Try to sublimate crystalls. When heated NH4Cl ought to decompose for NH3 and HCl, and in a cold place they should react with formation of ammonium chloride again. Anyway we purified NH4HCO3 in such manner

Thanks but will it be 99.5% pure ??

Еhat depends on many factors. We achieved purity of ammonium bicarbonate more than 99.9%. I think, this an effective method to eliminate metal impurities even in one stage.

Good luck

I think you should recrystallize it several times. It has high solubility in water, so, you can recrystallize it using water. You should optimize other parameters like temperature and solvent evaporating rate.

The most important thing here is to look for a solvent that can completely dissolve your 'crude' ammonium chloride at some elevated temperature. That is, in a cold condition, the NH4Cl would have been sparingly soluble in that solvent. Then, heat NH4Cl in that solvent and cool to make the NH4Cl crystal crash out. That will also improve the purity of your compound. The matrix of the solvent system would have trap substantial % of the impurities.

re-crystallisation from water and ether (Diethyl-) sererval times

What will be % mixture of water and diethyl ether used as solvent for recrystallisation of water

solve it in water (closed to saturated or better with a high concentration) than add (in the beginning) 20 - 50% Et2O. the last cryst step with 5% Et2O....so decrease the amount of the ether gradually, each step

Additionally you can increase the amount of water.....lower concentration, and it`s better not to "play" with the temperature, so work at roomtemp.

hey i could not get. what i get is we are subliming NH4Cl in solvent by adding formed crystals at elevated temp around 90 degree and then cooling to 10 degrees to recrystalize. so anyway temp will vary. Normally solvent used it water but for better purity we are using Et2O. Is it right ??

Mr premin as per your comment if i mix NH3, CO2 and H2O in their molar compositions at 140 degree celcius and cool the mixture to 35 degree, Solid NH4HCO3 will be formed ??. if yes then what will happen when instead of pure CO2 Gas i pass flue gas with 30% CO2 by volume and let inert gases be realeased at same temp.

370g of NH4Cl solves at 20°C in 1L water, so no need for higher temp (90°C means decompostion (little) to NH3 and HCl, you generat your own impurity)...the ether is to change the polarity of the solvent (water) and that makes the salt less soluble!.....so it precipitate....

Mr Singh, it is known that dry NH3 reacts with CO2 forming carbamin acid, which can be easy hydrolyzed by water. So, if you will heat NH4HCO3 crystals at ~60 C degr. (not necessary 140 degree) in a close system, it will decompose to CO2, NH3 and H2O. In a cooled part of the system back reaction would realize.

I’m not sure about flue gas, you should see some papers in Net (attached file).

And what are the main impurities in your 99.5% NH4HCO3 (metals, anions, or something else?)

I must apologize...stupid idea ...water and Et2O (it`s immiscible!). About my experience: we purified Bu4NPF6, Bu4NBF4 or Et4NPF6, for electrochemical investigations (>99.8%), with different ratios of CH2Cl2 and Et2O.......

To purify NH4Cl by crystallisation you must find a solvent which is miscible with water and changes the polarity of the solution......so that NH4Cl is precipitating "earlier" (maybe MeCN?).

Another (stupid?) idea: open a bottle 37% HCl and 25% NH3 (both aqueous solution) and let the smoke "crystallize" at a glass plate above both bottles.....