Biodegradação de hidrogéis à base de alginato de sódio e quitosana em solo argiloso

Abstract

In this dissertation, the biodegradation of hydrogels based on sodium alginate and chitosan in ultisol was investigated. The soil was obtained from a private property located in the municipality of Campos dos Goytacazes, in the northern region of the state of Rio de Janeiro, promising for the agricultural expansion of soybeans and corn. Biodegradation tests were carried out, where pH and soil moisture were monitored. The degraded hydrogels were analyzed by infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetry (TG), scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). In order to obtain more information about the microorganisms responsible for the biodegradation of the hydrogels, a microbiological study of the soil was carried out. Biodegradability tests revealed that the hydrogels were completely biodegraded within six weeks. Soil with hydrogel remained wetter than soil without hydrogel after seven days for up to eight weeks. Such results indicated the potential of the material as a soil conditioner. Using FTIR and Raman, it was possible to identify the breaking of polymeric chains through the glycosidic bond, even with electrostatically crosslinked polysaccharides. SEM and confocal microscopy analysis showed fragmentation of the hydrogel structure, thus altering its morphology. The microbiological tests proved that the hydrogels based on sodium alginate and chitosan were used as a source of carbon by fungi isolated from the clayey soil used, with indications that fungi of the genera Aspergillus, Penicillium and Cunninghamella, in addition to yeasts, were responsible, among others, for such consumption.