Azo dyes are extensively used in textile dying processes and are characterized by extreme resistance to biodegradation and consequently persistence during conventional wastewater treatment processes. In this work the reductive degradation of azo dyes was studied using zero-valent iron. At optimized experimental conditions (pH 7 and 10 g of commercial iron wool) complete decolorization of the model dye (reactive black 5) was afforded in a continuous system operating with hydraulic retention time of 6 min. At these conditions the released total soluble iron reaches a concentration compatible with the limits imposed by the current Brazilian legislation (12 mg L-1). That is a very promising result, mainly taking into account the high recalcitrant character of azo dyes and the simplicity of the proposed system.
Zero-valent iron; azo-dyes; decolorization; treatment
