Keiko SASAKI Department Earth Resources Engineering

Kyushu University

12:15-12:40 Nov 24th 2021Brown Bag Seminar, QAOS

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Metallurgy integrated with biotechnology for gold recovery

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biohydrometallurgy

bio hydro metallurgy

バイオ ハイドロ メタラジー

バイオハイドロメタラジー

Environmental microbiologyBiogeochemistry

Chemical engineeringMetallurgy

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bio·hydro·metallurgy

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⽣物 湿式 冶⾦学

Micron scale miners

Microorganisms acquire energy through decomposition of minerals.

OresExtraction of

valuable metals

Cu

U

Zn

Ni

CoAu

Bioleaching（生物的浸出）

l Successful biotechnology business (annually 10 billion USD)

l 10％ of Cu production is from bioleaching

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Biooxidation（生物的酸化）

Why Biohydrometallurgy ?

● Low grade ore can be explored 従来廃石とされていた低品位鉱石の開発が可能

● Advantages in environment, energy, safety and cost 環境面・エネルギー面・安全面・コスト面での優位性

● Depletion of high grade ore 高品位鉱石の枯渇

Indispensable technology for SDGs

● Necessity to recover rare metals from urban mines 都市鉱山からのレアメタル回収技術開発の必要

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CuNiZn

CuNiPbZn

Major producing countries of “base metals”(Cu, Ni, Pb, Zn)

PbMetal resources are localized in the specific areas, in particular developing countries.

Total share of the top 3 countries

オーストラリア

Copper price fluctuations are a barometer of the economy 7

Copper (Cu) is highly conductive and versatile material used everywhere.

Around 100 kg Cu is spent per one family!

10 yen coinCu 95%Zn 3-4%Sn 1-2%

電解銅Electrolyte copper

Cu 99.99%

銅鉱石Copper oreCu 0.1-1%

Natural copper

銅精鉱Cu concentrate

Cu 20-40%

MiningOre body blast

DiggingOpen cut

Mineral processing

GrindingMineral processing（Flotation）

RefiningFlash smelter

ConverterPurified furnace

Electrolytic furnace

Process from Cu ores to Cu products 8

採鉱

鉱物処理(選鉱）

製錬

biohydrometallurgy

2 x 3 km wide, 810 m depth

www.min.tu-clausthal.de

World largest scale of open pit Cu mines

Chuquicamata copper mines, Chile9

Chuquicamata

Clark et al., Hydrometallurgy, 2006

10Copper Extraction Technologies

EU largest scale of bioheap leaching Tarvivaara mines, Finland

2.4 km wide, 800 m deep, 15 m tall. Grain side: P80 = 8 mmAir up-flow, lixivium down-flow

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Tarvivaara

Bioleaching (生物的浸出）

Success in bioleaching reduced the number of employees from 2000 to 500.

Ni ore (with grade 0.22%) 1550 Mt

12Reaction inside the heap

~70ºC 15 m

eter

http://www.talvivaara.com/

Black shale from Talvivaara mines

Chalcopyrite CuFeS2 à CuPentlandite (Fe,Ni)9S8 à NiPyrrhotite Fe1-xSà NiPyrite FeS2 à CoSphalerite ZnS à ZnMicas (biotite/phlogopite) Graphite

Selective recovery depending on the solubility product (Ksp).

Sasaki and Tokoro, J. MMIJ, 127 (2011) 724-728.

M2++ S2- = MSKsp = [M2+][S2-] at

25˚C

CuS 8.0 x 10-36

ZnS 3.0 x 10-22

NiS 2.0 x 10-21

CoS 8.0 x 10-23

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14

tons

15Gold price chart

Au

16World largest open pit Au mines

Kalgoorlie gold mines, Australia

3.5 km long, 1.5 km wide and over 600 m deep1.5 g/ton, around 15 million ton of rock per year

Biooxidation (⽣物的酸化） 17

Bioreacter typeBirthplace of biooxidation

South AfricaBarberton mine

BIOX® Plant (1986~)

(340 m3 62 tpd)

Biooxidation of sulfides prior to cyanidation of gold

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Osseo-Asare et al, 1984, Prec. Met.: Min. Extrac. Proc.

Adsorption of Au(CN)2- on carbonaceous matter

CYANIDATION

Ag

Ag

Au

Au

Gold recovery from DRGO is <50%.

https://www.uky.edu/KGS/coal/coal-diagram-download.php

How to recover Au(0)?

Au(CN)2-

What is double refractory gold ore (DRGO)? 18

sulfides

silicates

gold

carbonaceous matter

Challenging history in recovery of gold from DRGO

Conventional method causes recovery loss by adsorption of Au(CN)2-on residual carbon.

