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Uranium (U) contamination in groundwater of the uranium mines exploited using the in-situ leaching (ISL) technology (also referred to as the ISL uranium mines) has attracted wide international attention. Since the adsorption of U in groundwater by aquifer media in uences the migration scope of U, understanding the U adsorption by aquifer media is of great signi cance for accurately predicting the in uencing scope of ISL uranium mines on groundwater. This study collected sandstone samples from the ore-bearing aquifer outside a typical mining area in a uranium mine exploited using the acid ISL (AISL) technology (also referred to as an AISL uranium mine) in northern China. Using these sandstone samples, this study conducted batch adsorption experiments and column experiments of U to reveal the characteristics and major in uencing factors of U adsorption under different conditions. The results show that the adsorption of U by sandstones in the ore-bearing aquifer outside a mining area satis es the pseudo-second-order kinetic equation and the linear isothermal adsorption model. In the batch U adsorption experiments, the adsorption e ciency and capacity for U reached maxima of 77.45% and 0.069 mg/g at pH 7, respectively. As shown by column experiments, the sandstones showed a signi cant increase in the U adsorption and retardation as pH increased. The SO 4 2− concentration has minor effects on U adsorption under experimental conditions. Sandstones from different monitoring wells exhibited different U adsorption characteristics. Sandstone cores with relatively high contents of clay minerals such as illite showed strong U adsorption. Under the same experimental conditions, the U distribution coe cient K d (6.91×10 − 2 L/g) obtained from column experiments is much less than that (0.14 L/g) obtained from the batch U adsorption experiments. These results suggest that it is necessary to take into account the U adsorption and retardation by aquifer media in predicting the impacts of ISL uranium mines on the groundwater environment.
Uranium (U) contamination in groundwater of the uranium mines exploited using the in-situ leaching (ISL) technology (also referred to as the ISL uranium mines) has attracted wide international attention. Since the adsorption of U in groundwater by aquifer media in uences the migration scope of U, understanding the U adsorption by aquifer media is of great signi cance for accurately predicting the in uencing scope of ISL uranium mines on groundwater. This study collected sandstone samples from the ore-bearing aquifer outside a typical mining area in a uranium mine exploited using the acid ISL (AISL) technology (also referred to as an AISL uranium mine) in northern China. Using these sandstone samples, this study conducted batch adsorption experiments and column experiments of U to reveal the characteristics and major in uencing factors of U adsorption under different conditions. The results show that the adsorption of U by sandstones in the ore-bearing aquifer outside a mining area satis es the pseudo-second-order kinetic equation and the linear isothermal adsorption model. In the batch U adsorption experiments, the adsorption e ciency and capacity for U reached maxima of 77.45% and 0.069 mg/g at pH 7, respectively. As shown by column experiments, the sandstones showed a signi cant increase in the U adsorption and retardation as pH increased. The SO 4 2− concentration has minor effects on U adsorption under experimental conditions. Sandstones from different monitoring wells exhibited different U adsorption characteristics. Sandstone cores with relatively high contents of clay minerals such as illite showed strong U adsorption. Under the same experimental conditions, the U distribution coe cient K d (6.91×10 − 2 L/g) obtained from column experiments is much less than that (0.14 L/g) obtained from the batch U adsorption experiments. These results suggest that it is necessary to take into account the U adsorption and retardation by aquifer media in predicting the impacts of ISL uranium mines on the groundwater environment.
Soil contamination by uranium presents a burgeoning global environmental concern, exerting detrimental effects on both agricultural production and soil health. Biochar, a carbonaceous material derived from biomass pyrolysis, exhibits considerable potential for remediating uranium-contaminated soils. However, a comprehensive review of the effects of biochar on the fate and accumulation of uranium in soil–plant systems remains conspicuously absent. In this paper, uranium sources and contamination are reviewed, and the impact of biochar on uranium immobilization and detoxification in soil–plant systems is analyzed. We reviewed the status of uranium contamination in soils globally and found that mining activities are currently the main sources. Further meta-analysis revealed that biochar addition significantly reduced the soil uranium bioavailability and shoot uranium accumulation, and their effect value is 58.9% (40.8–76.8%) and 39.7% (15.7–63.8%), respectively. Additionally, biochar enhances the soil microenvironment, providing favourable conditions for promoting plant growth and reducing uranium mobility. We focused on the mechanisms governing the interaction between biochar and uranium, emphasising the considerable roles played by surface complexation, reduction, ion exchange, and physical adsorption. The modification of biochar by intensifying these mechanisms can promote uranium immobilisation in soils. Finally, biochar alleviates oxidative stress and reduces uranium accumulation in plant tissues, thereby mitigating the adverse effects of uranium on plant growth and development. Overall, our review highlights the capacity of biochar to remediate uranium contamination in soil–plant systems through diverse mechanisms, providing valuable insights for sustainable environmental remediation.Highlights Biochar reduces uranium mobility through a variety of mechanisms, including surface complexation, reduction, ion exchange, and physical adsorption. Biochar significantly reduces uranium bioavailability in soil and limits its accumulation in plants. Modified biochar has been shown to enhance its effectiveness in immobilising uranium. Biochar application to soil not only promotes uranium remediation but also improves soil quality. Graphical Abstract
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