.accessioned2018-12-07T06:54:25Z
dc.date.available2018-11-23T12:46:19Z
dc.date.available2018-12-07T06:54:25Z
dc.date.issued2018-12
dc.identifier.urihttp://hdl.handle.net/10019.1/104996
dc.descriptionThesis (MSc)--Stellenbosch University, 2018.en_ZA
dc.description.abstractENGLISH ABSTRACT: Sphalerite exhibits multiple flotation responses because of its intricate mineral chemistry which arises from its ability to incorporate different metal impurities. Historical work has focussed largely on the influences of Fe impurities on the flotation behaviour of sphalerite. This has created a broad knowledge gap related to the influence of associated metal impurities (e.g. Cd, Co etc.) on the structure and surface chemistry and the consequent flotation response of sphalerite. The current study seeks to address the knowledge gap using sets of analytical techniques (XRD, Raman spectroscopy, UV-vis and zeta potential) to build a molecular-level link between the crystal structure distortions, surface characteristics, and electronic structure alteration. These properties are related to the ultimate flotation response of synthetic sphalerite doped with variable amounts (0-4 wt.%) of Cd, Co and Fe. Sets of impurity (Cd, Co, Fe) bearing sphalerite samples were synthesised using a dry experimental method to ensure a controlled sphalerite composition when evaluating the influence of individual cation substitutions. The structural evaluations with XRD revealed that each metal impurity induced lattice distortion, as reflected by the varied unit cell constants with increasing impurity concentration. The magnitude of the lattice distortions can be correlated with impurity concentration and ionic size of each metal impurity. Raman spectroscopy showed that the different metal impurities induce new surface features in the form of an impurity mode, the position of which reflects the chemical nature of the metal impurity bond formed within sphalerite molecular cluster. The stronger bonds (Co and Fe) require higher vibrational energies thus occur at higher wavenumber (Fe 300 cm-1, Co 303 cm-1) compared to the weaker bonds of Cd (295 cm-1). The intensity ratios between the Zn-S mode (TO) and the impurity mode can be correlated (r2 = 0.9403 Cd, r2 = 0.7915 Fe, r2 = 0.961 Co) as a function of increases in impurity concentration. My UV-Vis data indicates that the variations in the band gap of sphalerite changed as a function of cation substitution (Cd>Fe>Co), and these were found to correlate well (r2 = 0.99) with the measured position of the Raman impurity mode of the corresponding cation substituent. The influence of each individual cation on the surface charge, Cu-activation and collector adsorption was assessed using electro-kinetic techniques (zeta potential), which provided valuable information on the surface reactivity of impurity bearing sphalerite. The study illustrates different electro kinetic characteristics of sphalerite depending on the nature of the substituting metal, which resulted in the formation of multiple surface products. The zeta potential responses varied between the different trace element substituted sphalerite reflecting differences in their nucleophilic and electrophilic properties. The results presented herein thus provide a systematic correlation between the structure and surface chemistry and illustrate how such changes manifest to the variation to the electronic structure and consequently the flotation response. This illustrates that maximum recovery of zinc can only be achieved through multidisciplinary study and fundamental understanding of the effects of cation substitution on mineral structure and surface chemistry, the latter necessarily affecting the flotation response.