tcfh - 22-9-2011 at 12:04
Hello,
I have to synthesize magnesium potassium phosphate (K-Struvite) to test it in a transesterification reaction.
The most articles I have found yet are about phosphate precipitation from urine and waste water.
But I want to precipitate it from pure chemicals.
I have found an article about the synthesis from magnesium hydroxide, potassium di hydrogen phosphate and boric acid as a setting retardant.
Preparation and Characterization of Chemically Bonded Phosphate Ceramics
But I think it could be difficult to separate the pure Magesium potassium posphate from solid megnesium hydroxide particles. So I thought of mixing a
completely solualbe Mg-salt (chloride oder acetate,...) with a soluable K-salt (in correct molar ratio) in water with heavy stirring and slowly
adding phosphoric acid to cristallize out the insoluable phosphate.
Has someone a source of a systhesis to get the pure product?
And has someone information about the melting point of magnesium potassium phosphate or a possible thermal decomposition, because I thought about
calcinating it to free the surface from water.
Thank you for answers.
tcfh
Some Help
Takron - 22-9-2011 at 20:24
I'm not sure how to complex it into magnesium potassium phosphate, but I do know how to get you part way and make potassium phosphate but it takes
about 24 hours and you end up with a highly illegal chemical as a by-product.
High heat, a condenser, 245mL 85% phosphoric acid and 425g potassium iodide will yield potassium phosphate after sufficient time and heat is applied.
You will either need to scrap a boiling flask and directly heat with a Bunsen burner or use a heating mantle as you'll need about 700F I think it is,
to completely turn the batch. I'm not gonna say what the condensate is but you should get rid of it as you don't wanna get pinched by the feds.
P.S. Make sure you have a fume hood or don't even attempt this.
Chemistry Alchemist - 22-9-2011 at 22:37
What ever the condensate is, most likly what im thinking off (dont see how its so illegal but then again, not a experienced chemist) if its a compound
of Iodine, isnt there good way to convert it but into a workable salt to recycle the Precious Iodine?
tcfh - 23-9-2011 at 02:51
I don't need the by-product you thought of... I just want to synthesize KMgPO4 and Iodine is not nessecary for the reaction.
The problem is to separate the partially soluable Mg(OH)2 from the crystallized KMgPO4 and to crystallize the KMgPO4 correctly to separate it.
Chemistry Alchemist - 23-9-2011 at 02:59
my last message was actually for Takron, im not good with finding out things but would there be a solvent that can dissolve one but not the other?
barley81 - 23-9-2011 at 06:13
Phosphoric acid and an iodide salt produce hydrogen iodide when reacted. It's used for making meth, and KI is expensive. It's an impractical way for
making potassium (dihydrogen) phosphate.
I think that simply adding trisodium phosphate to a solution of equal moles of a potassium salt and magnesium salt would work. TSP can be bought from
home depot, magnesium sulfate heptahydrate from CVS, and No-Salt (KCl) from a grocery store.
Chemistry Alchemist - 23-9-2011 at 06:25
yeah i waas gonna say, you could just oxidize the Hydrogen Iodide to form Water and Elemental iodine
4HI + O2 = 2H2O + 2I2
That way you can recover the iodine to produce more KI 
tcfh - 25-9-2011 at 11:43
Thanks for the answers.
I will try it tomorrow from several magnesium and potassium salts and phosporic acid and from MgO and potassium hydrogen phosphate and try to dissolve
residual MgO with dilutes HCl.