# Magnetically Modified Bentonite for Optimized Erythromycin Removal via RSM and DFT Analysis

## TL;DR

This paper introduces a new magnetic bentonite material that efficiently removes the antibiotic erythromycin from water.

## Contribution

The novel magnetic modification of bentonite with Fe3O4 nanoparticles significantly enhances erythromycin removal efficiency.

## Key findings

- Optimized conditions achieved 96.2% erythromycin removal using 41.9 mg of adsorbent at 29.1°C for 9.6 hours.
- DFT analysis confirmed strong interactions between erythromycin and the magnetic bentonite composite.
- The Dubinin–Radushkevich and pseudo-first-order models best describe the adsorption behavior.

## Abstract

Erythromycin (ERY), an antibiotic widely used in human and veterinary medicine, persists in the environment due to its low degradability, accumulating in wastewater and soil. This study presents a novel adsorbent synthesized by magnetically modifying calcined natural bentonite with Fe3O4 nanoparticles to enhance ERY removal. The modification increased the surface area, with the highest adsorption observed at pH 11. Adsorption studies revealed that the Dubinin–Radushkevich isotherm model and pseudo-first-order kinetic model best described the adsorption behavior. Response surface methodology (RSM) was employed to optimize key parameters, including adsorbent dosage, temperature, and contact time. The quadratic model indicated optimal conditions of 41.9 mg adsorbent, 29.1 °C, and 9.6 h of contact time, yielding a maximum ERY removal efficiency of 96.2%. Density functional theory (DFT) analysis provided a molecular-level understanding of the adsorption mechanism, identifying strong interactions between ERY, Fe3O4, and bentonite. The theoretical binding energy aligns with experimental results, confirming the role of magnetic modification in promoting ERY adsorption. This study demonstrates a promising approach for mitigating ERY contamination in aqueous environments.