The Collaborative International Dictionary of English v.0.48:

desalt \desalt\ v.
   to remove the salt from (a solution of salt).

   Note: This term is used in a more general sense than
         desalinate, which usually refers to the removal of
         common salt (sodium chloride) from a water solution,
         such as sea water. Desalt is commonly used to refer to
         any laboratory or industrial process in which any salt
         may be removed from a mixture of substances dssolved in
         a solvent, usually water. It is thus used as a method
         of purification in chemical processes. The methods for
         desalting are very varied.

   Syn: desalinate, desalinize.
        [PJC]

WordNet (r) 3.0 (2006):

desalt
    v 1: remove salt from; "desalinate water" [syn: desalinate,
         desalt, desalinize, desalinise] [ant: salinate]