Lnh. Arakaki et al., Ethyleneimine anchored on thiol-modified silica gel surface - Adsorption of divalent cations and calorimetric data, J COLL I SC, 228(1), 2000, pp. 46-51
Activated silica gel was previously modified by the silylant agent 3-mercap
topropyltrimethoxysilane. The organofunctionalized silica gel containing pe
ndant groups ended with the -SH functions reacted with the three-member cyc
lic ethyleneimine molecules to yield the new ligand attaching sulfur and ni
trogen basic centers available to complex cations. This final anchored surf
ace adsorbs MX2 (M = Co2+, Ni2+, Cu2+, and X = Cl-, NO3-) at 298 +/- 1 K. A
considerable increase in adsorption capacity was observed for nitrate coun
teranions. This process of extraction was followed by the batch method and
the order of the maximum capacities found was Ni2+ > Cu2+ > Co2+ for both s
eries of salts. The pendant immobilized groups-cation interaction processes
showed exothermic enthalpies. Those values are more pronounced for chlorid
es, with the largest values obtained for cobalt. The calculated Delta G val
ues are in agreement with the spontaneity of the proposed reactions and the
complexation is entropically favored. (C) 2000 Academic Press.