In situ photodecyanation of steel industry wastewater in a pilot scale

Abstract

The photodegradation of cyanide from steel industry wastewater was explored in pilot plant scale using hydrogen peroxide (H₂O₂) under UV irradiation. However, it was interesting to notice that only H₂O₂ or only UV was inefficient to degrade the cyanide from industrial wastewater. There was a synergy between H₂O₂ and UV radiation for the degradation of cyanide. The generated hydroxyl radicals from irradiated H₂O₂ were responsible for the efficient degradation of cyanide. Besides, the dissolved oxygen had a significant role on the degradation process. The photodecyanation rate was faster initially and decreased gradually thereafter ensuring the industrial viability of the process. The dozing rate of H₂O₂ and the UV lamp power were systematically optimized and they were found to be 8 l/m³ and 640 W, respectively. The photodecyanation kinetics was also explored simultaneously and the rate constant was found to be 3.21 × 10^-2 min^-1 at the selected dosage of 8 l/m³. This work demonstrates a scalable and facile decyanation technique from steel plant effluent without generation of toxic by-products.

Keywords: Cyanide; Degradation; Hydroxyl radical; Industrial wastewater; Photodecyanation; Pilot plant.