Binglin Guo

FeCl3-activated biochar (Fe-MBC) was synthesized from dairy manure via a one-step activation/pyrolysis process and subsequently applied for the degradation of perfluorooctanoic acid (PFOA) in an Fe-MBC/persulfate (PS)/H2O2 system. The FeCl3 activation significantly increased the specific surface area of the biochar and promoted the formation of iron oxides (Fe3O4 and Fe2O3) on its surface, thereby enhancing both adsorption capacity and catalytic activity toward PFOA in aqueous solutions. Under ambient conditions, the Fe-MBC/PS/H2O2 system achieved nearly complete removal (~100%) of 40 mg L−1 PFOA within 120 min. Mechanistic investigations revealed that superoxide radicals (O•– 2) would play a dominant role in PFOA degradation, facilitating carbon–carbon bond cleavage and fluoride ion release. The identification of shorter-chain perfluorinated intermediates further confirmed a stepwise carbon-chain shortening pathway. Toxicity assays demonstrated that the treated effluent exhibited significantly reduced biotoxicity compared to the initial PFOA solution. Additionally, the catalyst maintained high stability and reusability, retaining 94% removal efficiency after three consecutive cycles. The system also performed effectively in real wastewater, achieving 92% PFOA removal, highlighting its potential as a robust and efficient technology for PFAS remediation.

The increasing presence of antibiotics in water sources threatens public health and ecosystems. Various treatments have been previously applied to degrade antibiotics, yet their efficiency is commonly hindered by the presence of natural organic matter (NOM) in water. On the contrary, we show here that nine types of NOM and NOM model compounds improved the removal of trimethoprim and sulfamethoxazole by ferrate(VI) (Fe^VIO₄^2-, Fe(VI)) under mild alkaline conditions. This is probably associated with the presence of phenolic moieties in NOMs, as suggested by first-order kinetics using NOM, phenol, and hydroquinone. Electron paramagnetic resonance reveals that NOM radicals are generated within milliseconds in the Fe(VI)-NOM system via single-electron transfer from NOM to Fe(VI) with the formation of Fe(V). The dominance of the Fe(V) reaction with antibiotics resulted in their enhanced removal despite concurrent reactions between Fe(V) and NOM moieties, the radicals, and water. Kinetic modeling considering Fe(V) explains the enhanced kinetics of antibiotics abatement at low phenol concentrations. Experiments with humic and fulvic acids of lake and river waters show similar results, thus supporting the enhanced abatement of antibiotics in real water situations.

Elucidating the interactions between metal ions and dissolved organic matter and deciphering mechanisms for their mineralization in the aquatic environment are central to understanding the speciation, transport, and toxicity of nanoparticles (NPs). Herein, we examine the interactions between Ag⁺ and Au³⁺ ions in mixed solutions (χ_Ag = 0.2, 0.5, and 0.8) in the presence of humic acids (HAs) under simulated sunlight; these conditions result in the formation of bimetallic Ag–Au NPs. A key distinction is that the obtained alloy NPs are compositionally and morphologically rather different from NPs obtained from thermally activated dark processes. Photoillumination triggers a distinctive plasmon-mediated process for HA-assisted reductive mineralization of ions to bimetallic alloy NPs which is not observed in its dark thermal reduction counterpart. The initial nucleation of bimetallic NPs is dominated by differences in the cohesive energies of Ag and Au crystal lattices, whereas the growth mechanisms are governed by the strongly preferred incorporation of Ag ions, which stems from their greater photoreactivity. The bimetallic NPs crystallize in shapes governed by the countervailing influence of minimizing free energy through the adoption of Wulff constructions and the energetic penalties associated with twin faults. As such, assessments of the stability and the potential toxic effects of bimetallic NPs arising from their possible existence in aquatic environments will depend sensitively on the origins of their formation.