Solvent Extraction Application in Non-Ferrous Metals Recovery

1
Solvent Extraction Application in Non-Ferrous
Metals Recovery
SYMPOSIUM ON SOLVENT EXTRACTION REVISTED IIP
IIChE 05-06 FEBRUARY 2010 NEW DELHI
2
HYDROMETALLURGY

• Hydrometallurgy is part of the field of
  extractive metallurgy involving the use of
  aqueous chemistry for the recovery of metals from
  ores, concentrates and recycled or residual
  materials. Hydrometallurgy is typically divided
  into three general areas
• Leaching
• Solution Concentration and Purification
• Metal Recovery

3
LEACHING

• Leaching involves the use of aqueous solutions
  containing a lixiviant ( liquid medium that
  selectively extracts the desired metal from the
  ore or material to be leached rapidly and
  completely and from which the desired metal can
  then be recovered in a concentrated form ) which
  is brought into contact with a material
  containing a valuable metal.
• The lixiviant in solution may be acidic or basic
  in nature.
• The type and concentration of the lixiviant is
  normally controlled to allow some degree of
  selectivity for the metal or metals that are to
  be recovered.
• In the leaching process, oxidation potential,
  temperature, and pH of the solution are important
  parameters and are often manipulated to optimize
  dissolution of the desired metal component into
  the aqueous phase.

4
Solution Concentration And Purification

• After leaching, the leach liquor must normally
  undergo concentration of the metal ions that are
  to be recovered by solvent extraction.
• Additionally, some undesirable metals may have
  also reported into solution during the leach
  process.
• The solution is often purified to eliminate the
  undesirable components. The processes employed
  for purification include
• Precipitation
• Cementation

5
Solvent Extraction

• A mixture of an extractant in a diluent is used
  to extract a metal from one phase to another eg
  LIX 64.
• In solvent extraction this mixture is often
  referred to as the "organic" because the main
  constituent (diluent) is some type of oil eg.
  Kerosene.
• The PLS (pregnant leach solution) is mixed to
  promote contact with the stripped organic and
  allowed to separate in Mixer Settler.
• The valuable metal will be exchanged from the PLS
  to the organic.
• The resulting streams will be a loaded organic
  and a raffinate.

6
SOLVENT EXTRACTION - STRIPPING

• Before electro-winning, the loaded organic is
  then mixed to promote contact with a lean
  electrolyte and allowed to separate in mixer
  settler
• The metal will be exchanged from the organic to
  the lean electrolyte.
• The resulting streams will be a stripped organic
  and a rich electrolyte.
• The organic stream is recycled back to the
  solvent extraction section
• Rich electrolyte is sent to Electro-winning
  section after filtering to arrest any entrained
  organic.

7
ELECTROWINNING

• Electro-winning involves the recovery and
  purification of metals using electrodeposition of
  metals at the cathode.
• The resulting products are metal cathode and
  lean electrolyte
• The lean electrolyte is cooled and recycled back
  for stripping unit.
• Metal cathode sheets are sent to for melting and
  casting

8
Application Of Solvent Extraction In Metals

• The practice of hydrometallurgy contains examples
  of a great number of diverse solvent extraction
  processes.
• Solvent extraction of metals such as copper,
  uranium, cobalt and nickel, besides being of
  great economic significance has been the spur for
  the development of the engineering aspects of
  solvent extraction
• Besides the major metals there are commercial
  solvent extraction processes operated for the
  recovery of metals such as tungsten, rare-earths,
  thorium and vanadium.
• Metals for which solvent extraction has
  succeeded and the circumstances, which caused
  these metals to become candidates for recovery by
  solvent extraction, have some common features

9
Application Of Solvent Extraction In Metals

• They are soluble in suitable lixiviants such as
  sulphuric acid, ammonia and cyanide
• They are relatively valuable. Copper, which is
  the lowest priced metal recovered in significant
  quantities by solvent extraction. Nickel, uranium
  and the precious metals are more valuable.
• They can be recovered from the concentrated strip
  solution in a suitable marketable or intermediate
  form by processes such as electro-winning
• Suitable solvent extraction chemistry has been
  developed and available for copper, nickel,
  uranium and other precious metals.

