Application of High-Speed Silver Electrorefining

Arif Tirto Aji

Application of High-Speed Silver Electrorefining

Julkaisun otsikon käännös: Korkean tuotantonopeuden soveltaminen hopean puhdistuselektrolyysissä

Arif Tirto Aji

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Tässä väitöskirjassa tutkittiin hopean elektrolyysiprosessia korkealla virrantiheydellä operoituna hyödyntäen prosessin empiiristä mallintamista. Mallinnuksen ensimmäinen osa koostui anodin pinnalla tapahtuvista ilmiöistä, kuten hopean liukenemisesta, kullasta johtuvasta passivaatiosta, ja kuparin liukenemisesta. Mallinnuksen toinen osa käsitteli prosessioptimointia mallintamalla elektrolyytin ominaisuuksia, kuten johtavuutta, tiheyttä, viskositeettiä ja elektrolyytin kierrätysjärjestelmää. Kaikki mallinnus perustui laboratoriomittakaavan kokeellisiin tuloksiin synteettisissä elektrolyyteissä ja teollisuuden parametreillä operoituna. Hopean liukenemisen kineettinen mallinnus tässä tutkimuksessa viittaa siihen, että korkean virrantiheyden käyttö on teknisesti mahdollista. Kokeellisten tulosten perusteella hopea-anodin passivoitumisen pääasiallinen syy on anodin kultapitoisuus, koska kulta ei liukene elektrolyysissä käytettyyn laimeaan typpihappoliuokseen. Samalla anodin sisältämä kupari liukenee ja kertyy hopeaelektrolyyttiin. Vaikka liuennut kupari lisäsi elektrolyytin johtavuutta, aiheuttaa korkea kuparipitoisuus samalla myös hopeakatodin kontaminaatiota. Mallintamalla anodilta liukenevien metallien liukenemiskinetiikkaa pystyttiin löytämään sopivat kupari- ja kultapitoisuudet optimaaliselle operoinnille korkealla virrantiheydellä. Elektrolyytillä on kaksi pääroolia elektrolyysiprosessissa; se mahdollistaa varauksen siirron ja toimii hopeaionien kuljettajana. Vastaavasti elektrolyytin koostumuksen optimointi mahdollistaa energiankulutuksen minimoinnin sekä varmistaa katodituotteen korkean puhtauden. Tässä väitöskirjatyössä määritettiin optimaaliset elektrolyyttiolosuhteet ja elektrolyytin kiertojärjestelmä korkean virrantiheyden operaatiolle hopeaelektrolyysissä. Optimaaliset anodi- ja elektrolyyttiolosuhteet olivat korkeimmillaan 6-8% Au anodissa ja 100-150 g/dm3 [Ag+], 50-75 g/dm3 [Cu2+], 5-7 g/dm3 [HNO3] elektrolyytissä.

Julkaisun otsikon käännös	Korkean tuotantonopeuden soveltaminen hopean puhdistuselektrolyysissä
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Ohjaaja	Lundström, Mari, Vastuuprofessori Aromaa, Jari, Ohjaaja
Kustantaja	Aalto University
Painoksen ISBN	978-952-64-0376-2
Sähköinen ISBN	978-952-64-0377-9
Tila	Julkaistu - 2021
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

hopean elektrolyyttinen puhdistus
korkea virrantiheys
kokeellinen mallinnus

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-64-0377-9

Raaka-aineiden tutkimusinfrastruktuuri
Karppinen, M. (Manager)
Kemian tekniikan korkeakoulu
Laitteistot/tilat: Facility

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@phdthesis{b509edb1f9a54726a3604f3756c36ae3,

title = "Application of High-Speed Silver Electrorefining",

abstract = "The main focus of the current study was on the investigation of high current density (HCD) operation of silver electrorefining through empirical modelling of the process. The first part of modelling consists of the phenomena on the anode surface i.e. silver dissolution, passivation due to gold, and copper dissolution. Second part of modelling was optimization of the process by modelling of the electrolyte properties i.e. conductivity, density, viscosity and electrolyte circulation system. All of the modelling was conducted based on the experimental results of laboratory-scale measurements in synthetic electrolyte, under conditions similar to industrial operation. Kinetic modelling of silver dissolution in the current study suggests that the application of HCD is technically feasible. Based on the experimental results, the main cause for silver anode passivation is the gold content in the anode, since gold did not dissolve in the dilute nitric acid solution used in electrolysis. Meanwhile, copper present in the anode dissolved during the process and accumulated in the silver electrolyte. Though copper increased the conductivity of the electrolyte, the high copper content also resulted in copper contamination of the silver cathode. By modelling the kinetics of the dissolution of anode metals, limitations for copper and gold content could be established for optimum HCD operation. Electrolyte has two main roles in the electrorefining process; it is the medium for current transfer as well as the inventory and supplier of silver ions. Accordingly, optimization of the electrolyte composition allows the minimization of energy consumption while maintaining the purity of the deposit. In the current work, the optimal electrolyte conditions and circulation system were established as a function of a HCD operation. The optimal anode and electrolyte conditions in HCD silver electrorefining were found to be at max. Au of 6-8\% in the anode and 100-150 g/dm3 [Ag+], 50-75 g/dm3 [Cu2+], 5-7 g/dm3 [HNO3] in the electrolyte.",

