Department of Civil and Environmental Engineering, William & Cloy Codiga Resource Recovery Center, Center for Sustainable Development & Global Competitiveness, Stanford University, Stanford, CA 94305-4020, USA; Key Laboratory for Heavy Metal Pollution Control and Reutilization, School of Environment and Energy, Peking University Shenzhen Graduate School, Shenzhen 518055, China; Institute of New Energy Technology, Tsinghua University, Beijing 100084, China.
Department of Civil and Environmental Engineering, William & Cloy Codiga Resource Recovery Center, Center for Sustainable Development & Global Competitiveness, Stanford University, Stanford, CA 94305-4020, USA.
J Environ Sci (China). 2019 Nov;85:156-167. doi: 10.1016/j.jes.2019.05.028. Epub 2019 Jun 12.
This study evaluated uranium sequestration performance in iron-rich (30 g/kg) sediment via bioreduction followed by reoxidation. Field tests (1383 days) at Oak Ridge, Tennessee demonstrated that uranium contents in sediments increased after bioreduced sediments were re-exposed to nitrate and oxygen in contaminated groundwater. Bioreduction of contaminated sediments (1200 mg/kg U) with ethanol in microcosm reduced aqueous U from 0.37 to 0.023 mg/L. Aliquots of the bioreduced sediment were reoxidized with O, HO, and NaNO, respectively, over 285 days, resulting in aqueous U of 0.024, 1.58 and 14.4 mg/L at pH 6.30, 6.63 and 7.62, respectively. The source- and the three reoxidized sediments showed different desorption and adsorption behaviors of U, but all fit a Freundlich model. The adsorption capacities increased sharply at pH 4.5 to 5.5, plateaued at pH 5.5 to 7.0, then decreased sharply as pH increased from 7.0 to 8.0. The O-reoxidized sediment retained a lower desorption efficiency at pH over 6.0. The NO-reoxidized sediment exhibited higher adsorption capacity at pH 5.5 to 6.0. The pH-dependent adsorption onto Fe(III) oxides and formation of U coated particles and precipitates resulted in U sequestration, and bioreduction followed by reoxidation can enhance the U sequestration in sediment.
本研究通过生物还原后再氧化的方式评估了富含铁（30g/kg）沉积物中铀的固定性能。田纳西州橡树岭的野外试验（1383 天）表明，生物还原后的沉积物重新暴露于污染地下水中的硝酸盐和氧气后，沉积物中的铀含量增加。微宇宙中用乙醇还原污染沉积物（1200mg/kg U）可将水中 U 的浓度从 0.37mg/L 降低至 0.023mg/L。将生物还原的沉积物等分试样分别用 O、HO 和 NaNO 再氧化 285 天，结果在 pH 6.30、6.63 和 7.62 时，水中 U 的浓度分别为 0.024、1.58 和 14.4mg/L。原始沉积物和三种再氧化沉积物的 U 解吸和吸附行为不同，但均符合 Freundlich 模型。在 pH 4.5 至 5.5 之间，吸附容量急剧增加，在 pH 5.5 至 7.0 之间达到平台期，然后随着 pH 从 7.0 增加到 8.0 急剧下降。在 pH 高于 6.0 时，O 再氧化沉积物的解吸效率较低。NO 再氧化沉积物在 pH 5.5 至 6.0 之间具有较高的吸附容量。吸附到 Fe(III)氧化物上的 pH 依赖性和 U 包裹颗粒和沉淀物的形成导致了 U 的固定，生物还原后再氧化可以增强沉积物中 U 的固定。
