I presume you mean Dicyanoamide, in this case I would suggest either to extract the iodine with an organic solvent such as ether, or to change your synthetic route.

Precipitate I- as AgI or PbI2?

When I synthesized other strutures using Finkelstein reaction, I used 5% of sodium thiosulphate aqueous solution to wash away the excessive iodine. I don't know whether your product is stable to this solution, but you can try in small amount first.

this is simply an exchange reaction I hope............ Due to incomplete exchange of Iodine,,,,,,,,it results dark color...... You can easily avoid it if you do the same experiment in presence of excess amount of cyanide source............

Sajal, I believe the problem is not the iodide, as ion, but the free iodine

Sajal, is correct because during metathesis, water is used in reaction during that time some percentage of iodine is remain in product i.e i should try to use excess of silver dicyanamide.

Vikas, you will then have the problem of removing the excess Ag salt, and Ag will start to precipitate as black powder in your IL.

Go for filtration simply.....................

well, filtering your IL every 3 days until all of the reduced Ag is removed is also an option, I was going for the cleanest, cheapest and simplest way.

by adding KI, I form KI3 ,

I ran into something similar with C1C1ImNTf2 from C1C1ImI.

You have the IL, some water from metathesis...add benzene then reflux it...you'll get a nice purple colored benzene. Remove the top layer, repeat the extraction couple of times and get the clean IL.

Another suggestion: iodide left under light and air turns to iodine; iodine can be easily removed with active carbon; easy and definitive; carbon is difficult to regenerate and has to be disposed

Can you wash with Sodium thiosulfate?

No, i haven't washed by sodium thiosufate then i will try, thank you.

Hope it will work for you. Good luck!

Thank very much for all suggestions