Silicic acid magadiite as a host for n-alkyldiamine guest molecules and features related to the thermodynamics of intercalation

Abstract

Somen-alkyldiamines with thegeneral formulae H2N(CH2)nNH2 (n = 2–5) were intercalated into the layered silicic acid magadiite, from aqueous solution, causing an increase in the original interlayer distance of 1172 pm. The synthetic magadiite and all intercalated compounds were characterized by elemental analysis, infrared vibrational spectroscopy, X-ray diffractometry, 29Si nuclear magnetic resonance in the solid state, thermogravimetry, scanning electron microscopy, surface area and porosity. The intercalation was followed through a batch-wise method at 298±1 K and gave the maximum amounts 3.70, 2.80, 1.75 and 1.18 mmol g−1, for n varying from 2 to 5, respectively. The well characterized magadiite was calorimetrically titrated in a heterogeneous medium, to obtain the thermodynamic data of intercalation at the solid/liquid interface. Linear correlations were obtained for the number of moles intercalated (Nf), th einterlamellar distance (d) and the specific enthalpy (Δinth) values of the interactive process as a function of the number of C atoms of the aliphatic organic chains (nC) for n-alkyldiamine: Nf = (5.36±0.25) − (0.86±0.07)nC, d = (1406.6±1.9) + (20.9±0.5)nC and Δinth = (5.96±0.25) + (0.06±0.01)nC. The basic N guest atom/silanol acidic center interactions inside the host nanospace gallery gave exothermic enthalpies, positive entropies and negative Gibbs free energy values. This set of data suggests the spontaneity of these intercalation reactions.

RETRACTED: Immobilization of 5-amino-1,3,4-thiadiazole-thiol onto analogue of heulandite for divalent toxic metals removal

“…These thermodynamic data confirmed the energetically favorable condition of such interactions at the solid/liquid interface for all systems. The preparation of modified heulandite with groups that present chemical affinity with these contaminants is one of proposed solutions for these environmental problems [12][13][14].The original heulandite, HEU, showed for the silicon [15] nucleus two main peaks located at À100.0 and À112.0 ppm. These signals named Q 3 and Q 4 , respectively.…”

Mercury adsorption on natural and organofunctionalized smectites - thermodynamics of cation removal

“…As expected, the silylating agent is covalently bonded inside the free cavity formed by smectite layers, through the reaction with the available hydroxyl groups inside the inorganic surfaces. 25 Based on the inorganic tetrahedral-octahedral-tetrahedral smectite arrangement 15 with a layer thickness of 0.89 nm, the immobilized pendant chains can be accommodated along the original 0.10 nm. From these values, net expansions of 0.95 and 1.12 nm values corresponds to the final arrangements after inserting the silylating agents inside the free cavity space.…”

“…However, the mercury cation is originally solvated and identically the available basic centers attached to the pendant chains. As the reaction takes place, the bonded solvent molecules will be free and disturb the original structure of the reaction medium to promote disorganization of the system and, consequently, lead to an increase in entropy, [25][26][27][28][29] to yield favorable thermodynamic data for this system.…”

Adsorption of thorium(IV) on chemically modified Amazon clays

“…In fact, this cation acts as on acidic Lewis center that interacts with the basic Lewis centers attached to the pendant molecules covalently bonded to the modified clay surfaces. [19][20][21][22][23][24][25][26][27] Processes occurring at the solid/liquid interface give the isotherms that demonstrate the saturation of the natural and modified clay samples with a definite number of moles of tetravalent metallic cations, as clearly shown in Figures 5a and 5b with the highest pronounced adsorption for S HOM and S HET , respectively. Based on the ability of the pendant groups attached to the inorganic backbone in coordinating this metallic cation, the quantity can be related to N f max , which presents the values for the metal/clay system of 9.57, 9.89, 8.29 and 8.86 × 10 -1 mmol g -1 for S HOM , S HET , K HOM and K HET , respectively (see Table 3).…”

“…The series of exothermic enthalpic data did not permit distinguishing a preference of any particular cation to bond with the available basic centers attached to the pendant groups covalently bonded to the backbone. [20][21][22] However, the positive entropic values for all interactions that contribute to the favorable interactive process are associated with solvent molecule displacement, initially bonded to the modified clay samples, which is reinforced by desolvation of the metallic cations before interacting with basic centers. In such interactive processes the increase in free molecules in the reaction medium gives a positive entropy, thus demonstrating a favorable set of thermodynamic data for this kind of system.…”