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Author:Lundström, Mari
Title:Leaching of chalcopyrite in cupric chloride media
Kalkopyriitin liuottaminen kuparikloridiliuoksessa
Publication type:Master's thesis
Publication year:2004
Pages:96+1      Language:   eng
Department/School:Materiaali- ja kalliotekniikan osasto
Main subject:Korroosionestotekniikka   (Mak-85)
Supervisor:Aromaa, Jari
Instructor:Barker, Michael
OEVS:
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Location:P1 Ark V80     | Archive
Keywords:chalcopyrite
leaching of chalcopyrite
cupric chloride
sodium chloride
HydroCopperTM
kalkopyriitti
kalkopyriitin liuottaminen
kuparikloridi
natriumkloride
HydroCopperTM
Abstract (eng):The Outokumpu HydroCopper™ technology was developed and registered by Outokumpu Oyj. It is a novel leaching process for chalcopyrite, based on the good leaching properties of cupric chloride solutions. The leaching is operated at atmospheric pressure in a stirred tank reactor near the boiling point and the pH is kept between 1.5-2.5. The aim of this work is to find the optimum conditions for chalcopyrite leaching in the HydroCopper™ process to leach as much copper as possible.

A laboratory study of the dissolution behavior of chalcopyrite was made electrochemically in a sodium chloride solution (250 g/l) with variable cupric ion concentrations in the range 0.09-26.6 g/l. The effects of pH (1-3) and temperature (70 - 90 °C) were also studied. In order to investigate the chalcopyrite composition and the reaction product layers, the electrodes were analyzed with SEM. The rotating disk electrode technique was used to define the controlling step in the leaching process.

The results suggest that at pH < 2, sulfur concentrates on the chalcopyrite surface and rapidly forms a reaction product layer that prevents dissolution. At pH>- 2.25 mainly goethite and iron hydroxides gather on the chalcopyrite surface slowly forming a rusty colored reaction product layer. A critical cupric ion concentration was found around 9 g/l. [Cu2+] <-9 g/l do not affect the dissolution rate. [Cu2+] > 9 g/l increase the dissolution rate. Increase in the temperature was also found to increase the dissolution rate. The controlling step in the leaching process was suggested to be diffusion when [Cu2+] > 9 g/l. The diffusion coefficient was calculated to be 4.4 x 10-6 cm2/s. With [Cu2+] = 9 g/l the controlling step was suggested to be diffusion through the reaction product layer and with [Cu2+] < 9 g/l the control was due to electron transfer or mixed control.
Abstract (fin):HydroCopper™ prosessi on Outokumpu Oyj:n kehittämä ja rekisteröimä uudenlainen liuotusprosessi, joka perustuu kalkopyriitin liuotukseen kloridiliuoksessa kahdenarvoisen kupari-ionin toimiessa hapettimena. Rikaste liuotetaan reaktorissa väkevään suolaliuokseen, jonka pH on 1.5-2.5. Prosessi toimii normaalissa ilmanpaineessa. Tämän diplomityön tarkoitus on löytää optimiolosuhteet, joissa kuparin liukeneminen kalkopyriitistä tapahtuu mahdollisimman tehokkaasti.

Työn kokeellisessa osassa tutkittiin kalkopyriitin liukenemista sähkökemiallisesti natriumkloridiliuoksessa (250 g/l). Mittauksissa selvitettiin kuparipitoisuuden (0.0926.6g/l), lämpötilan (70-90 °C) ja pH:n (1-3) vaikutusta liukenemiseen. Kalkopyriitin koostumuksen sekä muodostuneiden reaktiotuotekerrosten analysoinnissa käytettiin SEMiä. Pyörivää elektrodia käytettiin reaktiota kontrolloivaa mekanismia määritettäessä.

Mittausten perusteella saatiin selville, että kalkopyriitin pinnalle syntyy liuotuksessa nopeasti passivoiva rikkipitoinen reaktiotuotekerros, kun pH < 2. Korkeammissa pH:ssa (pH >-2.25) syntyy hitaammin toisenlainen reaktiotuotekerros, joka sisältää pääasiassa götiittiä ja rautahydroksia. Kuparipitoisuudelle määritettiin kriittiseksi pitoisuudeksi 9 g/l. Mittauksissa havaittiin, että kun [Cu2+] <- 9 g/l, kuparin määrä ei vaikuta kalkopyriitin liukenemisnopeuteen. Kun [Cu2+] > 9 g/l, liukenemisnopeus kasvaa kuparipitoisuuden kasvaessa, samoin kuin lämpötilan nousun myötä. Liukenemisprosessia kontrolloiva mekanismi on luultavasti diffuusio, kun [Cu2+] > 9 g/l ja diffuusio reaktiotuotekerroksen läpi, kun [Cu2+] = 9 g/l. Diffuusiokertoimen laskettiin olevan 4.4 x 10-6 cm2/s, kun [Cu2+] > 9 g/l. Alhaisemmilla kuparipitoisuuksilla liukenemista säätelee kemiallinen tai sekä-kontrolli.
ED:2004-03-18
INSSI record number: 25073
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