General

Question 1

What are the types of extractive metallurgy?

Answer 1

Physical Metallurgy: This includes heat treatments, alloying, forging, casting, and improving material properties.

Chemical Metallurgy: Hydromet and pyromet

Question 2

Hydrometallurgy

Answer 2

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)

Question 3

Leaching formula

Answer 3

(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.

Question 4

Leaching formula using ammonia or cyanide

Answer 4

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.

Question 5

What are the common copper oxides and sulfides?

Answer 5

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

Question 6

Extractive metallurgy of copper sulfides

Answer 6

Mining, crushing, grinding, froth flotation, smelting (matte and blister copper), electrorefining

Question 7

Extractive metallurgy of oxides

Answer 7

Mining, crushing, heap leaching, solvent extraction, electrowinning

Question 8

Matte and blister copper

Answer 8

Matte copper is 50-70% Cu and comes from smelting which is not direct-to-smelting which produces blister copper anodes of 99% Cu.

Question 9

Electrorefining

Answer 9

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

Question 10

Mass balance formula

Answer 10

Weight_f*Grade_f = Weight_T*Grade_T + Weight_C*Grade_C

Question 11

General properties of water as a function of temperature

Answer 11

Diaeletric constant: Decreases with increasing temperature

Refractive index: decreases very slightly

Surfact tension: Decreases

Density: Max @ 4 ^oC

Viscosity: Decreases

Question 12

Density of an aqueous suspension of solids

Answer 12

ρ_m = W_m /(V_S + V_L)

ρ_m = 100/ [(W%/ρ_S)+(100-W%/ρ_L )

Where: ρ_m = density of the suspension

W = weight

W% = % of suspension is solid

V= Volume

Question 13

Hardness

Answer 13

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

Question 14

Hydrophilic-liphilic balance

Answer 14

This is the measure of the degree to which a surfactent is hydro or lipo philic

Griffin’s method: HLB = 20 * M_h /M

M_h= molecular mass of the hydrophillic portion of the molecule

M=molecular mass of whole molecule

Davies method: HLB = 7+ ΣH_i -n*,475

H_i = table value for the group of hydrophillic molecule

n = # of lipophillic molecules

Question 15

Davies method for HLB vs. Griffin’s

Answer 15

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.

Question 16

Acid baking

Answer 16

This is a process where acid is mixed with ore and heated to over 100^oC

Question 17

Agglomeration

Answer 17

The process of immobilizing fine material into clusters using water and binders like cement

Question 18

Anode and Cathode

Answer 18

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.

Question 19

anolyte and catholyte

Answer 19

These are the solutions that surround a cathode or anode, respectively, a membrane usually seperates the two solutions.

Question 20

Breakthrough capacity

Answer 20

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.

Question 21

Chelating agent

Answer 21

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.

Question 22

Crud

Answer 22

A mixture of organic, aqueous, and solid matter that can become a problem during solvent extraction process

Question 23

Diluent

Answer 23

A compound used for dilution. To describe an organic solvent used as a carrier for a solvent extractent

Question 24

effluent

Answer 24

solution leaving a given process

Question 25

E_h

Answer 25

The electrochemical potential or oxidation reduction potential of a solution relative to the standard H half-cell.

Question 26

Electrolyte

Answer 26

A medium containing dissolved ions through which charge can be transported. Most often used in association with solution used for electrochemical purposes.

Question 27

Elutriation

Answer 27

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

Question 28

Emulsion

Answer 28

A dispersion of tiny immiscible droplets of one liquid in another liquid

Question 29

Extractant

Answer 29

An ion or compound capable of dissolving otherwise insoluble matter through chemical interaction or association

Question 30

extraction coefficient

Answer 30

The ratio of metal in the extractant phase relative to that in the aqueous phase in solvent extraction or ion exchange processes

Question 31

inversion

Answer 31

Transition from one continuous phase to another in processes involving two immiscible liquids such as solvent extraction

Question 32

ligand

Answer 32

Species such as chloride that complexes with a desired species such as a metal ion

Question 33

Lixivant

Answer 33

An ion or compound capable of dissolving otherwise insoluble matter through chemical interaction or association

Question 34

Modifier

Answer 34

A chemical additive used to modify the action of another species. Most often associated with additives used to enhance solvent extraction effectiveness.

Question 35

ORP

Answer 35

Oxidation-reduction-potential which is the same as E_h when converted to true values and not the product of hydrogen half cell values

Question 36

Oxident

Answer 36

An ion or compound capable of increasing the oxidation state of another entitty by means of an electrochemical reaction

Question 37

pH, pK, pKa, pH50

Answer 37

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

Question 38

Raffinate

Answer 38

Solution from which a valuable entity has been removed

Question 39

Refractory

Answer 39

The ore’s resistence to traditional leaching in gold often associated with dispersed, sub-micron gold in sulfides. Combatted through oxidation of sulfides.

Question 40

Scrubbing

Answer 40

The process of selectively removing contamination from a chemical process (solvent extraction)