# Preparation, Adsorption Performance and Mechanism of Low-Cost Desert Sand-Based Pb (II) Ion-Imprinted Composites

## TL;DR

Researchers created a low-cost, efficient material from desert sand to selectively remove lead ions from contaminated water.

## Contribution

A novel, low-cost Pb (II) ion-imprinted composite using desert sand is developed for efficient and selective lead removal from wastewater.

## Key findings

- The composite achieved a maximum adsorption capacity of 107.44 mg·g−1 for Pb (II) ions.
- The material showed high selectivity for Pb (II) and retained 80.3% efficiency after eight reuse cycles.
- Adsorption was confirmed to be spontaneous, endothermic, and entropy-increasing.

## Abstract

Pb (II) contamination in wastewater represents a grave threat to the environment and ecosystems. Consequently, there is an urgent need to prepare low-cost and highly efficient Pb (II) adsorbents. To address this need, abundant and low-cost natural silica-based desert sand (DS) was innovatively utilized as a carrier to develop efficient and selective Pb (II) adsorbents. Modified desert sand (MDS) was first prepared via 1 M HCl pretreatment for 2 h and subsequent KH550 silane modification. Pb (II)-imprinted composites (Pb (II)-IIP@MDS) were then fabricated via ion-imprinted polymerization, using Pb (II) as the template ion and N-hydroxymethacrylamide (NHMA)/hydroxyethyl methacrylate (HEMA) as dual functional monomers with a molar ratio of 1:1. The synthesized Pb (II)-IIP@MDS was comprehensively characterized by X-ray photoelectron spectrometer (XPS), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR). The adsorption capacity, selectivity, and reusability of this material for lead ions were evaluated through three experiments conducted within the optimized pH range of 6–7, with error bars indicated. In adsorption isotherm experiments, the initial Pb (II) concentration ranged from 50 to 500 mg·L−1, conforming to the Langmuir model (R2 = 0.992), with a theoretical maximum adsorption capacity reaching 107.44 mg·g−1; this indicates that the adsorbate forms a monolayer adsorption on the homogeneous imprinted sites. Kinetics data indicate that the process best fits a quasi-first-order kinetic model (R2 ≥ 0.988), while the favorable quasi-second-order kinetic fit (R2 ≥ 0.982) reflects the synergistic effect of physical diffusion and ion-imprinting chemistry, reaching equilibrium within 120 min. Thermodynamic parameters (ΔH0 = 12.51 kJ·mol−1, ΔS0 = 101.19 J·mol−1·K−1, ΔG0 < 0) confirmed endothermic, entropy-increasing, spontaneous adsorption. In multicomponent systems, Pb (II)-IIP@MDS showed distinct Pb (II) selectivity. It retained 80.3% adsorption efficiency after eight cycles. This work provides a promising strategy for fabricating low-cost, high-performance Pb (II) adsorbents, and Pb (II)-IIP@MDS stands as a practical candidate for the remediation of Pb (II)-contaminated wastewater.