Fenton treatment method

The photoelectro-Fenton method [98] complements the photo-Fenton and electro-Fenton reactions. In the latter, a potential is applied between two electrodes immersed in a solution containing Fenton reagent and the target compound. The recent study of the herbicide 2,4,5-T, performed in an undivided cell with a Pt anode and an 02-diffusion cathode, showed that the photo-electrochemical process was more powerful than the electro-Fenton process, which can yield only about 60-65% of decontamination. The electro-Fenton method provides complete destruction of all reaction intermediates, except oxalic acid, which, as already mentioned, forms stable complexes with Fe3+ that remain in the solution. The fast photodecarboxylation of such Fe(III)-oxalate complexes by UV fight explains the highest oxidative ability of the photoelectro-Fenton treatment, which allows a fast and total mineralization of highly concentrated acidic aqueous solutions of 2,4,5-T at low current and temperature. A similar behavior was found for the herbicide 3,6-dichloro-2-methoxybenzoic acid [99]. 

Bauer R, Fallmann H (1997) The Photo-Fenton Oxidation - A Cheap and Efficient Wastewater Treatment Method, Res. Chem. Intermed. 23, No. 4 341-354. 

AFT was developed as an improvement to die electrochemical Fenton treatment (EFT) method. By separating the anode and cathode half cells, the Fenton reaction could occur at an optimum pH. Since water is being reduced at the cathode and forming hydroxide ions (eq. 3), effluent from the anode and cathode half cells can be mixed after the reaction, providing wastewater close to neutral pH. 

Lignin, a major structural component of wood, was also degraded by a photo-Fenton technique [80]. Although this report demonstrated the ability of the method to degrade lignin, the study did not elaborate on potential applications in the pulp-and-paper industry. The treatment of kraft mill bleaching effluent by Fenton and photo-Fenton methods has been studied, and was reportedly more effective and more economical than several other techniques [81]. 

Chou S, Huang YH, Lee SN, Huang GH, Huang C. Treatment of high strength hexamine-containing wastewater by Electro-Fenton method. Water Res 1999 33 751-759. 

Fem complexes were reported as effective photocatalysts for oxidation of many different organic pollutants, eg alcohols and their derivatives [20,29] organic acids, such as formic [50,53,56], oxalic [37], citric [57], and maleic [58] EDTA [11,20-23], phenol and its derivatives [35, 36, 45,59,60], other aromatic pollutants [38,43,51, 61-64], non-biodegradable azo dyes [40, 41, 48, 55, 59, 65], herbicides [54, 66-70], pesticides [32, 46, 71, 72], insecticides [44], pharmaceuticals and wastewater from medical laboratories [39,47,73], chlorinated solvents [33,74], municipal wastewater [75], and many others [20], The photo-Fenton process was explored as photochemical pre-treatment to improve its biodegradability, especially of biorecalcitrant wastewater from the textile industry [76, 77] the method was also proposed for water disinfection [78,79],... 

One of the most friendly, attractive and economically justified techniques used in homogeneous systems consists of the photo-Fenton method. The photo-Fenton reagent (Fe3+/Fe27H202) is an efficient and cheap reagent, which in a very simple way produces OH radicals for wastewater treatment, due to the fact that iron is a very abundant and non-toxic element and hydrogen peroxide is easy to handle and environmentally safe. Iron in its ferrous and ferric forms acts as a photocatalyst and requires a working pH <4. At higher pH values, iron precipitates as a hydroxide. The Fenton reaction, which usually operates at or near ambient temperature and pressure ... 

The photo-Fenton method of wastewater treatment is developed in two main fields fitting of the usable radiation range to the solar light and immobilization of the photo-Fenton catalyst. 

The feasibility of applying solar radiation as a source of UV-visible radiation has made the photo-Fenton system an economical and competitive process. Within this context an alternative method has been developed based on solar photocatalytic oxidation and natural processes of wastewater treatment [5], as well as sunlight-driven degradations of many compounds, such as EDTA [30], phenols [7,13], pesticides [31-33], surfactants [34], diclofenac [24], formic acid [22], azo-dyes [19], non-biodegradable chlorinated solvents [35], nitroaniline [16], and other organic compounds [21, 36]. 

The great oxidation power of electro-Fenton with BDD has also been confirmed in the comparative treatment of acidic aqueous solutions containing up to 0.9 g dm-3 of the dye Indigo Carmine by electro-Fenton and photoelectro-Fenton using BDD/02 and Pt/02 cells (Flox et al. 2006). The application of both methods... 

---