Organic Arsenic Removal by Using Covalently Bonded Iron–Aluminum Loaded Activated Carbon: Synergistic Mechanisms of Enhanced Adsorption and in Situ Hydrogen Peroxide Oxidation

In this study, iron–aluminum covalently bonded modified activated carbon (CAFM@PAC) was prepared by a constant-temperature infiltration method, which demonstrated highly efficient removal capability against p-aminobenzoic acid (p-ASA). The complete degradation of 30 μM p-ASA was achieved within 6 h at a dosage of 2.0 g/L CAFM@PAC, which was attributed to the enhanced adsorption mechanism involving electrostatic, hydrogen bonding, and π–π EDA interactions, as well as synergistic interactions between the Fe/Al/C fractions for the in situ production of H2O2 under acidic conditions, which triggered a Fenton-like reaction for the generation of ROS. The Fe/Al covalent structure promotes rapid electron transfer and accelerated Fe2+/Fe3+ cycling, resulting in a highly efficient H2O2 generation system. DFT calculations and product analysis confirmed that the C3 and C6 sites of p-ASA were the key sites for ROS attack. CAFM@PAC exhibited strong environmental adaptability and high recyclability, and maintains excellent removal efficiencies even in a multi-ionic system, with very low leakage of metal ions. CAFM@PAC showed excellent removal efficiency even in a polyconic system and very low metal ion leakage, demonstrating its potential as a sustainable water treatment material.