Spectral induced polarization investigations in presence of metal sulphide minerals: implications for monitoring the generation of acid mine drainage

Edmundo Roguer Placencia-Gómez

Spectral induced polarization investigations in presence of metal sulphide minerals: implications for monitoring the generation of acid mine drainage

Julkaisun otsikon käännös: Indusoidun polarisaation spektritutkimukset metallisten sulfidimineraalien läsnäollessa: mahdollinen sovellus happamien kaivosvesien muodostumisen seurantaan

Edmundo Roguer Placencia-Gómez

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Metallipitoisten partikkelien, erityisesti sulfidimineraalien hapettuminen konsolidoitumattomissa maa-aineksissa tuottaa veteen liuonneita haitallisia ioneja, jotka voivat johtaa pohja- ja pintavesien pilaantumiseen. Kaivosjätteissä, kuten rikastushiekkassa, muodostuu happamia suotovesiä, mikä on keskeinen ongelma kaivostoiminnan ympäristövaikutusten kannalta. Siksi kaivosjätteiden stabiilisuuden arviointiin sekä happamien kaivosvesiin liittyvien pilaantumisriskien seurantaan tarvitaan yleisesti uusia menetelmiä. Tässä työssä osoitetaan, että tasavirtavastusmittauksella voidaan kuvata ja mallintaa Haverin Au-Cu-kaivoksen rikastushiekka-alueen rakenne. Yhdistämällä maavastusmittauksen tulokset rikastushiekkanäytteiden geokemiallisiin ja mineralogisiin tutkimuksiin voidaan karakterisoida alueet, joissa happamia suotovesiä voi muodostua, ja rajata alueet, joissa rikastushiekan huokosvesi on pilaantunutta. Happamia suotovesiä syntyy mineraalin ja elektrolyytin rajapinnoilla hapetus-pelkistysreaktiossa, joiden mekanismeja tutkittiin indusoidun polarisaation spektrimittauksilla (engl. spectral induced polarisation, SIP). Huokosveteen liuenneen hapen ja huokosilman vaikutuksesta hapettuvien sulfidimineraalien (rikkikiisu, magneettikiisu) SIP-vastetta tutkittiin synteettisessä kvartsihiekkaseoksessa. Liuenneen ferriraudan (Fe3+) vaikutuksesta tapahtuvaa hapettumista tutkittiin pyriitti-hiekka-seosten ohella myös käyttäen todellisia rikastushiekkanäytteitä. Tutkimuksissa selvitettiin myös hapetuspelkistysreaktioihin osallistumattomien ionien ja pH:n vaikutusta SIP-vasteeseen. SIP-menetelmä osoittautui olevan erityisen herkkä arvioitaessa sulfidien hapettumista, jossa metallipitoisten mineraalirakeiden pinnan kapasitiivisuusominaisuudet kuten varautuvuus laskevat. SIP-menetelmään perustuvaa hapetusolosuhteiden diagnostiikkaa tukee myös Wongin esittämä elektrokemiallinen malli, jossa indusoitu polarisaatio esitetään mineraalin ja elektrolyytin rajapinnalla tapahtuvien hapetus-pelkistysreaktioiden ja niiden yhteydessä tapahtuvien faradisten varaussiirtymien avulla. Vastaavalla tavalla SIP-metodilla voidaan havainnoida in-situ veden kyllästämien rikastushiekkojen hapettumiseen liittyviä tekstuurin muutoksia. Sulfidimineraalipitoisessa rikastushiekan kaltaisessa huokoisessa väliaineessa vallitsevat fysikaalis-kemialliset olosuhteet muuttuvat happamien suotovesien kehittyessä emäksisistä (pelkistävistä) happamiin (hapettaviin). Muutos on nähtävissä indusoidun polarisaation spektrissä selvänä maksimirelaksaation siirtymisenä kohti korkeampia taajuuksia, mikä merkittävästi vaikuttaa relaksaation aikaan.

