# Dual-modification of biochar via Fenton oxidation and in situ α-FeOOH synthesis for enhanced Cu(ii) removal: experimental investigation and theoretical calculation analysis

## TL;DR

A new biochar material was developed to efficiently remove copper ions from wastewater using Fenton oxidation and iron oxide modification.

## Contribution

The dual-modified biochar FOBC shows enhanced Cu(ii) removal through chemisorption mechanisms confirmed by experimental and theoretical analysis.

## Key findings

- FOBC exhibited higher Cu(ii) adsorption capacity compared to unmodified and single-modified biochars.
- Adsorption was found to be endothermic, monolayer, and dominated by ion exchange and complexation.
- Density functional theory calculations identified OA-sites in α-FeOOH as strong Cu(ii) binding sites forming bidentate complexes.

## Abstract

In the present study, a facile method combining Fenton oxidation and subsequent α-FeOOH deposition for dual-modification of biochar was developed to prepare an efficient adsorbent for removing Cu(ii) from wastewater. Compared to pristine and single-modified biochars, the dual-modified biochar FOBC had a larger adsorption capacity for Cu(ii). Comprehensive investigations encompassing adsorption isotherms, kinetic studies, and thermodynamic analysis showed that the FOBC-based adsorption of Cu(ii) was dominated by an endothermic, monolayer, chemisorption process. Multiple characterization results showed that the primary mechanisms for the adsorption of Cu(ii) were ion exchange and complexation reactions. The α-FeOOH deposited on the FOBC matrix played the most pivotal role during the adsorption of Cu(ii). To explore the adsorption mechanisms at the electron scale, the density functional theory calculations were conducted. The findings suggested that the OA-site of α-FeOOH was an extremely robust adsorption site, binding with Cu(ii) to form the bidentate complexes. Moreover, FOBC presented remarkable feasibility, reusability, and structural stability, demonstrating its potential application for treating Cu(ii)-containing wastewater.

An innovative composite adsorbent from bamboo biochar was successfully synthesized by dual-modification of Fenton oxidation and surface generation of α-FeOOH and exhibited highly efficient Cu(ii) adsorption.