鸟粪石法回收废水中磷的沉淀物的组成和晶形

Study on the composition and crystal shape of the precipitate obtained by struvite precipitation from wastewater for phosphorous recovery

利用镁盐为沉淀剂,以磷酸铵镁沉淀的形式回收模拟废水中的磷.采用扫描电镜和X射线衍射对生成的沉淀物的晶形进行表征,利用ICP和化学分析方法测定沉淀物的组成,并结合饱和度的计算对回收的沉淀物的晶形和纯度进行研究.结果显示:沉淀物为斜方型晶体时才是纯的鸟粪石,针形晶体不是纯的鸟粪石;沉淀物的晶形与溶液的初始饱和度有一定的关系,当溶液的初始饱和度较低时,不管pH或镁或氨氮的浓度在一定范围如何变化,其沉淀物都为斜方形晶体;当溶液的初始饱和度高过一定程度后,其沉淀物中都会出现针形的晶体,且不同条件下所生成的针形晶体的X射线衍射峰都与磷酸镁的特征峰有很好的对应关系,说明针形晶体与磷酸镁有一定的关联.

Using magnesium salt as settling agent, phosphorous in synthetic wastewater was recovered as struvite precipitate. In order to analyze the crystal shape and the purity of the precipitate, the morphology of the precipitate was studied with Scanning Electron Microscope （ SEM ） and X-ray Diffraction （XRD）, the composition of the precipitate was analyzed with ICP and chemical analysis, and the initial saturation of the solution was calculated. The result indicated that pure struvite has an orthorhombic shape, and the needle-like crystal is not purity strnvite. Besides, the crystal shape and purity of the precipitate have a certain relation with the initial saturation of the solution. When the initial saturation in solution is low, the precipitate has an orthorhombic shape, while the precipitate has needle-like shape when the initial saturation surpasses a certain value. And the patterns of XBD showed that the needle-like crystal has similar diffraction peaks with Mg3 （ PO4 ） 2, so it can be induced that there is some relationships between them.