Extraction and Characterization of Sodium Alginate from Brown Algae Collected from Siran Valley, Mansehra, Pakistan

Abstract

This study focused on the extraction, purification, and characterization of sodium alginate from brown algae collected from Jabori, Siran Valley, Mansehra, Pakistan, and its evaluation for membrane-based bioseparation applications. Sodium alginate was extracted through formaldehyde pretreatment, acid leaching, alkaline extraction with sodium carbonate, ethanol/acetone precipitation, and neutralization. The extracted product was compared with commercial sodium alginate using FTIR, DSC, XRD, SEM, EDX, fluorescence spectroscopy, intrinsic viscosity, and rheological analyses. FTIR confirmed the presence of hydroxyl, carboxylate, glycosidic, mannuronic, and guluronic acid-related functional groups, showing close similarity with commercial sodium alginate. DSC revealed dehydration peaks near 63–68°C and thermal decomposition around 243–251°C, indicating comparable thermal behavior. XRD showed that the extracted alginate was semi-crystalline, while commercial alginate was mainly amorphous. SEM confirmed compact polymeric morphology, and EDX indicated sodium, oxygen, and trace inorganic elements from the natural algal source. Rheological analysis showed pseudoplastic shear-thinning behavior, suitable for membrane casting. Cross-linked sodium alginate membranes exhibited useful hydrophilicity, porosity, and filtration potential for bovine serum albumin separation. The results demonstrate that locally sourced brown algae can provide sustainable sodium alginate for biodegradable membrane fabrication, supporting regional algal biomass utilization and future low-cost biopolymer membrane development and wider environmentally friendly industrial applications.