Synthesis and characterization of a new adsorbent for capture of metal from aqueous solutions
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A new material containing a potential ligand for transition metals was prepared through the reaction of 3-aminopropyltrimethoxysilane and thioglycolic acid. The new adsorbent was characterized by elemental analyses, infrared spectroscopy, solid-state 13C nuclear magnetic resonance, thermogravimetric analysis, transmission electron microscopy, and specific surface area calculations. The formulated material was used in the removal of cobalt, copper, and nickel cations from aqueous solutions. Calorimetric titration was applied to study the interaction of these cations with the new adsorbent; the latter displayed a chelating moiety with basic centers containing nitrogen, oxygen, and several sulfur atoms, capable of capturing cations from aqueous solutions. This process of extraction was carried out by a batch method to yield the following order of maximum retention capacity: Ni > Co > Cu. The process of cation interactions showed exothermic enthalpies. The calculated ΔG values are in agreement with the spontaneity of the proposed reactions and conformed to the values found by applying the Langmuir model to these systems. The positive entropy and negative enthalpy values indicated that the reactions are favorable.
KeywordsThioglycolic acid Adsorption Calorimetric titration Thermodynamic data
The authors are indebted to Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—CAPES and Conselho Nacional de Desenvolvimento Científico e Tecnológico—CNPq for fellowships and financial support.
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