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Alkaline materials were used to neutralize acidic waste residue. Open and closed experimental environments were set up with different dosing ratios and pH conditions.By monitoring the changes in pH, U, and $\mathrm{HCO}_{3}^{-}$ in the supernatant of the neutralization residue, and analyzing the mineral composition of the neutralization residue using XRD, the effect of CO2 on U stability during the neutralization process of acidic waste residue was studied. The results show that CO2 in the surrounding air during neutralization treatment affects the stability of pH and U in the neutralization residue. The fixation of CO2 by the neutralization residue under alkaline conditions is an acidification process. As the pH of the neutralization residue decreases, the CO2 fixed in the air transforms into $\mathrm{HCO}_{3}^{-}$, which gradually accumulates and causes the already stabilized U in the neutralization residue is leached out again. The pH adjustment experiment shows that there is no significant correlation between U and pH. The pH range for U leaching is 7.68~8.41, and $\mathrm{HCO}_{3}^{-}$ accumulates significantly in this range. There is a positive correlation between U and $\mathrm{HCO}_{3}^{-}$, with a correlation coefficient of 0.95. The production of $\mathrm{HCO}_{3}^{-}$ is a key factor affecting the stability of U in neutralization residue. When Ca(OH)2 is added excessively, secondary mineral CaCO3 will be generated in the neutralization residue. As CO2 is fixed, the pH of the neutralization residue decreases, and CaCO3 will partially dissolve and transform into $\mathrm{HCO}_{3}^{-}$. In the open experimental environment, only the 2.5% Ca(OH)2 experimental group and the 2.5% Mg(OH)2 experimental group maintain extremely low U leaching levels. After neutralization treatment, the pH of the neutralization residue is low, and very little CO2 is fixed in the air. $\mathrm{HCO}_{3}^{-}$ which affects U stabilityis hardly produced.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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