NGWA Event and Education Recordings Archive

Polluted waste water from mines is neutralized, filtered to remove coarse particles and precipitated heavy metals, then pumped through an ion exchange battery to remove all the dissolved ions leaving a water of any designed quality.The ionex battery is regenerated with dilute nitric acid for the cation resin bank and ammonia solution for the anion resin bank. The nitrate blend is treated with sodium carbonate to cause all the multicharged cations to precipitate and to be separated for use in agriculture as a soil ameliorant. The residual sodium nitrate solution is mixed with an equimolal amount of potassium chloride and evaporated with the result that the least soluble salt – sodium chloride – crystallizes out and is separated pure and dried for supply to the chlor-alkali industry. The residual liquor is cooled to produce a pure crystalline potassium nitrate which is separated and dried for supply to horticulture as a primary fertilizer. Another option is to use vegetable ash which has a very high potassium carbonate content as a raw material to precipitate out the multicharged elements, giving an even more economic route to the formation of this potassium nitrate.The anion regenerant solution is treated with methanol to precipitate out most of the ammonium sulfate almost chloride free and is separated, dried and supplied to agriculture as a fertilizer. The residual liquor is treated with sodium hydroxide to recover the ammonia content for recycling and the remaining sodium chloride is recovered by evaporation and added to the cation arisings for supply to industry. The overall economic picture of the process reveals that the sale of the potassium nitrate pays for the purchase of all the raw materials and the costs of operating the process and even leaves a reasonable profit.