Mechanism of incorporation Pb<sup>2+</sup> and Сd<sup>2+</sup> into crystal structure of murmanite, Na<sub>2</sub>Ti<sub>2</sub>(Si<sub>2</sub>O<sub>7</sub>)O<sub>2</sub> ·2H<sub>2</sub>O
The ion-exchange and sorption properties of murmanite with respect to Pb 2+ and Cd 2+ cations have been studied. Murmanite is able to fully exchange Na+ cations for Cd 2+ and Pb 2+ in chloride solutions at 160 ° С. Lead incorporation into interlayer space of murmanite occurs according to the isomorphic scheme 2Na + ↔ Pb2 + + □, replacing sodium in octahedral positions. The ordering of occupied and vacant octahedral positions for the Cd-sub- stituted form leads to a change in the unit cell from the original Sp.gr. a = 5.3822(6), b = 7.0538(8), c = 11.6477(15), α = 86.385(9), β = 81.967(10), γ = 89.970(9) to diagonal α = 8.8154(11), b = 8.8363(11), c = 11.694(4), α = 98.786(17), β = 90.954(17), γ = 106.039(11).