Abstract
Novel triethoxysilane and dimethyl phosphonate functional vinylidene fluoride (VDF)-containing terpolymers, for potential applications in Eu ion extraction from water, were produced by conventional radical terpolymerization of VDF with vinyltriethoxylsilane (VTEOS) and vinyldimethylphosphonate (VDMP). Although initial attempts for the copolymerization of VTEOS and VDMP failed, the successful terpolymerization was initiated by peroxide to lead to multiple poly(VDF-ter-VDMP-ter-VTEOS) terpolymers, that had different molar percentages of VDF (70–90 mol.%), VTEOS (5–20 mol.%) and VDMP (10 mol.%) in 50–80% yields. The obtained terpolymers were characterized by 1H, 19F, 29Si and 31P NMR spectroscopies. The crosslinking of such resulting poly(VDF-ter-VDMP-ter-VTEOS) terpolymers was achieved by hydrolysis and condensation (sol–gel process) of the triethoxysilane groups in acidic media, to obtain a 3D network, which was analyzed by solid state 29Si and 31P NMR spectroscopies, TGA and DSC. The thermal stability of the terpolymers was moderately high (up to 300 °C under air), whereas they display a slight increase in their crystallinity-rate from 9.7% to 12.1% after crosslinking. Finally, the dimethyl phosphonate functions were hydrolyzed into phosphonic acid successfully, and the europium ion extraction capacity of terpolymer was studied. The results demonstrated a very high removal capacity of Eu(III) ions from water, up to a total removal at low concentrations.
Highlights
As for the crystallinity rate (χ), was not possible, as evidenced by the presence of two signals centered at 44 ppm and at 25 ppm (attributed to the totally hydrolyzed parameters: (i) the formation of a stiff non-flexible network that may slightly increase the terpolymer phosphonic acid groups)
These data indicate that this crosslinked terpolymer can be employed efficiently for europium extraction from heterogeneous medium, and it may be expected that such results can be extended to other lanthanides and rare earth metals
Novel functional vinylidene fluoride (VDF)-based terpolymers for a specific metal extraction application were prepared, characterized, and involved in Eu3+ extraction. These terpolymers were synthesized by simple radical terpolymerization of VDF with commercially available VTEOS and VDMP
Summary
The potential risks of pollution by metal ions in aqueous environmental is still a major environmental issue, due to their high toxicity, persistence and potential carcinogenic effects [1]. Due to their excellent chelating properties [35], abundant examples of phosphorus functional polymers are present for employment as SPEs. Kabanov et al [36] prepared crosslinkable polymers from the copolymerization of diethyl vinyl phosphonate and acrylic acid with N,N-methylene diacrylamide for extracting Cu2+ ions. Zhao et al [46,47] reported the preparation of chelating membranes based on melamine-diethylenetriaminepentaacetic acid/PVDF (MA–DTPA/PVDF) and bearing polyaminecarboxylate groups for Ni(II) removal from wastewater. Various investigations deal with the functionalization of PVDF-based membranes by multiple functional groups for wastewater treatment [49,50,51,52], but only one recent study has reported the prominence of phosphorus functional PVDF involved in Rare Earth metal extraction in strong acidic media [53,54]. The choice of europium as a representative of lanthanides is due to its possessing similar behavior as other lanthanides during extraction [73,74] and because it forms complexes with xylenol orange [75,76], a commonly used indicator in colorimetric titrations [77]
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