Efficient fluoride recovery from poly(vinylidene fluoride), poly(vinylidene fluoride-co-hexafluoropropylene) copolymer and poly(ethylene-co-tetrafluoroethylene) copolymer using superheated water with alkaline reagent

Mineralization of poly(vinylidene fluoride) (PVDF), fluoride-co-hexafluoropropylene) [poly(VDF-co-HFP)] copolymer, and poly(ethylene-co-tetrafluoroethylene) copolymer (ETFE) in superheated water the presence an alkaline reagent was investigated with aim developing a technique to recycle fluorine element. These polymers underwent almost complete defluorination form fluoride ions (F–) reaction solution at relatively low temperature (250 °C) under Ar atmosphere. When PVDF reacted aqueous KOH (1.0 M) for 6 h, amount which corresponds 10 times molar content (as atoms) PVDF, yield F– released into reached 95 %. This transformation accompanied by formation carbon rich reside, consists amorphous carbon. In contrast, treatment performed O2 instead Ar, significant differences were observed products: while efficiently produced solution, residue did not major species that composed total organic oxalate. Four consecutive runs (that is, after one 250 °C complete, new charged mixture then again) caused no decrease yield. treated poly(VDF-co-HFP) ETFE copolymers also completely mineralized 100 98 % yields, respectively. Introducing Ca(OH)2 resulting solutions these (co)polymers pure CaF2, i.e., artificial fluorspar.