Qiang He

Heterogeneous electro-Fenton (HEF) systems hold great potential for decentralized water purification, yet concurrently achieving high catalytic activity, structural stability, and controlled reactive oxygen species (ROS) selectivity remains challenging. Herein, we propose a spatiotemporal magnetic decoupling strategy to concurrently address these design objectives. The carbon shell spatially separated exterior Fe0 satellites from the FeNx core, eliminating deleterious short-range magnetic quenching and altering the local magnetic environment to modulate the internal Fe(III) spin state. The resulting low-spin Fe(III) sites suppressed electron back-donation into the H2O2 σ∗ antibonding orbital, favoring an additional 1O2 generation pathway. Spatial decoupling also enabled a gradient cascade activation of H2O2 across the Fe0 and FeNx domains, synergistically boosting the evolution of both •OH and 1O2, with steady-state concentrations reaching 18.25 and 5.27 μM, respectively. Consequently, the FeNx@C–Fe0-based HEF achieved complete naproxen degradation within 60 min with significantly suppressed Fe leaching (0.85 mg L–1), outperforming all comparative systems. Comprehensive characterizations and density functional theory (DFT) calculations established a definitive relationship between topological engineering and spin-state dynamics. Furthermore, the system demonstrated proof-of-concept applicability in real hospital wastewater, highlighting the potential of spatiotemporal spin-state engineering for regulating ROS evolution in HEF systems.

Algal blooms, carbon emission hotspots in aquatic ecosystems, typically are accompanied by high microplastics (MPs) levels. However, the role of MPs in algae-driven carbon cycling remains elusive. Here, Microcystis aeruginosa(M. aeruginosa) was used to investigate the responses of CO₂ and CH₄ emissions to MPs during cyanobacterial harmful algal blooms (cHABs, a predominant algal bloom type), integrating physicochemical analysis and high-resolution chemical and microbial approaches to elucidate the role of MPs in carbon emissions throughout growth-decline phases of algal blooms. The results exhibited three phases. In phase I, MPs facilitated M. aeruginosa growth, thereby stimulating aerobic CH₄ production through photosynthesis-coupled reactive oxygen species mechanisms. As aggregate settling dynamics varied with heteroaggregation, the survival patterns of M. aeruginosa changed, reducing CO₂ and CH₄ production through decreasing carbon substrates in phase II. However, M. aeruginosa decay, accelerated by MPs, not only enhanced anaerobic organic matter utilization in water, but also elevated the nominal oxidation state of carbon in sediment, promoting hydrogenation and altering the balance between methanogenesis and methanotrophy, subsequently increasing CO₂ and CH₄ production in phase III. Ultimately, MPs exacerbated cumulative carbon emissions of cHABs, suggesting MPs as facilitators behind algal blooms being foci of carbon emissions.

Introduction: Simultaneous chemical phosphorus removal process using iron salts (Fe(III)) has been widely utilized in wastewater treatment to meet increasingly stringent discharge standards. However, the inhibitory effect of Fe(III) on the biological phosphorus removal system remains a topic of debate, with its precise mechanism yet to be fully understood.Methods: Batch and long-term exposure experiments were conducted in six sequencing batch reactors (SBRs) operating for 155 days. Synthetic wastewater containing various Fe/P ratios (i.e., Fe/P = 1, 1.2, 1.5, 1.8, and 2) was slowly poured into the SBRs during the experimental period to assess the effects of acute and chronic Fe(III) exposure on polyphosphate-accumulating organism (PAO) growth and phosphorus metabolism.Results: Experimental results revealed that prolonged Fe(III) exposure induced a transition in the dominant phosphorus removal mechanism within activated sludge, resulting in a diminished availability of phosphorus for bio-metabolism. In Fe(III)-treated groups, intracellular phosphorus storage ranged from 3.11 to 7.67 mg/g VSS, representing only 26.01 to 64.13% of the control. Although the abundance of widely reported PAOs (Candidatus Accumulibacter) was 30.15% in the experimental group, phosphorus release and uptake were strongly inhibited by high dosage of Fe(III). Furthermore, the abundance of functional genes associated with key enzymes in the glycogen metabolism pathway increased while those related to the polyphosphate metabolism pathway decreased under chronic Fe(III) stress.Discussion: These findings collectively suggest that the energy generated from polyhydroxyalkanoates oxidation in PAOs primarily facilitated glycogen metabolism rather than promoting phosphorus uptake. Consequently, the dominant metabolic pathway of communities shifted from polyphosphate-accumulating metabolism to glycogen-accumulating metabolism as the major contributor to the decreased biological phosphorus removal performance.