How to separate a mixed acid of sulfuric acid and *ao acid?

A mixed acid formed from sulfuric acid and *ao acid is aqua regia, which can melt gold. It’s amazing to use membrane separation! I wonder if there are any experts in this forum who know something about this?

The concentration of this mixed acid is very low; aqua regia has a specific ratio

Aqua regia is a mixed acid of nitric acid and hydrochloric acid, and it has nothing to do with sulfuric acid

A mixed dilute aqueous solution of sulfuric acid and nitric acid can be concentrated using membrane distillation, for example to 30-50%, and a polytetrafluoroethylene microporous hydrophobic membrane should be used. As for separating them, membrane distillation cannot do that either. If membrane separation is necessary, there is a specific approach: use sodium hydroxide to neutralize them into sulfates and nitrates, then filter the solution using special nanofiltration membranes (which have a retention rate of 98% for sodium sulfate; our company produces such nanofiltration membranes). The fluid retained by the nanofiltration process is continuously diluted with pure water, resulting in a final product that contains almost no sodium nitrate, while the concentration of sodium sulfate can reach 12%. The fluid that passes through the membrane is a dilute solution of sodium nitrate, which can be concentrated to 10–20% using reverse osmosis or electrodialysis. Such aqueous solutions of sodium nitrate and sodium sulfate were each \"separated\" using bipolar membrane electrodialysis, yielding 7-10% nitric acid, 8-12% sulfuric acid, and 7-9% sodium hydroxide, respectively. The three dilute aqueous solutions were concentrated to the desired concentration using multi-effect membrane distillation; the sodium hydroxide solution was reused in the neutralization reaction, while nitric acid and sulfuric acid were separated. The membrane separation processes involved here include: nanofiltration, reverse osmosis, electrodialysis, bipolar membrane electrodialysis, and multi-effect membrane distillation. In addition to reverse osmosis and electrodialysis, our company manufactures other membrane equipment. It’s too complicated; it’s not worth it.

Vacuum heating evaporation allows the extraction of *ao acid; we just tested this at Baosteel, and for stainless steel pickling solutions, the denitration rate is over 95%

Okay, thank you. Can *ao acid radicals and sulfate ions be separated by membrane separation? I can’t determine the sizes of these two ions either right now. Vacuum evaporation is quite energy-intensive, which isn’t cost-effective for me; I’m looking for an energy-saving method

Thank you, your method is great. But the cost of separation is too high, so it’s not very suitable for me.

This post was last edited by yjqin1 on 2015-8-12 09:57. So, give up the idea of separating dilute *ao acid from dilute sulfuric acid. If, after recycling, it must be converted into concentrated sulfuric acid and concentrated *ao acid in order to be reused, you can use any concentration technique (including multi-effect evaporation, multi-effect membrane distillation, and special MVR) to deeply concentrate the mixed acid, and then take advantage of the volatility of *ao acid to evaporate it and obtain a relatively pure form of *ao acid. It seems to me that you are also a person who takes scholarship seriously, still seeking out the differences between *ao acid and sulfuric acid. However, membrane separation is not equal to membrane filtration nor membrane screening; membrane separation can take advantage of any differences in the physicochemical properties of the substances to be separated.

Are you sure this is aqua regia? Is aqua regia a salt acid or sulfuric acid?

Aqua regia seems to be *ao acid and salt acid, right?