"H4EDTA, the precursor to that ligand. At very low pH (very acidic conditions) the fully protonated H6EDTA2+ form predominates, whereas at very high pH or very basic condition, the fully deprotonated Y4− form is prevalent." from wiki
Can EDTA be used for chelating metal ions (eg. Fe2+, Fe3+, Mn2+) in acidic medium ? if it become fully protonated and is positively charged,ie. H6EDTA2+, can it still act as ligand to positive metal ions? Or does it work only in akali medium, when it is negatively charged and the "six-toothed" ligand is deprotonated?
However, some literature show that iron is more solubilized under ph 3 to 4, can EDTA be used under such condition? ( or that EDTA do not need to iron to be solubilized in the first place?)
Also, I am not sure about the difference in practical uses of disodium and tetrasodium salt of EDTA. Disodium EDTA is acidic in water while tetrasodium one is alkaline. Which one is better in chelating iron from its oxides?