Mechanisms of Fenton-like reactions for reduction of refractory compounds.

摘要

Mechanisms of Fenton-like reactions for reduction of refractory compounds were investigated through four different studies on: (1) developing a methodology for detection of hydroxyl radicals (OH·), superoxide anions (O2·−), and hydroperoxide anions (HO2−) using reaction-specific probe molecules; (2) determining the relative generation of OH·, O2·−, and HO2− in modified Fenton's reaction; (3) studying the generation of OH ·, O2·−, and HO2− in Fenton-like reactions catalyzed by nine traces minerals: anatase, bauxite, calcite, cuprite, ilmenite, magnesite, manganite, siderite, and willemite; (4) inspecting the Fenton's catalytic activity of Fe3+ exchanged on three model exchange materials: montmorillonite, kaolinite, and natural soil.; In the first study, oxidants and reductants were generated separately in three systems: (1) dilute hydrogen peroxide (H₂O₂ ) catalyzed by ferrous perchlorate for OH; (2) dissolution of potassium superoxide in water for O₂·− ; (3) decomposition of H₂O₂ at pH 12 for HO₂−. 1-Hexanol, CT, and TNB as probes reacted only with OH·, O₂· −, and HO₂−, respectively. The generation of OH· oxidation products in modified Fenton's reactions catalyzed by ferric sulfate was found not to be fully recovered comparing to the degraded probes.; Based on the results in the first study, the following research was investigated using 1-hexanol, CT, and TNB as the probes for detecting the oxidative and reductive mechanisms in different Fenton-like systems. In modified Fenton's systems catalyzed by ferric sulfate, increasing pH significantly decreased the generation of HO₂− and OH· but O₂·−. The generation of HO₂− generally required high concentrations of H₂O₂.; In trace minerals-catalyzed Fenton-like reactions, the systems catalyzed by cuprite, manganite, and siderite generated OH·. All the systems generated O₂·− except those with anatase. The generation of HO₂− generally required high concentration of H₂O₂, but was not achieved with manganite and siderite even using high concentration of H₂O₂.; All the oxidant and reductants were generated in Fe3+-exchanged montmorillonite-catalyzed Fenton-like system. Only OH· and O₂·− were formed in Fe3+-exchanged kaolinite system. Only O₂ ·− was generated in the Fe3+-exchanged soil system, which was related to natural soil.