High strength chitin/chitosan-based aerogel with 3D hierarchically macro-meso-microporous structure for high-efficiency adsorption of Cu(II) ions and Congo red

A high-strength aerogel with a 3D hierarchically macro-meso-microporous structure (HPS-aerogel) was designed based on biological macromolecules of chitin and chitosan. The macropores can be created within HPS-aerogel after CaCO3 removal, and meso-micropores resulting from water sublimation during freeze-drying. The macro-meso-microporous structure endowed HPS-aerogel with high porosity, good mechanical properties, and excellent compression strength (1472 kPa at strain of 80 %). The HPS-aerogel exposed many adsorption sites and was used as an adsorbent to simultaneously remove Cu(II) and Congo red (CR) from water for the first time. The adsorption capability for Cu(II) and CR was 59.21 mg/g and 2074 mg/g at 303 K, respectively, and the adsorption processes matched Pseudo-second-order and Langmuir models with spontaneous and endothermic nature. Additionally, HPS-aerogel showed good anti-interference ability for coexisting pollutant. Importantly, HPS-aerogel exhibited an effective fixed-bed column adsorption performance for dynamic Cu(II) and CR with superior reusability and stability. Furthermore, HPS-aerogel showed outstanding adsorption efficiencies for Cu(II) and CR in real samples. The main adsorption mechanism for Cu(II) was attributed to the electrostatic attraction and chelation, and which was electrostatic attraction, Schiff base, and hydrogen bonding for CR. Therefore, HPS-aerogel should to be a promising adsorbent for removing both heavy-metal ions and dyes from wastewater.