Ask the Expert Question-and-Answer Archive
by Mike McGinness, EcoShield Environmental Systems, Inc.
Nitric Aidic Pickle Liquor Waste Treatment
Do your have or know of a process for treating very strong nitrate waste (25 -50,000 mg/L) pickle waste from a SS mill? Location in China.
I really need to know more about what else is in the waste. If it was just nitric acid with traces of iron I would consider pH neutralization with potassium hydroxide to make a potasium nitrate fertilizer, but alas, I suspect the SS means stainless steel, and thus nickel and chrome are involved. I have heard of dialysis, and electrodialysis units being used successfully to purify the nitric acid for reuse as far back as 16 years ago, and to concentrate the metal salts, but I have not had any hands on experience with them myself. Reverse osmosis is another potential candidate with a track record. Lastly, ion exchange resins to remove trace metals, and restore or purify the nitric acid is another option that has been used.
I would look for a way to purify the nitrates for reuse, or recycling first by removing the metals.