The anodic oxidation of aqueous solutions containing dimethyl phthalate （DMP） up to 125 mg/L with sodium sulfate （Na2SO4） as supporting electrolyte within the pH range 2.0-10.0 was studied using a one-compartment ...The anodic oxidation of aqueous solutions containing dimethyl phthalate （DMP） up to 125 mg/L with sodium sulfate （Na2SO4） as supporting electrolyte within the pH range 2.0-10.0 was studied using a one-compartment batch reactor employing a boron-doped diamond （BDD） as anode. Electrolyses were carded out at constant current density （1.5-4.5 mA/cm^2）. Complete mineralization was always achieved owing to the great concentration of hydroxyl radical （-OH） generated at the BDD surface. The effects of pH, apparent current density and initial DMP concentration on the degradation rate of DMP, the specific charge required for its total mineralization and mineralization current efficiency were investigated systematically. The mineralization rate of DMP was found to be pH-independent and to increase with increasing applied current density. Results indicated that this electrochemical process was subjected, at least partially, to the mass transfer of organics onto the BDD surface. Kinetic analysis of the temporal change of DMP concentration during electrolysis determined by High Performance Liquid Chromatography （HPLC） revealed that DMP decay under all tested conditions followed a pseudo first-order reaction. Aromatic intermediates and generated carboxylic acids were identified by Gas Chromatography- Mass Spectrometry （GC-MS） and a general pathway for the electrochemical incineration of DMP on BDD was proposed.展开更多
The species transformation and structure variation of fulvic acid (FA) during ozonation were investi- gated in this study. The molecular weight (MW) distribution, the species of intermediate products and the variation...The species transformation and structure variation of fulvic acid (FA) during ozonation were investi- gated in this study. The molecular weight (MW) distribution, the species of intermediate products and the variation of polar functional groups were studied by ultrafiltration, gas chromatography/mass spectrometry (GC/MS) and titration analyses respectively. The average MW of FA decreased signifi- cantly during ozonation. The amount of polar functional groups (carboxylic and phenolic (ph-OH) groups) per unit DOC (mol/kg C) increased with increasing ozonation time. Furthermore, GC/MS ex- periments demonstrated the formation of polar species (e.g., hexadecanoic acid, benzoic acid and oc- tadecanoic alcohol) and less-polar species (e.g., aliphatic hydrocarbons and butanedioic acid, bis(2-methylpropyl) ester). Electron spin resonance (ESR) measurements proved the presence of ·OH radicals in the ozonation system. Based on our experimental results, it appears that the oxidations by ozone molecule and ·OH radicals were responsible for the transformation of organics (FA and its oxi- dation products) during ozonation. These two oxidants showed significant influence on organics transformation and exhibited different mechanisms contributing to these processes.展开更多
基金supported by the National Natural Science Foundation of China (No 50778172) the Funds for Creative Research Groups of China (No 50621804)
文摘The anodic oxidation of aqueous solutions containing dimethyl phthalate （DMP） up to 125 mg/L with sodium sulfate （Na2SO4） as supporting electrolyte within the pH range 2.0-10.0 was studied using a one-compartment batch reactor employing a boron-doped diamond （BDD） as anode. Electrolyses were carded out at constant current density （1.5-4.5 mA/cm^2）. Complete mineralization was always achieved owing to the great concentration of hydroxyl radical （-OH） generated at the BDD surface. The effects of pH, apparent current density and initial DMP concentration on the degradation rate of DMP, the specific charge required for its total mineralization and mineralization current efficiency were investigated systematically. The mineralization rate of DMP was found to be pH-independent and to increase with increasing applied current density. Results indicated that this electrochemical process was subjected, at least partially, to the mass transfer of organics onto the BDD surface. Kinetic analysis of the temporal change of DMP concentration during electrolysis determined by High Performance Liquid Chromatography （HPLC） revealed that DMP decay under all tested conditions followed a pseudo first-order reaction. Aromatic intermediates and generated carboxylic acids were identified by Gas Chromatography- Mass Spectrometry （GC-MS） and a general pathway for the electrochemical incineration of DMP on BDD was proposed.
基金Supported by the National Natural Science Foundation of China (Grant No. 50538090)the Funds for Creative Research Groups of China (Grant No. 50621804)
文摘The species transformation and structure variation of fulvic acid (FA) during ozonation were investi- gated in this study. The molecular weight (MW) distribution, the species of intermediate products and the variation of polar functional groups were studied by ultrafiltration, gas chromatography/mass spectrometry (GC/MS) and titration analyses respectively. The average MW of FA decreased signifi- cantly during ozonation. The amount of polar functional groups (carboxylic and phenolic (ph-OH) groups) per unit DOC (mol/kg C) increased with increasing ozonation time. Furthermore, GC/MS ex- periments demonstrated the formation of polar species (e.g., hexadecanoic acid, benzoic acid and oc- tadecanoic alcohol) and less-polar species (e.g., aliphatic hydrocarbons and butanedioic acid, bis(2-methylpropyl) ester). Electron spin resonance (ESR) measurements proved the presence of ·OH radicals in the ozonation system. Based on our experimental results, it appears that the oxidations by ozone molecule and ·OH radicals were responsible for the transformation of organics (FA and its oxi- dation products) during ozonation. These two oxidants showed significant influence on organics transformation and exhibited different mechanisms contributing to these processes.
