Degradation of 2-chlorophenol by the Heterogeneous Photo-Fenton Reaction Using Goethite as Catalyst

GUADALUPE B. ORTIZ DE LA PLATA; ORLANDO M. ALFANO; ALBERTO E. CASSANO

Santa Fe, Argentina

Congreso; LAPRW 2009, 2nd Latin American Pesticide Residue Workshop; 2009

The 2-Chlorophenol (2-CP) is used as germicide/disinfectant and as precursor for pesticides and other chlorophenols. It can also be produced as a byproduct in water disinfection and in pulp bleaching. In the present work the beneficial effect of UVA radiation was studied for the degradation of 2-CP employing the Heterogeneous photo-Fenton reaction using goethite as catalyst. The Fenton reaction has been known for many years and provides a useful tool for pollutant degradation. A subsequent step was the inclusion of UVA radiation to improve yields and facilitate the process economics with the possibility of using solar radiation.However, the question of the post treatment operations was always raised, concerning the separation of dissolved iron compounds existing in the homogeneous operation of the treated aqueous solution. In the last years it has been suggested to use immobilized iron containing compounds in many different forms to overcome this problem. This technology, known as Heterogeneous Fenton, uses hydrogen peroxide and a solid iron carrier and also offers the possibility of using solar radiation as a primary source of energy for a photo Fenton alternative when using goethite as catalyst.In this work the influence of catalyst loading, intensity of irradiation and molar ratio between hydrogen peroxide and contaminant were examined. The work was performed in a cylindrical, perfectly stirred, batch reactor equipped with internal glass heat exchangers connected to a thermostatic bath for controlling temperature and an external insulation made of K-Wool.During the progress of the degradation of 2-CP, the reaction shows an unusual acceleration. This autocatalytic behavior, with stronger tendencies at higher temperatures, implies a completely different behavior than the one typically expected.The autocatalytic performance is successfully explained by the joint action off two factors. The dissolution of small quantities of iron in the homogeneous phase during the course of the reaction, and the autocatalytic contribution of some of the reaction intermediates in the several steps of the reaction.When comparing the values of conversion of 2-CP under different operating conditions, it is possible to conclude that: greater loads of catalyst and higher ratios of hydrogen peroxide to 2-CP concentrations, always implies higher conversions. Upon application of UVA radiation this tendencies are maintained and the addition of irradiation traduces in higher 2-CP conversions and mineralization.