Elimination of phenol and aromatic compounds by zero valent iron and EDTA at low temperature and atmospheric pressure

This work deals with a new abiotic oxidation process designed as a suitable pre-treatment step within a biological depuration of wastewater containing phenol or its derivatives (o-cresol, 2-chlorophenol and p-nitrophenol) or aniline. The reaction was carried out in a stirred tank reactor at 20 °C and atmospheric pressure in presence of the organic compound, 150 mg l−1, zero valent iron particles (10 g), ethylenediamine tetraacetic acid (EDTA, 101 mg l−1) and air. The experimental results show that 85% of phenol conversion can be achieved after 360 min. 2-Chlorophenol was found to be more easily degradable and it is completely eliminated after 300 min. The oxidation of o-cresol and aniline behaved more closely to phenol obtaining after 360 min 70% and 68% of conversion respectively. p-Nitrophenol was a very refractory compound, giving only 28% of conversion after 360 min. Moreover, the influence of some operating variables was studied over the following ranges: temperature from 20 to 50 °C, initial phenol concentration from 150 to 1000 mg l−1, EDTA concentration from 50 to 200 mg l−1 and iron particles from 5 to 20 g. As expected, temperature strongly enhances phenol conversion. Also, an increase of the catalyst to phenol ratio or the iron or EDTA to phenol ratio improves the reaction rate. A preliminary kinetic analysis of the data shown that the rate of phenol disappearance is not first order with respect to the phenol.