缓释铁源耦合气体扩散电极强化电芬顿降解环丙沙星

Enhanced degradation of the antibiotic ciprofloxacin by electro-Fenton using a sustained-release iron source coupled with a gas diffusion cathode

气体扩散电极(GDE)气液固三相界面可高效产生H_(2)O_(2),但对铁离子还原能力较弱。针对这一问题,本文构建了一种基于缓释铁源的电芬顿体系(SRIS-EF),通过引入柱状铁棒与GDE电极协同作用加强体系的氧化能力。该体系旨在改进Fe^(2+)投加方式,通过电场与溶液酸碱度协同作用持续生成Fe^(2+),提高羟基自由基(·OH)的生成和利用率,加速污染物的降解与矿化。以100 mg·L^(-1)环丙沙星(CIP)为目标物,通过定量分析体系内生成的主要活性氧化物质(ROS)表征其氧化能力,结果表明SRIS-EF能够持续生成更高浓度的·OH。对比了不同体系对CIP的矿化能力,发现SRIS-EF的TOC矿化率与常规EF相比提高了12.1%。此外,考察了SRIS-EF体系中柱状铁棒面积、初始pH、电流密度等因素对降解效能的影响,得出了SRIS-EF体系的最佳条件为:铁棒面积2.89 cm^(2),初始pH 3.00,电流密度30 mA·cm^(-2),在此条件下反应60 min即可被完全去除CIP,处理360 min后TOC去除率可达47.3%。还对体系中无机离子和小分子有机酸的生成情况进行了测定,检测出CIP内的N和F主要以NH_(4)^(+)、NO_(3)^(-)和F-形式释放,降解过程中生成了草酸、甲酸、富马酸和丙二酸等四种短链羧酸,其中甲酸浓度较高。研究证实了SRIS-EF体系在降解水中难降解有机污染物方面优异的氧化性能。

The electro-Fenton(EF) using the gas diffusion electrode(GDE) can produce H_(2)O_(2)efficiently at the gas-liquid-solid three-phase interface, but its reduction ability for Fe3+is very weak. A novel EF process of SRIS-EF based on slow-release iron source(SRIS) was constructed, in which the oxidation capacity was enhanced by the synergistic effect of the columnar iron rod and GDE electrode. In SRIS-EF, SRIS can continuously generate Fe^(2+)by the coeffect of the electric field and the acidity of solution, the generation and utilization of hydroxyl radicals(·OH) are enhanced, the degradation and mineralization of pollutants were accelerated accordingly. The oxidative capacity was characterized by quantifying the major reactive oxygen species(ROS) generated during treating 100 mg·L^(-1)ciprofloxacin(CIP). The results showed that SRIS-EF could consistently generate more ·OH than EF alone. The mineralization ability of different processes was also compared, the TOC removal rate of SRIS-EF process was 12.1% higher than that of the conventional EF process. In addition, the effects of iron rod area, initial pH and current density of SRIS-EF were studied. The optimal conditions were determined as follows: the area of iron rod was 2.89 cm^(2), the initial pH was 3.00, and the current density was 30 mA·cm^(-2). Under the optimal condition, CIP was completely degraded within 60 min,and 47.3% TOC was removed after 360 min treatment. The generations of inorganic ions and organic acids in different processes were measured. The N and F atoms of CIP were mainly released as NH_(4)^(+), NO_(3)^(-)and F-. Four short-chain carboxylic acids: oxalic acid, formic acid, fumaric acid and malonic acid were detected, the higher concentration of formic acid was generated in SRIS-EF process. The study verified the excellent oxidation performance of SRIS-EF process on the degradation of refractory organic pollutants in water.