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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