self-purification
noun
self-pu·ri·fi·ca·tion ˌself-ˌpyu̇r-ə-fə-ˈkā-shən 
-ˌpyər-
1
: purification by natural process
self-purification of water
2
: purification of oneself
Word History
First Known Use
1654, in the meaning defined at sense 2