Thermally targeted mineralization of perfluorooctanoic acid for fluorine resource transformation through tricalcium phosphate-cleaved interfacial reactions.

There is lack of innovative fluorine conversion strategies and whereas the fact-limited fluorine ore. Therefore, the harmless degradation of perfluoroalkyl and polyfluoroalkyl substances (PFAS) and the fluorine (F) transformation products are crucial. Here, we proposed a novel thermally targeted mineralization (TTM) approach to promote the conversion of perfluorooctanoic acid (PFOA) into valuable fluorapatite (FAP) using inorganic calcium minerals (tricalcium phosphate (TCP), CaO) as reactants by combining experimental and machine learning (ML) explorations. Our results demonstrate that the highest fluorine TTM efficiency (FTE) of 45% and an accurate multitask ML model (test R2 ≥ 0.80) was developed to build up connections between TTM process and product compositions. Furthermore, the FTE was temperature and TCP lattice structure dependent. Our models further revealed that temperature of reaction and TCP relaxation were the primary drivers of FAP formation. Deep mineralization is achieved as F- from PFOA pyrolysis adsorbs onto the TCP surface and diffuses into crystal through these channels since the pre-existing calcium vacancies and ionic channels in TCP provided a "highway" for it. Moreover, the successful mineralization of perfluorodecanoic acid (PFDoA) and other Ca-P mineral confirms the broad applicability of this approach for destroying persistent PFAS for environmental remediation and resource recovery.