Azo dye degradation by recycled waste zero-valent iron powder

In this paper an efficient method for azo dye degradation using an environmentally friendly zero-valent iron powder source is presented (iron particles discarded from a manufacturing process). The influence of several experimental parameters (such as pH, iron mass, particle size, substrate concentration, oxidizing and inert atmospheres) on the ability of zero-valent iron to reduce the chromophoric groups and total organic carbon content of the azo dye Remazol Black B was evaluated. Kinetic studies revealed that the azo degradation by Fe0 appeared to be first-order with respect to substrate, with an observed rate constant (k obs) of 0.153 min-1. Under the optimized operational conditions (pH 3, [Fe] = 5 g L-1, iron particle size < 250 µm), the iron-based process produced net a reduction in color and total organic carbon of about 95% and 70%, respectively. The process was also evaluated for the degradation of textile effluent. The studied process showed good characteristics, which can make it an effective alternative for polluted aquatic system remediation.