SIMULATION OF STRUVITE PRECIPITATION FROM SWINE WASTE IN THE PRESENCE OF NICKEL AND ZINC

Struvite, MgNHPO©þ·6H©üO, was the main focus of our laboratory study because phosphorus is a very important nutrient that can possibly be extracted from wastes using the mineral. Struvite is also an essential component of ground fertilizers. Observing the formation and activity of struvite with other ions can possibly improve ground fertilizer quality and manufacture from wastes. Solutions of swine waste and greenhouse waste were successfully simulated by adding major ions independently to solution. Both solutions were oversaturated with respect to struvite by adding Mg, and NaOH to increase the pH, in the presence of struvite seed; thereby inducing the formation of struvite. Precipitated solids were collected by vacuum filtration. Because not enough solid was collected from the simulated greenhouse waste; simulated swine waste was the main focus of the experimental analysis. From the gathered data it was observed that struvite incorporates other ions in solution. Nickel (Ni) and zinc (Zn) were added to a simulated swine solution during precipitation of struvite at concentrations measured in actual swine waste. Precipitates from the simulated swine solution and the simulated swine solution with the Ni and Zn were characterized by x-ray diffraction (XRD), and the patterns were comparable and matched well to the struvite standard. The Ni and Zn concentrations from a simulated swine waste solid was compared to an actual swine waste solid sample from a batch reactor. The solid samples were collected and dissolved in 2% dilute nitric acid, and the Ni and Zn concentrations were measured using Atomic Absorption Spectroscopy (AAS) to identify if any Zn and Ni were present in the solid yields. For every one kilogram of simulated swine solid there was 123.5 mg of Zn and 69.3 mg of Ni. For every kilogram of the actual swine solid there was 432.4 mg of Zn and 3.05 mg of Ni.