Fe3+/Fe2+ cycling drove novel ammonia oxidation and simultaneously removed lead, cadmium, and copper

Using sludge biochar@waste pellet ore@kelp extract to enhance Feammox and removal of heavy metals: Performance evaluation and possible metabolic mechanisms

The co-occurrence of nitrogen (N) and heavy metals (HMs) in industrial wastewater has emerged as a critical environmental challenge. Feammox-mediated N removal remains constrained by limited iron (Fe(III)) bioavailability and microbial susceptibility to HMs toxicity. This study developed a multifunctional composite through strategic integration of sludge-based biochar (SBC), pellet ore (PO), and kelp extract (KE) to overcome these limitations. The optimized bioreactor configuration, leveraging synergistic interactions among three distinct waste-derived resources, achieved exceptional removal efficiencies of 90.1, 96.4, and 93.4% for NH4+, NO3-, and COD, respectively. Immobilization mechanisms of HMs involved bio-Fe precipitate adsorption and Fe-EPS-HMs chelation. Microbial community analysis demonstrated selective enrichment of Fe-cycling genera (Geothrix, Zoogloea, and Aquabacterium) and metal-resistant species (Cloacibacterium, Paenibacillus). These advancements establish a sustainable paradigm for industrial wastewater management, while simultaneously addressing critical challenges of resource recovery and waste valorization within circular economy frameworks.

Biotransformation of iron oxide nanoparticles and their impact on biokinetics in rats following intratracheal instillation

Understanding the biokinetics of inhaled nanomaterials is essential for evaluating their potential adverse effects, yet current analytical methods may not account for biotransformation-where nanoparticles are transformed into new particle types. This study compared the biokinetics of partially soluble Fe2O3 and poorly soluble TiO2 to investigate how biotransformation influences lung clearance kinetics. Test nanoparticles (140 µg/rat) were instilled into the lungs of rats, and quantitative and qualitative assessments were performed on samples collected from the lungs on days 0, 1, 7, 14, 28, and 90 post-instillation. Notably, this study focused on the biokinetics of particulate forms within the lungs to specifically address particokinetics. Fe2O3 exhibited biphasic clearance kinetics, with rapid clearance in the early phase (days 0-14; half-life of 13 days) and slow clearance in the late phase (days 14-90; half-life 123 days). This biphasic pattern was attributed to the erosion of Fe2O3 into smaller, nanometer-sized particles, approximately 40 % of which persisted in the lungs for over 3 months. These retained particles showed reduced oxidative potential and were sequestered in ferritin protein, mitigating potential toxicity. In contrast, TiO2 exhibited a monophasic clearance pattern with a half-life of 88 days and did not exhibit particle degradation. These findings underscore the critical role of biotransformation in understanding the long-term safety and toxicity of inhaled nanomaterials, highlighting the need for comprehensive studies to assess their biological fate and potential risks. Further research should focus on potential adverse effects due to particle overload, interactions with biomolecules, and disruptions in metal homeostasis.

Nano-Fe3O4/FeCO3 modified red soil-based biofilter for simultaneous removal of nitrate, phosphate and heavy metals: Optimization, microbial community and possible mechanism

The pollution of nitrogen, phosphorus and heavy metals in surface water is becoming more and more serious, affecting the safety of water quality. In this study, three biofilters were constructed using iron-modified red soil-based filler carriers (RSC, nano-Fe3O4@RSC, and FeCO3@RSC) combined with strain Zoogloea sp. ZP7 to simultaneously remove nitrate (NO3--N), phosphate (PO43--P), copper (Cu2+), and zinc (Zn2+). The long-term operation results showed that the three groups of biofilters could remove 85.0 %, 90.0 %, and 89.8 % of NO3--N, respectively. Furthermore, the addition of iron compounds enhanced the removal of PO43--P and the resistance to the stress of Cu2+ and Zn2+ in the biofilter. The analysis illustrated that iron modification improved the redox activity and zeta potential of RSC surface. The secondary structure analysis of the protein showed that the microbial secreted proteins were more compact on the surface of the iron-modified RSC, which facilitated the formation of biofilm on the carrier surface. In addition, the iron-modified RSC-based biofilter also showed excellent NO3--N and PO43--P removal efficiency in the treatment of actual surface water. The microbial community analysis results showed that Zoogloea became the dominant species in the biofilter. On the other hand, the presence of iron-reducing bacteria and the expression iron cycle-related genes may contribute to denitrification under low nutrient conditions.