Murmanite and lomonosovite as Ag-selective ionites: kinetics and products of ion exchange in aqueous AgNO3 solutions |
| |
Authors: | Inna S Lykova Nikita V Chukanov Anatoliy I Kazakov Viktor P Tarasov Igor V Pekov Vasiliy O Yapaskurt Nadezhda A Chervonnaya |
| |
Institution: | 1. Faculty of Geology, Moscow State University, Moscow, Russia 2. Fersman Mineralogical Museum Russian Academy of Sciences, Moscow, Russia 3. Institute of Problems of Chemical Physics Russian Academy of Sciences, Chernogolovka, Russia
|
| |
Abstract: | Products and kinetics of ion exchange of heterophyllosilicate minerals lomonosovite and murmanite with aqueous AgNO3 solutions under low-temperature conditions have been studied using scanning electron microscopy, electron microprobe analysis, single-crystal X-ray diffraction, infrared spectroscopy, 23Na nuclear magnetic resonance spectroscopy and dynamic calorimetry. Both minerals show strong affinity for silver in cation exchange. Simplified formulae of Ag-exchanged forms of murmanite and lomonosovite are (Ag3.0Ca0.5Na0.5) (Ti,Nb,Mn,Fe)3.7?4 (Si2O7)2O4·4(H2O,OH) and (Ag8.2Na1.2Ca0.3) (Ti,Nb,Mn,Fe)3.9?4 (Si2O7)2 (PO4)1.9O4·xH2O, respectively. The reaction of ion exchange for murmanite follows the first-order kinetic model up to ca. 70–80 % conversion. The rate of the process is described by the equation k(h?1) = 107.64±0.60 exp?(12.2 ± 0.9)·103/RT]. The average heat release value in the temperature range 39.4–72 °C is 230 J g?1. The cation exchange is limited by processes in solid state, most probably binding of silver. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|