General Flashcards
What are the types of extractive metallurgy?
Physical Metallurgy: This includes heat treatments, alloying, forging, casting, and improving material properties.
Chemical Metallurgy: Hydromet and pyromet
Hydrometallurgy
The extraction of metal from an ore by preparing an aqueous solution to dissolve and then precipitate a metal of interest. It usually involves the beneficiation of the solution which contains the metal before precipitation.
Generally, precipitation occurs by chemical (adsorbents) or electrolytic means (electro-plating/winning/refining)
Leaching formula
(M+)O + H2SO4 = (M+)SO4 + H2O
Key features: On the left the metal oxide is a solid on the right it is aqueous. It is a metal OXIDE, not a sulfide.
Sulfuric acid is the most common leaching agent, it is a strong acid which makes it amenable for this application.
Leaching formula using ammonia or cyanide
Ni + 6NH3 + H2O + O = Ni(NH3)62+ + 2OH-
Au + 4NaCN + O2 +2H2O = 2Na[Au(CN)2] + 2 NaOH + H2O2
Cyanide is a salt which is why it is able to leach gold and ammonia forms interesting compounds which enables it to be useful in this context.
What are the common copper oxides and sulfides?
Sulfides: Chalcocite (Cu2S), Covellite (CuS), Bornite (Cu5FeS4), Chalcopyrite (CuFeS2)
Oxides: Cuprite (Cu2O), malachite CuCO2*Cu(OH)2, azurite 2CuCO2*Cu(OH)2, chrysocolla CuO*SiO2*H2O
Extractive metallurgy of copper sulfides
Mining, crushing, grinding, froth flotation, smelting (matte and blister copper), electrorefining
Extractive metallurgy of oxides
Mining, crushing, heap leaching, solvent extraction, electrowinning
Matte and blister copper
Matte copper is 50-70% Cu and comes from smelting which is not direct-to-smelting which produces blister copper anodes of 99% Cu.
Electrorefining
This is the process used for sulfides where the blister Cu (99%) is the anode and then is dissolved and precipitated as the 99.99% pure cathode
Mass balance formula
Weightf*Gradef = WeightT*GradeT + WeightC*GradeC
General properties of water as a function of temperature
Diaeletric constant: Decreases with increasing temperature
Refractive index: decreases very slightly
Surfact tension: Decreases
Density: Max @ 4 oC
Viscosity: Decreases
Density of an aqueous suspension of solids
ρm = Wm /(VS + VL)
ρm = 100/ [(W%/ρS)+(100-W%/ρL )
Where: ρm = density of the suspension
W = weight
W% = % of suspension is solid
V= Volume
Hardness
A measure of the resistence to localized plastic deformation induced by mechanical indentation or abrasion measured through scrath hardness, indetation hardness, and rebound test.
Generally characterized by strong intermolecular bonds but dependent upon many things
Hydrophilic-liphilic balance
This is the measure of the degree to which a surfactent is hydro or lipo philic
Griffin’s method: HLB = 20 * Mh /M
Mh= molecular mass of the hydrophillic portion of the molecule
M=molecular mass of whole molecule
Davies method: HLB = 7+ ΣHi -n*,475
Hi = table value for the group of hydrophillic molecule
n = # of lipophillic molecules
Davies method for HLB vs. Griffin’s
Davies method is out of 100 and values different hydophobicities differently. Griffin’s method is more universal and values materials out of 20 with 20 being highest hydrophilic properties.
Acid baking
This is a process where acid is mixed with ore and heated to over 100oC
Agglomeration
The process of immobilizing fine material into clusters using water and binders like cement
Anode and Cathode
OIL RIG and AN OX and RED CAT
Anodes oxidize (lose electrons). They are positively charged (lack electrons)
Cathodes reduce (gain electrons) metal precipitates when it gains electrons. These are negatively charged and donate electrons to the metal.
anolyte and catholyte
These are the solutions that surround a cathode or anode, respectively, a membrane usually seperates the two solutions.
Breakthrough capacity
The capacity of an absorbent to absorb a given species in a vessel or collumn without allowing leakage of the entity above a threshold level in the effluent.
Chelating agent
A chemical capable of multiple attachments to a central metal atom in a complexed form. An example is ethylenediamine (MeNH2) forms two negative “arms” that both bond with one of the positive charges on a copper ion.
Crud
A mixture of organic, aqueous, and solid matter that can become a problem during solvent extraction process
Diluent
A compound used for dilution. To describe an organic solvent used as a carrier for a solvent extractent
effluent
solution leaving a given process
Eh
The electrochemical potential or oxidation reduction potential of a solution relative to the standard H half-cell.
Electrolyte
A medium containing dissolved ions through which charge can be transported. Most often used in association with solution used for electrochemical purposes.
Elutriation
Process of seperating solids by means of a liquid or the washing of solids. Elution is the process of extraction that is most often associated with stripping of ion exchange resin. Eluant is the solution exiting the elution process
Emulsion
A dispersion of tiny immiscible droplets of one liquid in another liquid
Extractant
An ion or compound capable of dissolving otherwise insoluble matter through chemical interaction or association
extraction coefficient
The ratio of metal in the extractant phase relative to that in the aqueous phase in solvent extraction or ion exchange processes
inversion
Transition from one continuous phase to another in processes involving two immiscible liquids such as solvent extraction
ligand
Species such as chloride that complexes with a desired species such as a metal ion
Lixivant
An ion or compound capable of dissolving otherwise insoluble matter through chemical interaction or association
Modifier
A chemical additive used to modify the action of another species. Most often associated with additives used to enhance solvent extraction effectiveness.
ORP
Oxidation-reduction-potential which is the same as Eh when converted to true values and not the product of hydrogen half cell values
Oxident
An ion or compound capable of increasing the oxidation state of another entitty by means of an electrochemical reaction
pH, pK, pKa, pH50
pH = log([H+])
pK = log(K) where K is the equilibrium constant
pKa = log(Ka) where Ka is the equilibrium constant for acidification equilibria and represent the equilibria K
pH50 is the pH at which an ion is equally between aqueous and organic phases during solvent extraction or the pH at which the extraction coefficient is 1
Raffinate
Solution from which a valuable entity has been removed
Refractory
The ore’s resistence to traditional leaching in gold often associated with dispersed, sub-micron gold in sulfides. Combatted through oxidation of sulfides.
Scrubbing
The process of selectively removing contamination from a chemical process (solvent extraction)
