J Environ Qual. 2019 Jan;48(1):193-198. doi: 10.2134/jeq2018.08.0287.
Phosphorus recovery from wastewater as struvite (MgNHPO⋅6HO) or dittmarite (MgNHPO⋅HO) can decrease water pollution risk, as well as produce a P-rich material suitable as fertilizer. However, most studies to date have focused on the removal of P from wastewater, rather than on characterization of the recovered P materials. The objective of this work was to apply microfocused X-ray fluorescence (XRF) spectroscopy, and both bulk and microfused X-ray absorption near edge structure (XANES) spectroscopy, to provide insight into the speciation of recovered P in various struvite-containing and struvite-like materials. Three materials were investigated: homogeneous crystalline struvite on apatite seed, homogeneous dittmarite, and heterogeneous struvite with sand contamination (referred to as the "sandy" material). The struvite materials were recovered from dairy wastewater, whereas the dittmarite was from a cheese processing plant. Phosphorus speciation in the crystalline struvite on apatite seed material was ∼17% apatite and 83% struvite; in the "sandy" material, P was ∼24% apatite and ∼76% struvite, with an uncertainty of approximately ±15%. The P -edge XANES spectra of recovered dittmarite appeared pure. These findings highlight the heterogeneity of recovered P materials and underscore the importance of P speciation to understand P release behavior and bioavailability from recovered phosphates.
从废水中回收磷作为鸟粪石（MgNH4PO4·6H2O）或 Dittmarite（MgNH4PO4·H2O）可以降低水污染风险，同时还可以生产出富含磷的肥料。然而，迄今为止，大多数研究都集中在从废水中去除磷，而不是对回收的磷材料进行特性描述。本工作旨在应用微聚焦 X 射线荧光（XRF）光谱，以及整体和微熔 X 射线吸收近边结构（XANES）光谱，深入了解各种含鸟粪石和类似鸟粪石的材料中回收磷的形态。研究了三种材料：磷灰石种子上的均匀结晶鸟粪石、均匀的 Dittmarite 以及含有沙子污染的异质鸟粪石（称为“沙质”材料）。这些鸟粪石材料是从奶制品废水中回收的，而 Dittmarite 则来自奶酪加工厂。磷灰石种子上结晶鸟粪石材料中的磷形态约为 17%的磷灰石和 83%的鸟粪石；在“沙质”材料中，磷约为 24%的磷灰石和 76%的鸟粪石，不确定性约为±15%。回收 Dittmarite 的 P 边 XANES 光谱显示为纯相。这些发现突出了回收磷材料的异质性，并强调了磷形态对理解回收磷酸盐的磷释放行为和生物有效性的重要性。