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1000ºC

500ºC

calcinationSOx, As2O3 + Fe oxides

BIOX

sulfur-oxidizing bacteria

Lignin-degrading enzymes

CN-

Au(CN)2-

Au(CN)2-

Au(CN)2-

air pollution

“Gold-robbing”30~70%

Conventional

Novel

activated carbon adsorption

White-rot fungus

O2

CN-

CN-

O2

CN-

O2

carbonaceous matter

Sulfides(Fe, As, S)

gold(Au(0))

Past

Arriagada and Osseo-Asare, 1984

Konadu and Sasaki, 2017

Elemental compositions of DRGO (example) 20

Elements (wt%)

Fe S As C Si Al Na Mg Others

10.19*1 8.56*1 1.60*1 5.86*2 19.32*3 7.59*3 0.38*3 0.078*3 -

11.09*4 8.42*4 1.14*4 0.51*4 8.55*4 1.8*4 0.17*4 0.13*4 16.86

ØFlotation concentrate from an anonymous mine

ØEthanol washing to remove flotation reagent P80 of 75 µm

ØAu content 40.39 g/t

*1 acid digestion, *2 CHN analysis, *3 XRF analysis

Background 351800 2.9202952802…Fe Sulphides 3081956 25.583347244…Arsenopyrite 389568 3.2338078218…Gold 31 0.0002573313…Other Sulphides

12302 0.1021190236…Jarosite17 0.0001411171…Dolomite

8613 0.0714965982…Calcite3372 0.0279910053…Siderite

33 0.0002739333…Amphibole11530 0.0957106440…Illite/Kaolinite

741470 6.1549498050…Carbonaceous Illite1941246 16.114302249…C-Si-Al

1941724 16.118270132…Muscovite

161196 1.3380895906…K-feldspar

575411 4.7764924032…Quartz

2385398 19.801212395…Fe-oxyhydroxide

606264 5.0326034615…Carbonaceous Fe Oxide

43307 0.3594918354…Rutile

127587 1.0591009491…

Apatite

13487 0.1119557204…

Other

2215 0.0183867369…

Mineral Name Area (Mine… Area %

Liberated pyriteAssociated with quartz

Associated with carbonaceous illite Others

-100

0/+5

3 µm

-53/

+10 µm

-10 µm

QEMSCAN* map for DRGO 21

Mineral wt%Fe sulphides 15.04Arsenopyrite 2.45

Dolomite 0.09Calcite 0.03

Amphibole 0.07Illite/Kaolinite 3.44

Carbonaceous illite 7.62C-Si-Al 1.61

Muscovite 0.54K-feldspar 2.74

Quartz 9.62Fe-oxyhydroxide 3.56

Carbonaceous Fe Oxide 0.48Rutile 1.08

Apatite 0.14Others 0.02

Total (-1000 µm/+10 µm) 48.6710 µm

50 µm

200 µm

*Quantitative Evaluation of Minerals by SCANning electron microscopy

Au

C

Decomposition of powder activated carbon (PAC) in spent medium for Phanerochaete chrysosporium

Konadu, et al., Hydrometallurgy 168 (2017) 76–83.

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Abu

ndan

ce/ a

rb. u

nit

200 150 100 50 0Chemical shift/ ppm

biotreated PAC

PAC

arom

atic

C-H

alip

hatic

C-H

arom

atic

C=C

PAC1480 m2/g48 mmol-Au/g-AC

10 um

13C-NMR

biotreated PAC911 m2/g16 mmol-Au/g-AC

10 um

Phanerochaetechrysosporium

White rot fungusto release oxidizing enzymes

(LiP, MnP etc) and H2O2

Sequential biotreatment should be performed to decompose in the order of sulfides and then graphitic carbon. Konadu, et al., Mineral. Engng., 138 (2019) 86-94.

iron-oxidizing archaeon

LiP, MnP

Gold recovery after sequential biotreatments of DRGO 23

pH 1.5@70ºC

pH 4.0@37ºC

Phanerochaetechrysosporium

Comminution

Cyanidation for gold recovery

pH adjustment & enzyme treatment

Fungal culturepH 4.0 and 37°CEnzyme

treatmentpH 4.0 and 37°C

Mill

DRGO

Cell Free Spent

Medium (CFSM)

P. chrysosporium

medium

Alkaline washing0.1~1 M NaOH, RT

NaOH and Ca(OH)2

CyanidationpH 11

KCN

Alkaline washing

Biooxidation of sulfides

BiooxidationpH 1.5 and 70°C

A. brierleyi

Proposed process to treat double refractory gold ore 24

Konadu, et al., Hydrometallurgy, 196 (2020) 105434.

References and acknowledgements 25

JSPS KAKENHI 18HP0703JSPS KAKENHI JP19KK0135

JSPS International Exchange Program JPJSBP120196505 JSPS International Exchange Program JPJSCCB20200003 JSPS International Exchange Program JPJSBP120219929

公益財団法⼈ 新井科学技術振興財団 ARAI SCIENCE AND TECHNOLOGY FOUNDATION

Interdisciplinary fusion with agriculture Academic-industrial collaboration

Collaborators:Hirofumi Ichinose

Kojo T. Konadu (Ghana)Diego M. Mendoza (Peru)

Ryotaro SakaiCindy (Indonesia)

Ikumi Suyama

External collaborators:Yuji Aoki (SMM)

Nana Murase (SMM)Jacques Eksteen (AUS)

Richmond Asamoah (AUS)Susan Harrison (SA)

Didi Manuka (SA)Takashi Kaneta (Okayama)

Grace Ofori-Sapong (Ghana)Clement Owusu (Ghana)

International collaboration with Ghana and US

International collaboration with South Africa

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JSPS KAKENHI 18HP0703

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40% ladies!

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JPJSCCB20200003FY2020-2022

超難処理⾦鉱⽯のバイオハイドロメタラジー研究拠点の形成

Advanced Research Network for Biohydrometallurgy of Double Refractory Gold Ore

Coordinator: Keiko Sasaki(Kyushu University)40% ladies!

International MOU through international collaboration 29