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Author:Bonsdorff, Robert von
Title:Dissolution of gold in cupric chloride solution
Guldets löslighet i kopparkloridlösning
Publication type:Master's thesis
Publication year:2004
Pages:69+6      Language:   eng
Department/School:Materiaali- ja kalliotekniikan osasto
Main subject:Korroosionestotekniikka   (Mak-85)
Supervisor:Aromaa, Jari
Instructor:Barker, Michael
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark TKK  114   | Archive
Keywords:gold
dissolution of gold
cupric chloride
sodium chloride
HydroCopper
guld
guldets löslighet
kopparklorid
natriumklorid
Abstract (eng):HydroCopper™ is the name of a hydrometallurgical chloride-based copper production process. This new method is a more environmentally safe way of producing copper. Leaching includes a three-stage counter current atmospheric leaching of copper concentrate followed by solution purification and precipitation of cuprous oxide. The aim of this work is to find the optimum circumstances in the solution purification stage of the HydroCopper™ process to get as much gold leached as possible. The examination was made with electrochemical methods.

Gold has a very limited reactivity and high nobility and in order to substantially, dissolve the gold, the gold-ions have to be bound as a complex. Gold forms compounds in two oxidations states +1 and +3. In the presence of a strong oxidant and chloride ions gold can be dissolved as chloroaurate.

In the experiments the behavior of the gold was measured in a [NaCI] = 10-300 g/l, [Cu2] = 0.372 -40 g/l, T = 80 - 90 °C, pH 1-3. In the measurements, a gold wire was used with the dimensions 2.53 cm long and 1.5 mm in diameter. The other electrode was fabricated by Outokumpu Oyj and was a 10 mm long section of gold rod sealed into a plastic PTFE rod.

The dissolution of gold increases with increasing CuCI2 concentration, increasing chloride concentration, increasing temperature and with adequately acidic (pH<3) so that cupric ion precipitation as CU2{OH)3CI does not occur. Gold dissolves as [AuC12] complex when the potential is 0.8 V vs. SCE or lower and as [AuC14] at higher potentials.
Abstract (swe):HydroCopper™ är namnet på en hydrometallurgisk kloridbaserad kopparframställningsprocess. Den nya metoden är att mera miljövänligt sätt att producera koppar. Avlakningen består av en tre stegs avlakning av kopparkoncentrat följd av rening av lösningen samt avfallning av kopparoxid. Målet med detta arbete är att finna de mest gynsamma omständigheterna i lösningens reningsprocess, så att guldets löslighet kan optimeras. Undersökningarna gjordes med elektrokemiska metoder.

Guld har en väldigt begränsad reaktivitet och är en mycket ädel metall. För att guld skall lösa sig avsevärt måste guldionerna bindas till ett komplex. Guld bildar två föreningar med oxidationstalen +1 och +3. I samband med en stark oxidant och kloridioner kan guld lösas som kloroaurat.

I experimenten undersöktes guldets beteende i en lösning där det fanns [NaCI] = 10 300 g/l, [Cu2+] = 0.372 - 40 g/l, T = 80 - 90°C och pH 1-3. I mätningarna användes en guldelektrod med längden 2.53 cm och diametern 1.5 mm. Den andra elektroden, en 10 mm lång stav av guld gjuten i en PTFE stav, framställdes av Outokumpu Oyj.

Guldets löslighet ökar genom höjning av CUCl2 koncentration, ökning av kloridkoncentration, ökning av temperatur och i pH under 3 så att bildning av CU2(OH)3CI inte förekommer. Guld löser sig som [AuC12] komplex när potentialen är 0.8 V vs. SCE eller lägre och som [AuC14] i högre potentialer.
ED:2004-03-10
INSSI record number: 21311
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