Treatment of a Mixture of Chloromethoxyphenols in Hypochlorite Medium by Electrochemical AOPs as an Alternative for the
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Treatment of a Mixture of Chloromethoxyphenols in Hypochlorite Medium by Electrochemical AOPs as an Alternative for the Remediation of Pulp and Paper Mill Process Waters Claudio Salazar & Ignasi Sirés & Claudio A. Zaror & Enric Brillas
# Springer Science+Business Media New York 2013
Abstract Here, 100 mg L−1 of dissolved organic carbon of aromatics including chloromethoxyphenols were prepared by exposition of a mixture of guaiacol, syringol, and vanillin in 200 mM NaClO at pH 3.0 and 25 °C for 14 h and further degraded by electrochemical advanced oxidation processes (EAOPs) like anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF), and photoelectro-Fenton (PEF). Electrolyses were performed with a cell containing either a Pt or boron-doped diamond (BDD) anode and an air-diffusion cathode at constant current density. Oxidants were hydroxyl radicals (•OH) formed at the anode surface from water oxidation and in the bulk from Fenton’s reaction between added Fe2+ and H2O2 generated at the cathode, as well as active chlorine species produced from the anodic oxidation of HClO. Oxychlorine ions like ClO3− using Pt and ClO3− +ClO4− using BDD were detected in the electrolyzed solutions. A poor mineralization was found using the Pt/air-diffusion cell, with increasing relative oxidation ability in the sequence AO-H2O2 97 % purity) were supplied by Sigma-Aldrich. Sodium hypochlorite solution (14 % active chlorine), heptahydrate ferrous sulfate, potassium chlorate, and lithium perchlorate were of analytical grade supplied by Prolabo, Fluka, and Panreac. Solutions were prepared with high-purity water from a Millipore Milli-Q system with resistivity >18 MΩ cm at 25 °C and their pH was adjusted to 3.0 with analyticalgrade phosphoric acid purchased from Panreac. All the other chemicals used were either of HPLC or analytical grade purchased from Panreac, Merck, and Avocado. Preparation of the Mixture of Chlorinated Pollutants Based on the work of Michalowicz et al. [44], who analyzed the efficiency of chlorination of several aromatic compounds exposed to sodium hypochlorite, the following procedure was used to obtain the chloromethoxyphenols solutions. Guaiacol, syringol, and vanillin were weighted and gently mixed with 100 mL of 200 mM NaClO at pH 3.0 and 25 °C for 14 h using a magnetic stirrer. At the beginning, the solutions became dark brown, but pH adjustment with H3PO4 left them pale yellow. Once completed the reaction, the resulting solution with 100 mg L−1 of initial dissolved organic carbon (DOC) was used for the electrolytic treatments. A freshly synthesized mixture was prepared for each new experiment. Synthetic solutions from 100 and 400 mM NaClO were prepared in a similar way. Electrolytic Systems All the electrolytic trials were conducted in an open and undivided cylindrical glass cell of 150 mL capacity with a double jacket for circulation of external thermostated water to regulate the solution temperature at 25 °C. The anode was either a 3-cm2 Pt sheet of 99.99 % purity supplied by SEMPSA (Barce
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