Laboratório de Pesquisas em Eletroquímica, Departamento de Química, Universidade Federal de São Carlos, CP 676, 13560-970 São Carlos-SP, Brazil.
Chemosphere. 2012 Oct;89(6):751-8. doi: 10.1016/j.chemosphere.2012.07.007. Epub 2012 Jul 31.
The degradation of 100 mL of 244 mg L(-1) of the azo dye Acid Red 29 (AR29) has been studied by photoelectro-Fenton (PEF) using an undivided cell containing a boron-doped diamond (BDD) anode and an air-diffusion cathode under UVA irradiation. The effect of current density, concentration of catalytic Fe(2+) and pH on the process was examined. Quick decolorization and almost total mineralization were achieved due to the synergistic action of UVA light and oxidant hydroxyl radicals formed in the bulk from Fenton's reaction between electrogenerated H(2)O(2) at the cathode and added Fe(2+), as well as in the BDD surface from water oxidation. Optimum PEF conditions were found for 0.5-1.0 mM Fe(2+) and pH 3.0. Comparable electro-Fenton (EF) degradations in the dark yielded much poorer mineralization. The decay kinetics of AR29 followed a pseudo-first-order reaction with similar rate for EF and PEF. The azo dye disappeared much more rapidly than solution color, suggesting the formation of colored conjugated products with λ(max) similar to that of AR29. Ion-exclusion HPLC allowed the detection and quantification of tetrahydroxy-p-benzoquinone, oxalic, oxalacetic, tartronic, tartaric, oxamic, malonic and fumaric acids as intermediates in the PEF process. Oxalic acid, accumulated in large extent, was quickly destroyed by the efficient photolysis of Fe(III)-oxalate complexes with UVA light, whereas tartronic and oxamic acids were the most persistent byproducts because of the larger stability of their Fe(III) complexes. The mineralization of the initial N of the azo dye yielded NH(4)(+) ion and NO(3)(-) ion in smaller proportion.
采用 UVA 辐照的无分隔电池，研究了光电-Fenton（PEF）法降解 100 mL 浓度为 244 mg L(-1)的偶氮染料酸性红 29（AR29）。考察了电流密度、催化 Fe(2+)浓度和 pH 对该过程的影响。由于 UVA 光和氧化剂羟基自由基的协同作用，以及在阴极生成的电生 H(2)O(2)与外加 Fe(2+)之间的芬顿反应和在 BDD 表面的水氧化作用在本体中形成的羟基自由基，使得快速脱色和几乎完全矿化得以实现。在 0.5-1.0 mM Fe(2+)和 pH 3.0 时找到了最佳的 PEF 条件。在黑暗中进行可比的电-Fenton（EF）降解，矿化程度要差得多。AR29 的衰减动力学符合准一级反应，EF 和 PEF 的反应速率相似。偶氮染料的消失速度远快于溶液颜色的消失速度，这表明形成了具有与 AR29 相似 λ(max)的有色共轭产物。离子排斥高效液相色谱允许检测和定量 PEF 过程中的四羟基对苯醌、草酸、草酰乙酸、酒石酸、酒石酸、氨甲酰基乙酸、丙二酸和富马酸等中间产物。草酸以很大的程度积累，然后通过 UVA 光有效地光解 Fe(III)-草酸盐络合物迅速被破坏，而酒石酸和氨甲酰基乙酸是最持久的副产物，因为它们的 Fe(III)络合物更稳定。偶氮染料初始 N 的矿化生成 NH(4)(+)离子和 NO(3)(-)离子的比例较小。
