Estudio cinético de la degradación térmica de quitina y quitosano de camarón de la especie “Heterocarpus vicarius” empleando la técnica termogravimétrica en modo dinámico
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Fecha
2010-03
Autores
Benavides Rodríguez, Luis Gerardo
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Universidad Nacional (Costa Rica)
Resumen
Uno de los temas de mayor auge en la actualidad es la preservación del medio ambiente. Por esta razón, la utilización de materiales no perjudiciales al ambiente es una obligación, y a la vez una necesidad imperante para el desarrollo del ser humano. Este hecho ha llamado la atención de la comunidad científica mundial y ha provocado que el estudio de este tipo de materiales sea de importancia para disminuir el alto grado de contaminación presente en la vida cotidiana.
En este campo los biopolímeros han tomado un papel preponderante, puesto que con la implementación de este tipo de materiales en distintas aplicaciones, se busca sustituir muchos de los comúnmente utilizados por otros compuestos con un mayor grado de biodegradabilidad, todo esto en búsqueda de productos y procesos que no impacten el medio ambiente.
La quitina es uno de los biopolímeros más abundantes, por su parte el quitosano es el derivado desacetilado de la quitina. Estos dos compuestos son de gan importancia debido a la aplicación en distintos campos, entre los que se pueden mencionar la agricultura, industria farmacia, la medicina, el tratamiento de aguas residuales y la industria cosmética. Dos características de la quitina y el quitosano, que hacen que estos compuestos sean tan versátiles, son la biodegradabilidad y la biocompatibilidad. Todos estos factores en conjunto hacen que el estudio de estos biopolímeros sea una prioridad, y de esta forma aprovechar mejor el potencial de éstos.
Uno de los métodos utilizado para la caracterización de biopolímeros es el estudio cinético de degradación térmica. Este tipo de análisis brinda información valiosa del proceso de degradación de un material y para determinar las condiciones óptimas en las cuales se lleve a cabo el procesamiento del material analizado. En otras palabras, se utilizan los valores cinéticos como herramientas predictivas del comportamiento de un compuesto.
Este estudio implicó el análisis cinético de degradación térmica de la quitina y el quitosano utilizando la técnica temogravimétrica (TGA) en modo dinámico. El análisis TGA se llevó a cabo en atmósfera inerte de nitrógeno, utilizando un ámbito de temperaturas de 30 hasta 6000C, además con valores de rapidez de calentamiento (P) de 5, IO, 15, 20, 25 y 30
0C/min.
Con los resultados obtenidos en el análisis TGA se aplicaron los modelos cinéticos de degradación de Ozawa, Friedman, Kissinger y Broido. Para la degradación del quitosano todos los modelos aplicados presentaron buen ajuste, por otro lado para la quitina el comportamiento fue diferente, puesto que el único modelo que presentó un buen ajuste lineal fue el de Broido.
A partir de los termogramas obtenidos se determinó que la temperatura de descomposición es mayor para la quitina que para el quitosano, esto debido a la mayor cristalinidad y menor grado de polimerización de la quitina. No obstante, en los valores cinéticos, se obtuvo una mayor energía de activación para el quitosano, producto del entrecruzamiento propiciado por el grupo amino libre. En la aplicación del modelo de Ozawa para quitosano se manifestó el efecto de compensación cinética, de manera que al darse un aumento de la energía de activación, el factor preexponencial incrementa, manteniendo el valor de la constante de velocidad invariable.
