Authors:Edson C. da Silva Filho, Pedro D. R. Monteiro, Kaline S. Sousa, and Claudio Airoldi
In this work Chitosan (Ch) was chemically modified with ethylenesulfide (Es) under solvent-free conditions to give (ChEs), displaying a high content of thiol groups due to opening of the three member cyclic reagent. ChEs was used in studies of lead and cadmium adsorption from aqueous solution, using the batchwise method and calorimetric studies were accomplished to those interactions, through the calorimetric titration technique. The obtained results show that the modified Ch, ChEs is a material, that besides presenting the advantages of being a biopolymer, it showed a good adsorption capacity of the lead and cadmium cation metallic, that are extremely poisonous and harmful to the environment. The results of the calorimetric titration showed that the related thermodynamic parameters to those adsorptions shown favorable thermodynamic data.
Authors:Edson da Silva Filho, Sirlane Santana, Júlio Melo, Fernando Oliveira, and Claudio Airoldi
Cellulose was chemically modified with SOCl2 to obtain chlorodeoxycellulose, followed by a reaction that gave bonded ethylene-1,2-diamine (en), producing 6-(2′-aminoethylamino)-6-deoxycellulose.
The reactions were carried out without the presence of solvent, in water or in N,N′-dimethylformamide, in which the highest amount of amino compound was incorporated onto the biopolymer backbone. The X-ray
diffraction patterns for the chlorodeoxycellulose indicate new crystallinities that result from hydrogen bonds established
through bonded chorine atoms and the remaining hydroxyl groups, while all the aminodeoxycelluloses were amorphous compounds.
Thermal stabilities, for all aminated celluloses gave lower final mass losses than for the chlorinated biopolymer, whose value
is lower than unmodified cellulose.
Authors:Maria da Fonseca, Ramon Almeida, Albaneide Wanderley, Ulysses Ferreira, Luiza Arakaki, José Simoni, and Claudio Airoldi
Polar n-alkylmonoamines of general formula H3C(CH2)nNH2 (n = 1, 3, 5) interacted with layered silicate vermiculite at the solid/liquid interface. The maximum amount of amine intercalated
(Nf) inside the interlamellar space were 0.62, 0.46, and 0.38 mmol g−1, to give the following order of intercalation ethyl → butyl → hexylamines. The layered vermiculite solid was suspended in
deionized water and calorimetrically titrated with this series of amines, to give favorable thermodynamic data, such as exothermic
enthalpy, negative Gibbs free energy and positive entropy data.
Authors:Luiza N. H. Arakaki, V. H. A. Pinto, V. L. S. Augusto Filha, M. G. Fonseca, J. G. P. Espínola, Tomaz Arakaki, and Claudio Airoldi
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.
Authors:Alexandre G. S. Prado, Sheila M. Evangelista, Jurandir R. SouzaDe, Jeane G. S. Matos, Marco A. A. Souza, Denise A. Oliveira, and Claudio Airoldi
A microcalorimetric method was applied to study microbial soil activity of ornamental flower (Dahlia pinnata) plantations when irrigated with potable water and wastewaters. The samples were irrigated with potable water PW sample (reference) and treated wastewaters from Municipal Wastewater Treatment Station of Asa Norte in Brasilia City (Brazil). Three different water treatments were applied to irrigate soil samples, named TW1, TW2, and TW3 samples. The increase of the microbial soil activity observed in TW1 sample must have occurred because of the high amount of organic waste dissolved in wastewater used for irrigation. This rise indicates that the present treated wastewater can affect natural life cycle. However, only a low alteration in microbial soil activity was observed in the TW2 and TW3 samples, which suggests that these wastewater treatments can be normally used to irrigate soils without bringing environmental consequences, once they offer a great opportunity to upgrade and protect the environment.