The optimization of phosphorus recovery from high-speed rail fecal sewage using magnesium salt based on a response surface method

Through response surface method (RSM), phosphorus recovery from high-speed rail fecal sewage was improved along with the chemical analysis of the harvested product. Initially, the effects of pH (8~10), molar ratio of magnesium to phosphorus (2~6), reaction time (5~25 min), and reaction temperature (5~25℃) among other factors on phosphors recovery efficiency were investigated. The RSM-derived findings indicate that the optimal set of operational parameters was pH 9.5, magnesium-to phosphorus-molar ratio 5.7, reaction time 6.4 min and temperature 5.0℃. Under the above combined condition, the phosphorus recovery rate could reach at 95.3%. Based on the results of Fourier Transform infrared spectroscopy and scanning electron microscopy, it could be easily found that the majority of the recovered product consisted of magnesium ammonium phosphate and magnesium phosphate. With further analysis by energy dispersive X-ray approach, the phosphorus content was observed to account for nearly 17.1% of the recovered product. Overall, this work proves the feasibility of using magnesium salt to recover phosphorus from high-speed rail fecal sewage, providing a scientific reference for further exploration in the related field.