Hello spiritnoname,
You don't 'purify' it - you get rid of it by devoting yourself to consistent sila, study and practice so that understanding and wisdom grow.
Have a look at this sutta excerpt:
MN 148 Chachakka Sutta: The Six Sextets ...............
"Now, this is the path of practice leading to the cessation of self-identification. One assumes about the eye that 'This is not me, this is not my self, this is not what I am.' One assumes about forms... One assumes about consciousness at the eye... One assumes about contact at the eye... One assumes about feeling... One assumes about craving that 'This is not me, this is not my self, this is not what I am.'
"One assumes about the ear...
"One assumes about the nose...
"One assumes about the tongue...
"One assumes about the body...
"One assumes about the intellect that 'This is not me, this is not my self, this is not what I am.' One assumes about ideas... One assumes about consciousness at the intellect... One assumes about contact at the intellect... One assumes about feeling... One assumes about craving that 'This is not me, this is not my self, this is not what I am.'
........................
http://www.accesstoinsight.org/tipitaka ... tml#selfidmetta
Chris