Chitosan aerogel beads production by supercritical gel drying, and their application to methylene blue adsorption

Water contamination from synthetic dyes is an urgent issue often addressed by means of adsorption, which is an easy, cost-effective, and flexible unit operation employed for contaminants removal. In this work, chitosan-based highly porous adsorbents were produced through supercritical drying, featuring a regular, nanostructured, and fiber-like morphology. Methylene blue withdrawal was assessed, exploring the effect of pH, temperature, and adsorbent dosage. The optimal operating conditions were at pH= 8 and T = 25 °C, resulting in an estimated saturation capacity of 196.538 mg/g. Adopting the multi-step strategy, it was possible to reach a value of adsorption efficiency of 88.0 ± 1.1 %. Lastly, chitosan aerogels are recyclable: they retain 88.0 ± 3.2 % of the initial adsorption capacity after five adsorption cycles. Kinetic analysis proved that most of dye withdrawal takes place in the first 10 min, accessing a fast and effective process. Overall, this research aims at proving the effectiveness of nanostructured devices for water remediation, moving a step further the full exploitation of aerogels into industrial scenarios.