10
Application Of Solvent Extraction In Metals

• Copper
• Around 25 of the worlds copper is recovered
  using solvent extraction
• The scope of solvent extraction for copper is
  only limited by the availability of acid
  leachable ore oxides.
• Solvent extraction is considered to be the lowest
  cost production route for the production of
  quality cathode from low grade oxide ores.
• Considerable attention is being directed towards
  development of suitable leaching techniques for
  chalcopyrite, the most ubiquitous of all copper
  minerals yet no commercial process is available.
• Oxime based extractants took a giant step
  forward in 1974 when ZCCM commissioned their
  80,000 tonne per annum SX-EW plant at Nchanga

11
COPPER RECOVERY CURCUIT
12
Typical Flow-Sheet of SX/EW Plant

• The Slide shows a typical flow-sheet of
  hydrometallurgical copper processing, which
  consists of three fundamental unit operations
• Leaching of copper ore with a week acidic
  solution, which usually is sulfuric acid,
• Solvent Extraction In which the aqueous pregnant
  leach solution (PLS) is vigorously mixed with an
  organic solvent, selectively recovers copper from
  PLS, being acidic or ammonia solution. The
  organic solvent is then separated and the copper
  stripped from it with a recycled lean electrolyte
  solution to produce a concentrated, relatively
  pure copper electrolyte suitable for the final
  stepelectrowinnig.
• Eectrowinning Copper-rich solution is filtered
  to remove entrained organics, heated and then
  passed through a series of electrolytic cells to
  yeild high quality copper cathodes.

13
Major Copper Extractants

• Developments of extractants based on
  hydroxyoximes were the key for copper solvent
  extraction.
• The important issue for researchers has been an
  increase of extractant strength and consequently
  an improvement of stripping efficiency
• The mixture, LIX64N, (blend of LIX 64 and LIX 63)
  extractant has been the popular choice for
  commercial copper extraction from acidic leach
  solution
• Chelating hydroxyoxime extractants for copper

TYPE TRADE NAME
Ketoxime LIX 64
Ketoxime LIX 65N
Ketoxime LIX 84
Aldoxime Acorga P50
Aldoxime LIX 860
14
Application Of Solvent Extraction In Metals

• NICKEL
• In comparison to copper and uranium the
  percentage of the worlds nickel which is
  recovered using SX is relatively small
• Today a number of Australasian laterite projects
  are developing nickel SX circuits which are in
  part based on the Queensland Nickel SX technology
• PROCESS AND EXTRACTANTS
• Sulphide nickel is usually treated using
  pyrometallurgical routes but in recent years
  there has been intensive activity in the
  development of hydrometallurgical routes for both
  sulphide concentrates and laterite ores
• Nickel deposits may contain valuable quantities
  of cobalt and copper and these must also be
  recovered by SX if they are present in sufficient
  quantity.
• There is a number of potential nickel extractants
  and circuit configurations

15
Application Of Solvent Extraction In Metal

• CIRCUIT-1 Direct solvent extraction of copper,
  cobalt and nickel from acid leach solutions using
  oximes, phosphinic acids and versatic acids to
  extract copper, cobalt and nickel in sequence.
• CIRCUIT-2. Matte leach chloride solutions may be
  purified by iron extraction with TBP followed by
  cobalt and copper co extraction as chloride
  complexes with tertiary amine.
• Nickel does not form chloride complexes and
  remains in the raffinate. It may be recovered by
  crystallization and hydrogen reduction.
• CIRCUIT-3 The base metals (Ni, Cu, Co, Zn) may be
  precipitated as hydroxides from sulphate leach
  solutions , re-dissolved in ammonia, the cobalt
  may be oxidised and the copper and nickel
  co-extracted with ketoxime
• Of the above circuits, the ammonia leach circuit
  has received the greatest interest in the recent
  years for the recovery of nickel

