Publication Date:
2020-02-12
Description:
The nucleation and crystallization of Al and Fe phosphate phases directly from aqueous solutions were investigated experimentally in batch reactors at 50 to 200 degrees C and pH 1.6. The mineralogy, elemental composition, and morphology of the formed solids were characterized by X-ray diffraction, spectroscopy, and high-resolution microscopic techniques. The corresponding dissolved aqueous Al, Fe,and P concentrations were analyzed by spectroscopic and chromatographic techniques. In all experiments Al and Fe phosphate phases readily precipitate from supersaturated solutions. Precipitation is initiated by the nucleation and growth of amorphous Al or Fe phosphate precursors. These crystallize at T = 100 degrees C to either variscite and metavariscite or strengite and phosphosiderite, respectively. At T 〉= 150 degrees C, these Al and Fe amorphous phases recrystallize to either berlinite or ferric giniite, respectively. The composition of the aqueous solution in all cases evolves rapidly to near saturation with respect to variscite and strengite. These observations suggest that Al and Fe phosphates may be critical to limiting aqueous phosphate availability in many natural environments.
Language:
English
Type:
info:eu-repo/semantics/article
