Decomposing monoammonium phosphate?

[croc]

How can I destroy monoammonium phosphate (MAP) into gases or change it into a very soluble or insoluble compound? I could find hardly any information after searching for a month of reading MSDS’s etc.

I need to extract KNO3 form fertilizer which is 70% KNO3 and the other 30% is mainly MAP and urea with 1% unknown nitrate.
MAP decomposes at nearly 200C and I only have access to this temp in my fan oven but I don’t want to fill my house with toxic gases (NH3, POx, NOx)

I was also thinking reacting MAP with a hydroxide or carbonate for it is incompatible with strong bases.
NH4HPO4 + NaOH = NH3 + H2O + NaHPO4
NH4HPO4 + CaOH = NH3 + H2O + CaHPO4
NH4HPO4 + NaCO3 = NH4CO3 + NaHPO4
NH4HPO4 + CaCO3 = NH4CO3 + CaHPO4

Any help will be greatly appreciated, thank you.

[FUTI]

Question is very interesting (the idea behind I do not approve but as Confucius sad ...I do and I understand). What is wrong with the logic? Well you can't convert that salt into a gas ( no matter that all ammonia salt can be sublimated, or decomposed by heat), that way you will only get some polyphosphoric acid salts (which maybe can be used as start for some purification procedure) but reason why I don't advice this procedure is the nitrate present in mixture. Remember that sometimes chemist used it as an oxidant for various material in molten carbonate mixture, not to mention it can decomose at slow or high speed :eek: evolving heated oxygen seeking reductant. Playing with solubility is better idea to some point. One thing that you mentioned is not bad idea, use of CaCO3 (with small amount of Ca(OH)2 to make pH to the right value) in warm (about 70 degrees Celsius for the CO2 to escape) water solution of fertiliser should convert all phosphate to almost insoluble salt. Cool it down and filter the precipitate and excess of CaCO3. Now you can evaporate most of the water present (again carefully), and your nitrate should crystallise upon cooling (don't expect to much salt that salt is very soluble). Urea that is an other impurity should remain in water (it takes 8 or 10 mole of this substance to make a saturated solution so I believe you are safe to that point). Solubility tables are very wide spread this days on the net and if you do not find any, I got one somewhere :) I believe that KNO3 is the salt with sharpest temperature-solubility curve I ever saw which help the
process I described. I hope that I get some credit for this

[croc]

Your post has been a great help and I will probably try that later on today.

You seem quite an experienced chemist to still be remaining on newbie status.

Another idea I thought up was to put the fertilizer on a filter and heat, the ammonium phosphates with a lower melting point than the nitrate would creep through the filter whilst the KNO3 remains.

The problem with the carbonate or hydroxide method is I won’t know if it worked because calcium hydroxide carbonate and phosphate are all very insoluble I just hope the acid won’t react with the nitrate to form NO2.

how would i reach temp between 200-300C for the reaction to take place… unless there is a way to change it to diammonium phosphate which has a lower melting point?

[FUTI]

I have join this place recently and I guess after the iDefence mess up...people are getting little paranoid so it's harder to prove yourself:)
Anyway I forget to mention don't do that inside as ammonia will evaporate to, it can be dangerous in closed space (bad stench!). I will think about that melting purification procedure you sugested...hard to tell if it will work, I need to look up! Nitrate have problem with high temperature decomposes itself, but playing around with temperature issue can lead to somewhere if the substances mixed together would obey and act as separate ones (look for the meaning eutectic). When you disolve fertiliser and add CaCO3 and Ca(OH)2 (to pH 12) your phosphate will go down as Ca3(PO4)2. Only problem you have is that little nitrate can be traped there too. After filtration you work with filtrate that first precipitate is thrown away (or used as fertiliser for plant:)). Concentrate your filtrate, cool it and the crystal that you get is you stuff. Enjoy!