It is critical to both effectively remove and recover phosphate (P) from wastewater given the wide-ranging environmental (i.e., preventing eutrophication and restoring water quality) and economic (i.e., overcoming P resource scarcity) benefits. More recently, considerable academic effort has been devoted towards harvesting P as vivianite, which can be used as a potential slow-release fertilizer and possible reagent for the manufacture of lithium iron phosphate (LiFePO₄), the precursor in fabricating Li-ion secondary batteries. In this study, we propose an innovative P recovery process, in which P is first preconcentrated via a flow-electrode capacitive deionization (FCDI) device followed by immobilization as vivianite crystals in a fluidized bed crystallization (FBC) column. The effects of different operational parameters on FCDI P preconcentration performance and energy consumption are investigated. Results show that 63% of P can be removed and concentrated in the flow-electrode chamber with a reasonable energy requirement under optimal operating conditions. The FBC system resulted in immobilization of ~80% of P as triangular or quadrangular pellets, which were verified to be high-purity vivianite crystals by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and extended X-ray absorption fine structure (EXAFS) spectroscopy. This study provides a pathway for efficient recovery of P as a value-added product (i.e., vivianite) from P-rich wastewaters.

考虑到广泛的环境（即，防止富营养化和恢复水质）和经济（即，克服磷资源的匮乏）的好处，有效地从废水中去除和回收磷酸盐（P）至关重要。最近，人们投入了相当多的学术努力来收获磷（如堇青石），它可以用作潜在的缓释肥料和生产磷酸铁锂的潜在试剂（LiFePO ₄），是制造锂离子二次电池的前身。在这项研究中，我们提出了一种创新的P回收工艺，其中P首先通过流电极电容去离子（FCDI）装置进行预浓缩，然后固定为流化床结晶（FBC）柱中的Vivianite晶体。研究了不同操作参数对FCDI P预浓缩性能和能耗的影响。结果表明，在最佳操作条件下，可以以合理的能量要求将63％的P去除并富集在流电极室中。FBC系统将约80％的P固定为三角形或四边形小球，通过扫描电子显微镜，能量色散X射线能谱（SEM-EDX）和扩展X射线吸收精细结构（EXAFS）光谱被证实是高纯度的堇青石晶体。这项研究提供了一条途径，可从富含磷的废水中有效回收作为增值产品（即，云母石）的磷。