Julkaisun otsikon käännös	Indusoidun polarisaation spektritutkimukset metallisten sulfidimineraalien läsnäollessa: mahdollinen sovellus happamien kaivosvesien muodostumisen seurantaan
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Leveinen, Jussi, Vastuuprofessori Slater, Lee, Ohjaaja, Ulkoinen henkilö
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-6303-4
Sähköinen ISBN	978-952-60-6304-1
Tila	Julkaistu - 2015
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

metallisulfidit
kaivosten happamat suotovedet
polarisoituvuus
varautuvuus
imaginaarijohtavuus
spektri-IP
rikastushiekka
hapetus-pelkistys

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-60-6304-1Lisenssi: Määrittelemätön

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@phdthesis{4331ec904b85459d81e749f392d844a9,

title = "Spectral induced polarization investigations in presence of metal sulphide minerals: implications for monitoring the generation of acid mine drainage",

abstract = "The oxidation of metallic particles, e.g., sulphide minerals, present in unconsolidated soils is a source of harmful dissolved ions which poses a contamination risk to groundwater and surface water. When associated with mine waste deposits such as tailings impoundments, the contaminated water discharges are known as acid mine drainage (AMD); this is a major environmental concern in the mining industry. Therefore, methodologies which can help to improve the long-term stability assessment of mine waste deposits and monitoring of contamination risk by AMD are needed. This thesis shows that the dc-resistivity method was suitable for imaging the subsurface structure of the Haveri Au-Cu mine tailings (SW Finland). When coupled with geochemical and mineralogical studies of tailings samples it was possible to characterize a potential reactive zone of AMD generation, as well as to delimit the associated contaminated water (i.e., the AMD discharge) inside the tailings material. The oxidation-reduction reactions at the metal sulphide mineral-electrolyte interface, i.e., the mechanisms which generate the AMD discharges, were investigated by means of the spectral induced polarization (SIP) method at the laboratory scale. The SIP response to oxidation of sulphide minerals (pyrite and pyrrhotite) promoted by dissolved and atmospheric O2 was analysed for synthetic mixtures of silica sand, whereas the SIP response to oxidation promoted by dissolved Fe3+ was analysed on a pyrite-sand mixture and real tailings material, respectively. The effect of redox-passive ions (non-oxidizing agents) and pore water pHw on the SIP response was also investigated. The SIP method shows unique sensitivity in detecting oxidation of sulphide minerals linked to a reduction in the capacitive properties at the metallic mineral surface-electrolyte interface, which diminishes the polarization magnitude given in terms of the imaginary conductivity and total chargeability. This SIP oxidation diagnostic is supported by the electrochemical model of Wong, which defines the IP-phenomenon on the basis of the activation of charge-transfer oxidation-reduction reactions or faradaic process at the metal mineral-electrolyte interface. Similarly, the SIP method is able to distinguish the in-situ oxidation-driven textural features of tailings (i.e., the oxidation degree of sulphide minerals) under saturated conditions. Additionally, the evolving physicochemical conditions from basic (reductive) to acid (oxidant) in the porous medium containing metal sulphide minerals, as expected during the development of AMD discharges, is well defined by the shift of the maximum relaxation of the SIP response towards higher frequencies, significantly impacting the relaxation time.",

keywords = "metallic sulphides, acid mine drainage, polarizability, chargeability, imaginary conductivity, spectral induced polarization, tailings, oxidation-reduction, metallisulfidit, kaivosten happamat suotovedet, polarisoituvuus, varautuvuus, imaginaarijohtavuus, spektri-IP, rikastushiekka, hapetus-pelkistys, metallic sulphides, acid mine drainage, polarizability, chargeability, imaginary conductivity, spectral induced polarization, tailings, oxidation-reduction",

author = "Placencia-G{\'o}mez, {Edmundo Roguer}",

year = "2015",

language = "English",

isbn = "978-952-60-6303-4",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "102",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Spectral induced polarization investigations in presence of metal sulphide minerals: implications for monitoring the generation of acid mine drainage

