Three-dimensional porous sodium alginate/gellan gum environmentally friendly aerogel: Preparation, characterization, adsorption, and kinetics studies

Three-dimensional porous sodium alginate/gellan gum aerogels (SAG aerogels) were prepared by the method of freeze-drying and ion cross-linking for the removal of methylene blue (MB) in wastewater. The physical morphology and chemical structure of the SAG aerogels were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The results revealed that the addition of gellan gum (GG) formed interpenetrating double network structures by ion cross-linking and hydrogen bonding interaction with sodium alginate (SA), which improved the chemical resistance of SAG aerogels and the adsorption capacity of aerogel for MB at a mass ratio of 3:1. The pseudo-second-order kinetic model and Langmuir isothermal model could be used to describe the adsorption process of MB, and the maximum adsorption capacity of the SAG aerogel for MB was 1456.45 mg/g, at 313 K. The adsorption thermodynamic analysis results showed that the adsorption process of MB was spontaneous and exothermic. After 5 adsorption-desorption cycles, the adsorption capacity of SAG aerogel only decreased 1.44% compared with their initial adsorption capacity. The obtained results indicated that the SAG aerogels could be successful and effective used to remove the MB in wastewater.