Help! A refiners Nightmare - Aqua Regia Overflowed

[ken.marjo]

A refiners nightmare :shock:


I got into a bit of a mess . its been a while since the accident , and im clueless on how to tackle the issue.

During refining, a valve to the water supply line was shut only halfway , over 100+ litres of water ended up diluting the reactor vessel and ended up overflowing to the floor, the grout in-between the acid-proof tiles had given away in places , and quite a bit of the solution (aqua regia+water) seeped in-between and went down to the concrete and into the soil below the concrete.
we removed the tile, cracked open the concrete and excavated a small portion of soil below. used Ph paper to test for acidity and collected mud+concrete bits soaked in the "solution". sent this for cementation (SMB + urea ) and ended up recovering only a fraction of what was lost.

The present scenario - a large portion of undisturbed soaked mud and concrete remains , the moisture has drained from it. the soaked area is about 500sqft. metal to be recovered is about 11pounds/5kg . I think its unviable to put all the mud for cementation, we believe that the solution seeped in only certain area and expect small veins of deposits in the mud, hence putting the whole area of mud for cementation may not be a good idea and unviable.

I plan to use my portable XRF to do spot checks on the soil ( unsure if aqua regia will pop up as Au on it ) , also thinking of doing spot tests in the mud with a Ph meter to find out these "veins" of acidity. even if I find them , I am clueless on how I can process the huge volume of mud , in certain areas it could have seeped to deeper depths.

There are several seasoned refiners in the forum , I hope no ones had to go through this but at the same time, I pray someones had some experience with a situation similar to this.Any and all suggestions are welcomed , and I hope others can learn my my mistake.

Moral of the story
1. always have a properly sealed collection pit with at least 5 times the capacity of the liquid volume one handles.
2. All acids , water and other solution should be kept at ground level ( I was using gravity to dispense liquid , to do away with a motor)
3. invest in more secure valves that have only "on or off" and no in-betweens (if they exist).
4. Definitely upgrading to an epoxy resin flooring after this.

thanks,
KM

 

[goldenchild]

Off the top of my head I think you'll need much more and bigger equipment than originally used to recover from this. Most likely won't be 100% recovery either. Sorry that I don't have any actual advice. Good luck!

 

[Martijn]

Having absolutely no experience in treating "soils and ores":
Could it be that the values have cemented out on basemetals in the soil, leaving only a small fraction of liquid goldchloride to be leaked/washed out of the soil.
A range of more reactive metals, like magnesium and such, could be present in the soil and might have displaced the AuCl back to elemental state? Resulting in a soil contaminated with very fine gold powder, that has to be leached out again?
So if you're looking for the lowest Ph readings, the gold powder could have settled above that level.
Gravity separation on gold powder, I have no clue if that works.
Call someone in that can do spot checks (perhaps by fire assay of small samples) to determine how far and deep the spread of contamination is and what the concentrations of gold are. Then you can set up a plan which areas are economically interesting to refine as an ore?

Completely cleaning the ground to acceptable levels of metal salts and acids would be the responsible thing to do, you don't want that to leak in anyone's drinking water.

There are basically two types of valves: control valves and on off valves, the latter are used to securely close off a line, and most of the time have some mechanism to block the valve stem. this prevents accidentally opening of the valve. on-off valves are generally cheaper than control valves, with exceptions, obviously.
I hope my guesses help you out a bit.

Martijn.

 

[ken.marjo]

thanks a lot Martjin for the information, useful info. will keep you updated on the progress . thanks