I have used Iodine with good results. It can be very selective and is somewhat slow. Yes as you will see, you can recover the Iodine and re-use it. Here is the procedure I use.
IODINE LEACH PROCEDURES
1. Mix in clear container:
1 part scrap ( may contain Gold, or any of the PGMs)
1 part 7% or 10% iodine
10 parts water
Agitate (I use a bubbler like used in a aquarium)
Let set (Leach) 24 – 48 hrs-should get darker (the darker the better)
Filter to clear (3 coffee Filters)
filtered leach will be clear but colored
Retain clear leach
2. Drop Iodine:
Add ½ t of Sodium Nitrate
Wait to drop
Filter
Alternate procedure:
Add Clorox slowly (Iodine will coagulate & drop as blue layer/black precipation)
Filter (to remove Iodine)
(Keep the Iodine in a covered container, as it will vaporize in air.)
3. Drop PGMs:
Mix equal parts Clorox and household Ammonia in small amount, use fresh.
Add small amount to Iodine free leach to precipitate yellow powder (Platinum)
Filter & dry (3 coffee filters)
Wait 1 hr
Palladium should fall out as dark precipitant
Filter & dry (3 coffee filters)
4. Gold:
Gently raise leach pH to near but not over 7 with Sodium Hydroxide (lye solution), pH will continue to rise as gold falls out. White precipitants are Mono-atomic.(you got the pH above 7)
Wait to complete drop, gold should fall out
Filter with 3 coffee filters to clear
CAUTION:
Mono-atomics: Become radioactive when heated. It's best to just discard them, it is very unlikely that any of us amiatures can coax it back to a non mono-atomic state
I obtaine this procedure from Mike . Here is the link, but the information is no longer available free. Now you have to buy the report and all of this is not in there. I got it when He had it posted openly on the site, several years ago.
http://www.goldmineworld.net/
Her is another patent you might find interesting since is based on this procedure
Rainmaker