An investigation of the molecular-level mineral chemistry of metal-bearing pyrite and its electrochemical behaviour under flotation related conditions

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dc.contributor.advisorVon der Heyden, Bjornen_ZA
dc.contributor.advisorTadie, M.en_ZA
dc.contributor.authorBabedi, Lebogangen_ZA
dc.contributor.otherStellenbosch University. Faculty of Science. Dept. of Earth Sciences.en_ZA
dc.date.accessioned2023-01-20T06:51:46Z
dc.date.accessioned2023-05-18T06:56:22Z
dc.date.available2023-01-20T06:51:46Z
dc.date.available2023-05-18T06:56:22Z
dc.date.issued2023-03
dc.descriptionThesis (MSc)--Stellenbosch University, 2023.en_ZA
dc.description.abstractENGLISH ABSTRACT: Pyrite (FeS₂) is an iron disulphide mineral found in hydrothermal ore deposits, including gold ore deposits, each having its unique physicochemical conditions (e.g., pH, temperature, salinity) at the emplacement site. Pyrite can incorporate several trace elements into lattice sites, making it an n- or p-type semiconductor in nature. Due to this semiconducting variance, numerous investigations have observed diverse flotation responses for pyrite from different ore sources. This study investigates how lattice-incorporated metals (As, Au, Co, and Ni) affect electronic structure and flotation collector (xanthate) response in an alkaline media. This is done by compiling a global dataset of pyrite trace element data to understand its trace element signatures and then utilizing these signatures to guide chemical vapour transport synthesis of high-purity crystals. This work uses X-ray photoelectron spectroscopy and rest potential analysis to investigate the impact of metal geochemical type and concentration on pyrite valence bands and reactivity. Valence band assessments demonstrate that metals in the pyrite lattice shift orbital contributions and Fermi levels depending on geochemical origin and concentration. The metal's nature dictates whether it effects valence band contributions around the Fermi level (Au, Co, Ni) or deeper ones (As). Pyrite's changing chemistry affects its oxidation and interaction with xanthate collector under alkaline conditions. Pyrites (pure, Co, Ni, and Au + Co-bearing) are noble and do not induce mineral surface oxidation, while As- bearing pyrite is the least noble and promotes oxidation. Noble pyrites (pure, Co, and Ni) associated with n-type semiconducting have a weaker collector interaction than the least noble (As-bearing) associated with p-type. The lack of dixanthogen on As-bearing pyrite compared to Co- and Ni-bearing pyrite shows that a greater collector-mineral interaction does not oxidize the collector on the mineral surface. Dixanthogen is present at low Ni concentrations but absent at higher concentrations, showing that collector oxidation on the mineral surface depends on metal concentration. Reactivity and electronic structural trends are correlated. The potency of collector-mineral interactions and the size of Fermi level variations as a function of metal concentration and geochemical nature are comparable. This thesis shows how synthetic minerals grown experimentally may answer important questions regarding the molecular chemistry and reactivity of sulphide minerals like pyrite. This study shows how metals impact pyrite's valence band contributions and how they affect the collector interaction. The behavior of pyrite with a xanthate collector gives important knowledge that may be used to adjust flotation collectors to best show minerals' selectivity and reactivity independent of their semiconducting qualities controlled by chemistry.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Piriet (FeS₂) is 'n ysterdisulfiedmineraal wat in hidrotermiese ertsafsettings voorkom, insluitend goudertsafsettings, wat elk sy unieke fisies-chemiese toestande (bv. pH, temperatuur, soutgehalte) by die plek waar dit geplaas word, het. Piriet kan verskeie spoorelemente in roosterplekke inkorporeer, wat dit 'n n- of p-tipe halfgeleier van aard maak. As gevolg van hierdie halfgeleidende variansie, het talle ondersoeke uiteenlopende flotasiereaksies vir piriet uit verskillende ertsbronne waargeneem. Hierdie studie ondersoek hoe rooster-geïnkorporeerde metale (As, Au, Co en Ni) elektroniese struktuur en flotasieversamelaar (xanthaat) reaksie in 'n alkaliese media beïnvloed. Dit word gedoen deur 'n globale datastel van piriet-spoorelementdata saam te stel om sy spoorelement- handtekeninge te verstaan en dan hierdie handtekeninge te gebruik om chemiese dampvervoersintese van hoë-suiwer kristalle te lei. Hierdie werk gebruik X-straalfoto- elektronspektroskopie en ruspotensiaalanalise om die impak van metaal geochemiese tipe en konsentrasie op pirietvalensbande en reaktiwiteit te ondersoek. Valensiebandbepalings toon dat metale in die pirietrooster orbitale bydraes en Fermi-vlakke verskuif, afhangende van geochemiese oorsprong en konsentrasie. Die metaal se aard bepaal of dit valensiebandbydraes rondom die Fermi-vlak (Au, Co, Ni) of dieper (As) beïnvloed. Piriet se veranderende chemie beïnvloed sy oksidasie en interaksie met xanthaat versamelaar onder alkaliese toestande. Piriete (suiwer, Co, Ni en Au + Mede-draend) is edel en veroorsaak nie minerale oppervlak-oksidasie nie, terwyl As-draende piriet die minste edel is en oksidasie bevorder. Edelpiriete (suiwer, Co en Ni) wat met n-tipe halfgeleier geassosieer word, het 'n swakker versamelaarinteraksie as die minste edel (As-draend) wat met p-tipe geassosieer word. Die gebrek aan diksantogeen op As-draende piriet in vergelyking met Ko- en Ni-draende piriet toon dat 'n groter versamelaar-minerale interaksie nie die versamelaar op die mineraaloppervlak oksideer nie. Dixantogeen is teenwoordig by lae Ni-konsentrasies, maar afwesig by hoër konsentrasies, wat wys dat kollektoroksidasie op die mineraaloppervlak afhang van metaalkonsentrasie. Reaktiwiteit en elektroniese strukturele neigings word gekorreleer. Die sterkte van versamelaar-mineraal-interaksies en die grootte van Fermi- vlakvariasies as 'n funksie van metaalkonsentrasie en geochemiese aard is vergelykbaar. Hierdie tesis wys hoe sintetiese minerale wat eksperimenteel gekweek word belangrike vrae rakende die molekulêre chemie en reaktiwiteit van sulfiedminerale soos piriet kan beantwoord. Hierdie studie toon hoe metale piriet se valensbandbydraes beïnvloed en hoe hulle die versamelaarinteraksie beïnvloed. Die gedrag van piriet met 'n xantaatversamelaar gee belangrike kennis wat gebruik kan word om flotasieversamelaars aan te pas om minerale se selektiwiteit en reaktiwiteit die beste te toon, onafhanklik van hul halfgeleidende eienskappe wat deur chemie beheer word.af_ZA
dc.description.versionDoctoralen_ZA
dc.format.extentxv, 189 pages : illustrationsen_ZA
dc.identifier.urihttp://hdl.handle.net/10019.1/126931
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshPyritesen_ZA
dc.subject.lcshTrace elementsen_ZA
dc.subject.lcshFlotationen_ZA
dc.subject.lcshMineralogical chemistryen_ZA
dc.subject.lcshGeochemistryen_ZA
dc.subject.nameUCTDen_ZA
dc.titleAn investigation of the molecular-level mineral chemistry of metal-bearing pyrite and its electrochemical behaviour under flotation related conditionsen_ZA
dc.typeThesisen_ZA
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