Micro-mechanism insights into the adsorption of anionic dyes using quaternary ammonium-functionalised chitosan aerogels

The development of adsorbents with outstanding adsorption capacities, wide versatility, and excellent recycla-bility for the removal of organic dyes remains a challenge. In this study, a quaternised chitosan-based aerogel (QCSA) was fabricated via a facile method to effectively treat concomitant anionic dyes. Porous QCSA with high hydrophilicity, nontoxicity, excellent thermal stability, and sustainability exhibits adsorption properties superior to most previously reported adsorbents. The equilibrium adsorption capacities for Congo red, Sunset yellow, and Methyl orange were 1259.6, 550.2, and 607.5 mg/g, respectively. Notably, the spent QCSA exhibits excellent cyclic performance. The multilayer adsorption, external-internal mass transfer resistance, and adsorption on the active site models were employed to enable a more accurate description of the dynamic characteristics, con-firming that double-layer chemisorption was the dominant process. A quantitative analysis of the electrostatic potential and the independent gradient model further verified that electrostatic interactions, hydrogen bonding, and van der Waals forces led to the highly efficient adsorption of dye molecules. Therefore, the eco-friendly and recyclable QCSA is a promising adsorbent for trapping anionic dyes from aquatic systems.

Automated summary

In this study, a quaternised chitosan-based aerogel (QCSA) was fabricated to effectively treat anionic dyes. QCSA exhibits superior adsorption properties, including high hydrophilicity, non-toxicity, excellent thermal stability, and sustainability. The adsorption capacities for Congo red, Sunset yellow, and Methyl orange were 1259.6, 550.2, and 607.5 mg/g, respectively. The spent QCSA also demonstrates excellent cyclic performance. The study confirms that double-layer chemisorption is the dominant process and electrostatic interactions, hydrogen bonding, and van der Waals forces contribute to the highly efficient adsorption of dye molecules. Therefore, QCSA is a promising eco-friendly and recyclable adsorbent for trapping anionic dyes from aquatic systems.