How bis-pyridine N cellulose aerogels highly selectively adsorb Cu2+ from acidic wastewater: An experimental, Molecular dynamics and Density functional theory investigation

To evaluate the potential of aerogel materials for selectively recovering Cu 2+ from highly acidic wastewater, the adsorption behavior of Cu 2+ by bis-pyridine N-functionalized cellulose (PEIPD/CMC) aerogel was systematically investigated. Characterization of structural and chemical properties of the absorbent revealed that the bis-pyridine N plays a crucial role in the adsorption process. The PEIPD/CMC aerogel exhibited excellent adsorption capacity and selectivity for Cu 2+ in multi-component acidic solutions (Cu 2+ /Zn 2+ /Pb 2+ ), achieving a maximum adsorption capacity of 1.19 mmol/g at pH = 2. The adsorption process was well-described by the pseudo-second-order model and the Langmuir model, indicating monolayer chemisorption. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses confirmed the involvement of bis-pyridine N groups in the adsorption of heavy metals. To further elucidate the interaction mechanisms between PEIPD/CMC and heavy metals at the microscopic level, Molecular dynamics (MD) simulations and Density functional theory (DFT) were conducted. MD simulations revealed that the adsorption process is predominantly governed by chemisorption, with the binding strength of the adsorbent to heavy metals following the order Cu 2+ > Zn 2+ > Pb 2+ . DFT calculations provided direct evidence of the chelation mechanism, highlighting the role of energy and electron transfer in the selective adsorption of Cu 2+ . These findings conclusively demonstrate that bis-pyridine N is the key functional group responsible for the selective adsorption of Cu 2+ .