Abstract

Adverse effect of the highly biorecalcitrant compound phenol to the environment iswell established and its concentrations in industrial effluents vary greatly from 2.8 to 6,800 mg/l depending on the source. Fenton process effectively mineralises to CO₂and H₂O but reported works consumed more reagents and require longer reactiontimes. Due to the strong interaction between the several predictor variables in theFenton oxidation, response surface methodology was used to optimise themineralization treatment. Efficient, faster and economical operating conditions for phenol removal were explored by investigating four parameters namely theconcentration ratio of hydrogen peroxide to phenol - ((H₂O₂):(Phenol)), mass  ratioof hydrogen peroxide to ferrous ions - ((H₂O₂):(Fe²⁺)), initial phenol concentration - ([Phenol]_o) and reaction time - (t_r). The optimal TOC % reduction obtained were 35 and 88% for initial phenol concentrations of 100 and 5 mg/l, respectively. Reaction conditions corresponding to this phenol mineralization a reaction time of 20 min atratios of 6 and 15 for [H₂O₂]:[Phenol] and [H₂O₂]:[Fe²⁺], respectively. For mineralisation at 52.5 mg/l phenol concentration, the optimal conditions were 20 min, ratios 10 and 15 for the reaction time, [H₂O₂]:[Phenol] and [H₂O₂]:[Fe²⁺], respectively. The soluble iron content of the analysed supernatant was found to be below the 15 mg/l (the maximum limit allowable for total iron discharges required bycommon regulative subscribed). This indicated that, the Fenton reagents wereutilised during the peroxidation reaction evident from the almost near consumptionof all Fe²⁺ introduced in about 85% of the samples, thus, negating the need forimmobilising the Fe²⁺ catalyst or its removal by post treatment. The work proves that the optimized Fenton process can be potentially used for treatment of any phenol containing wastewater.

Key words: Fenton process, phenol mineralization, response surfacemethodology.

Abbreviation

TOC, Total organic carbon; COD, comparatively values of degradation; CCD, central composite design; OVAT, one variable at a time