Hydrogen Peroxide Induced Efficient Mineralization of Poly(vinylidene fluoride) and Related Copolymers in Subcritical Water

Decompositions of poly(vinylidene fluoride) (PVDF), poly(vinylidene fluoride-co-chlorotrifluoroethylene) copolymer (poly(VDF-co-CTFE)), and poly(vinylidene fluoride-co-hexafluoropropylene) copolymer (poly(VDF-co-HFP)) in subcritical water were investigated with the aim of developing a technique to recover the fluorine component. By use of H2O2, these (co)polymers can be efficiently mineralized at a relatively low temperature (300 °C). When PVDF was heated with 3.0 M H2O2 for 6 h, which corresponds to 31 times the molar amount of fluorine and 32 times the molar amount of carbon in the polymer, both F– and CO2 yields reached 98%. Poly(VDF-co-CTFE) copolymer was also mineralized under the same reaction conditions (the yields of F–, CO2, and Cl– were 98, 95, and 97%, respectively). Poly(VDF-co-HFP) copolymer was more readily decomposed than poly(VDF-co-CTFE), leading to almost complete mineralization (F– yield, 96%; CO2 yield, 92%) with 2.0 M H2O2. Addition of stoichiometric Ca(OH)2 to the reactions formed CaF2 well-identified by X-ray diffraction spectrometry.