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Study of the Gelling Process in the La‐Co ‐Citric Acid System
Author(s) -
Predoana Luminita,
Jitianu Andrei,
Malic Barbara,
Zaharescu Maria
Publication year - 2012
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2011.04965.x
Subject(s) - citric acid , lanthanum , chelation , cobalt , chemistry , aqueous solution , inorganic chemistry , reagent , metal , metal ions in aqueous solution , nuclear chemistry , organic chemistry
The gelling process in the aqueous lanthanum‐cobalt‐citric acid system was studied using UV‐VIS and IR spectroscopic methods, as well as viscosity measurements, to establish the gelling mechanism of transition metal ions ( La 3+ and Co 2+ ) in the presence of chelating agent. Lanthanum and cobalt nitrates and lanthanum and cobalt acetates, respectively, were used as starting reagents, and the citric acid was used as chelating agent. The gelation process was investigated at room temperature and at 80°C. At elevated temperature, the gels were obtained after 30 h, whereas at room temperature, these were obtained in 1 month. Complex gels were formed for the both studied systems. The Co 2+ ions mainly present an octahedral symmetry during the whole gelation process, whereas the citric acid acts as monodentate or bridging ligand depending on the metal precursors used. The mechanism of formation of the La‐Co‐CA based gels with the coordinative structures was proposed.