# Mechanistic Insights into the Cooperative Removal of NH3 and H2S by Persimmon Polyphenols with Natural Deep Eutectic Solvent Systems

## TL;DR

This study explores how persimmon polyphenols, when combined with natural deep eutectic solvents, can effectively remove ammonia and hydrogen sulfide odors through specific chemical interactions.

## Contribution

The novel use of natural deep eutectic solvents to enhance persimmon polyphenols' odor-removal capabilities through cooperative microenvironment regulation.

## Key findings

- Chloride-citric acid NADES was optimal for persimmon polyphenol extraction and ammonia removal.
- Betaine-urea NADES was more effective for hydrogen sulfide removal due to acid-base and hydrophobic interactions.
- NADESs enhance deodorization by regulating microenvironments rather than causing irreversible chemical changes.

## Abstract

Persimmon polyphenols (PP) are natural polyphenols with high reactivity and strong deodorization potential; however, their practical application in odor control is limited by their poor solubility. In this study, natural deep eutectic solvents (NADESs) were employed for the green extraction of PP, and the capabilities of extracts on the removal of ammonia (NH3) and hydrogen sulfide (H2S) were investigated. In addition, the underlying mechanisms were explored by integrating spectroscopic analysis, molecular dynamics simulations, and quantum chemical calculations. The results showed that chloride-citric acid (CC-CA) was the optimal system in both PP extraction and sustained NH3 removal, while the betaine-urea (B-U) system was more effective for H2S removal. NH3 removal was governed by acid-base neutralization, with the resulting ammonium species being further stabilized within the PP-regulated NADES hydrogen-bond network. In contrast, H2S interacted with the solvent network not only through acid-base neutralization but also via Van der Waals forces and hydrophobic contacts. Our data supported that NADESs enhanced the deodorization performance of PP through cooperative microenvironment regulation rather than irreversible chemical conversion. This work highlighted that NADESs could not only function as highly efficient extraction media for polyphenols, but also active platforms for enhancing selective gas-capture capability for polyphenols. Furthermore, it provided a new strategy for the rational design of green, persimmon-derived deodorants.