School of Life and Environmental Science, Wenzhou University, Wenzhou, 325035, China.
Key Laboratory of Surficial Geochemistry, Ministry of Education, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023, China.
Environ Sci Pollut Res Int. 2019 Mar;26(9):8516-8524. doi: 10.1007/s11356-018-04091-0. Epub 2019 Jan 7.
Most prevailing processes are incapable of removing Cr(III)-organic complexes efficiently and facing the problem of in-process formation of highly toxic Cr(VI) based on oxidation. The efficient decomplexation of Cr(III) complexes and simultaneous abatement of Cr with low Cr(VI) accumulation would be desirable in treatment of Cr(III)-complexed wastewater. Here, we found efficient degradation of Cr(III)-EDTA and simultaneous removal of Cr by forming CrO precipitate from simulated solution as well as an electroplating effluent under UV irradiation. The results showed a complete degradation of Cr(III)-EDTA after reaction time of 60 min and 70-80% of TOC mineralization within 180 min as well. About 90% of Cr(III) precipitated as CrO simultaneously, with the residual total Cr below 1.5 mg/L. The degradation of Cr(III)-EDTA was a stepwise de-acetate group process, as proven by the obvious attenuation of peaks related to carboxyl groups and C-C bond from FT-IR spectra of Cr(III)-EDTA and significant mineralization of TOC after UV irradiation. Based on negligible accumulation of Cr(VI) (less than 0.1 mg/L) under N-sparged condition, the C-centered radicals from the β-fragmentation of O-centered radicals formed by photo-induced ligand-to-metal charge transfer were responsible for the in situ reduction of intermediate Cr(VI), resulting in the low accumulation of Cr(VI). The addition of 20 mg/L Fe was capable of removing the remaining Cr(VI) and total Cr, with Cr(VI) and total Cr less than 0.1 and 1.0 mg/L, respectively. Moreover, the photo-oxidation process combined with Fe addition were efficient in removing other Cr(III) complexes, such as Cr(III)-citrate and those from a realistic electroplating effluent. We believe that this study would provide an alternative option for efficient degradation of Cr(III) complexes and simultaneous abatement of Cr from contaminated water.
大多数常见的处理方法都无法有效地去除 Cr(III)-有机络合物，并面临基于氧化形成高毒性 Cr(VI)的问题。在处理 Cr(III)-络合废水时，理想的情况是有效地使 Cr(III)络合物去络合，并同时去除 Cr，同时避免 Cr(VI)的积累。在这里，我们发现，在模拟溶液以及在 UV 照射下的电镀废水中，Cr(III)-EDTA 的高效降解以及通过形成 CrO 沉淀物同时去除 Cr 是可行的。结果表明，反应 60 分钟后，Cr(III)-EDTA 完全降解，180 分钟内 TOC 矿化率达到 70-80%。同时，约 90%的 Cr(III)沉淀为 CrO，残留的总 Cr 低于 1.5mg/L。Cr(III)-EDTA 的降解是一个逐步去乙酰基的过程，这可以从 Cr(III)-EDTA 的 FT-IR 光谱中与羧基和 C-C 键相关的峰明显减弱以及 UV 照射后 TOC 的显著矿化得到证明。在氮气曝气条件下，Cr(VI)的积累可以忽略不计（低于 0.1mg/L），这表明光诱导的配体到金属电荷转移产生的 O 中心自由基的 β-断裂形成的 C 中心自由基负责中间 Cr(VI)的原位还原，从而导致 Cr(VI)的低积累。添加 20mg/L 的 Fe 能够去除剩余的 Cr(VI)和总 Cr，分别使 Cr(VI)和总 Cr 低于 0.1 和 1.0mg/L。此外，光氧化过程结合 Fe 的添加能够有效地去除其他 Cr(III)络合物，如 Cr(III)-柠檬酸盐和来自实际电镀废水的络合物。我们相信，这项研究将为有效去除受污染水中的 Cr(III)络合物并同时去除 Cr 提供一种替代选择。
