Copper solvent extraction reagent, Nickel Cobalt extractant, DEHPA & Rare earth leaching solvent

Classification and comparison of metal extractants

by:Deyuan      2020-12-17

basic introduction
Chelating extractant, ion pair extractant, neutral or solvent extractant, organic acid extractant

Comparison of four types of extractants

Chelating extractant
1.1 Structural formula
Among them: R=C9H9 or C12H25

Ketooxime A=CH3

Salicylaldoxime A=H

1.2 Extraction Chemistry
2RH(org)+MSO4 R2M(org)+H2SO4

2RH(org)+M(NH3)4+2 R2M(org)+ 2NH3 + 2NH4

1.3 Features
Mainly a commercial extractant for copper

?For hydrogen ion circulation, back extraction is the reverse reaction of extraction

?Works on acid leaching and ammonia leaching

? Better selectivity than other types of extractants

?Slower dynamics than ion-pair extractant

?Good physical properties for phase separation, slow water solubility, stable chemical properties

? Relatively expensive production costs

Ion pair extractant
2.1 Molecular formula
Tetraamine R3R'N+CL-

Monoamine RNH2

Diamine R2NH

Triamine R3N

2.2 Extraction chemistry-quaternary and tertiary amines
R3R'N+(org) +M-R3R'N+M-(org)

R3N(org) + H+ R3NH+(org) Protonation

R3NH+ + M- R3NH+M-(org) + H+

2.3 Features
? Commercial extractant for uranium, thorium, vanadium, gold, cobalt and other metals

? The modifier promotes the solubility of the extractant-metal mixture in the diluent

? Both extraction kinetics and back extraction kinetics are fast

? The extraction is generally a metal anion mixture, such as AU(CH)2- or U02(SO4)34-

?The selectivity is not very high, other anions can compete with the extracted metal ions

?Back extraction is all types of ion exchange, or deprotonation of mono-, di-, and tri-amines and trialkylguanidines

? Triamine and trialkylguanidine are more selective than monoamine and diamine

? For all amines except quaternary amines, extraction must be carried out at a pH lower than pKb of the extractant

?Selectivity is determined by pH

? The production of mono-, di- and tri-amines is relatively simple

Neutral or solvent extraction agent
3.1 Molecular formula or structure
Trioctyl phosphine oxide (TOPO): R3P=O, where R= C8H17;

Tributyl phosphate (TBP): (RO)3PO; where R=C4H9;

Ketones: R2CO;

Alcohol: ROH

Where R = CH3 or C4H9

3.2 Extraction Chemistry
Extraction is formed by adduct

2(RO)3PO(org) + UO2(NO3)2 UO2(NO3)2 2(RO)3PO(org)

Concentrated nitric acid

3.3 Features
Tributyl phosphate is widely used in nuclear fuel recovery

・ Fast dynamics

・Extract neutral metal mixture

・Low selectivity

・The organometallic complex must be dissolved in the organic phase

Edit this paragraph organic acid extractant
4.1 Molecular formula or structure
Phosphinic acid R3P(O)OH

Sulfuric acid RS02OH

Acids R3C-COOH, branched chain acid

Phosphoric acid (C4H9CH(C2H5)CH2O)2 POOH, D2EHPA

4.2 Extraction Chemistry
4RH(org) + Zn+2R2Zn2RH(org) + 2H+

4.3 Features
ü Phosphonic acids are widely used in cobalt extraction

üBranched chain carboxylic acids are widely used in the extraction of copper and nickel

üDi(2-ethylhexyl) phosphoric acid can be used to extract a variety of metals

It works on the hydrogen ion cycle, but cannot show the exact stoichiometric process of hydrogen ion, because the extraction process often includes the formation of adducts. Generally, for every mole of hydrogen produced in the extraction process, 1-2 moles of extractant are needed

üPoor selectivity, pH must be strictly controlled to achieve proper selectivity
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