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 8l/m3 and 640W, respectively. The photodecyanation kinetics was also explored simultaneously and the rate constant was found to be 3.21 × 10-2min-1 at the selected dosage of 8l/m3. This work demonstrates a scalable and facile decyanation technique from steel plant effluent without generation of toxic by-products.