Characterization and extraction of sodium alginate from Tunisian algae: synthesizing a cross-linked ultrafiltration membrane

Tunisian algae are abundantly present in our sea coasts and can be easily extracted and used for the production of biopolymers such as sodium alginate. The aim of the present study was to extract sodium alginate and to synthesize an ultrafiltration membrane by phase inversion method. The synthesized sodium alginate was characterized using differential scanning calorimetry (DSC), X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The FTIR spectra of synthesized sodium alginate exhibited strong similarity with those of the commercial sodium alginate. The XRD peaks of extracted sodium alginate demonstrated a semi-crystalline structure, while the commercial sodium alginate showed an amorphous structure. The SEM of extracted sodium alginate showed a smooth and porous structure. The DSC results displayed that the decomposition temperature values are 243 and 251 degrees C for commercial sodium alginate and 243 degrees C for extracted sodium alginate. The dehydration process of commercial and extracted sodium alginate was 68 and 63 degrees C, respectively. Membranes were immersed completely in a reaction solution at 25 degrees C that contained a specific content (2.5% by weight) of calcium chloride (CaCl2) as a source of divalent cation. Membranes were immersed in the above solution for cross-linking for 2 h followed by immersion in glutaraldehyde (GA) solution (5% by weight) for 5 h. ALG3 showed the highest effectiveness in the removal of bovine serum albumin around 90% at 2 bar. The flux showed the values of 25.51 and 22.86 L/h m(2) for ultrapure water and BSA, respectively. The ALG3 was chosen as the best membrane. [GRAPHICS] .