Effective adsorptive removal of a cationic dye from aqueous solutions using a biosorbent derived from Sargassum sp.

Abstract

The present research evaluated the potential use of the macroalgae biomass Sargassum sp., which was modified with a filamentous fungus Cunninghamella echinulata for the biosorption of methylene blue (MB) dye. The modified fungal biomass (FERsarg) was obtained through solid-state fermentation. The FERsarg showed a pHPZC of 7.9, a low mass loss, material micro/mesoporous, and the presence of hydroxyl, carboxylic, phenolic, and carbonyl functional groups. The influence of dosage, solution pH, contact time, initial concentration, and temperature were evaluated for MB biosorption, and the best results were obtained at 2 g L-1 and pH 6. The kinetic study revealed a better fit for the pseudo-second-order model, while the Sips model best described the equilibrium experimental data. The equilibrium was attained within 180 min and showed qmax yielding of 115.49 mg g-1 at 323 K. The thermodynamic understanding of the present research revealed that the biosorbent exhibited spontaneous, exothermic, and physical nature of MB removal. The adsorptive mechanism shows that the process was controlled by electrostatic attraction. The present results reveal the viability of using fermented biomass as a potential adsorbent, contributing to the follow-up of zero waste, and support the concept of circular bioeconomy.