Iron-Complexed Dyes: Colorants in Green Chemistry

Abstract

Few textile and dye chemists would argue against the suggestion that textile wastewater containing toxic metal ions is a matter of considerable concern, and that a pollution prevention/source reduction approach to addressing this concern would be better than currently available waste treatment methods. With that point in mind, this chapter reflects work pertaining to the design and synthesis of metal-complexed dyes that contain potential replacements for metals now designated as "priority pollutants". The focus of the present report is on dye structures and their properties rather than the synthetic reactions employed. The goal of this research was the development of environmentally friendly metal complexed dyes. It was hoped that this would provide a green chemistry approach to minimizing the need to treat wastewater after the dyes are manufactured and/or applied to textiles, by eliminating the source of dye wastewater containing toxic metals. Our strategy was to identify alternative metal complexes that could replace chromium-, cobalt-, and copper-based synthetic dyes. This chapter includes discussion of the metals that are used to prepare metal-complexed dyes and the properties of key intermediates (ligands) from which the dyes are made.