Explain the Role of complexing Agent in Solvent Extraction?

In general, organic solute (covalent solute) are more soluble in non polar (organic) solvents than water and hydrated salts are more soluble in water (polar) solvent. The inorganic salts in the solution are in the form of ions. In solvent extraction, we must see that solubility of inorganic salts in water should be less and solubility in organic solvent must be increased. The solubility of the metal ions in water is due to the association of water molecules with charged metal ions. in other words due to the hydration. Therefore, if the charged on the metal ions is neutralised, the solubility of the metal ions in the watt will be decreased. The charge on the metal ion is neutralised by reaction of metal ions with the appropriate complexing agent to form the metal-chellate complex. The bulkier the complex and if it is more hydrophobic in nature better will be extraction. .. Each ion will have to be treated differently. Thus, aluminium ions in the solution are usually converted into hydroxy aluminium quinolate by the addition of 8-hydroxy quinolene. The chellate thus formed can be extracted by using benzene or chloroform. It is possible to extract aluminium at pH 5:18, 3 in the presence of iron Nickel and Vanadium. The other complexing agents are dimethyl - glyoxime, acetyl acetone cupferron, \(\alpha\) - nitroso \(\beta\) - naphthol dithizone etc.