The Collaborative International Dictionary of English v.0.48:

Purifier \Pu"ri*fi`er\, n.
   One who, or that which, purifies or cleanses; a cleanser; a
   refiner.
   [1913 Webster]

WordNet (r) 3.0 (2006):

purifier
    n 1: an apparatus for removing impurities

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "purifier":
   abstergent, cathartic, clarifier, cleaner, cleaning agent,
   cleaning solvent, cleanser, cleansing cream, colander, cold cream,
   cradle, cream, cribble, dentifrice, depurant, detergent, diuretic,
   emetic, enema, filter, holystone, lixiviator, lotion, mouthwash,
   nauseant, percolator, pumice stone, purgative, purge, refiner,
   refinery, riddle, rinse, rocker, screen, shampoo, sieve, sifter,
   soap, solvent, strainer, synthetic detergent, tooth powder,
   toothpaste, wash, winnow, winnowing basket, winnowing fan,
   winnowing machine