Try to stabilize the cation by adding a crown-ether, preferably 18-crown-6 or by adding 2 equiv of tetremethylethylenediamine (TMEDA).

thanks sir Balakrishna Maravanji but can you kindly tell me how tetremethylethylenediamine help for crystallization. i am also thinking for cation exchanging. is it possible by adding 2 eqv of PPh4Cl in the solution and will exchange with K+ without doing resin column???

TMEDA or crown ethers stabilize cations so that crystallization is easier [they stabilize K through coordination]. One can also try to replace K by PPN [Ph3P=N=PPh3][Cl] . Look for the preparation of PPN+Cl- in the literature.

Balakrishna Maravanji thanks sir.

If your compounds are soluble in ether-type solvents and if you don't want to exchange the K+ ion for other cations, you could try to recrystallize your samples form solvents like DME (1,2-dimethoxyethane) of (preferably) diglyme (bis(2-methoxyethyl) ether). Both of them tend to form stable solvates with the potassium cation which often crystallizes much better than the unsolvated species. Exchange of the K+ with large organic cations such as [NnBu4]+ or [PPh4]+ can often be achieved just by stirring the K salts with the respective chlorides in THF without the need of using a column. Under these conditions, insoluble KCl will precipitate, which can be removed by filtration.