The synthesis and characterization of a novel Fe-complex as a substitute for the Cr-complex and Co-complex acid azo dyes was carried out and the subsequent use of ultra-filtration was studied with the aim of purifying the metal complex dyes and thus increasing dye strength and solubility and additionally reducing the free heavy metal present in the final dye. A drastic reduction in the content of inorganic additives and free metal was achieved by the ultra-filtration process. The ultra-filtrated and non-ultra-filtrated dyes were used to dye wool and nylon fabric. Colour measurements and fastness properties were performed on the dyeings made on wool and nylon and compared with the Cr-complex dyeings thus examining the possibility of using successfully the Fe-complex dye as possible replacement of the Cr- and Co-complex dyes. The synthesis of the Fe-complex dye combined with the implementation of ultra-filtration technology results in producing a more environmentally friendly innovative dye with greatly improved purity and solubility.