Determining the Effect of Nickel and Cadmium Ions in Struvite Crystallization Process

Struvite is an eco-friendly fertilizer widely produced from waste streams. Landfill leachate, rich in ammonium-nitrogen (NH4-N), encourages the recovery of NH4N in the form of struvite. However, the presence of heavy metals, particularly cadmium (Cd) and nickel (Ni), may affect the purity of struvite crystals, thereby hindering its applicability as a fertilizer. While previous studies have examined the effects of various heavy metals on struvite crystallization, the specific impact of Cd and Ni, especially in landfill leachate, remains insufficiently studied. This study aimed to fill this gap by investigating the effect of Cd and Ni on the purity and morphology of struvite crystals obtained from synthetic solutions (Phase 1) and synthetic landfill leachate (Phase 2). Additionally, a kinetics study was conducted to determine the fate of Ni and Cd during struvite crystallization. Batch experiments of struvite precipitation were performed with varying concentrations of Cd and Ni. Aqueous analysis results indicated a minor reduction in NH4-N recovery in both phases when Cd or Ni were present. Furthermore, XRD and SEM analyses of solid samples demonstrated that all crystals were highly pure struvite. The impact of Cd and Ni in Phase 2 was slightly more significant than in Phase 1. The kinetics study suggested that struvite can be safely recovered from landfill leachate contaminated with Cd and Ni. However, further research is needed on actual landfill leachate to fully understand the combined and advanced effects of heavy metals on struvite crystallization.