The degradation of sulfonamide pollutants in high-salinity wastewater is hindered by chloride radicals scavenging hydroxyl radicals. This study aims to achieve efficient degradation of sulfonamides in high-salinity wastewater by enabling a mechanistic switch from hydroxyl radicals (•OH) to singlet oxygen (1O2). To this end, we fabricated MMFeP-800 °C porous carbon spheres via in-situ growth of MIL-100(Fe) on a MET 6/PVDF/PVP substrate followed by carbonization. In the low-temperature plasma system, we selected nine different types of target pollutants and found that the catalyst was particularly effective toward sulfonamide pollutants. This is attributed to (i) the Fe/N-doped catalyst inducing the generation of 1O2, which enhances the efficient removal of sulfonamide pollutants; (ii) the in-situ growth strategy ensuring full exposure of active components and accelerating interfacial reactions; and (iii) the high-salinity background itself, under plasma action, also promoting the •OH→1O2 conversion, producing a synergistic benefit. Quenching experiments, LC–MS, and DFT calculations elucidated degradation pathways. Cycling tests and biotoxicity assays demonstrated good stability and reduced toxicity, confirming the catalyst's practical potential. This work provides a promising strategy for treating high-salinity wastewater containing sulfonamides.
Nanoscale zero-valent iron (nZVI) is widely investigated for environmental remediation but aggregation, poor transport, and unstable interfacial reactivity continue to limit its practical deployment. This perspective examines nanocellulose (NC) not simply as a stabilizer, but as an interfacial platform that can tune nZVI nucleation, dispersion, transport and redox behavior across multiple length scales. The importance of interfacial stabilization is illustrated by the reported decrease in the interaction energy barrier of nZVI from 124.2 kBT in deionized water to 31.6 kBT under groundwater conditions. We discuss how coordination chemistry, surface charge, and hierarchical confinement influence iron nucleation, particle dispersion, and surface accessibility, while emphasizing that improved stability does not necessarily translate into higher reactivity. CNC, CNF, and BNC are then considered as complementary platforms for electrosteric transport control, macroscopic formability and continuous-flow operation, and biocompatible iron–support interfaces, respectively. Finally, we discuss how groundwater chemistry, scalable processing, manufacturing cost, and life-cycle performance affect practical implementation. Together, these considerations provide a framework for designing nZVI@NC systems that balance particle stabilization, reactive surface accessibility, and application-specific requirements.
Continuous-flow anammox granulation requires effective biomass retention together with sufficient hydrodynamic selection, yet how their balance governs granule development remains unclear. Two continuous stirred-tank reactors with height-to-diameter ratios of 5.17 and 2.30 were operated under comparable loading conditions, and multiphase CFD was integrated with rheological, EPS, surface-interaction, and microbial analyses. At 150 r/min, the power density and mean turbulent dissipation rate in R1 were 2.05 and 2.77 times those in R2, respectively, although both reactors developed similar particle sizes and mechanical strengths by day 92. Thereafter, their trajectories diverged. Increasing R1 to 180 r/min enhanced axial suspension and hydrodynamic selection, accompanied by moderate particle growth to 412.34 μm and an increase in storage modulus to 23.43 kPa. R1 also exhibited a protein-rich tightly bound EPS matrix, favorable interparticle interactions, and sustained enrichment of Candidatus Kuenenia. In contrast, reducing R2 to 120 r/min improved biomass retention but weakened hydrodynamic selection, resulting in rapid particle enlargement to 537.59 μm, while the storage modulus declined to 10.93 kPa and anammox bacterial dominance decreased. These responses defined two distinct trajectories, namely selection-driven mechanical maturation in R1 and retention-driven aggregate enlargement in R2. Granule maturation therefore depended on coordinated particle growth, mechanical consolidation, and functional enrichment rather than particle enlargement alone. For engineering applications, mixing intensity should be selected according to reactor-specific suspension and biomass-retention requirements rather than prescribed as a fixed stirring rate.
Hydrogen peroxide (H2O2) is an eco-friendly oxidant widely used in clean synthesis, water treatment, and energy conversion. Graphitic carbon nitride (g-C3N4) has been explored as a photocatalyst for sustainable H2O2 production, but achieving high selectivity in pure water remains challenging. Here, a controllable vacancy-engineering strategy is developed to introduce nitrogen (NV) and carbon vacancies (CV) into g-C3N4 via alkali-assisted thermal treatment. The optimized CV-g-C3N4 and NV-g-C3N4 achieve remarkable H2O2 selectivity in the pure water increasing from 49.7% to 81.2% and 87.5%, with a surface-area-normalized H2O2 production rate of 65.3 μmol/(L·m2·h). Vacancies reshape the electronic structure by introducing defect states and shifting the N-2p p-band center upward. NV generates shallow defect states that promote electron delocalization, favor end-on O2 adsorption and lower the Gibbs free energies for *OOH formation, thereby promoting selective two-electron oxygen reduction reaction (2e– ORR). In contrast, CV forms deeper defect states that strengthen H2O adsorption and reduce the Gibbs free energies for *OH formation, enabling a coupled 2e– ORR and two-electron water oxidation reaction (2e– WOR) pathway. This study elucidates the distinct redox roles of Nv and CV in photocatalysis and provides a vacancy-engineering blueprint for designing efficient, metal-free photocatalysts toward sustainable H2O2 generation.
Stormwater runoff contains high levels of dissolved organic matter (DOM) that serve as precursors for disinfection byproducts (DBPs) during chlorination. The effect of advanced oxidation processes (AOPs) pretreatment on subsequent DBP formation remains uncertain, particularly under varying water matrices. Stormwater runoff from four functional zones (residential, commercial, transportation, and educational) was treated with three UV-based AOPs (UV/H2O2, UV/persulfate, and UV/ferrate), followed by chlorination. DOM transformation was characterized by dissolved organic carbon (DOC) removal, molecular weight (MW) distribution, hydrophobicity, and fluorescence indices. All three AOPs achieved > 87% DOC removal, near-zero aromaticity, and a shift of MW to < 1 kDa. However, subsequent chlorination revealed divergent DBP formation patterns governed by ammonia-nitrogen (NH4+-N) concentration. In high-NH4+-N runoff (residential and commercial, 15 and 6 mg/L), the ammonia-induced chlorine demand largely depleted free chlorine during post-chlorination, forming monochloramine as the dominant chlorinating agent. AOP converted DOM into low-MW intermediates that exhibited enhanced reactivity toward monochloramine, increasing both trihalomethanes (THMs, up to 6-fold) and haloacetonitriles (HANs, up to 10-fold). In low-NH4+-N runoff (transportation and educational, 2–3 mg/L), free chlorine dominated and AOPs directly degraded DBP precursors, reducing both THMs (up to 65%) and HANs (up to 67%). Thus, high NH4+-N drives a risk shift toward increased DBPs, whereas low NH4+-N enables effective DBP control. These findings suggest that for high-NH4+-N stormwater, ammonia pre-removal is advisable before AOP + chlorine, while for low-NH4+-N runoff, AOPs alone can serve as an effective DBP control strategy.
