Novel films prepared from spirulina and chitosan for textile pollutant removal: Experiments and theoretical study of adsorption equilibrium via an advanced theoretical approach

This study reports the theoretical analysis of the methylene blue (MB) adsorption equilibrium using films prepared from spirulina and chitosan. Experimental isotherms for the dye adsorption were quantified at 24 - 65(degrees)C and pH 8 where the maximum experimental adsorption capacities ranged from 119 to 342 mg/g. A multilayer statistical physics model was applied to simulate and interpret the adsorption data. The modeling showed that the removal of this textile pollutant was associated with a multi-molecular process where dye molecular aggregation was present under tested operating conditions. It was found that the spirulina film showed better adsorption properties at low temperature (i.e., saturation adsorption capacity of 445 mg/g at 25(degrees)C), while the spirulina/chitosan film improved its dye removal performance at high temperature (i.e., saturation adsorption capacity of 336 mg/g at 55(degrees)C). It was deduced that the methylene blue removal was exothermic using spirulina film, while the adsorption of this dye using the spirulina/chitosan film was endothermic. Physical interactions are expected to govern the adsorption of this dye using both biomaterial films. These results allow the understanding of removal mechanism of organic pollutants like textile dyes on novel adsorbents prepared from biomaterials.