Abstract
Phosphogypsum (PG), a waste by-product of the phosphate fertilizer industry as well as a point-source P contaminant, has caused serious environmental problems particularly in estuarine and coastal regions. However, in-depth understanding of P speciation in PG, which is critical for its restoration and management, remains largely unknown. Using solid-state 31P NMR spectroscopy, density functional theory calculations of the NMR parameters and NanoSIMS, we for the first time reported that P in PG ubiquitously exists as phosphate incorporated into gypsum and minor fluorapatite. The occasional presences of mineral phosphate phases mainly associated with Ca and Al were also detected. The molecular environment of the incorporated phosphate is HPO42− substituting for SO42− in the gypsum lattice with the H atom away from the H2O molecules and almost parallel to the a–c plane. A high spatial heterogeneity was observed for the distribution of this phosphate species in PG at the submicron scale. Upon heating, at least 64% of the incorporated phosphate could be converted to the easy-to-recover fluorapatite or amorphous calcium phosphate by thermal treatments at above 750 °C for 2–4 h. This information of P speciation transformation may pave a solid basement for the sustainable recovery of P from PG.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.