Andrew Abbott Chemistry Department University of Leicester

Processing Metal Oxides Using Processing Metal Oxides Using Ionic LiquidsIonic Liquids

SUMEEPnet19th March 2008Henry Ford College Loughborough

ContentsContents

IntroductionIonic liquids & deep eutectic solventsSolubility of metal oxidesElectrochemistryApplication to EAF dustOther applicationsConclusions

Ph N+(CH3

)3

Cations

BF4-

PF6

-

Al2

Cl7-

(CF3

SO2

)2

N-

Anions

N N+

N+

BMIM PF6

Principle is to use large,non-symmetrical ions –Lower lattice energy

Ionic LiquidsIonic Liquids

Ionic Liquids Ionic Liquids ––

Proposed usesProposed uses

SynthesisDesulfurisation of fuelUranium processingBatteriesMetal Plating

Look at the cost of the solvent and the value of the productMost will never work!

Niche Low-Spec

applications have

been commercialisedGas storagePaint bindersPhase transfer catalyst

Non-toxic (vitamin B4)Produced on Mt scale (chicken feed additive) hence costs about £1/kgBiodegradable

HON+

CH3

CH3

CH3

Cl-

Why Choline Chloride?Why Choline Chloride?

m.p. 301 oC

Company StrengthsCompany Strengths

Three patents cover over a million

ionic liquids

Choline like cations with various complexing agents

R1

R2

R3

R4

N+

X. z Y

Patent 1 Y = MClx, M = Zn, Sn, Fe

Patent 2 Y = MClx.yH2O

Patent 3 Y = RZ, Z = CONH2, COOH, OH

cation

anion

complexingagent

Just mix two solids to make a liquid!

Endothermic reaction

So entropy drives the reactionSalt and ice

ΔTf

=

200oC

Ionic Liquid SynthesisIonic Liquid Synthesis

UNIVERSITY of LEICESTER• Electrochemistry• Synthesis• Inorganic Chem.• Analytical Chem.

WHYTE GROUP Ltd• Bulk Chemistry• Logistics• Distribution• Accounting

GENACYS Ltd• Intellectual Property• Licensing• Start-up Expertise• Finance

+ + =

What is What is ScionixScionix??

10 ILs have been produced in over 200 kg batches One IL made on the tonne scale

Many HBDs are INEXPENSIVE (c.a. £1/kg), Non-toxic, Non-flammable, Biodegradable, Versatile (>105 liquids), Unusual solvent properties.

HO2C-R1 Acids

H2N-C=O-R2 Amides

HO-R3 Alcohols

A. P Abbott et al. Chem. Comm., 2003, 70A. P Abbott et al. JACS 2004, 126, 9142

Choline chloride –

A vitamin in chicken feed

Urea –

A common fertiliser

Deep Eutectic SolventsDeep Eutectic Solvents

Physical properties change markedly

20 40 60 80 100

0

2

4

6

8

10

12

14

Conductivity Viscosity

T / oC

Con

duct

ivity

/ m

S c

m-1

0

200

400

600

800

1000

1200

Viscosity / cP

with composition

With temperature

0 20 40 60 80 100

0

50

100

150

200

250

300

350

T f / o C

mol % Urea

Urea: Choline ChlorideUrea: Choline Chloride

Solvent properties can be markedly changed by altering the HBD

Freezing points of mixtures of hydrogen bond donors with choline chloride in a 2:1 ratio.

Deep Eutectic SolventsDeep Eutectic Solvents

Hydrogen bond donor Fr Pt. /oCAmidesUrea, NH2CONH2 12Acetamide, CH3CONH2 51Thiourea, NH2CSNH2 69AcidsTrichloroacetic acid Cl3CCO2H -24Phenlyacetic acid C6H5CH2CO2H -5

Malonic acid, HO2CCH2CO2H 3Oxalic Acid, HO2CCO2H 13p -Toluene sulfonic acid CH3C6H4SO3H

27

Alcoholsm – Cresol, CH3C6H4OH < –35Phenol C6H5OH –30p – Cresol, CH3C6H4OH –10o – Cresol, CH3C6H4OH –8D (-) Fructose, C6H12O6 5

Wide range of solutes show high solubilities

In general those capable of forming H bonds show the highest solubilities.

