As part of my Advanced Oxidation Process in water purification using UV- hydrogen peroxide, I would want to filter out the nitrate ions and permit the humic acids to enter with the rest of the feed water into the UV reactor.
Is there any suitable pre-filtration method like ion-exchange or membrane seperation that would allow me to do so.
yes I believe you could use ion exchange to selectively remove nitrates, but it should all be filtered prior to ion exchange to reduce fouling. Maybe larger resin beads could help. Why are you intent on leaving humic acids, I admit I don't know about it other than people seem to think it's in dirt and is some sort of wonder substance. my google of humic acid show's me snake oil salesmen.
Its better to use membrane after AOP as tertiary treatment because there is chance of fouling.But nitrate can also be reduced to nitrogen gas by reducing agent.
One possibility could be to use electrodialysis and separate the nitrate ions (smaller) from the humic acids. It also depends on the feed you have and if you only want to separate nitrates, because in this case other anions could be separated too (like chlorides, for example).