https://orcid.org/0000-0001-6039-4046
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Abstract
Galactomannans can be extracted from various plant species, including those of the Cassia grandis Linn. f. (Fam. Caesalpiniaceae), a native Brazilian tree. The objective of this work was to obtain galactomannans by three different extraction methods and to characterize them owing to structure and rheological behavior in aqueous saline fluids that are typically applied for enhanced oil recovery. The largest yield obtained was 23.4 wt% and the mannose/galactose ratios were between 1.1 and 1.5. All the gums extracted were characterized by Proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, Elementary Analysis (CHN) and X-Ray Diffraction demonstrating their galactomannan structures. Thermogravimetric analyses allowed determining the real concentration of organic matter present in the final extraction product, which was near 70 wt%. The greatest molar mass of the Cassia gum was Mw = 1.01 × 106 g/mol, determined by Size-exclusion chromatography and since it is a nonionic biopolymer, it was not influenced by the salinity of the prepared synthetic aqueous solutions with high salt concentrations (TDS = 29,711 mg/L and 68,317 mg/L), including the solutions containing divalent cations. Under a shear rate of 7.3 s−1, Cassia gum from method A showed the highest apparent viscosity values that were approximately 158, 78 and 55 mPa s, at concentration of 5,000 ppm and temperatures of 25, 60 and 80 °C, respectively. Thus, Cassia gum stood as a promising biopolymer for enhanced oil recovery application.
Graphical Abstract
Cassia gum extraction and characterization from Cassia grandis seeds obtained by method A, B and C.
Acknowledgments
This research was carried out in association with the ongoing R&D project registered as ANP 20700-1, “Desenvolvimento de biopolímeros para aplicação em recuperação avançada de petróleo” (Universidade Federal do Rio de Janeiro (UFRJ)/Shell Brasil/ANP) – Development of biopolymers for EOR application, sponsored by Shell Brasil as part of its Research and Development Investment required by the ANP.