Oneal, there are several ways to recycle your waste, much depends on how you collect the waste, if you have kept the nitric acid waste separate from chlorides, it would not have chloride involved, if you added chlorides then that should be considered if reusing the waste.
The 50 gallons of nitric is a large volume to have around, my guess is it is a dilute solution, the mud in the bottom of the storage vessel has a high potential of being valuable, leave this mud undisturbed.
What I am saying here next you will have to determine if the solution had added chlorides, and if so and solutions you get from this later should be tested for gold or other values.
One way is reuse this dilute solution concentrating it (for less waste to have to treat), and get some work done with it at same time.
Decant the solution and add to crock pot, add gold plated pins or other materials you wish to remove base metals (if the contain copper it will work, and will work better is base metals are above copper in the series of metals), put crock pot on low heat, this will concentrate solution and dissolve some base metals as the solution concentrates, cover pot, to keep out, rain and snow and dirt, also keep out of reach of children or pets, this is done outside as it will fume off some gases but mainly water at first, let this evaporate, and depending if the nitric had free nitric acid can determine how far you can let this evaporate (if too high of nitric acid content on evaporation it is possible for a boil-over if excess acid and greater than 68% concentration, and heat is too high), with low heat and not letting concentrate too far you should not have trouble with boil-over from the solution, every day check on it add some more of the used nitric as it evaporates off, let this dissolve the base metals, (if powder form let them, but after they build up you remove powders to a selling jar, also when solution gets very concentrated move it to this settling jar, (this could be a gallon jar, that after letting settle the concentrated solution from this selling jar decanted to 5gallon pail), when you get to the bottom of the 55 gallon drum you can add your powders to the settling jar, now you have 5 gallons of concentrated copper nitrate solution and some copper powder that can have values, these powders can be cleaned up with fresh acids, and the 5gallons of concentrated solution still has use, (you could use it as an electrolyte, or crystallize to salts and get some nitric from it or just cement the copper and other metals with iron and treat it for waste).
Chloride solutions you can treat similar, but also if you added a chemical or reagent to them like SMB or sodium sulfite or like ferrous sulfate the can form sulfate salts when concentrating, as the HCl fumes from these either make metal chloride salts or vaporize off in the evaporation process. So if your chloride solution does not contain sulfate’s you can use it like copper II chloride, or you can use it to dissolve copper in heated crock pot letting it get very thick and dissolving copper to powders, these powders again settled to be cleaned up later, this lowers the volume of waste to treat (concentrating it), and gets some use out of it at the same time,
now these copper powders with some gold or gold flakes can be used in a new stock pot, as you refine add you solutions to them it will clean these powders up this way you do not have to waste new acids to clean them up, and the solution if values involved will replace the copper (or other base metal from these powders), your now solutions will be more concentrated as the pick up as much metal as they can from these powders……
As far as sulfates solutions these are still useful, even if they have some chlorides, as they can also dissolve base metals, and as they concentrate with metals, the HCl can be driven from them (as chloride metal salts, or fumes), and as you go you can remove the chloride salts, and eventually you will end up with sulfate metals salts, ferrous sulfate can be made this way or copper sulfate, again useful items in refining.
Some principles need to be understood doing this, like what the salts look like, so you have an idea as to which ones your making, these salts can also be re-crystallized for higher purity, also understanding what gases and acids leave the solutions first and which ones may not leave the solution is also important, also what temperatures or conditions these leave your solutions, or form metal salts.
Water is more volatile than nitric so it leaves first, then nitric, then chlorides, and sulfates will not leave unless temperature is extremely hot and salts are roasted,
So from this you can see if you had a mixture of all of these the end product would be a sulfate salt. (But the solution could be making salts of other metals as it was evaporating from this soup).
I will stop here as this is getting long and it gives you plenty to consider for now.
Hope I wrote this where it is understandable.
