On the performance of HOCl/Fe2+, HOCl/Fe2+/UVA, and HOCl/UVC processes using in situ electrogenerated active chlorine to mineralize the herbicide picloram

Abstract

Four different treatment methods based on the HO% production were assessed to oxidize and mineralize the herbicide picloram (PCL), which is considered very toxic and so is a potential contaminant of surface and ground water. The processes based on the Fenton type (homolysis reaction of HOCl by Fe 2+ ions) and photo-Fenton type reaction (using a 9 W UVA light) with in situ electrogenerated HOCl species, using a commercial DSA ® anode in the presence of Cl − ions, led to poor mineralization performances in comparison to the HOCl/UVC process. In that case, the homolysis reaction of HOCl mediated by a 5 or 9 W UVC light resulted in almost complete removal of the organic load within 12 h of treatment, from acidic to neutral solutions and using 1 g L −1 of NaCl concentration after optimization of the experimental conditions. When the HOCl/UVC process using a 5 W UVC light is compared to the electrochemical method using a boron-doped diamond anode (electrochemical/BDD), the oxidation and mineralization rates of the HOCl/UVC process were always superior, with ∼95% removal of total organic carbon (TOC) after 12 h treatment. The energy consumption per unit mass of removed TOC remained around 4 and 8 kW h g −1 for the HOCl/UVC and electrochemical/BDD treatment processes after 90% removal of TOC, respectively, even considering the energy consumption of the UVC lamp. In the final treatment stages, high CO 2 conversions were obtained using both methods, as the generated intermediates were almost completely eliminated. Finally, the HOCl/UVC process is a reasonable option to treat solutions contaminated with organic pollutants as the common problems associated with the Fenton based (acidic solution, Fe 2+ ion recovery, generation of H 2 O 2) and electrochemical/BDD (mass transport) processes can be readily circumvented.

Fe2+/HClO Reaction Produces FeIVO2+: An Enhanced Advanced Oxidation Process

“…27 Because of the similarity in the structures of H 2 O 2 and HClO (both contain the −OH group), it has been considered that the reaction between Fe 2+ and HClO occurs in the same manner as that between Fe 2+ and H 2 O 2 , and it is thus labeled a Fenton-like reaction, as proposed by Candeias et al in 1994. 42 It was thought that the HClO molecule undergoes a oneelectron activation by Fe 2+ to produce • OH and Cl − , 43 analogous to the one-electron activation of H 2 O 2 by Fe 2+ . This radical-involved pathway may not occur in the case of HClO activation, as evidenced by a set of reference experiments in which a mild reducing agent (e.g., NH Thermodynamic DFT Calculations on the Fe 2+ /HClO Reaction.…”

Electrochemical Technologies to Decrease the Chemical Risk of Hospital Wastewater and Urine

“…Solar photo-Fenton was applied using three Fe 2+ additions approach (5 mg L −1 of Fe 2+ each, with an initial H2O2 concentration of 150 mg L −1 ) achieving 58% degradation in 120 min. For the adsorption The Fenton process can be enhanced by the irradiation of UV light (photo-Fenton) since it promotes the massive production of hydroxyl radicals from the photoactivation of both hydrogen peroxide and catalyst, depending on the wavelength applied [62][63][64]. Papoutsakis et al [48] studied the treatment of urine polluted with iohexol (600-6000 mg dm −3 ) by photo-Fenton under simulated solar light.…”

PELÍCULAS DELGADAS DE ZnSe MODIFICADAS CON Fe2+ Y Cu2+ PARA LA FOTOELECTROCATÁLISIS DE ANARANJADO DE METILO CON ESPECIES ACTIVAS DE CLORO

“…Además, también se podría producir una reacción tipo-Fenton, ec. 4 y 5, entre el Fe de la película y el hipoclorito en solución 12 .…”