# Spectroscopic, Thermally Induced, and Theoretical Features of Neonicotinoids’ Competition for Adsorption Sites on Y Zeolite

## TL;DR

This study explores how neonicotinoid pesticides compete for adsorption on Y zeolite using theoretical and experimental methods to understand their environmental behavior and removal potential.

## Contribution

The study introduces a combined theoretical and experimental approach to assess neonicotinoid adsorption competition on Y zeolite for environmental remediation.

## Key findings

- Acetamiprid and imidacloprid have similar adsorption energies (-2.2 eV), while thiamethoxam has a lower energy (-1.7 eV).
- Hydrogen bonding is the dominant adsorption mechanism confirmed by FTIR analysis.
- At higher concentrations, thiamethoxam's adsorption is reduced due to weaker binding energy.

## Abstract

The competitive retention of pollutants in water tables determines their environmental fate and guides routes for their removal. To distinguish the fine differences in competitive binding at zeolite adsorption centers, a group of neonicotinoid pesticides is compared, relying on theoretical (energy of adsorption, orientation, charge distribution) and experimental (spectroscopic and thermogravimetric) analyses for quick, inexpensive, and reliable screening. The MOPAC/QuantumEspresso platform was used for theoretical calculation, indicating close adsorption energy values for acetamiprid and imidacloprid (−2.2 eV), with thiamethoxam having a lower binding energy of −1.7 eV. FTIR analysis confirmed hydrogen bonding, among different dipole-dipole interactions, as the dominant adsorption mechanism. Due to their comparable binding energies, when the mixture of all three pesticides is examined, comparative adsorption capacities are evident at low concentrations, owing to the excellent adsorption performance of the FAU zeotype. At higher concentrations, competition for adsorption centers occurs, with the expected thiamethoxam binding being diminished due to the lower bonding energy. The catalytic impact of zeolite on the thermal degradation of pesticides is evidenced through TG analysis, confirming the adsorption capacities found by UV/VIS and HPLC/UV measurements. Detailed analysis of spectroscopic results in conjunction with theoretical calculation, thermal profiles, and UV detection offers a comprehensive understanding of neonicotinoids’ adsorption and can help with the design of future adsorbents.