Extraction equilibria:

If we look at the extraction equilibria involving carboxylic and phosphorus acids, they are not easily described by the distribution law equations. The acids are stronger than those forming chelates. Weak complexes are formed and a high ligand to metal ratio is required for their formation. They are more water soluble. Extraction of metals by organophosphorus, carboxylic and sulphonic acids is affected more by solvent phase properties than it is for chelating agents. Both organophosphorus and carboxylic acids often form dimers or polymers in the organic phase.

After having discussed the salient differences in the extractants within this category, it is essential to look into the characteristic features of their interaction and the important ones available for metal ion extraction.