Effective decomposition of antibiotic sulfadiazine (SD) in a Fe 0 -catalyzed sonochemical Fenton like system (Sono-FL) was demonstrated. By using the response surface methodology (RSM), an optimized experimental condition of pH 7.00, 0.94 mM Fe 0 , 1.90 mM persulfate (PS) and 20 W ultrasound (US) power was concluded, which could reach the predicted SD degradation efficiency of 90%. Afterwards, effects of wastewater matrix (five inorganic anions and two chelating agents) on the SD degradation were investigated in the system, respectively. It was found that the SD degradation could be inhibited by SO 4 2− , NO 3 − , HCO 3 − /CO 3 2− and H 2 PO 4 − to different extents. Cl − would lead to an enhancement with a low dosage (5 mM), but an inhibition with a high dosage (100 mM). Unexpectedly, chlorinated organic intermediates were also found as SD decomposed. Appropriate dosages of oxalic acid (OxA) or EDTA could benefit the SD degradation in the Sono-FL system, while excessive chelating agents would play as competitive pollutants. It was summarized that inorganic anions would mainly react with SO 4 − and/or OH to form sub-radicals of less oxidative potential. OxA and EDTA would not only participate in complexing dissolution of Fe 0 but also provide additional oxidants such as H 2 O 2 and [Fe IV O] 2+ , through the electron transfer reactions caused by the iron-ligands species.
The detrimental environmental effects of surfactant-like contaminants (SLCs) with distinctive amphiphilic structures have garnered significant attention, particularly since perfluorooctanesulfonate was classified as a persistent organic pollutant. Despite the numerous absorbents developed for SLCs removal, the underlying interaction mechanisms remain speculative and lack experimental validation. To address this research gap, we elucidate the mechanistic insights into the selective removal of SLCs using mesoporous polydopamine nanospheres (MPDA) fabricated via a novel soft-template method. We employed low-field nuclear magnetic resonance to quantitatively characterize the hydrophilicity of the absorbents using water molecules as probes. The results demonstrated that MPDA with uniform mesopores exhibited a remarkable threefold enhancement in SLCs’ adsorption capacity compared to conventional polydopamine particles via intraparticle diffusion. We further demonstrated the dominant effects of electrostatic and hydrophobic interactions on the selective removal of SLCs with MPDA by regulating the isoelectric pH value and performing a comparative analysis. The mechanism-inspired SLC-removal strategy achieved an average removal rate of 76.3% from highly contaminated wastewater. Our findings offer new avenues for applying MPDA as an efficient adsorbent and provide innovative and mechanistic insights for targeted SLC removal in complex wastewater matrices.
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