Investigation of the effect of compositional variations on the flotability of pyrite in a gold ore

Naidoo, Omeshan (2020-03)

Thesis (MEng)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: Gold is associated with pyrite, arsenopyrite and arsenian pyrite in refractory gold ores. Due to the presence of arsenic or other compositional variations in the pyrite, the semiconductor properties are expected to differ from that of bulk pyrite. Semiconducting properties play a role in the attachment of a flotation collector to the mineral surface, an improvement in recovery in froth flotation may be possible if the compositional variations of pyrite can be related to the optimisation of collector reagent suites in froth flotation. The project aim was to relate the variation in pyrite composition to its impact on recovery in a flotation system and the effectiveness of reagent suites in overcoming the challenges presented by compositional variations in valuable mineral recovery. Batch flotation of are fractory ore from the Barberton Greenstone Belt in South Africa, using SIBX, PAX and SIBDTP as collectors is investigated as a case study for this phenomenon. Two different “pure” pyrite samples were floated in a micro-flotation cell to fundamentally study the differences in flotation of different pyrite samples. Pyrite in the case study ore had, among others, compositional variation of differing amounts of arsenic within the pyrite. Gold in the case study ore was associated with pyrite containing high arsenic content. SIBX and PAX in batch flotation achieved a pyrite recovery of 30.63% and 38.25% respectively, while SIBDTP recovered 27%. SIBDTP only recovered 20.97% of gold compared to 70.97% by SIBX and 73.89% by PAX. SIBDTP recovered less gold because SIDTP was shown to selectively recover pyrite with no arsenic or a low weight percentage arsenic, compared to SIBX and PAX which selectively recovered pyrite with a higher weight percentage arsenic. Compositional variations in pyrite thus impacted the recovery of the pyrite in the batch flotation system via the selective attachments of different collectors to pyrite with different compositional variations. Pyrite samples for micro flotation showed trace amounts of copper and lead (Pyrite 1) and cobalt (Pyrite 2). Pyrite 1 and Pyrite 2 differences extended to zeta potential measurements, where Pyrite 2 showed a zeta potential of approximately 10 mV lower across the pH range than Pyrite 1. Even though variations were present, no trends of differences were seen between the two pyrite samples in micro-flotation recovery.When SIBDTP and the Xanthates were mixed, an increased recovery of pyrite was seen over single collectors alone. Collector mixtures of 75% SIBX and 25% SIBDTP (massbasis) in batch flotation recovered the most pyrite (69.92%) at the highest pyrite grade (6.4%) with the most gold recovered(100%) at the highest gold grade (50.6g/ton). A recovery increase of up to 5.88% of pyrite after 20 minutes of microflotation was observed with 25% SIBDTP and 75% xanthate.The result of increased recovery of pyrite in batch flotation and inmicro-flotation with 75% xanthate and 25% SIBDTP lead to the conclusion of collector mixtures are beneficial to the recovery of pyrite when applied in the correct ratio and can overcome the mineralogical barrier posed by varying compositions.

AFRIKAANSE OPSOMMING: Goud word geassosieer met piriet, arsenopiriet en arseniese piriet in vuurvaste gouderts. As gevolg van die teenwoordigheid van arseniese of ander komposisionele variasies in die piriet, word dit verwag dat die halfgeleiereienskappe sal verskil van die vandie grootmaat piriet. Halfgeleidingseienskappe speel ’n rol in die aanhegting van ’n flottasieversamelaar aan die mineraaloppervlak. ’n Verbetering in herwinning van skuimflottasie kan moontlik wees as die komposisionele variasies van piriet verwant is aan die optimering van versamelaarreagentsuites in skuimflottasie. Die projek het beoog om die variasies in pirietkomposisies in verband te bring met sy impak op herwinning in ’n flottasiestelsel en die doeltreffendheid van reagentsuites om die uitdagings voorgestel deur komposisionele variasies in waardevolle mineraalherwinning te oorkom. Lotflottasie van ’n vuurvaste erts uit die Barberton Greenstone Belt in Suid-Afrika, wat SIBX, PAX en SIBDTP as versamelaars gebruik het, is as ’n gevallestudie vir hierdie fenomeen ondersoek. Twee verskillende “suiwer” pirietsteekproewe is in ’n mikroflottasiesel gedryf om die verskille in flottasie van verskillende pirietsteekproewe fundementeel te bestudeer. Piriet in die gevallestudie-erts het onder andere komposisionele variasies van verskillende hoeveelhede arseen binne die piriet gehad. Goud in die gevallestudie-erts is geassosieer met piriet wat hoë arseen inhoud bevat het. SIBX en PAX in lotflottasie het ’n pirietherwinning van 30.63% en 38.25% onderskeidelik bereik terwyl SIBDTP 27% herwin het. SIBDT het slegs 20.87% goud herwin, in vergelyking met 70.97% deur SIBX en 73.89% deur PAX. SIBDTP het minder goud herwin want dis gewys dat SIBDTP piriet selektief herwin met geen arseen of ’n lae gewigspersentasie arseen,in vergelyking met SIBX en PAX wat piriet selektief herwin het met ’n hoër persentasie arseen. Komposisionele variasies in piriet het dus die herwinning van die piriet in die lotflottasiestelsel via die selektiewe aanhegtings van verskillende versamelaarsaan piriet met verskillende komposisionele variasies beïnvloed. Pirietsteekproewe vir mikro-flottasie het baie klein hoeveelhede koper en lood (Piriet 1) en kobalt (Piriet 2) aangetoon. Piriet 1-en Piriet 2-verskille het gestrek na zeta-potensiaalafmetings, waar Piriet 2 ’n zeta-potensiaal van ongeveer 10 mV laer oor die pH-bestek aangeteken het as Piriet 1. Selfs al was variasies teenwoordig, is geen tendense van verskille gesien tussen die twee pirietsteekproewe in mikroflottasie nie. Toe SIBDTP en die xanate gemeng is, is ’n verhoging van herwinning van piriet gesien oor slegs enkelversamelaars. Versamelaarmengsels van 75% SIBX en 25% SIBDTP (massa basis) in lotflottasie het die meeste piriet (69.92%) herwin by die hoogste pirietgraad (6.4%) met die meeste goud herwin (100%) by die hoogste goudgraad (50.6 g/ton). ’n Herwinningsverhoging van tot 5.88% van piriet na 20 minute van mikroflottasie is waargeneem met 25% SIBDTP en 75% xanaat. Die resultaat van verhoogde herwinning van piriet in lotflottasie en in mikroflottasie met 75% xanaat en 25% SIBDTP het tot die gevolgtrekking gelei dat versamelaarmengsels voordelig is vir die herwinning van piriet as dit in die korrekte ratio toegepas word en kan die mineralogie versperring oorkom wat deur variërende komposisies gestel word.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/108211
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