Preparation of alginate foam via freeze-drying and post-cross-linking method and its application for dye removal from aqueous solution

Adsorption is an effective method for the treatment of dyed wastewater contaminants the aqueous environments. In this study, an alginate-based foam adsorbent was prepared via freeze-drying and post-cross-linking method and then used to remove methylene blue dye from aqueous solutions. Characterization using different analyzes, kinetics, isotherm, swelling, and regeneration experiments, and the parameters affecting the dye adsorption process such as dye concentration (2-10 mg/L), pH (3-11) were investigated. The findings obtained from the adsorption process indicated that the adsorption of methylene blue using synthetic adsorbents has good conformity with conventional kinetic and isotherm models and the kinetics and isotherm are adjusted with the pseudo-second-order and the Freundlich models, respectively. The adsorption capacity of methylene blue was 3.80 mg/g with 97% removal efficiency for alginate-based foam. With the increase in initial solution pH and dye concentration, better adsorption performance was observed. The prepared adsorbent presented remarkable chemical stability and was readily recyclable after three reuse cycles.