The role of ferrous ion in Fenton and photo-Fenton processes for the degradation of phenol.

The efficiency of different Fenton-related oxidative processes such as Fenton, solar-Fenton and UV-Fenton were examined using phenol as a model compound in simulated and industrial wastewater. A batch study was conducted to optimize parameters like pH, hydrogen peroxide concentration and ferrous ion concentration governing the Fenton process. At optimum conditions, different Fenton-related processes were compared for the degradation of phenol. Increased degradation and mineralisation efficiency were observed in photo-Fenton processes as compared to conventional Fenton process. The maximum mineralising efficiency for phenol with Fenton, solar and UV-Fenton processes were 41%, 96% and 97% respectively. In Fenton process, carboxylic acids like acetic acid and oxalic acid were formed as end products during the degradation of phenol while in photo-Fenton processes, both these ions were identified during the early stages of phenol degradation and were oxidized almost completely at 120 min of the reaction time. In photo-Fenton processes (solar and UV light) complete degradation were observed with 0.4 mM of Fe2+ catalyst as compared to 0.8 mM of Fe2+ in conventional Fenton process. In Fenton and solar-Fenton processes, an iron reusability study was performed to minimize the amount of iron used in treatment process. The efficacy of Fenton and solar-Fenton processes was applied to effluent from phenol resin-manufacturing unit for the removal and mineralisation of phenol.