Effective adsorption of methylene blue by biodegradable superabsorbent cassava starch-based hydrogel

Superabsorbent hydrogels were synthesized from cassava starch (CS) and polyacrylamide (PAM) via radical po-lymerization. Scanning electron microscope revealed the porous structure of the hydrogels. Pore size was smaller at higher CS contents. Hydrogel containing 50 wt% CS (CS50) showed excellent water absorbency of >8000%, which was much greater than that of CS0 (pure PAM) hydrogel. This CS50 hydrogel removed >85% of methylene blue (MB) in <10 h with the greatest adsorption capacity of 2000 mg MB/g. The experimental results fitted the Freundlich and pseudo-second order models. After 4 cycles of use, the hydrogel could still remove >50% of MB in solution. Interestingly, the hydrogels were photodegradable and biodegradable. Buried in soil, the CS50 hydro -gel was 80% degraded within 30 days whereas pure PAM was only 22% degraded. p (C) 2020 Elsevier B.V. All rights reserved.