Sorption and thermodynamic of cation–basic center interactions of inorganic–organic hybrids synthesized from RUB-18

Synthesized nanostructured hybrids from RUB-18 layered silicate, containing one (N) or three (3N) basic nitrogen atoms attached to pendant chains were applied for copper, nickel and cobalt sorptions. The isotherms obtained from batchwise processes were adjusted to the Freundlich and the Langmuir–Freundlich models for heterogeneous systems. The basic nitrogen centers/acidic cation interactions were followed by calorimetry under batchwise conditions and the results were analyzed by a modified Langmuir equation. The exothermic enthalpic values of −2.50 ± 0.30, −1.62 ± 0.10 and −1.35 ± 0.20 and −15.61 ± 0.20, −8.05 ± 0.14 and −20.48 ± 0.15 kJ mol−1, obtained for Cu2+, Ni2+ and Co2+ titrations with C-RUB-xN (x = 1, 3) materials, suggest a favorable process at the solid/liquid interface for inorganic/organic hybrid cation sorptions. These thermodynamic data, expressed also by reaction spontaneity, infer the use of such hybrids for cation removal from aqueous solution.