Keywords: chemical oxidation, Fenton oxidation, spent caustic, coagulation, refinery waste, pre–treatment, total COD, chemical oxygen demand, total phenols, sludge, wastewater treatment
Pre–treatment of refinery spent caustic by Fenton's reaction
Experimental results for applying Fenton oxidation as a pre–treatment method for spent caustic are presented. A combination of dilution and Fenton's reaction is proposed as a method for reduction of total COD and total phenols in spent caustics. This approach was used to obtain a decrease in total phenols from 5,200 mg/L to less than 130 mg/L. The greatest removal occurred within a pH range of 2.7–6, with a (Fe3+/H2O2) mass ratio of 1 : 3, Fe3+ concentration of 2.85 g/L and a stoichiometric w/w H2O2/COD ratio of 0.3. Under these conditions, and over 30 min reaction time, 99.5% of total phenols and 95.5% of COD were removed, while sulphides and mercaptans decreased to <0.1 mg/L.