How much EDTA or citric acid minimum required to remove iron from water?

I want to make a simple 1% sodium salicylate solution with a cationic surfactant. The problem is the iron in water changes the color of solution so i need a chelating agent for iron but the cationic surfactant forms insoluble salt with chelating agents. 

I have tried even 0.008% EDTA and it still produced insoluble salt. 

My question is: what is the minimum amount of EDTA or citric acid required to remove iron from water? 
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