Photochemical Degradation and Mineralization of Phenol: A Comparative Study

Abstract

In this study, photochemical advanced oxidation processes (AOPs) utilizing the combinations of UV, UV/H2O2, and UV/H2O2/Fe2+ (Photo-Fenton process) were investigated in lab-scale experiments for the degradation and mineralization of phenol. The major parameters investigated were the initial phenol concentration, pH, hydrogen peroxide, and iron doses, and the effect of the presence of radical scavengers (PO4(-3), SO4(-2), and Cl- ions). It was observed that the phenol degradation efficiency decreased with increasing phenol concentration and pH in UV process. Maximum phenol oxidation efficiency for an initial concentration of 100 mg L(-1) and at pH 3 was around 30% in direct photolysis. The efficiency increased to 97% with UV/H2O2 process, however, there was still negligible mineralization (9%) and the required irradiation time was still long (300 min). The results showed that the Photo-Fenton process was the most effective treatment process under acidic conditions. Complete disappearance of 100 mg L(-1) phenol was achieved in 2.5 min and almost complete mineralization (97%) was also possible after 300 min of irradiation. The efficiency was negatively affected from H2O2 in UV/H2O2 process and Fe2+ in Photo-Fenton process over a certain concentration. The highest negative effect was observed with solution containing PO4(-3) ions. Required reaction time for complete disappearance of 100 mg L(-1) phenol increased from 2.5 min for an ion-free solution to 60 min for that containing PO4(-3). The photodegradation of phenol was found to follow the first-order law.

Degradation of Prototype Pesticides Submitted to Conventional Water Treatment Conditions: The Influence of Major Parameters

“…40 h). Similar results were reported by other authors (Bali et al 2003), who also verified that under identical experimental conditions (in an acidic media) organophosphorus pesticides tend to be much more susceptible to degradation than organochlorine varieties. The explanation for this unusual behavior is Degradation of the pesticides, disulfoton (a) and endosulfan sulfate (b), in aqueous solution (at pH 2, 4.5, and 7) monitored as a function of exposure time to the UV radiation.…”

The role of iron on the degradation and mineralization of organic compounds using conventional Fenton and photo-Fenton processes

“…These values have been reported optimal for the treatment of aromatics by Fenton and photo-Fenton processes [11][12][13]16,17,26]. Furthermore, these values of pH and temperature have been widely applied as optimal for the Fenton or photo-Fenton treatment of different substances and wastewaters [11][12][13][14][16][17][18][19][20]22,23,[26][27][28][29]. In order to perform proper comparisons, the same conditions of initial COD and reagents concentrations have been applied in all the treatments.…”

“…Several studies have reported the successful photo-Fenton treatment of various organic chemicals (e.g. phenol [1,11,26], nitrophenols [17], p-chlorophenol [27], EDTA [18] and acetic acid [23]), herbicides [28], and wastewaters (e.g. landfill leachate [22] and paper mill wastewaters [29]), showing that the treatment efficiency was better than when applying the conventional Fenton process without the participation of UV light.…”

Mathematical modelling of phenol photooxidation: Kinetics of the process toxicity

“…Degradation of phenol by different AOPs, including UVbased processes, has been reported in the literature [8][9][10][11][12][13][14]. It is well known that phenol oxidation treatments lead to the generation of highly toxic intermediate products [1], and there is scarcity of toxicity and environmental impact studies.…”