National Engineering Technology Research Center for Desert-Oasis Ecological Construction, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, 818 South Beijing Road, Urumqi, 830011, China; Xin Jiang Key Laboratory of Environmental Pollution and Bioremediation, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, 830011, China.
J Environ Radioact. 2024 Oct;279:107523. doi: 10.1016/j.jenvrad.2024.107523. Epub 2024 Sep 1.
Coal fly ash (CFA) is an essential raw material in brickmaking industry worldwide. There are some coal mines with a relatively high content of uranium (U) in the Xinjiang region of China that are yet understudied. The CFA from these coal mines poses substantial environmental risks due to the concentrated uranium amount after coal burning. In this paper, we demonstrated a calcifying ureolytic bacterium Halomonas sp. SBC20 for its biocementation of U in CFA based on microbially induced calcite precipitation (MICP). Rectangle-shaped CFA bricks were made from CFA using bacterial cells, and an electric testing machine tested their compressive strength. U distribution pattern and immobility against rainfall runoff were carefully examined by a five-stage U sequential extraction method and a leaching column test. The microstructural changes in CFA bricks were characterized by FTIR and SEM-EDS methods. The results showed that the compressive strength of CFA bricks after being cultivated by bacterial cells increased considerably compared to control specimens. U mobility was significantly decreased in the exchangeable fraction, while the U content was markedly increased in the carbonate-bound fraction after biocementation. Much less U was released in the leaching column test after the treatment with bacterial cells. The FTIR and SEM-EDX methods confirmed the formation of carbonate precipitates and the incorporation of U into the calcite surfaces, obstructing the release of U into the surrounding environments. The technology provides an effective and economical treatment of U-contaminated CFA, which comes from coal mines with high uranium content in the Xinjiang region, even globally.
煤矸石（CFA）是全球砖制造业的重要原材料。中国新疆地区的一些煤矿铀含量相对较高，但目前研究较少。这些煤矿燃烧后的 CFA 铀含量集中，存在很大的环境风险。本文基于微生物诱导碳酸钙沉淀（MICP），利用可钙化产脲的嗜盐菌 Halomonas sp. SBC20 对 CFA 中的铀进行生物固化。采用细菌细胞从 CFA 中制造出矩形 CFA 砖，并使用电子试验机测试其抗压强度。通过五阶段铀连续提取法和淋溶柱试验，仔细检查了 U 的分布模式和对降雨径流的不活动性。采用 FTIR 和 SEM-EDS 方法对 CFA 砖的微观结构变化进行了表征。结果表明，与对照样品相比，经细菌细胞培养后的 CFA 砖的抗压强度显著提高。生物固化后，U 的迁移性在可交换态显著降低，而在碳酸盐结合态的含量明显增加。经过细菌处理后，淋溶柱试验中 U 的释放量明显减少。FTIR 和 SEM-EDX 方法证实了碳酸盐沉淀的形成以及 U 掺入到方解石表面，阻止了 U 向周围环境的释放。该技术为来自新疆高铀含量煤矿甚至全球的 U 污染 CFA 提供了一种有效且经济的处理方法。
