Sericin-derived activated carbon-loaded alginate bead: An effective and recyclable natural polymer-based adsorbent for methylene blue removal.

Activated carbon has been widely used as an effective adsorbent for removing contaminants from the water stream. Preparation of activated carbon using agricultural by-products is environmentally friendly and can greatly contribute to the virtuous cycle of natural polymers. In this study, highly porous activated carbon was prepared using silk sericin, a secondary protein of the sericulture industry. For easy processability and regeneration stability, the bead-type adsorbent was prepared using alginate (Alg) as a matrix. After that, methylene blue (MB) removal behavior of sericin-derived activated carbon (S-AC)/Alg beads was investigated. S-AC obtained by NaOH chemical activation had a larger BET surface area (2150.1 m2/g), and this porous structure of S-AC was well maintained after S-AC/Alg bead preparation (1215.4 m2/g). S-AC/Alg beads had an excellent MB adsorption capacity (502.5 mg/g) with stable regeneration stability, and 90.1% of the original removal efficiency was maintained after 5 cycles of the repeated adsorption-desorption process. These findings reveal that S-AC/Alg composite beads can be used as low-cost adsorbents for the removal of contaminants in aqueous solutions.