Uranium Removal from Groundwater by Permeable Reactive Barrier with Zero-Valent Iron and Organic Carbon Mixtures: Laboratory and Field Studies

Abstract

Zhovty Vody city, located in south-central Ukraine, has long been an important center for the Ukrainian uranium and iron industries. Uranium and iron mining and processing activities during the Cold War resulted in poorly managed sources of radionuclides and heavy metals. Widespread groundwater and surface water contamination has occurred, which creates a significant risk to drinking water supplies. Hydrogeologic and geochemical conditions near large uranium mine tailings storage facility (TSF) were characterized to provide data to locate, design and install a permeable reactive barrier (PRB) to treat groundwater contaminated by leachate infiltrating from the TSF. The effectiveness of three different permeable reactive materials was investigated: zero-valent iron (ZVI) for reduction, sorption, and precipitation of redox-sensitive oxyanions; phosphate material to transform dissolved metals to less soluble phases; and organic carbon substrates to promote bioremediation processes. Batch and column experiments with Zhovty Vody site groundwater were conducted to evaluate reactivity of the materials. Reaction rates, residence time and comparison with site-specific clean-up standards were determined. Results of the study demonstrate the effectiveness of the use of the PRB for ground water protection near uranium mine TSF. The greatest decrease was obtained using ZVI-based reactive media and the combined media of ZVI/phosphate/organic carbon combinations.

Influence of mechanochemical and microwave modification on ion-exchange properties of tin dioxide with respect to uranyl ions

“…(i) sorption of U (VI) ions under optimal pH 5.4 in the absence of background; (ii) pH 5.4 but in the presence of NaCl; (iii) pH 5.4 in the absence of background but in the presence of Cs(I) and Sr(II) cations which often accompany the U (VI) ions when liquid radioactive wastes are cleaned; (iv) sorption of U (VI) ions at pH 3.0, which corresponds to acid mine waters and acid radioactive wastes, in the absence of background but in the presence of Cs + and Sr 2+ cations; The third and fourth experimental solutions ((iii) and (iv)) contained a mixture of U (VI), Cs (I) and Sr (II) ions in the quantities of 1:0.2:0.2 mEq/L, respectively. (v) the pH value was 8.2 during sorption of ions U (VI) on the background of 0.1 M NaHCO 3 ; these conditions corresponds to composition of "block" waters of the Chornobyl Nuclear Power Plant (ChNPP) and waste in storage of tailings (Kornilovych et al 2018); under these conditions U (VI) is present in the solution as anionic carbonate complexes (Odintsov et al 2009).…”

Adsorption of U(VI)-CO3/Ca-U(VI)-CO3 by Amidoxime-functionalized Hydrothermal Carbon

“…Rn 和 210 Po 等衰变子体具有化学毒性和放射性毒 性, 如果在环境中大量累积, 将会对人类的生存和 发展构成潜在的威胁 [1][2][3] 。因此, 铀污染土壤和地下 水的治理是有核国家所面临的最具挑战性的问题 之一 [4][5][6] 。 目前, 土壤和地下水修复技术主要有植物修 复 [7] 、物理修复 [8] 、化学修复 [9] 、微生物修复 [10] 和 可渗透性反应墙(PRB)技术 [11] 。其中, PRB 技术具有 高效、运行简单和管理费用低等优点, 弥补了传统 修复手段的不足, 且适用于大范围污染场区土壤及 地下水的修复 [12][13] 。PRB 是由充满介质的可渗透隔 膜组成, 可以垂直拦截受污染的地下水流。当水通 过自然流动过程流经 PRB 时, 污染物会被介质捕获 或降解, 通过物理、化学、生物或混合过程对含水 层进行修复 [14][15] 。常用的介质有水热碳、活性炭和 零价铁等 [15][16][17] 。其中, 水热碳材料具有制备方法简 单、原料易得、合成条件温和及耗时短等优点。但 水热碳材料表面官能团含量低且单一, 对铀的吸附 容量小 [18] , 不能直接用作 PRB 的介质。 铀 在 污 染 土 壤 和 地 下 水 中 以 U(VI)-CO 3 / Ca-U(VI)-CO 3 的形态存在, 与海水中铀的赋存形态 相似 [19][20] 。偕胺肟基团能够提高吸附材料表面的活 性位点, 降低吸附材料与海水中铀酰络合阴离子之 间的静电斥力, 通过偕胺肟基团中 N 原子和 O 原子 与铀酰离子络合, 增强偕胺肟基团与铀酰离子的亲 和性, 从而提高吸附材料的吸附容量 [21] 。基于此, 偕 胺肟改性材料有望作为 PRB 介质治理铀污染土壤 或地下水。本课题组以可溶性淀粉为原料, 在硝酸 铈铵催化作用下, 将丙烯腈开环接枝到淀粉分子上, 通过水热反应和盐酸羟胺还原成功制备偕胺肟化水 热碳球(AO-HTC), 在 pH=5 时, AO-HTC 吸附铀的 饱和容量 724.6 mg•g -1 , pH=1~5 的范围内, 吸附铀 的选择性高于 60% [22] 。 本工作采用静态吸附和动态吸附实验相结合, 重点研究溶液 pH、 碳酸根和钙离子浓度对 AO-HTC 吸附铀性能的影响, 利用 Yoon-Nelson 和 Thomas 模 型研究 AO-HTC 对铀的动态吸附过程, 进一步探讨 AO-HTC 吸附土壤和地下水环境中铀的可行性。 1 实验方法…”

Adsorption of U(VI) onto Amidoxime-functionalized Hydrothermal Carbon in the Presence of Ca-U(VI)-CO3 Complexes

“…Nowadays, the soil has been polluted to varying degrees around the uranium smelter and the tailings pond, causing serious damage to the surrounding environment, and the groundwater has been seriously threatened with the migration of nuclide in the soil [1,2] . Groundwater is an important resource for human being survival, it is a limited ecological resource that only accounts for a small part of the total water resources.…”