Recycling phosphorus from spent LiFePO4 battery for multifunctional slow-release fertilizer preparation and simultaneous recovery of Lithium

• Recycling phosphorus increased the economic value of recycling spent LFP battery. • The P-SRF with acid-resistance was successful synthesized. • HPO 4 2− /H 2 PO 4 − reduced E a of the condensation reaction between urea and acrylic acid. • The buffering effect of HPO 4 2− /H 2 PO 4 − eliminated negative impact of low pH on P-SRF. • Mechanisms of P extraction from spent LFP battery and P-SRF synthesis were proposed. Comprehensive utilization of phosphorus from spent LiFePO 4 (LFP) battery has aroused considerable interest aiming to enhance the economic profit of recycling this type of low value-added battery. In the current study, a green and novel process was developed to recover phosphorus from spent LFP battery, which was further directly converted into phosphorus grafted slow-release fertilizer (P-SRF) with acid-resistance. Meanwhile, Li was simultaneously recovered. Effect of several parameters on the leaching efficiency of P was investigated, and the properties of P-SRF in acid and neutral conditions were clarified. In the whole process, the recovery efficiencies of Li and P were more than 99.5%, and furthermore, the synthesized P-SRF had high water-absorbing capacity and low release rate in both acid and neutral conditions. Mechanism study indicated phosphorus was recovered in the form of HPO 4 2− /H 2 PO 4 − from spent LFP battery. HPO 4 2− /H 2 PO 4 − reduced the activation energy of the condensation reaction between urea and acrylic acid to accelerate the reaction. Meanwhile, the low release rate of P-SRF in low pH was ascribed to the buffering effects of HPO 4 2− /H 2 PO 4 − . Furthermore, pot experiments showed P-SRF effectively promoted the growth of maize. This study provided a profitable approach for high value-added recovery of spent LFP battery, and the recovered hydrophosphate could be further transferred into P-SRF with considerable acid-resistance, which has potential application in acid soil, horticulture and slope treatment.