Simulation of the XRD patterns, structural properties of a synthetic Na-Hectorite exchanged Cu²⁺and Ca²⁺

Structural Properties of Synthetic Na-Hectorite Exchanged with Heavy Metals

“…The mineralogical and structural characteristics were determined by comparing the experimental X-ray patterns with the theoretical patterns calculated from structural models [10,11] and permits determination of the number and the position of the intercalated water molecules. The XRD patterns were calculated using the z-coordinates, where the origin of the atomic coordinates was taken at the basal oxygen atoms [2]. The diffracted intensity for a unit-cell along the 00 rod of the reciprocal space is given by the following expression [12]: The relationships between these probabilities and the abundances W A and W B of the different types of layers are given by Drits and Tchoubar [11]: 1) the segregation tendency is given by: W A < P AA and W B < P BB , 2) The total demixion is obtained for P AA = P BB = 1, 3) The regular tendency is obtained if: W A < P BA < 1 and W B < P AB < 1 and finally the limit between the last distribution labelled random distribution when W A = P BA = P AA and W B = P AB = P BB ; with ΣW A = 1, ΣP AB = 1.…”

“…Clay mineral stability in changing environment is the function of their origin, structure, elementary cell charge and dispersion [1][2][3]. Heavy metal cations can be immobilized on silicates by two mechanisms: ion-exchange and chemisorption [4].…”

“…The removal of Cu (II) from aqueous solution by using kaolinite, montmorillonite and their modified adsorbents [8]. In other hand, Ni(II) and Cu(II) were trapped in smectite structure using ion-exchange mechanism [2,5].…”

“…Isomorphic substitution within the tetrahedral and/or octahedral sheets causes a negative charge on the layers, which is balanced by hydrated exchangeable cations in the interlayer space (mainly Ca 2+ , Mg 2+ and Na + ). The hydration states varies and depends on many factor related to the composition of the layers and the nature of the interlayer cation [2,3].…”

Hydration behaviour of synthetic saponite at variable relative humidity

“…Saponite is a trioctahedral smectites with all the octahedral positions occupied by divalent cations, generally Mg(II). Isomorphic substitutions with cations of lower oxidation state may occur in both sheets, producing a negatively charged layer, which is balanced by interlayer hydrated cations (Güven 1988;Karmous et al 2006Karmous et al , 2007. The moderate charge of the layers allows water molecules to penetrate the interlayer space and hydrate the interlayer cations, which results in a swelling of the crystal structure.…”