Urea: Choline ChlorideUrea: Choline Chloride

Solute Solubility / mol/l

Lithium chloride >2.5Silver Chloride >0.66D-alanine >0.38benzoic acid >0.82Copper (I) oxide >0.11Calcium carbonate >0.21SDS >0.36

Wide range of solutes show high solubilities e.g. metal oxides

Urea: Choline ChlorideUrea: Choline Chloride

Dissolved oxides can be recovered electrochemically

Metal Oxide M.pt. / oC Solubility / ppmAl2

O3 2045 <1CaO 2580 6CuO 1326 470Cu2

O 1235 8725Fe2

O3 1565 49Fe3

O4 1538 40MnO2 535 493NiO 1990 325PbO2ZnO

888 91571975 8466

Solubility of metal oxides in a 2:1 urea: choline chloride eutectic at 60 oC.

Metal oxide solubilityMetal oxide solubility

High solubility demonstrated for a range of metal oxides

Metal oxide solubilityMetal oxide solubility

Characterise the solubility of a range of metal oxides in 4 ionic liquids

A. P. Abbott et al. J. Chem. Eng. Data 2006, 51, 1280-1282

Solubility / mol dm-3

CuO Fe3

O4 ZnO

1 Malonic

acid: 1ChCl 0.246 0.071 0.554

1 Oxalic acid: 1ChCl 0.071 0.341 0.491

2Phenylpropionic acid: 1ChCl

0.473 0.014 >0.491

TuneableTuneable

metal oxide solubilitymetal oxide solubility

Cyclic voltammograms of ZnO, PbO2

, CuO, NiO

and Ag2

O in a 2:1 urea: choline chloride mixture on a Pt microelectrode at 60 oC.

Metal ElectrochemistryMetal Electrochemistry

Soluble metals can be electrodeposited

Metal ElectrochemistryMetal Electrochemistry

Metals that tend to form linear or tetrahedral complexes show reversible metal deposition. Metals with octahedral geometry are irreversible.

Comparing the reduction potentials for metals with similar geometries gives similar differences compared with those in aqueous solutions. e.g. EPb

2+/Pb

– EZn2+

/Zn

= 0.65 V c.f.

0.63 V in waterEAg

+/Ag

– ECu+

/Cu

= 0.31 V c.f.

0.28 VBut the differences between metals of different geometries is significantly changede.g. EAg

+/Ag

– EZn2+

/Zn

= 1.00 V c.f.

1.56 V

EAF DustEAF Dust

EAF produces c.a. 15 - 20 kg of dust per tonne of steel. The dust is classed as a toxic waste because of the high heavy metal content. Several million tonnes of dust are produced per annum. Dust forms when volatile metals, e.g. Pb and Zn vaporise at the high operating T and are oxidized in the airflow through the furnace.

Metal Content in EAF dust /wt %

Solubility of metal oxide /ppm

Solubility from EAF dust /ppm

Al 12 Al2

O3

– < 1 <1

Cu 1 CuO

-

470

Cu2

O -

8725

5

Fe 38 Fe2

O3

- 89Fe3

O4

– 4016

Mn 4.5 MnO2

–

493 -

Pb 4 PbO2 –

9157 113

Si 4 SiO2

- < 1 <1

Zn 33 ZnO

–

8466 4288

EAF DustEAF Dust

Composition of EAF dust sample

SEM image of the metal electrowon

from the extraction of EAF dust in ChCl:2 urea eutectic at 60oC.

