# New Insights into the Adsorption Mechanism of Vanadium Through Quaternary Ammonium Salt-Functionalized SiO2: Synergistic Experiments Utilizing Energy Decomposition Analysis

## TL;DR

This study explores how vanadium binds to silica modified with quaternary ammonium salts, revealing that chemical bonds and non-bonding interactions are key to the adsorption process.

## Contribution

The paper introduces energy decomposition analysis to quantify the roles of chemical and non-bonding interactions in vanadium adsorption by functionalized silica.

## Key findings

- SiO2@DMOA achieved 99.40% vanadium adsorption and a maximum capacity of 39.16 mg g−1.
- Chemical bonds contributed 80.26% to the interaction energy between functional groups and vanadium.
- Steric hindrance, charge, polarizability, and solvation effects significantly influence the adsorption process.

## Abstract

Introducing organic functional groups to adsorbent surfaces enhances vanadium adsorption, an effective strategy for vanadium enrichment. In a quest for a profounder comprehension of the above adsorption mechanism, this study synthesized five types of quaternary ammonium salt-functionalized silica (QAS-SiO2) and investigated the influence of functional groups, pH values, contact time, and temperature on vanadium (V) adsorption. The results indicated that the optimal QAS-SiO2 (SiO2@DMOA) achieved a vanadium adsorption rate of 99.40% and a maximum adsorption capacity of 39.16 mg g−1. SiO2@DMOA exhibited favorable adsorption selectivity for V over chromium (Cr), with a maximum separation factor (βV/Cr) of 135.42 at pH 3.3. SiO2@DMOA maintained efficient adsorption performance over five repeated cycles. A fusion of adsorption trials with energy decomposition analysis (EDA) tentatively unveiled that both chemical bonds and non-bonding interactions contributed to the interaction energy between organic functional groups and vanadium. Among them, chemical bonds accounted for 80.26%, while non-bonding interactions accounted for 19.74%. Based on EDA analysis, the interaction characteristics of different structural quaternary ammonium salts with vanadium in adsorption and extraction processes are discussed. Additionally, steric hindrance, the charge of the vanadium species, polarizability, and solvation effects, all played significant roles in the adsorption process.