Iron-Modified Bentonite as an Efficient Heterogeneous Electro-Fenton Catalyst for Amoxicillin Degradation

Abstract

Bentonite-supported iron catalysts (Bent-Fe) were synthesized and investigated for their application in the heterogeneous electro-Fenton process for amoxicillin (AMX) degradation. The synthesized catalyst was thoroughly characterized using BET, XRD and SEM-EDS analyses, which confirmed the successful incorporation and homogeneous distribution of iron within the bentonite matrix. Acid activation significantly increased the specific surface area from 32 to 216 m2 g−1, while subsequent iron impregnation reduced it to 152 m2 g−1, indicating effective iron immobilization within the porous structure. High-resolution XPS analysis of Bent-Fe indicates that the Fe(III) is embedded within the bentonite matrix. These results confirm the successful formation of the Fe(III)-bentonite catalyst, in which both components retain their structural integrity. Adsorption experiments showed that AMX adsorption onto Bent-Fe was negligible over the investigated pH range. Despite this limited adsorption, the electro-Fenton/Bent-Fe system exhibited high degradation efficiencies reaching 95% at pH 3 and 91% at pH 6 after 120 min of electrolysis. These degradation rates corresponded to chemical oxygen demand (COD) removals of 55% and 39%, respectively. The comparable performance near-neutral pH conditions demonstrates the feasibility of operating the heterogeneous electro-Fenton process at near-neutral pH conditions, highlighting the effectiveness of bentonite as a support material for iron stabilization and catalytic degradation of AMX.