EDX analysis shows only Zn No trace of other metals found

EAF DustEAF Dust

EAF Dust Pilot PlantEAF Dust Pilot Plant

Dust contains 38% Fe, 33% Zn, 4% Pb

EAF Dust

Zn/Pb/Cd

Zn dust

PbZn

Electrolysis Cell

Leach Tank

Cementation tank

Technology easily transferable to a variety of waste dusts, ashes and sludges.

Cementation of LeadCementation of Lead

•

Addition of an excess of zinc dust causes dissolved lead to precipitate out of ionic liquid

•

Process requires < 2 hours

Time (mins) Zinc (ppm) Lead (ppm)

0 4039.99 276.22

40 4202.27 93.21

120 4590.23 7.54

New DevelopmentsNew Developments

New methodology developed for oxidation of metals from

native state.

Has been applied to mixtures of metals

Electrocatalytic oxidation of metals has been achieved

Quantitative separation of Cu from Zn has been

demonstrated.

oxred

AnodeCathode

M+

Other ApplicationsOther Applications

•

Electro-dissolution of metals•

Electroplating of metals

•

Electroless

deposition of metals

DESs can be used to process metals with oxide coatings –e.g. electropolishing stainless steel

Opposite to electroplating i.e. dissolves metal off

Decreases wear and improves corrosion resistance

Uses sulphuric and phosphoric acids

Low current efficiency (10 – 20%)

Before After

ElectropolishingElectropolishing

Better surface finish (market)

Non-corrosive (social)

Benign liquid – ChCl/glycol (social)

Improved current efficiency (80%) (economic)

Less gas evolution (environmental)

Metal recoverable (environmental)

ElectropolishingElectropolishing

Currently running on a 1300 L scale in Birmingham

RecyclingRecycling

Spent Ethaline from the electropolishing

processEqual volumes of water added (b) and then distilled off (c)

A. P. Abbott, et al Phys. Chem. Chem. Phys. 2006, 8, 4214-4221.

Metal DepositionMetal Deposition

•

Brighteners have been developed for a variety of metals including Al

A. P. Abbott, Phys.Chem.Chem.Phys.

2006, 8, 4265

NiNi+Cr

ZnSn

Alloys

EU funded project 13M Euro33 partnerswww.ionmet.eu

ElectrolessElectroless

SilverSilver

Protective functional surfaces for electroniccomponentsSolderable finishes for PCB manufacturers(PW Circuits)Existing acid based aqueous process degradescircuit tracks

Deposit MorphologyDeposit Morphology

Photograph of silver metal coatings on polished Cu substrates deposited at r.t. for 15 min. from (a) 7 mM aqueous AgNO3 and (b) 10 mM AgCl in Ethaline.

Porous deposit obtained which allows this layers to be grown c.f. aqueous solutions

SolderabilitySolderability

•

Promising results obtained

Horizontal Reduced Brown Oxide Line which will be the same as Horizontal Reduced Brown Oxide Line which will be the same as Ionic Ionic Silver LineSilver Line

Line consists of :Line consists of :--

inlet conveyor, flood cleaner, 3 stage rinse, flood preinlet conveyor, flood cleaner, 3 stage rinse, flood pre--

dip, flood dip, 3 stage rinse, dry, outlet conveyordip, flood dip, 3 stage rinse, dry, outlet conveyor

Line Length 4.2 metres X 1.5 metres wide.Line Length 4.2 metres X 1.5 metres wide.

PW Circuits LtdIonic Silver

Ionic liquids based on choline chloride are useful for large-scale applicationsA variety of processes are being developedProperties strongly dependent on composition

ConclusionsConclusions

More InformationMore Information

•

Electrodeposition from Ionic Liquids•

Endres, MacFarlane and Abbott (Editors)

•

Wiley-VCH•

ISBN: 978-3-527-31565-9

•

440 pages

•

www.ionmet.eu•

www.scionix.co.uk