Structure, laser scattering, optical properties, adsorption, and dye removal studies by Ulvan extracted from the green seaweed Ulva lactuca

Abstract

Ulvan, a sulfated polysaccharide polymer derived from green seaweed, was extracted from the marine alga Ulva lactuca and characterized by static laser scattering technique and showed a molecular weight of 43513 g/mol. Using a precipitation method, ulvan film was fabricated with a thickness of 2 µm. X-ray diffraction studies indicated the semicrystalline nature of ulvan. The optical characteristics of the ulvan film were computed and revealed a direct energy gap of 3.39 eV, with the dispersion energy and single oscillator energy being determined to be 13.783 and 7.425 eV, respectively. Subsequently, ulvan was used as an adsorbent to extract methylene blue dye from a water solution. After 30 min, the dye had been removed to an 86.8 % proportion. Moreover, TD-DFT simulation was used for the isolated ulvan molecule to estimate several physio-chemical parameters from HOMO and LUMO energies as well as to examine the electron density and electrostatic potential diagrams. Furthermore, additional significant polymeric physical properties were estimated for the isolated ulvan molecule. Furthermore, TD-DFT/CASTEP simulation was used to theoretically estimate the optical properties, and the results were consistent with the experimental findings. Lastly, research on the molecular adsorption of ulvan and methylene blue revealed a positive interaction between the two.