Iron salts in the post-metallization of mordant dyes

Iron(II) and iron(III) salts are used as mordanting agents in lieu of chromium ions, as a source reduction approach to eliminating chromium in dye effluents following the post-metallization of acid mordant dyes. Specifically, wool fabric is dyed with Mordant Yellow 8, Yellow 30, Orange 3, Orange 6, Red 7, Red 19, Blue 1, Blue 9, Blue 13, Brown 40, Black 1, and Black 11, then treated with iron salts. The complexes are characterized by negative ion fast-atom bombardment mass spectrometry and absorption spectrophotometry, and the after-treated fabrics are evaluated for lightfastness and washfastness. Mordant dyes possessing either-ortho, ortho'-bis(hydroxy)phenylazopyrazole or ortho-hydroxy-phenylazonaphthol substituted chromophoric systems form the corresponding 1:2 metal : dye complex and undergo significant improvements in lightfastness and washfastness following metallization.