I have one problem. We have a solution of zinc phosphate, which is held at a pH value of 2 and at a temperature of about 55 °C. at certain times in our production we encounter a problem with rising concentrations of Fe (II) ions. When the concentration of Fe (II) ions rises to about 7 g/L the solution as a whole is not suitable for use and has to be discarded. So, do you have any idea how could selectively remove Fe (II) ions from this solution?