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					       Council for Mineral Technology




         reliable results even in field conditions



Application of titration techniques for analysis
       of hydrometallurgical solutions

                    By Volha Bazhko
                     Senior Scientist
                 Titration


Advantages of titration methods :


Do not require complicated and expensive
equipment


Simple and fast method


Reliable results even under plant conditions
                       Titration
Types of titration:

Acid-base titration

•determination of acidity of solutions
•determination of alkalinity of solutions
•neutralisation tests
•titration of mixtures of acid

Precipitation titration

•determination of Cl-
•determination of CN-
•determination of S2O32-
                      Titration
Types of titration:

Complexometric titration

•determination of base metals with EDTA

Redox titration

•determination of base metals and PGMs
•dissolved O2, H2O2 and anions
•determination of the oxidation state of Fe, Mn and
other elements in solution
                    Cu/Co processing

           Milled ore
                                                       Co bleed
 H2SO4                             Fe2+ /   Fe3+       product
              Leach
 SO2
                    1
 tails                        2                         3
                S/L                    Cu SX
                                       5           4

                                      Cu EW

                                            Cu0

1 PLS (Fe2+, Fe3+ and acid titration)
2 SX feed (Fe, Cu2+ and acid titration)
3 SX raffinate (Cu2+, Fe2+, Fe3+ and acid titration)
4 Advanced electrolyte (Cu2+ and acid titration)
5 Spent electrolyte (Cu2+ and acid titration)
     SO2, Fe2+ and Fe3+ determination
Titration1: Back dichromatometric
titration of the amount of Fe2+ and SO32-:

 6 Fe2+ + Cr2O72- + 14 H+ = 2 Cr3+ + 6 Fe3+ + 7 H2O

 3 SO32-+ Cr2O72- + 8 H+ = 2 Cr3+ + 3 SO42- + 4 H2O

Mixed acid (H2SO4+ H3PO4)
Indicator: diphenylamine.

Titration 2: Fe3+ titration with EDTA.

pH < 2
Indicator: sulphosalicylic acid
   SO2, Fe2+ and Fe3+ determination

Titration 3: Total iron determination
with EDTA.
Pre-oxidation of Fe2+ with H2O2
pH < 2
Indicator: sulphosalicylic acid

    CFe III (mol/L) = CEDTA * V2 / Vsample

    CFe II (mol/L) = CEDTA * (V3 - V2) / Vsample

     CSO (mol/L) = 3(CK Cr O * VK Cr O –
        2                  2   2   7   2   2   7

  - (CFeSO * V1 + CEDTA * (V3 - V2)) / 6 ) / Vsample
            4
         Cu and Fe determination

1 Titration: Determination of the amount
 of copper and iron

• Fe2+ pre-oxidation

• Reduction of Fe3+ and Cu2+ with excess of KI

  Fe2(SO4)3 + 2 KI = 2 FeSO4 + K2SO4 + I2
     2 CuSO4 + 4 KI = 2 CuI↓ + 2 K2SO4 + I2

• Titration of I2 liberated

      I2+ 2 Na2S2O3 = Na2S4O6 + 2 NaI

Indicator: starch.
         Cu and Fe determination

2 Titration: Determination of copper

• Masking of Fe3+ with fluoride

• Reduction of Cu2+ with excess of KI

• Titration of I2 liberated

         CCu (mol/L) = CNa S O * V2 / Vsample
                                 2   2   3




      CFe (mol/L) = CNa S O * (V1 - V2) / Vsample
                         2   2   3
      Sulphuric acid determination



H2SO4 + Na2CO3 = Na2SO4 + H2O + CO2


• Mixed indicator

• Use the solution remaining after the iron
  and copper titration or mask Fe3+ by
  addition of excess of KI and Na2S2O3

     CH SO (mol/L) = CNa CO * VNa CO / Vsample
       2   4             2   3   2   3
             U ore processing


            Milled ore
  H2SO4
              Leach
oxidant
                    1
  tails                        2                 3
                 S/L                  SX or IX




1- PLS (U, Fe2+, Fe3+, Cl- and acid titration)
2- feed (U and acid titration)
3- loaded strip liquor (U and acid titration)
       U determination: redox titration


Step 1: Pre-reduction of Uranium

      UO22+ + 2 Fe2+ + 4 H+ = U4+ + 2 Fe3+ + 2 H2O

Strong phosphoric acid medium


Step 2: Destruction of Fe(II) excess

4 Fe2+ + 2 HNO3 + 4 H+ = 4 Fe3+ + NO↑ + NO2↑ + 3 H2O

Catalyst: ammonium molybdate
      U determination: redox titration

Step 3: Destruction of NO or NO2 with
sulphamic acid
  2 (NH2)HSO3 + NO↑ + NO2↑= 2 H2SO4 + 2 N2↑+ H2O


Step 4: Dilution with H2SO4

Step 5: Oxidation of U(IV) into U(VI)
                U4+ + 2VO2+ = UO22+ + 2V3+
    or U4+   + 2 Fe3+ + 2 H2O = UO22+ + 2 Fe2+ + 4 H+
        U determination: redox titration
Step 6: Dichromatometric titration

      Cr2O72- + 6 V3+ + 2 H+ = 2 Cr3+ + 6 VO2+ + H2O
   or Cr2O72- + 6 Fe2+ + 14 H+ = 2 Cr3+ + 6 Fe3+ + 7 H2O

Indicator: diphenylamine
or Potentiometric titration

          C U (mol/L) = 3 * CK Cr O * VK Cr O / Vsample
                                2   2   7   2   2   7
Cl determination: precipitation titration

              Ag+ + Cl– = AgCl↓

•Indicator: potassium chromate or dichromate

          2 Ag+ + CrO42– = Ag2CrO4↓

•Fe2+ pre-oxidation

•pH from 6.5 and 10

       CCl (mol/L) = CAgNO * VAgNO / Vsample
                          3        3
            Thank you




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posted:8/9/2011
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