Synergistic enhancement of persulfate activation by Al-Fe‑carbon hybrid composite for aniline degradation in water

Abstract

Persulfate (PS)-based advanced oxidation process is an excellent technology for removing organic pollutants. Herein, an Al-Fe‑carbon hybrid composite (AlFeOH/CS) by hybridizing bimetal Al-Fe and carbon sphere was synthesized and its ability to activate PS was evaluated. Within 120 min reaction in the presence of PS, 70 % of aniline was removed by FeOH/CS, while >99.9 % of aniline was degraded by AlFeOH/CS. Moreover, AlFeOH/CS exhibited wide pH applicability, relatively high resistance to inorganic anions, and strong stability for PS activation. Electron paramagnetic resonance (EPR) and quenching tests revealed that aniline degradation in the AlFeOH/CS/PS system occurred via a radical pathway, with O₂⁻ the dominant reactive oxygen species. The enhanced photocatalytic activity of AlFeOH/CS was attributed to: Al doping could 1) increase the specific surface area and porosity, exposing more active sites, 2) facilitate electron transfer from Fe atoms to PS, and 3) enhance the generation of carbon-centered persistent free radicals (PFRs). Depending on the carbon-centered PFRs, carbonyl functional groups, sp² and sp³-hybridized carbon, and Fe/Al hydroxides on AlFeOH/CS, PS was effectively activated to produce free radicals for aniline degradation. These findings provide new insights into the design of functional hydrothermal carbonaceous material with high stability and PS activation efficiency for removing organic contaminants.