Methyl Orange Adsorption using Chitosan-Based Composite Aerogels Produced by Supercritical Gel Drying

Chitosan-based composites are interesting materials for dye adsorption. In this work, methyl orange (MO) adsorption using chitosan (CH) and chitosan-graphene oxide (CH-GO) aerogels produced by supercritical gel drying was assessed, by studying the effect of driving force (25-100 ppm) and adsorbent dosage (1-8 g/L). It was highlighted that the difference in the performance between the two adsorbents was non-negligible only at high concentrations, due to more intense interactions between the adsorbent active sites and MO molecules. Starting from a 10 ppm MO solution, using a dosage of 8 g/L it was possible to achieve adsorption efficiency of about 85%, meaning that small amounts of nanostructured devices can result in good process outcomes. Freundlich isotherm reliably describes the system behavior, leading to the consideration that adsorption between MO and CH-GO takes place between different active sites. Moreover, PSO kinetic describes the general trend of this system through time, unveiling heterogeneous chemisorption; lastly, the multi-linear IPD kinetic model confirms that in the case of nanostructured porous devices, there are different mass transfer phenomena that control molecule diffusion through the system.