DFT and Monte Carlo investigation and simulations of PA@Palygorskite nanosorbent in cadmium removal from water

Abstract

Removing cadmium pollutant from wastewater by natural adsorbents represents an eco-friendly and promising strategy. Materials like clay often suffer from low-moderate adsorption capacity, limited stability, and poor reusability, which restrict their practical use. To overcome these challenges, the current study is directed to focus on enhancing the performance of thermally treated Palygorskite (Pal500) clay via functionalization with pentetic acid (PA) to generate a novel nanosorbent (PA@Pal500). This was extensively characterized to assess its structural and surface properties. Adsorptive removal studies were optimized at pH (1–7), PA@Pal500 dosage (10–100 mg), temperature (15–55 °C), contact time (2–120 min), initial Cd(II) concentrations (1.0 and 5.0 mg/L), and ionic strength. Thermodynamic analysis indicated that Cd(II) adsorption by PA@Pal500 was correlated to endothermic and spontaneous reactions. Furthermore, PA@Pal500 exhibited excellent regeneration capability, confirming its successive reusability. The efficiency of PA@Pal500 in the removal of Cd(II) pollutant was validated by real polluted samples, achieving 92.0–95.0% efficiency. Computational results from both DFT and Monte Carlo simulations showed that Cd(II) could bind favorably to Pal500 as well as to PA. However, Pal500 provided more stable adsorption energies along with a wider variety of active sites on its surface. In contrast, PA tended to coordinate with Cd(II) in a more focused way, mainly through its oxygen‑based donor groups, with some additional contribution from nitrogen atoms. Collective findings elucidate that PA@Pal500 is a highly effective and sustainable material for cadmium pollutant removal from contaminated water, offering strong potential for real-world environmental remediation applications.