16
NICKEL LATERITE ORE TREATMENT
17
Application Of Solvent Extraction In Metals

• Uranium
• The first metal to be recovered in significant
  quantities using solvent extraction was uranium.
• In 1957 the first commercial solvent extraction
  plant using amines was opened in the USA.
• Today most of the worlds uranium is recovered in
  hydrometallurgical circuits involving solvent
  extraction
• Extractant used is Tertiary amines

18
Application Of Solvent Extraction In Metals

• PRECIOUS METALS
• Although the quantity of precious metals
  currently recovered using circuits that involve
  solvent extraction is small, the value of these
  metals is significant
• Mintek, South Africa has developed a gold
  refining process based on solvent extraction and
  there exists a potential for gold recovery by
  solvent extraction
• In the refining of platinum group elements
  solvent extraction plays an important role.

19
THE CHEMISTRY OF THE SOLVENT EXTRACTION OF THE
MAJOR METALS

• Sudderth and Kordosky have given a useful
  classification of the four basic classes of metal
  extractants and have compared these extractant
  classes on the basis of structure, extraction
  chemistry and the metal species extracted
• The four classes are
• 1. Chelation Extractants
• 2. Ion Pair Extractants
• 3. Neutral or Solvating Extractants
• 4. Organic Acid Extractants

20
EXTRACTANT CLASS CHELATING AGENT
FORMULA OR STRUCTURE
EXTRACTION CHEMISTRY
21
EXTRACTANT CLASS CHELATING AGENT

•  MODIFIERS
•  ALCOHOLS, PHENOLS, ESTERS (TXIB)
  KETOXIMES/ALDOXIME MIXTURES
• SPECIAL FEATURES
• Main commercial extractants for copper
• Operate on hydrogen ion cycle. Stripping is
  reverse of extraction
• Function with acid and ammoniacal leach solutions
• More selective than other extractant classes
• Kinetically slower than ion pair extractants
• Have good physical properties in terms of phase
  separation, low aqueous solubility, chemical
  stability
• Relatively expensive to manufacture

22
EXTRACTANT CLASS ION-PAIR EXTRACTANTS
  FORMULA OR STRUCTURE Quaternary Amines
R3RNCl- Primary Amines
RNH2 Secondary
Amines
R2NH Tertiary Amines
R3N     EXTRACTION CHEMISTRY
QUATERNARY AND Tertiary Amines  
23
EXTRACTANT CLASS ION-PAIR EXTRACTANTS

• MODIFIERS I
• SODECANOL OR TRIDECANOL, AROMATIC DILUENT
•  
• SPECIAL FEATURES
• Commercial extractants for uranium, thorium,
  vanadium, gold, cobalt and other metals
• Modifiers promote solubility of the extractant -
  metal complex in the diluents
• Kinetics, both extraction and stripping are fast
• Extraction is usually of a metal anion complex
• Selectivity is not high. Other anions can
  compete with the metal being extracted
• Tertiary amines are more selective than primary
  and secondary amines
• Selectivity can be pH dependent
• Primary, secondary and tertiary amines are
  relatively easy to produce

24
EXTRACTANT CLASS NEUTRAL OR SOLVATING
EXTRACTANTS

• FORMULA OR STRUCTURE
• Tri Octyl Phosphine Oxide(TOPO) R3P O
• Tri Butyl Phosphate (TBP)
  (RO)3PO
• Ketones (MIBK)
  R2CO
• Alcohols
  ROH
•   R CH3 and (CH3)2CHCH2
• EXTRACTION CHEMISTRY
• Extraction is by adduct formation
• Stripping is with concentrated HNO3
•  SPECIAL FEATURES
• ? TBP is used extensively in nuclear fuel
  reprocessing
• ? Kinetically fast
• ? Extract neutral metal complexes
• ? Selectivity is low
• ? Organometallic complex must be organic soluble

25
EXTRACTANT CLASS ORGANIC ACID EXTRACTANTS

• FORMULA OR STRUCTURE
• Phosphinic Acids R3 P(O) OH
• Sulphonic Acids R SO2OH
• Carboxylic Acids R3C - COOH, Versatic
  Acid
• Phosphoric Acids (C4H9CH(C2H5)CH2O)2 POOH,
  
