Hydrometallurgy Flashcards
the production of metals from
primary and secondary
metallurgical sources wherein
some of the chemical reactions
are carried out in aqueous
solutions at ambient temperature
Hydrometallurgy
Hydrometallurgy
Temp:
less than 300 degree C
Hydrometallurgy
Pressure
less than 2.07 MPa
ADVANTAGES of METALLURGY
a. have the ability to treat ores
b. may eliminate the requirements of waste
disposal
c. enables one to avoid emission of sulfur in
gaseous form
Advantages of Metallurgy
❖ minimum environmental impact; and
❖ no solid disposal problems
b. may eliminate the requirements of waste disposal
Advantages of Metallurgy
can improve the logistics and economics of
metal/mineral Extraction
a. have the ability to treat ores
Advantages of Metallurgy
❖ protects us from acid rain
c. enables one to avoid emission of sulfur in
gaseous form
most commonly used in GOLD hydro
Cyanidation
APPLICATIONS
90% production of ________
GOLD
80% production of ____
ZINC
APPLICATIONS
Production of ______
NICKEL AND COPPER
100% production of ____
ALUMINA
GENERAL STEPS
1 MINERAL BENEFICATION
2 ROASTING
3 LEACHING
4 SOLID/LIQUID SEPARATION
5 METAL/ MINERAL RECOVERY
6 SOLID/WASTE TREATMENT
What are the solid/waste treatment for sample?
Tailing Storage Facilities (TSF)
CHOOSING HYDROMETALLURGY
KADTONG 5 KABUOK YOT
- The amount of valuable mineral in the
deposit - Amenability of dissolving the valuable
mineral using available solvents - Presence of volatile toxic elements upon
melting, i.e. As, Sb, Pb, Hg - Cost of mining and bringing the ore to
the surface - Cost of milling and other pre-leaching
treatments
+Process of dissolving valuable minerals or
metals from an ore or concentrate feed and
extracting the metals of interest into the
solution
+Feed may also be secondary sources
(scraps)
+Metallic ions are extracted in the leach
liquor, leaving a residue or gangue, free of
the valuable minerals
LEACHING
Choice of leaching methods depends on:
oOre grade
oLeaching kinetics
o Reagent consumption
oType of minerals
oSize of operation
o Capital and operating cost
TYPES OF LEACHING
- In-situ Leaching
- Dump Leaching
- Heap Leaching
- Percolation Leaching
- Agitation Leaching
- Pressure Leaching
APPLICATIONS AND TECHNIQUES SA IN-SITU LEACHING
LAST FOR???
APPLICATION
a. Near-surface low grade ore
b. deep seated high grade ore
TECHNIQUES
a. stope leaching
b. bore-hole solution
YEARS
APPLICATIONS AND TEACHNIQUES OF HEAP LEACHING
LAST FOR???
APPLICAITON
a. mined low grade ore
b.20 cm in diameter
TECHNIQUES
a. piled into heaps on impervious ground
b. solvent is allowed to permeate the heap
MONTHS
APPLCATION OF DUMP LEACHING
IT TAKES????
APPLICATION
a. stripped marginal deposition
TECHNIQUES
a. dumping in the foot or cliff
b. leaching agent is sprayed on it regularly
YEARS
Stirred tanks with or without air
AGITATION LEACHING
APPLICATIONS AND TECHNIQUES OF PERCOLATION LEACHING
LAST FOR?
APPLICATION
a. porous and sandy material
b. regular size at 5mm diameter
TECHNIQUES
a. does not need S/L separation
b. counter current leaching
WEEKS
APPLCIATIONS AND TECHNIQUES OF AGITATION LEACHING
LAST FOR?
APPLICATIONS
a. particles with 0.5 mm or less in diameter
b. slurry is introduced in the process
Counter Current
TECHNIQUES
a. Mechanical agitation
b. compressed air agitation
c. COmbined mechanical and compressed-air
DAYS
UNSAY GINAGAMIT SA PRESSURE LEACHING???
