Mesoporous silica functionalized with diethylenetriamine moieties for metal removal and thermodynamics of cation–basic center interactions

Modified coupling agents based on thiourea, immobilized onto silica. Thermodynamics of copper adsorption

“…For this parameter there is a favorable contribution from the exothermic enthalpic values. On the other hand, with the exception of the NT surface, the other entropic values are also favorable with positive values, which normally are connected to the displacement of the solvent initially bonded either in the cation coordination sphere or through hydrogen bonds to the basic atoms attached to the pendant chains [32]. During the adsorption process, as the reaction is progressing, water molecules are displaced to the medium, to cause a degree of disorder of the system and, consequently, an increase in entropy [33].…”

RETRACTED: Immobilization of 5-amino-1,3,4-thiadiazole-thiol onto kanemite for thorium(IV) removal: Thermodynamics and equilibrium study

“…As observed, cation/basic center interactions for all system are spontaneous in nature as reflected in their negative enthalpic values. 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 [48,49]. 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 inorganic matrices, which is reinforced by desolvation of the cation before interacting with basic centers.…”

“…These values suggest that, during complex formation, desolvation disturbs the structure of the reaction medium to promote the disorganization of the system and, consequently, leads to an increase in entropy [18,19,25,48,49].…”

“…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 inorganic matrices, which is reinforced by desolvation of the cation 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 [48,49].…”

Materiais híbridos à base de sílica obtidos pelo método sol-gel

“…[110][111][112] Adicionalmente, é possível inserir nesses materiais grupos orgânicos quelantes, com sítios específicos, que possibilitam a adsorção de metais. Já foram desenvolvidos materiais adsorventes de metais pesados de interesse ambiental, tanto em meio aquoso 22,[113][114][115][116][117][118][119] como também em meio etanólico, 120,121 sendo que alguns apresentaram seletividade a cátions específicos como Cu(II) e Hg(II). [122][123][124] Além de adsorventes de metais, os materiais híbridos de classe II também têm sido usados na adsorção de compostos orgânicos de interesse ambiental.…”