  D2EHPA
• SPECIAL FEATURES
• Phosphinic acids are widely used for cobalt
  extraction
• Versatic acids can be used for Cu and Ni
  extraction
• D2EHPA extracts a wide range of metals
• Operate on a hydrogen ion cycle but do not
  display hydrogen ion stoichiometry. Often between
  1 and 2 moles of extractant are required for each
  mole of hydrogen produced during extraction.
• Selectivity is poor and careful pH control may be
  required to achieve reasonable selectivity

26
SOLVENT EXTRACTION- EXTRACTOR / EQUIPMENT S

• For the major metals recovered by solvent
  extraction the mixer-settler contactor design
  predominates
• There is a range of mixer settler designs
  available
• In recent years there has been some attention
  refocused on the use of pulsed columns for plants
  using the kinetically fast ion- exchange
  extractants
• Some features of mixer-settlers and columns are

27
MIXER SETTLER

• Mixer Settlers
• Well established with literally hundreds of
  operating units.
• Design parameters are well established and very
  large units treating over 1000 cubic metres per
  hour of Pregnant leach solution can be designed
  from bench scale
• Excellent mixing characteristics with control of
  the optimum droplet size claimed to be possible
  with modern turbine designs
• Prediction of capital and operating costs is
  accurate.
• The phases are readily accessible for sampling
  and examination in situ.
• Several design varieties are available

28
MIXER-SETTLERS
29
COLUMN CONTACTORS

• Column Contactors
• Advantages claimed for the column contactor
  include
•  
• Low area requirements
• Multiple stages within one unit
• Few moving parts
• Low entrainment
• Good vapor conservation
• Column installations require piloting for each
  installation and the flooding conditions for the
  column must be determined. Olympic Dam
  Corporation in South Australia has installed a
  large column plant for uranium extraction. The
  long residence times in a column compared to a
  mixer settler can influence the selectivity of
  the extraction if contaminants have slow
  extraction kinetics.

30
EIL EXPERIENCE IN SOLVENT EXTRACTION

• Feasibility Reports on Heap Leaching for Solvent
  Extraction of Copper Oxide ores.
• Scale up, Process package, Engineering and
  Setting up of Demonstration Pilot plant for
  recovery of copper, nickel and cobalt values from
  Poly Metallic Ocean Nodules (PMN).
• Plant successfully commissioned in 2002 and
  Demonstrated the design values through number of
  test campaigns in 2003- 2004.

31
PMN PILOT PLANT
A VIEW OF SOLVENT EXTRACTION AND ELECTROWINNING
CIRCUIT AT PMN PILOT PLANT
32
EIL EXPERIENCE IN SOLVENT EXTRACTION PMN

• The leaching of ocean nodules was done by IMMT
  (RRL-B) developed process- AMMONIA SO2 Leach
  Route
• Metals like copper, nickel, cobalt and zinc were
  solubalised as their amine complexes leaving iron
  and manganese as residues.
• Major portion of copper recovered using LIX 84 as
  extractant
• The raffinate from copper extraction was
  subjected to sulphide precipitation
• Bulk sulphide precipitate, on sulphuric acid
  leaching generated the leach liquor for further
  solvent extraction to recover the nickel and
  cobalt by a BARC developed three steps process.

33
EIL EXPERIENCE IN SOLVENT EXTRACTION PMN

• In the first step , the impurity metals (copper,
  zinc and iron) were removed by extraction with
  partially saponified 0.5M D2EHPA and 5
  isodecanol in kerosene.
• In the second step cobalt was extracted by PC88A
  from the raffinate solution coming out of first
  step containing cobalt and nickel.
• In the third step Nickel was extracted by
  partially saponified D2EHPA from the raffinate
  of second step
• The process was successfully demonstrated at
  specially set-up PMN Pilot Plant at HZL
• The PMN Plant also had EW circuit
• All the three metals were successfully recovered
  in the form of Cathode Sheets

34
METAL CATHODE SHEETS
NICKEL, COBALT AND COPPER CATHODE SHEETS
SUCCESSFULLY PRODUCED AT PMN PILOT PLANT
35
Thank You