Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong.
Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong.
Water Res. 2016 May 15;95:310-8. doi: 10.1016/j.watres.2016.03.032. Epub 2016 Mar 18.
The precipitation of struvite (MgNH4PO4·6H2O) from waste streams has attracted considerable attention due to its potential for recovering phosphorus for fertilization. As struvite is primarily acquired by means of precipitation and crystallization from aqueous solutions, it is important to evaluate the roles of common metal ions, particularly those that are commonly found in wastewater, in the struvite crystallization process. This study was performed to quantitatively evaluate the effects of calcium and ferric ions on struvite crystallization using the Rietveld refinement method, which is based on the analysis of X-ray diffraction data. The results indicate that both calcium and ferric ions significantly inhibit the formation of struvite crystals, and the effects vary under different pH conditions. There was a negative linear correlation between the struvite weight content in the precipitates and the Ca/Mg molar ratio in the initial solution. However, ferric ions were confirmed to be a more efficient inhibitor of struvite crystallization. Ca(2+) and Fe(3+) further modified the needle-like struvite into irregular shapes. An unambiguous and quantitative understanding of the effects of foreign ions on struvite crystallization will help to reliably improve the quality of struvite products recovered from wastewater and the control of struvite deposits in water and sludge piping systems.
由于从废水中回收磷以用于施肥具有潜力，因此鸟粪石（MgNH4PO4·6H2O）的沉淀引起了相当大的关注。由于鸟粪石主要通过水溶液中的沉淀和结晶获得，因此评估常见金属离子（特别是那些在废水中常见的金属离子）在鸟粪石结晶过程中的作用非常重要。本研究使用基于 X 射线衍射数据分析的 Rietveld 精修方法，定量评估了钙离子和铁离子对鸟粪石结晶的影响。结果表明，钙离子和铁离子均显著抑制了鸟粪石晶体的形成，并且在不同 pH 条件下，其影响也不同。沉淀物中鸟粪石的重量含量与初始溶液中 Ca/Mg 摩尔比呈负线性相关。然而，铁离子被证实是更有效的鸟粪石结晶抑制剂。Ca(2+)和 Fe(3+)进一步将针状鸟粪石修饰成不规则形状。明确和定量地了解外来离子对鸟粪石结晶的影响，将有助于可靠地提高从废水中回收的鸟粪石产品的质量，并控制水和污泥管道系统中的鸟粪石沉积物。