AUTOCLAVES
APPLICATIONS AND TECHNIQUES OF PRESSURE LEACHING
LAST FOR
APPLICATION
a. Minerals that are difficult to dissolve at STP
TECHNIQUES
a. mechanical agitation
b. compressed air agitation
c. combined mechanical and compressed-air
HOURS
Choosing a solvent
5 ni sila
- Readily available
- Relatively cheap
- Selective in its dissolution
- Non-corrosive to construction
materials - Easily regenerated in the operation
Choices of Solvents:
5 pud ni sila yot
- Aqueous salt solutions
- Chlorine water
- Water
- Bases
- Acids
+Must be able to withstand
the pressure produced
from the evaporation of the
leaching agent since
operation is done above
the boiling temperature of
the leaching agent
* When under oxidizing atmospheres, it must be
able to withstand the additional pressure of
the heated air or gas
AUTOCLAVES
OBJECTIVES SA ENRICHMENT PROCESS
produce smaller volume and richer pregnant solution
METHODS
ION EXCHANGE
FUNCTIONALIZED RESIN
METHODS
ADSORPTION
ACTIVATED CARBON
METHODS
SOLVENT EXTRACTION
ORGANIC SOLUTION
+the attached functional groups in the
resin undergo ionization to yield cations
(or anions of an anion exchange resin)
that selectively exchange with other
ions present in the solution in which the
resin is immersed
ION EXCHANGE METHOD
allow gold to enrich during the process
ION EXCHANGE METHOD
Dilute pregnant solution apply activated carbon so mabawasan si barren solution
SORPTION
2 types of ADSORPTION METHOD
SORPTION
ELUTION
stripping solution to get enriched pregnant solution
ELUTION
+the solid carbonaceous material coal such as coal, wood, nut
shells, sugar, synthetic resins pyrolyzed at about 600oC in the
absence of air
CARBONIZATION
The activated charcoal is a highly porous
carbon material made from coal, wood,
sugar, synthetic resins and nutshell
ACTIVATED CARBON
+Carbon is exposed to steam or air for a limited time at temperatures between 400 and 800oC
ACTIVATION
Properties of AC
+hard and abrasion resistant
+large surface area of 1200 m2/g
+high porosity at 0.7-0.8 cm3/g with 95%
macropores, then the remainder
comprises of meso- and micropores
+can act as reducing agents to metals in
salt solutions:
Methods of Adsorption
+Carbon-in-Leach
+Carbon-in-Pulp
+Hybrid CIL-CIP method
+carbon adsorbs the gold cyanide complex
from the slurry solution and is then removed by coarse screening
+6 tanks for leaching
+followed by 4-6 tanks for adsorption
Carbon-in-Pulp (CIP)
+adsorption is limited in the first tank
+carbon loading is 20- 30% less
+often used for carbonaceous gold ores
Carbon-in-Leach
+Similar to CIP process except that activated
carbon is used to extract gold from gold
cyanide solution streams, such as:
oHeap or dump leach solutions
oThickener overflow solutions
oUnclarified filtrates
oTailings reclaim solutions
Carbon-in-Solution
+Modified CIP process
+leaching and adsorption occurs simultaneously
+– in a series of tanks, i.e. 6 tanks, the slurry is
introduced into the 1st tank while the AC is introduced in the last tank (counter-current)
Carbon-in-Leach (CIL)
the loaded carbon is heated by a strong solution
of hot caustic and cyanide to reverse the
adsorption process and strip the carbon of gold
ELUTION or STRIPPING
- immediately maximizes the available surface
area of the activated carbon
Carbon-in-Pulp
- pretreat loaded AC with strongly alkaline cyanide
solution to convert calcium aurocyanide complex to sodium form - elution with deionized water at a temperature of
95 – 125oC
DAVIDSON PROCESS
- loaded carbon is soaked in a 1.5 – 5% NaCN and
0.5 – 2% NaOH solution for several hours at temp.
greater than 90oC - Au and Ag is eluted with several bed volumes of hot distilled water
- Reduced cycle time to 12 hrs
AARL – MODIFIED ZADRA
(US Bureau of Mines, late
1960’s)
* insulated tank
* 90 – 93oC working temp
* 0.2% NaCN
* 1% NaOH
* flow rate: 1 bed vol/hr
ZADRA PROCESS
- uses an addition of 20% alchohol to the Zadra
elution solution - elution is accomplished at 80oC for 6 – 8 hrs
- the alcohol used are ethyl, methyl, and isopropyl
DRUNKEN ZADRA
- elution is carried at 145oC which simply
means that elution is pressurized - elution time is 12 hours
PRESSURE ZADRA
+a distributive reaction wherein the valuable metal is allowed to partition itself between two immiscible phases with the eventual establishment of equilibrium
Solvent Extraction
- are organic solvents in which the extractants are soluble
- are immischible with water
- constitue the bulk of the organic phase
- are not able to extract metal ions but could influence behavior of extractants; inert component of the organic phase
Extractant + Carrier
- the formation from solution of a solid product
as a result of dilution or of the addition of a
reagent to the solution
Precipitation
Factors affecting Precipitation
a) pH
b) temperature
c) complexing ions
d) concentration of the reactants
factors sa precip
precipitates are only formed within a
certain pH range, since most of them are
redissolved outside this range
pH
most precipitates are either more soluble in
hot than in cold solutions or decompose
when precipitation is carried out at high
temperatures
temperature
the presence of a complexing ion in solution
prohibits the precipitation of the metal with
which it is complexed
complexing ions
large crystals are obtained by precipitation
from dilute solutions; fine precipitates are
obtained from supersaturated solutions
d) concentration of the reactants
+IONIC PRECIPITATION
+PRECIPITATION BY GASES
+PRECIPITATION BY METALS
Methods of Precipitation
