For strontium, it looks like it's relatively soluble in short chain alcohols (methanol/ethanol) compared to the other two, so you'd crash out the potassium perchlorate by dissolving the mixture in water, then reducing the temperature to cause perchlorate to drop out of solution, then mix in a moderate amount of methanol to crash the potassium nitrate out, being left with a reasonably pure strontium nitrate, that you could then hot filter and recrystallize in anhydrous methanol if you wanted >90% purity. One or two rounds of recrystallization will leave you in the high nineties, probably above 97%.
This is a classic chemistry workup kind of problem and there are interesting engineering challenges embedded in it.
Of course... practical people just buy technical grade strontium nitrate and make fireworks out of it directly, as the article says.
Most of the formulations in the table have charcoal, potassium nitrate or other oxidiser, and sulfur. Surely, to say they don't contain black powder is semantics, when they contain the ingredients of black powder?
Potassium perchlorate and powdered aluminum can be used to make flash powder. Just because road flare contains both doesn't mean it's going to explode in your hand.
https://en.wikipedia.org/wiki/Chemical_oxygen_generator#Oxyg...
https://minearc.com/oxygen-candles-providing-emergency-air/
https://www.youtube.com/watch?v=g3Ud6mHdhlQ
Unfortunately they are "boring" in comparison, no flame/glow
>Specified and approved by the Bureau of Explosives and Underwriters Laboratories. No expiration date on road flares, the date shown on the flare is manufactured date. Orion flares will burn in all weather conditions, waxed Flare w/Plastic Cap. 15 Minute Burn Time — Non Perchlorate Formula
Answered my question: https://www.youtube.com/watch?v=SldmXuV3cLI
Extracting strontium nitrate lets you .. build explosives from readily available materials? Or it would except, as the page shows, you need a pretty good chemistry set and knowledge to do this, at which point you probably don't need pyros.
I don't know if it's just a Europe thing, but pyros are illegally used a lot at soccer (EU: football) matches and other sporting events. Picture on this page: https://scottishfsa.org/pyros-burn-young-dundee-fan/