One of the most popular topics today is the preservation of the environment. For this reason, the use of materials that are not harmful to the environment is an obligation, and at the same time a prevailing necessity for the development of the human being. This fact has caught the attention of the world scientific community and has caused the study of this type of materials to be important to reduce the high degree of contamination present in daily life. In this field, biopolymers have taken a leading role, since with the implementation of this type of materials in different applications, it seeks to replace many of those commonly used by other compounds with a higher degree of biodegradability, all this in search of products and processes that do not impact the environment. Chitin is one of the most abundant biopolymers, while chitosan is the deacetylated derivative of chitin. These two compounds are of great importance due to their application in different fields, among which agriculture, the pharmaceutical industry, medicine, wastewater treatment and the cosmetic industry can be mentioned. Two characteristics of chitin and chitosan that make these compounds so versatile are biodegradability and biocompatibility. All these factors together make the study of these biopolymers a priority, and thus take better advantage of their potential. One of the methods used for the characterization of biopolymers is the kinetic study of thermal degradation. This type of analysis provides valuable information on the degradation process of a material and to determine the optimal conditions in which the processing of the analyzed material is carried out. In other words, kinetic values are used as predictive tools for the behavior of a compound. This study involved the kinetic analysis of thermal degradation of chitin and chitosan using the thermogravimetric (TGA) technique in dynamic mode. The TGA analysis was carried out in an inert nitrogen atmosphere, using a temperature range of 30 to 6000C, in addition with heating rate (P) values of 5, 10, 15, 20, 25 and 30. 0C/min With the results obtained in the TGA analysis, the kinetic models of degradation of Ozawa, Friedman, Kissinger and Broido were applied. For the degradation of chitosan, all the applied models presented a good fit, on the other hand, for chitin the behavior was different, since the only model that presented a good linear fit was the Broido model. From the thermograms obtained, it was determined that the decomposition temperature is higher for chitin than for chitosan, due to the higher crystallinity and lower degree of chitin polymerization. However, in the kinetic values, a higher activation energy was obtained for the chitosan, product of the crosslinking promoted by the free amino group. In the application of the Ozawa model for chitosan, the kinetic compensation effect was manifested, so that when there is an increase in the activation energy, the pre-exponential factor increases, keeping the value of the rate constant invariable.
One of the most popular topics today is the preservation of the environment. For this reason, the use of materials that are not harmful to the environment is an obligation, and at the same time a prevailing necessity for the development of the human being. This fact has caught the attention of the world scientific community and has caused the study of this type of materials to be important to reduce the high degree of contamination present in daily life. In this field, biopolymers have taken a leading role, since with the implementation of this type of materials in different applications, it seeks to replace many of those commonly used by other compounds with a higher degree of biodegradability, all this in search of products and processes that do not impact the environment. Chitin is one of the most abundant biopolymers, while chitosan is the deacetylated derivative of chitin. These two compounds are of great importance due to their application in different fields, among which agriculture, the pharmaceutical industry, medicine, wastewater treatment and the cosmetic industry can be mentioned. Two characteristics of chitin and chitosan that make these compounds so versatile are biodegradability and biocompatibility. All these factors together make the study of these biopolymers a priority, and thus take better advantage of their potential. One of the methods used for the characterization of biopolymers is the kinetic study of thermal degradation. This type of analysis provides valuable information on the degradation process of a material and to determine the optimal conditions in which the processing of the analyzed material is carried out. In other words, kinetic values are used as predictive tools for the behavior of a compound. This study involved the kinetic analysis of thermal degradation of chitin and chitosan using the thermogravimetric (TGA) technique in dynamic mode. The TGA analysis was carried out in an inert nitrogen atmosphere, using a temperature range of 30 to 6000C, in addition with heating rate (P) values of 5, 10, 15, 20, 25 and 30. 0C/min With the results obtained in the TGA analysis, the kinetic models of degradation of Ozawa, Friedman, Kissinger and Broido were applied. For the degradation of chitosan, all the applied models presented a good fit, on the other hand, for chitin the behavior was different, since the only model that presented a good linear fit was the Broido model. From the thermograms obtained, it was determined that the decomposition temperature is higher for chitin than for chitosan, due to the higher crystallinity and lower degree of chitin polymerization. However, in the kinetic values, a higher activation energy was obtained for the chitosan, product of the crosslinking promoted by the free amino group. In the application of the Ozawa model for chitosan, the kinetic compensation effect was manifested, so that when there is an increase in the activation energy, the pre-exponential factor increases, keeping the value of the rate constant invariable.
Descripción
Benavides Rodríguez, L. G. (2010). Estudio cinético de la degradación térmica de quitina y quitosano de camarón de la especie “Heterocarpus vicarius” empleando la técnica termogravimétrica en modo dinámico. [Tesis de Licenciatura]. Universidad Nacional, Heredia, C.R.
Palabras clave
BIODEGRADACION, BIODEGRADATION, CONTAMINACION, POLLUTION, PROTECCION AMBIENTAL, CINETICA, POLIMEROS