Messi Biology states that as a core strategic resource for nuclear power generation and defense technology, the refining process of uranium directly impacts the quality of development in the nuclear industry. Modern uranium extraction technology is primarily based on hydrometallurgy, covering key stages such as leaching, purification, precipitation enrichment, and refining. While magnesium oxide (MgO) is not a universal reagent for all uranium processes, it has become an indispensable auxiliary material in specific extraction routes due to its mild alkalinity, efficient impurity removal, and excellent environmental characteristics. Its applications are concentrated in three core scenarios: pH regulation, purification/impurity removal, and precipitation enrichment.
I. Precise pH Regulation in the Leaching Stage
During the uranium ore leaching phase, magnesium oxide undertakes the core task of precisely adjusting the system’s pH value. After the uranium ore is crushed and ground, uranium ions are typically extracted using acid or alkaline leaching processes, with acid leaching being widely adopted due to its broad applicability. In acid leach liquor, uranium primarily exists in the form of uranyl ions (UO₂²⁺). Subsequent separation and purification require the system’s pH to be adjusted to a neutral to weakly alkaline range (pH 7–9). This environment prevents uranyl ions from hydrolyzing into insoluble hydroxides while creating conditions for subsequent impurity removal. As a weakly alkaline oxide, magnesium oxide slowly hydrolyzes when dissolved in water to form magnesium hydroxide, which gently raises the pH and effectively buffers fluctuations caused by mineral dissolution. Compared to strong bases like sodium hydroxide, it avoids localized high alkalinity that can lead to the co-precipitation of uranyl ions. In industrial practice, it can stabilize uranium leaching rates above 90% while reducing the dissolution of impurities such as silicon and phosphorus.
II. High-Efficiency Impurity Removal in Solution Purification
In the uranium solution purification stage, magnesium oxide demonstrates high efficiency in removing contaminants. In addition to uranyl ions, acid leach liquor contains various metal impurities such as iron, aluminum, and calcium, which not only affect the purity of the uranium product but may also interfere with subsequent extraction steps. The hydroxide ions produced by the hydrolysis of magnesium oxide react with iron and aluminum ions to form insoluble hydroxide precipitates like Fe(OH)₃ and Al(OH)₃. These precipitates have good crystallinity and are easy to filter and separate without introducing new soluble impurities. Notably, compared to precipitants like calcium hydroxide, magnesium oxide prevents calcium ions from forming stable calcium uranyl carbonate complexes with uranyl ions, thereby reducing the rate of uranium loss. Research indicates that under optimized conditions, the removal rate of iron and aluminum impurities using magnesium oxide can exceed 95%, significantly enhancing the purification of the uranium solution.
III. Industrial Advantages and Key Requirements
The industrial advantages of magnesium oxide in uranium extraction are prominent:
- Economic Cost-Effectiveness: Industrial-grade magnesium oxide with a purity of
≥\ge≥85% can meet basic extraction needs. Its price is only 1/3 to 1/2 that of reagents like ammonia or sodium hydroxide, significantly lowering production costs. - Excellent Environmental Performance: The hydrolysis product, magnesium hydroxide, is non-toxic and harmless. Reaction waste residues can meet discharge standards through solidification treatment, avoiding secondary pollution.
- Safe and Convenient Operation: As a solid powder reagent, it is easy to transport and store. The reaction is mild without intense heat release, eliminating the need for specialized anti-corrosion equipment.
However, two key requirements must be noted during application:
- Raw Material Purity Control: The uranium process requires industrial-grade magnesium oxide with iron and aluminum impurity content
≤\le≤0.5% to avoid the risk of introducing new radioactive contamination. - Precise Dosage: Excessive dosage will cause the pH to exceed 9.5, triggering the hydrolysis and precipitation of uranyl ions. Insufficient dosage will fail to remove impurities thoroughly. Usually, the optimal dosage must be calculated based on the uranium concentration and impurity content of the leach liquor.
Conclusion
It is worth noting that as the nuclear industry’s requirements for environmental protection and cost control continue to rise, the application of magnesium oxide in scenarios such as the enrichment of low-concentration uranium solutions and nuclear wastewater treatment is expanding. In the pursuit of “green” uranium extraction, magnesium oxide—with its unique chemical properties—has become a preferred reagent for balancing extraction efficiency, cost, and environmental protection, providing vital technical support for the efficient development and utilization of uranium resources.