Pickling Waste as an Inexpensive Iron Source for Fenton Oxidation of Synthetic Dye Bath Waste

A simple, low cost, highly effective, and useful Fenton oxidation treatment of synthetic dye bath waste with pickling liquor as a source of iron (Fe²⁺ catalyst) is reported. Optimizations of contact time, Fe²⁺ and H₂O₂ doses are carried out. Oxidative de‐colorization and degradation of Reactive Blue 4 and Reactive Orange 16 was measured in terms of decrease in absorbance at their wavelength of maximum absorption (RB4, 599 nm; and RO16, 493 nm) and also as reduction in chemical oxygen demand (COD). Approximately, 62% COD was removed in 2 h at optimized doses of Fe²⁺ (8.95 mM) and H₂O₂ (61.8 mM) by using pickling waste as a source of Fe²⁺ catalyst. Similar performance efficiency was observed when neat FeSO₄ was used as a source of Fe²⁺, indicating that pickling liquor can be a low cost source of Fe²⁺ to treat synthetic dye bath waste by Fenton method.