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Sphalerite vertoon verskeie floteringsreaksies as gevolg van die ingewikkelde minerale chemie wat voortspruit uit die vermoë om verskillende metaal-onsuiwerhede in te neem, maar die groot interpretasies van sulke flotasiegedrag word hoofsaaklik toegeskryf aan Fe-konsentrasie. Dit het 'n breë kennisgaping geskep oor die invloed van geassosieerde metaal onsuiwerhede (bv. Cd, Co, ens.) Op die struktuur en oppervlakkemie en die gevolglike flotasie-respons van sphaleriet. Die huidige studie poog om die kennisgaping aan te spreek deur gebruik te maak van stelle analitiese tegnieke (XRD, Raman-spektroskopie, UV-vis en zeta-potensiaal om 'n molekulêre vlak te bou tussen die kristalstruktuurverdraaiings, oppervlakkenmerke, verandering van elektroniese struktuur en hul verhouding tot die flotasie reaksie van sintetiese sphalerite gedoteer met veranderlike hoeveelhede (0-4 gewig%) van Cd, Co en Fe. Setse van onsuiwerheid (Cd, Co, Fe) dra sphaleriet monsters is gesintetiseer met behulp van 'n droë eksperimentele metode om 'n beheerde samestelling te help en die invloed van individuele katioonvervanging te evalueer. Die strukturele evaluasies met XRD het aan die lig gebring dat elke metaal-onreinheid geïnduseerde roostervervorming weerspieël word deur die gevarieerde eenheidselle konstantes met toenemende onreinheidskonsentrasie. Die grootte van die roostervervorming kan korreleer word met onreinheidskonsentrasie en ioniese grootte van elke metaal-onreinheid. Raman-spektroskopie het getoon dat die verskillende metaal-onsuiwerhede nuwe oppervlakkenmerke in die vorm van 'n onreinheidsmodus veroorsaak, waarvan die posisie die chemiese aard van die metaal-onreinheidsbinding wat binne die sphaleriet molekulêre groep gevorm word, weerspieël. Die sterker bindings (Co en Fe) vereis hoër vibrasie-energieë, dus by hoër wawetal (Fe 300 cm-1, Co 303 cm-1) in vergelyking met die swakker bindings van Cd (295 cm-1). Die intensiteitsverhoudings tussen die Zn-S-modus (TO) kan gekorreleer word (r2 = 0.9403 Cd, r2 = 0.7915 Fe, r2 = 0.961 Co) met die toename in onreinheidskonsentrasie. Ons UV-Vis-data het aangedui dat die variasies in die bandgaping (Cd> Fe> Co) van sphaleriet verander as 'n funksie van kation-substitusie, en dit is gevind dat dit goed korrek is (r2 = 0.99) met die gemete posisie van die Raman-onreinheid modus van die ooreenstemmende katioensubstituent. Die invloed van elke individuele katioon op die oppervlaklading, Cu-aktivering en kollektor-adsorpsie is beoordeel met behulp van elektrokinetiese tegnieke (zeta potensiaal), wat waardevolle inligting verskaf het oor die oppervlakreaktiwiteit van onreinheid wat sphaleriet bevat. Die studie illustreer verskillende elektrokinetiese eienskappe van sphaleriet, afhangende van die aard van die vervangende metaal, wat gelei het tot die vorming van verskeie oppervlakprodukte. Die zeta potensiële reaksies het gewissel tussen die verskillende spoorelement-gesubstitueerde sphaleriet wat verskille in hul nukleofiele en elektrofiliese eienskappe weerspieël. Die resultate wat hierin aangebied word, bied dus 'n sistematiese korrelasie tussen die struktuur en oppervlakkemie en illustreer hoe sulke veranderinge manifesteer in die variasie van die elektroniese struktuur en gevolglik die flotasie-respons. Dit illustreer dat maksimum herwinning van sink dus slegs bereik kan word deur multidissiplinêre studie en fundamentele begrip van die effekte van katioonsubstitusie op minerale struktuur en oppervlakkemie, laasgenoemde wat noodwendig die drywingsreaksie beïnvloed.af_ZA
dc.format.extent159 pages : illustrationsen_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.subjectSphaleriteen_ZA
dc.subjectFlotationen_ZA
dc.subjectZeta potentialen_ZA
dc.subjectRaman effecten_ZA
dc.subjectUCTDen_ZA
dc.titleA Fundamental study on the effects of cation substitution on the molecular chemistry and surface reactivity of sphaleriteen_ZA
dc.typeThesisen_ZA
dc.rights.holderStellenbosch Universityen_ZA


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