purification has 3 distinct synonyms spread across 2 of its 4 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the act of cleaning by getting rid of impurities
the process of removing impurities (as from oil or metals or sugar etc.)
the act of purging of sin or guilt; moral or spiritual cleansing
“purification through repentance”
Synonyms, antonyms and the broader and narrower relations for purification come from Princeton University’s WordNet. Full sources and licences.