Messi Biology states that in the wet smelting process of tungsten ore, the presence of phosphorus impurities can seriously affect the purity of tungsten products and subsequent processing performance. Traditional phosphorus removal methods (such as lime precipitation) easily introduce calcium ion interference, while magnesium oxide (MgO) has gradually become a research hotspot in the field of phosphorus removal due to its high efficiency and environmental protection characteristics. This article focuses on exploring the chemical mechanism and process optimization direction of magnesium oxide for phosphorus removal.
1. Chemical Reaction Mechanism of Magnesium Oxide for Phosphorus Removal
Magnesium oxide reacts with phosphorus-containing solutions to generate magnesium phosphate precipitate. The core reaction is:
3MgO + 2H₃PO₄ → Mg₃(PO₄)₂↓ + 3H₂O
This reaction is carried out under neutral or weakly alkaline conditions. Magnesium oxide hydrolyzes to generate Mg²⁺, which combines with PO₄³⁻ in the solution to form insoluble magnesium phosphate (solubility product Ksp≈1×10⁻²⁵), thereby achieving efficient phosphorus removal. Compared to other precipitating agents, MgO has moderate alkalinity, which can avoid the loss of tungstate caused by local over-alkalinity.
2. Optimization of Process Parameters
pH control: The optimal pH range is 8.5~9.5. At this time, the phosphorus removal rate can reach more than 95%, and the tungsten loss rate is less than 1%.
Temperature and stirring: The reaction can be completed at normal temperature, but heating to 50~60℃ can shorten the reaction time to within 30 minutes.
Magnesium oxide dosage: The theoretical molar ratio is 3:2 (Mg:P), and the actual dosage needs to be dynamically adjusted according to the phosphorus content. An excess of 10%~15% can ensure the reaction is complete.
3. Technical Advantages and Cases
A tungsten mine concentrator adopted magnesium oxide instead of lime, and the phosphorus content dropped from 0.15% to 0.02%. At the same time, it avoided the pollution of calcium ions to the ion exchange resin and saved more than 2 million yuan in resin regeneration costs per year. In addition, magnesium phosphate precipitates have large particles and are easy to filter, which can reduce the difficulty of solid waste treatment.
The magnesium oxide phosphorus removal process has both high efficiency and economy. In the future, it can be used in combination with membrane separation technology to further improve the phosphorus resource recovery rate and promote the green development of tungsten smelting.