keywords = "silver electrorefining, high current density, empirical modelling, hopean elektrolyyttinen puhdistus, korkea virrantiheys, kokeellinen mallinnus, silver electrorefining, high current density, empirical modelling",

author = "Aji, \{Arif Tirto\}",

year = "2021",

language = "English",

isbn = "978-952-64-0376-2",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "66",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Application of High-Speed Silver Electrorefining

AU - Aji, Arif Tirto

PY - 2021

Y1 - 2021

N2 - The main focus of the current study was on the investigation of high current density (HCD) operation of silver electrorefining through empirical modelling of the process. The first part of modelling consists of the phenomena on the anode surface i.e. silver dissolution, passivation due to gold, and copper dissolution. Second part of modelling was optimization of the process by modelling of the electrolyte properties i.e. conductivity, density, viscosity and electrolyte circulation system. All of the modelling was conducted based on the experimental results of laboratory-scale measurements in synthetic electrolyte, under conditions similar to industrial operation. Kinetic modelling of silver dissolution in the current study suggests that the application of HCD is technically feasible. Based on the experimental results, the main cause for silver anode passivation is the gold content in the anode, since gold did not dissolve in the dilute nitric acid solution used in electrolysis. Meanwhile, copper present in the anode dissolved during the process and accumulated in the silver electrolyte. Though copper increased the conductivity of the electrolyte, the high copper content also resulted in copper contamination of the silver cathode. By modelling the kinetics of the dissolution of anode metals, limitations for copper and gold content could be established for optimum HCD operation. Electrolyte has two main roles in the electrorefining process; it is the medium for current transfer as well as the inventory and supplier of silver ions. Accordingly, optimization of the electrolyte composition allows the minimization of energy consumption while maintaining the purity of the deposit. In the current work, the optimal electrolyte conditions and circulation system were established as a function of a HCD operation. The optimal anode and electrolyte conditions in HCD silver electrorefining were found to be at max. Au of 6-8% in the anode and 100-150 g/dm3 [Ag+], 50-75 g/dm3 [Cu2+], 5-7 g/dm3 [HNO3] in the electrolyte.

AB - The main focus of the current study was on the investigation of high current density (HCD) operation of silver electrorefining through empirical modelling of the process. The first part of modelling consists of the phenomena on the anode surface i.e. silver dissolution, passivation due to gold, and copper dissolution. Second part of modelling was optimization of the process by modelling of the electrolyte properties i.e. conductivity, density, viscosity and electrolyte circulation system. All of the modelling was conducted based on the experimental results of laboratory-scale measurements in synthetic electrolyte, under conditions similar to industrial operation. Kinetic modelling of silver dissolution in the current study suggests that the application of HCD is technically feasible. Based on the experimental results, the main cause for silver anode passivation is the gold content in the anode, since gold did not dissolve in the dilute nitric acid solution used in electrolysis. Meanwhile, copper present in the anode dissolved during the process and accumulated in the silver electrolyte. Though copper increased the conductivity of the electrolyte, the high copper content also resulted in copper contamination of the silver cathode. By modelling the kinetics of the dissolution of anode metals, limitations for copper and gold content could be established for optimum HCD operation. Electrolyte has two main roles in the electrorefining process; it is the medium for current transfer as well as the inventory and supplier of silver ions. Accordingly, optimization of the electrolyte composition allows the minimization of energy consumption while maintaining the purity of the deposit. In the current work, the optimal electrolyte conditions and circulation system were established as a function of a HCD operation. The optimal anode and electrolyte conditions in HCD silver electrorefining were found to be at max. Au of 6-8% in the anode and 100-150 g/dm3 [Ag+], 50-75 g/dm3 [Cu2+], 5-7 g/dm3 [HNO3] in the electrolyte.

KW - silver electrorefining

KW - high current density

KW - empirical modelling

KW - hopean elektrolyyttinen puhdistus

KW - korkea virrantiheys

KW - kokeellinen mallinnus

KW - silver electrorefining

KW - high current density

KW - empirical modelling

M3 - Doctoral Thesis

SN - 978-952-64-0376-2

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Application of High-Speed Silver Electrorefining

Abstrakti

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