Starch-based self-assembled three-dimensional network nanostructure materials for sustainable cascade adsorption

Toward the development of a sustainable utilization strategy for adsorption materials, a starch-based adsorbent starch–chitosan–tannic acid (St–CTS–TA) with a three-dimensional (3D) structure was fabricated in water via electrostatic and hydrogen bonding reactions between St, CTS, and TA without using toxic reducing agents or special instruments. St-CTS-TA demonstrated a high specific surface area of 37 m 2 /g as well as a mesoporous/macroporous distribution ranging from 30 to 80 nm, which enhanced the mass transfer of adsorbate and the exposure of catechol groups in TA. The Langmuir isotherm adsorption model revealed that the highest adsorption capacities of St–CTS–TA for Fe 3+ and Co 2+ were 1678.2 and 944.8 mg/g, respectively. Surprisingly, the specific surface area of St–CTS–TA increased from 37 to 87 and 42 m 2 /g after Fe 3+ and Co 2+ adsorption, respectively, and the resulting St–CTS–TA–Fe and St–CTS–TA–Co could continuously adsorb basic fuchsin (BF) and rhodamine B (RhB). The adsorption capacities of St-CTS-TA-Fe and St-CTS-TA-Co for BF/RhB were found to be 1854.79/401.19 mg/g and 2229.77/537.49 mg/g, respectively, based on the Langmuir isotherm adsorption model.