Investigating the recovery of ferrous phosphate in a fluidized bed crystallizer by response surface methodology

Phosphorus recovery is essential, especially from wastewater containing high levels of phosphorus from the semiconductor industries, food companies, and livestock. This study aims to determine how pH, Fe/P molar ratio, and Zn/P molar ratio affect the crystallization of ferrous phosphate. Response surface methodology—central composite design was utilized to optimize the recovery efficiency of ferrous phosphate in a fluidized bed crystallization reactor. The pH and Fe/P molar ratio were adjusted within the ranges of 3.8 to 9.6 and 0.58 to 3.40, respectively, for the fluidized bed crystallization. The Zn/P molar ratio parameter was set between 0.1 and 1.0 to evaluate the impact of zinc. Following optimization by response surface analysis, the phosphorus removal efficiency was nearly 100% at pH 7.3, Fe/P molar ratio of 2.5, and the phosphate crystal efficiency was 60.3% at pH 6.8, Fe/P molar ratio of 1.9. In addition, the study discovered that zinc ion would significantly reduce the efficiency of ferrous phosphate recovery during the crystallization process, with the maximum phosphate crystal efficiency declines to 47% at Zn/P molar ratio of 0.5. Graphical abstract: (Figure presented.)