AU - Placencia-Gómez, Edmundo Roguer

PY - 2015

Y1 - 2015

N2 - The oxidation of metallic particles, e.g., sulphide minerals, present in unconsolidated soils is a source of harmful dissolved ions which poses a contamination risk to groundwater and surface water. When associated with mine waste deposits such as tailings impoundments, the contaminated water discharges are known as acid mine drainage (AMD); this is a major environmental concern in the mining industry. Therefore, methodologies which can help to improve the long-term stability assessment of mine waste deposits and monitoring of contamination risk by AMD are needed. This thesis shows that the dc-resistivity method was suitable for imaging the subsurface structure of the Haveri Au-Cu mine tailings (SW Finland). When coupled with geochemical and mineralogical studies of tailings samples it was possible to characterize a potential reactive zone of AMD generation, as well as to delimit the associated contaminated water (i.e., the AMD discharge) inside the tailings material. The oxidation-reduction reactions at the metal sulphide mineral-electrolyte interface, i.e., the mechanisms which generate the AMD discharges, were investigated by means of the spectral induced polarization (SIP) method at the laboratory scale. The SIP response to oxidation of sulphide minerals (pyrite and pyrrhotite) promoted by dissolved and atmospheric O2 was analysed for synthetic mixtures of silica sand, whereas the SIP response to oxidation promoted by dissolved Fe3+ was analysed on a pyrite-sand mixture and real tailings material, respectively. The effect of redox-passive ions (non-oxidizing agents) and pore water pHw on the SIP response was also investigated. The SIP method shows unique sensitivity in detecting oxidation of sulphide minerals linked to a reduction in the capacitive properties at the metallic mineral surface-electrolyte interface, which diminishes the polarization magnitude given in terms of the imaginary conductivity and total chargeability. This SIP oxidation diagnostic is supported by the electrochemical model of Wong, which defines the IP-phenomenon on the basis of the activation of charge-transfer oxidation-reduction reactions or faradaic process at the metal mineral-electrolyte interface. Similarly, the SIP method is able to distinguish the in-situ oxidation-driven textural features of tailings (i.e., the oxidation degree of sulphide minerals) under saturated conditions. Additionally, the evolving physicochemical conditions from basic (reductive) to acid (oxidant) in the porous medium containing metal sulphide minerals, as expected during the development of AMD discharges, is well defined by the shift of the maximum relaxation of the SIP response towards higher frequencies, significantly impacting the relaxation time.

AB - The oxidation of metallic particles, e.g., sulphide minerals, present in unconsolidated soils is a source of harmful dissolved ions which poses a contamination risk to groundwater and surface water. When associated with mine waste deposits such as tailings impoundments, the contaminated water discharges are known as acid mine drainage (AMD); this is a major environmental concern in the mining industry. Therefore, methodologies which can help to improve the long-term stability assessment of mine waste deposits and monitoring of contamination risk by AMD are needed. This thesis shows that the dc-resistivity method was suitable for imaging the subsurface structure of the Haveri Au-Cu mine tailings (SW Finland). When coupled with geochemical and mineralogical studies of tailings samples it was possible to characterize a potential reactive zone of AMD generation, as well as to delimit the associated contaminated water (i.e., the AMD discharge) inside the tailings material. The oxidation-reduction reactions at the metal sulphide mineral-electrolyte interface, i.e., the mechanisms which generate the AMD discharges, were investigated by means of the spectral induced polarization (SIP) method at the laboratory scale. The SIP response to oxidation of sulphide minerals (pyrite and pyrrhotite) promoted by dissolved and atmospheric O2 was analysed for synthetic mixtures of silica sand, whereas the SIP response to oxidation promoted by dissolved Fe3+ was analysed on a pyrite-sand mixture and real tailings material, respectively. The effect of redox-passive ions (non-oxidizing agents) and pore water pHw on the SIP response was also investigated. The SIP method shows unique sensitivity in detecting oxidation of sulphide minerals linked to a reduction in the capacitive properties at the metallic mineral surface-electrolyte interface, which diminishes the polarization magnitude given in terms of the imaginary conductivity and total chargeability. This SIP oxidation diagnostic is supported by the electrochemical model of Wong, which defines the IP-phenomenon on the basis of the activation of charge-transfer oxidation-reduction reactions or faradaic process at the metal mineral-electrolyte interface. Similarly, the SIP method is able to distinguish the in-situ oxidation-driven textural features of tailings (i.e., the oxidation degree of sulphide minerals) under saturated conditions. Additionally, the evolving physicochemical conditions from basic (reductive) to acid (oxidant) in the porous medium containing metal sulphide minerals, as expected during the development of AMD discharges, is well defined by the shift of the maximum relaxation of the SIP response towards higher frequencies, significantly impacting the relaxation time.

KW - metallic sulphides

KW - acid mine drainage

KW - polarizability

KW - chargeability

KW - imaginary conductivity

KW - spectral induced polarization

KW - tailings

KW - oxidation-reduction

KW - metallisulfidit

KW - kaivosten happamat suotovedet

KW - polarisoituvuus

KW - varautuvuus

KW - imaginaarijohtavuus

KW - spektri-IP

KW - rikastushiekka

KW - hapetus-pelkistys

KW - metallic sulphides

KW - acid mine drainage

KW - polarizability

KW - chargeability

KW - imaginary conductivity

KW - spectral induced polarization

KW - tailings

KW - oxidation-reduction

M3 - Doctoral Thesis

SN - 978-952-60-6303-4

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Spectral induced polarization investigations in presence of metal sulphide minerals: implications for monitoring the generation of acid mine drainage

Abstrakti

Tutkimusalat

Pääsy asiakirjaan

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