To my delight the finished solution was almost clear and almost odorless. A great advantage over the organic food approach. BUT will I get any nitrates purified ? !
The 2 liters of solution was boiled down.
I did not get any KNO3 crystals on cold crystalization attempts due to lack of sufficient potassium ions and contaminating ions such as Calcium, Sulfate etc. On boiling down the solution I did see some odd observations:
The first solution made an odd light flocculent precipitate on heating.
Later as it boiled down a second heavier white precipitate was seen.
This white precipitate was filtered out.
Thinking it might be a carbonate I added sulfuric acid to confirm my suspicions expecting to see carbon dioxide generated. I was totally surprised to see the orange gas nitrogen dioxide being generated. This precipitate was some type of nitrite.
Realizing I wanted all the nitrite to go to nitrate I looked up chemical ways to finish this step.
One page mentioned ozone. Not something I have around so I thought perhaps hydrogen peroxide might work in place of ozone so a quick search brought up a google book reference that says H2O2 will convert nitrite to nitrate in an acid environment.
Due to the contaminating chemical ions mentioned earlier I think the best way to isolate the nitrate would be as nitric acid by distillation. Excess H202 will hopefully remain behind in the distillation or convert to O2 and H20.
The resulting nitric acid could be converted to potassium nitrate by adding to potassium carbonate, available at ceramic supply stores, or by adding to potassium hydroxide.
At this point it became obvious that in order to make any appreciable amount of nitrate salts that one would need a larger reactor.
On the results page notice how the nitrate levels would max out at about 5,000 mg/L. Doing the math for my 2 liter reactor that would be about 10 grams of nitrate with a perfect harvest yield. Not enough for a potassium nitrate hungry rocketeer! :-) For that purpose one would need to scale up perhaps a large tub or barrel though I would avoid metal containers.
This may be a project to try someday.
reactor vessel page.
reactor media page.
reactor testing page.
reactor testing results page.
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