Sulfate Radicals for Industrial Wastewater Treatment

I am ​currently ​working with ​sulfate ​radicals to ​treat ​industrial ​wastewater ​containing high ​levels of ​metals such as ​nickel, zinc ​and copper. ​

Which sulfate ​radicals are the most efficient in wastewater treatment? Which are the most economical?

Which metals are sulfate radicals best for removing and for which metals should alternative treatment methods be used? ​