EXAFS and XRD studies in synthetic Ni-fluorohectorite

Abstract

16In the present work the synthetic clay mineral fluorohectorite was studied by means of extended X-17 ray absorption fine structure (EXAFS) in a powder sample with the intention to observe the number 18 of neighbouring atoms to the Ni interlayer cation. In addition X-ray Diffraction (XRD) was 19 performed in order to follow the hydration states of Ni-fluorohectorite in terms of basal-spacing 20 measurements. The sample conditions were the same for both types of experiments. The EXAFS 21 results show that Ni 2+ forms a Brucite-like structure in the form of Ni(OH)2, and that this structure 22 coexists with the clay mineral particles. This shows that the Ni atom observed by means of our 23 EXAFS measurements is predominantly the Ni which composes the Brucite-like structure and not 24 the interlayer Ni 2+ cation. In order to confirm the formation of the Brucite-like structure, the 25 EXAFS data from Ni-fluorohectorite were compared to Ni-salt water solutions at various pH.

Intercalation and Retention of Carbon Dioxide in a Smectite Clay promoted by Interlayer Cations

“…It is known that water intercalation experiments with NiFh can form a structure called Brucite (Ni[OH] 2 ). Such a structure is formed in the cation exchange process from LiFh to NiFh 60 . It is possible that a Brucite-CO 2 interaction could have an effect on the behavior.…”

“…At ambient conditions (23° and 40% of relative humidity), these clay mineral samples are in the monohydrated state 9 60 . Since the uptake of the CO 2 molecules may be affected by the initial H 2 O concentration 61 , we investigated dehydrated native samples.…”

Water vapor diffusive transport in a smectite clay: Cationic control of normal versus anomalous diffusion

“…For H 2 O molecules, particular molecular complexes and packings are energetically favored [26], which results in particular discrete values of d-spacing, depending on the environmental conditions, i.e. primarily on relative humidity and temperature [27][28][29][30]. Theses discrete d-spacing values correspond to different hydration states of the clay particles, and are denoted xWL (x = 0, 1, 2, 3, • • • ), where WL stands for "Water Layers".…”

Clay nanolayer encapsulation, evolving from origins of life to future technologies

“…There are several cases investigated and reported in the literature with respect to capturing and retention mechanisms for encapsulation of foreign molecules inside such clay interlayers ( Fig. 6), including H 2 O intercalation [12,13,[39][40][41][42][43][44][45][46], CO 2 capture and retention [36,[47][48][49][50][51], cation exchange [12,13,52], medical drug capture and release [12,13,39,[53][54][55][56][57][58][59], capture of surfactants [12,13,39,60,61], polymers [12,13,39,[62][63][64], or nanoparticles [65]. These encapsulation properties of clay nanolayered stacks are crucial for several engineering applications, e.g.…”