Green composite aerogel based on citrus peel/chitosan/bentonite for sustainable removal Cu(II) from water matrices

• Published in: Scientific reports Vol. 13; no. 1; p. 15443
• Main Authors: Nie, Jing, Feng, Dan, Shang, Jiangwei, Nasen, Bate, Jiang, Tong, Liu, Yumeng, Hou, Siyi
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 18-09-2023; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301; 704/172; Adsorption; Anions; Bentonite; Cations; Chelation; Chitosan; Copper; Freeze drying; Humanities and Social Sciences; Ionic strength; Ions; Metal ions; multidisciplinary; Organic matter; Science; Science (multidisciplinary); Wastewater
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-023-42409-2

Here, we propose a green and sustainable 3D porous aerogel based on citrus peel (CP), chitosan (CS), and bentonite (BT). This aerogel is prepared through a simple sol–gel and freeze-drying process and is designed for efficient capture of Cu(II) ions from water matrices. CCBA-2, with its abundance of active binding sites, exhibits an impressive Cu(II) adsorption yield of 861.58 mg/g. The adsorption isotherm and kinetics follow the Freundlich and pseudo-second-order models, respectively. In the presence of coexisting mixed-metal ions, CCBA-2 demonstrates a significantly higher selectivity coefficient (K
d
Cu
 = 1138.5) for removing Cu(II) ions compared to other toxic metal ions. Furthermore, the adsorption of Cu(II) ions by CCBA-2 is not significantly affected by coexisting cations/anions, ionic strength, organic matter, or different water matrices. Dynamic fixed-bed column experiments show that the adsorption capacity of Cu(II) ions reaches 377.4 mg/g, and the Yoon-Nelson model accurately describes the adsorption process and breakthrough curve. Through experiments, FTIR, and XPS analyses, we propose a reasonable binding mechanism between CCBA-2 and metal cations, involving electrostatic attraction and chemical chelation between Cu(II) and the functional groups of the aerogel. CCBA-2 saturated with Cu(II) ions can be successfully regenerated by elution with 1 M HNO
3
, with only a slight decrease in adsorption efficiency (5.3%) after 5 adsorption–desorption cycles. Therefore, CCBA-2 offers a cost-effective and environmentally friendly material that can be considered as a viable alternative for the green and efficient removal of toxic Cu(II) ions from wastewater.