Removal of the X-ray contrast media diatrizoate by electrochemical reduction and oxidation.
Removal of the X-ray contrast media diatrizoate by electrochemical reduction and oxidation.
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DOI：
10.1021/es403410p
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发表时间：
2013-11
影响因子：
11.4
通讯作者：
J. Radjenovic;V. Flexer;B. Donose;D. Sedlak;J. Keller
中科院分区：
文献类型：
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作者：
J. Radjenovic;V. Flexer;B. Donose;D. Sedlak;J. Keller
由于碘化x射线造影剂（ICM）对废水的生物处理具有抗性，在城市废水出水中检测到浓度相对较高（即高达100 μg L(-1)），医院是其主要来源。为了提供一种降低废水中ICM浓度的新方法，研究了三维石墨毡和掺杂纳米钯的石墨毡的电化学还原，作为常见ICM异质体的脱碘手段。钯纳米粒子的存在显著地增强了对邻苯三甲酸酯的去除，使其完全脱碘为3,5-二乙酰氨基苯甲酸。当该系统用于处理医院废水时，非水合水合物减少了，但由于与基质中的溶质发生竞争反应，电化学还原的程度降低了。将三羧酸酯电化学还原为3,5-二乙酰氨基苯甲酸，采用掺杂硼金刚石（BDD）阳极进行电化学氧化。3,5-二乙酰氨基苯甲酸从溶液中消失的速度与邻苯二甲酸相似，但比母体化合物更容易矿化。当电化学还原和氧化耦合在三室反应器中以连续模式运行时，在-1.7 V vs SHE的阴极电位下实现了完全脱碘，释放的碘离子在中央室中以80%的效率电渗析。由此产生的BDD阳极电位（即+3.4-3.5 V vs SHE）使还原步骤的产物能够有效氧化。在处理医院废水时，其他阴离子（如氯化物）的存在可能是导致I（-）分离效率下降的原因。与氧化降解相结合的还原性脱碘提供了优于氧化处理方法的优点，因为它不产生稳定的碘化中间体。然而，该工艺必须针对医院废水中遇到的条件进行进一步优化，以提高电氧化步骤之前卤化物离子的分离效率。
Due to their resistance to biological wastewater treatment, iodinated X-ray contrast media (ICM) have been detected in municipal wastewater effluents at relatively high concentrations (i.e., up to 100 μg L(-1)), with hospitals serving as their main source. To provide a new approach for reducing the concentrations of ICMs in wastewater, electrochemical reduction at three-dimensional graphite felt and graphite felt doped with palladium nanoparticles was examined as a means for deiodination of the common ICM diatrizoate. The presence of palladium nanoparticles significantly enhanced the removal of diatrizoate and enabled its complete deiodination to 3,5-diacetamidobenzoic acid. When the system was employed in the treatment of hospital wastewater, diatrizoate was reduced, but the extent of electrochemical reduction decreased as a result of competing reactions with solutes in the matrix. Following electrochemical reduction of diatrizoate to 3,5-diacetamidobenzoic acid, electrochemical oxidation with boron-doped diamond (BDD) anodes was employed. 3,5-Diacetamidobenzoic acid disappeared from solution at a rate that was similar to that of diatrizoate, but it was more readily mineralized than the parent compound. When electrochemical reduction and oxidation were coupled in a three-compartment reactor operated in a continuous mode, complete deiodination of diatrizoate was achieved at an applied cathode potential of -1.7 V vs SHE, with the released iodide ions electrodialyzed in a central compartment with 80% efficiency. The resulting BDD anode potential (i.e., +3.4-3.5 V vs SHE) enabled efficient oxidation of the products of the reductive step. The presence of other anions (e.g., chloride) was likely responsible for a decrease in I(-) separation efficiency when hospital wastewater was treated. Reductive deiodination combined with oxidative degradation provides benefits over oxidative treatment methods because it does not produce stable iodinated intermediates. Nevertheless, the process must be further optimized for the conditions encountered in hospital wastewater to improve the separation efficiency of halide ions prior to the electrooxidation step.