National Research and Development Institute of Radioactive Metals and Resources, Bdul Carol I No 70, 020917, Bucharest, Romania.
Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, Polizu Str. no 1-7, 011061, Bucharest, Romania.
Environ Sci Pollut Res Int. 2020 Feb;27(6):5941-5950. doi: 10.1007/s11356-019-07063-0. Epub 2019 Dec 20.
The ex situ decontamination of uranium polluted soils was performed by alkaline washing using mechanical agitation and ultrasound field. Two types of polluted soils were considered in terms of texture and organic content. The tests were performed using experimental design: a 2 factorial plan for mechanical washing and Taguchi L orthogonal matrix for ultrasound (US)-assisted decontamination. The factors considered in mechanical washing were temperature, duration, and pH. For ultrasound decontamination, the US frequency was added. The optimum was estimated based on statistical analysis and validated by confirmation experiments. The study revealed that in ultrasound field, the decontamination degree is increased with over 25% compared with mechanical stirring, while the duration of the process is drastically reduced (from 120 to 25 min). The most important factor leading to the increase of decontamination is the ultrasound frequency. To refine the result, artificial neural network modeling and subsequent optimization by genetic algorithms were also carried out for the decontamination in ultrasound field, and new optimum operating conditions were identified and validated. The best operating conditions identified were temperature around 50 °C, pH = 8, and ultrasound frequency of 24 kHz. In these conditions, the decontamination degree reached 85% for Soil 1 (characterized by low clay and organic content) and 69% for Soil 2 (with high clay and organic content).
采用机械搅拌和超声场的碱性洗涤对铀污染土壤进行了异位去污。根据质地和有机含量考虑了两种类型的污染土壤。使用实验设计进行了测试：机械洗涤的 2 因子计划和超声（US）辅助去污的 Taguchi L 正交矩阵。机械洗涤中考虑的因素是温度、持续时间和 pH 值。对于超声去污，添加了 US 频率。基于统计分析估计最佳值，并通过验证实验进行验证。该研究表明，在超声场中，与机械搅拌相比，去污程度提高了 25%以上，而处理时间大大缩短（从 120 分钟缩短至 25 分钟）。导致去污增加的最重要因素是超声频率。为了细化结果，还对超声场中的去污进行了人工神经网络建模和遗传算法的后续优化，并确定和验证了新的最佳操作条件。确定的最佳操作条件为 50°C 左右的温度、pH=8 和 24 kHz 的超声频率。在这些条件下，土壤 1（粘土和有机物含量低）的去污程度达到 85%，土壤 2（粘土和有机物含量高）的去污程度达到 69%。
