How should I remove tile adhesive from the edges of lifted tiles

[Steve_Bcs]

The saga of my hollow floor 50sqm continues. All tiles now lifted but there is adhesive around the edges of most tiles (800x800) and a small amount on the back. Whats the best method of cleaning these tiles ip ready for relaying? The tiles were not grouted and the adhesive residue is around the bottom area of the tiles.
Thanks

 

[AliGage]

Pain stakingly with a bit of sand paper

 

[Steve_Bcs]

Thanks. A sharp blade & scraping of the edges did the trick