Structural characterization of pure Na-nephelines synthesized by zeolite conversion route

Electrochemically controlled ion exchange: proton ion exchange with sodium zeolite X and A

“…NaA and NaX have both been employed as the starting material, where nepheline is formed at circa 1,173 K [20]. This is in agreement with the data shown in Figs.…”

“…5 and 6. It has been observed that both zeolites go through a carnegiete phases at circa 1,073 K [20]. This framework transformation was not observed for the data shown in Figs.…”

“…The fresh NaX sample is stable up to 1,023 K; at this temperature, it is converted to an amorphous phase. The amorphous phase is converted to a crystalline phase at 1,173 K; the diffraction pattern indicates that the crystalline phase is nepheline [20]. The electrochemical sample retained its original crystallinity up to 1,073 K and then remains amorphous.…”

“…Zeolite thermally induced transformation has been employed as a synthetic route for pure sodium nepheline [20]. NaA and NaX have both been employed as the starting material, where nepheline is formed at circa 1,173 K [20].…”

“…The Na + content of the as-purchased zeolites was >99 % as measured by inductively coupled plasma atomic emission spectroscopy (ICPAES) performed on the fresh samples. The organic solution was made using 1,2-dichloroethane (DCE, 99.8 %+, Aldrich, Dorset, UK) as the solvent, dibenzo-18-crown-6 (DB18c6, 98 %, Lancaster Chemicals Co., Morecambe, UK) was e m p l o y e d a s t h e c o m p l e x i n g a g e n t a n d b i s ( t r i p h e n y l p h o s p h o r a n y l i d e n e ) a m m o n i u m tetrakis(pentafluorophenyl) borate (BTPPATPBF 20 ) was used as the background electrolyte. The organic phase electrolyte was prepared by metathesis of bis(triphenylphosphoranylidene) ammonium chloride (99 %+, Aldrich) and lithium tetrakis(pentafluorophenyl) borate (Boulder Scientific, Mead, CO, USA), according to a previously reported procedure [16].…”