Nano zero-valent iron improves anammox activity by promoting the activity of quorum sensing system

nZVI-assisted fusion strain F14 for efficient remediation of octogen: Performance and synthetic mechanisms

High-energy explosives in aquatic ecosystems pose severe environmental and health risks due to their toxicity, mobility, and persistence. The efficacy of traditional microbial remediation is often hindered by high pollutant toxicity and limited electron donor. In this study, nanoscale zero-valent iron (nZVI) was employed to enhance the performance of the screened microbial strain, F14, addressing the challenge of octogen (HMX, a typical explosive) contamination in aquatic systems. The results demonstrate that the integration of nZVI significantly improved HMX degradation efficiency, achieving nearly complete removal (∼100 %) compared to a modest 10.1 % degradation with F14 alone. The underlying mechanism was further investigated, focusing on the sequential response and synergistic effect. Specifically, within the sequential response, nZVI rapidly detoxified HMX into bioavailable intermediates (such as (Z)-1,3,5-trinitro-1,2,3,4,5,6-hexahydro-1,3,5,7-tetrazocine (P5) and 1,3,5,7-tetranitroso-1,3,5,7-tetrazocane (P12)) through denitration and nitro-reduction, which primed the system for subsequent efficient degradation and complete mineralization by strain F14. Regarding the synergistic effect, the initial HMX degradation was augmented by the F14-mediated rejuvenation of nZVI's active surface. Concurrently, the subsequent breakdown of intermediate was intensified by the electron donor supplied by nZVI to F14, along with the nZVI-induced extracellular secretion from F14. This work provides theoretical and technical support for the efficient degradation of high-energy explosives.

Application of sponge iron-carbon to enrich anaerobic ammonia-oxidizing bacteria from sludge mixture and coupled denitrification for degradation of industrial wastewater

For the treatment of industrial wastewater, coupled iron‑carbon micro-electrolysis (ICME) with anaerobic ammonia oxidation (anammox) and denitrification was optimized under the following conditions: Fe/C = 2, C/N ≤ 2, and the temperature was 30 °C. The coupled ICME enriched ammonia-oxidizing bacteria (AnAOB) and denitrifying bacteria (DB) in the mixed sludge on the 76th day of the present experiment. Stable operation was achieved on the 78th day. The COD and TN removal rates during the operation were 86.20 % and 87.12 %, respectively, while the control group (without iron and carbon) had removal rates of 74.30 % and 60.31 % which were 11.9 % and 26.81 % higher, respectively. Notably, the abundance of AnAOB in the system increased from 0.44 % to 1.43 % during the operation from day 76 to day 100. High-throughput sequencing demonstrated that Candidatus_Kuenenia was a key anaerobic ammonia-oxidizing bacterium. Based on the experimental results, the ICME process could rapidly enrich anaerobic ammonia-oxidizing bacteria to change the microbial community structure of the sludge under the water quality conditions of industrial wastewater and increasing the tolerance of certain DB and Candidatus_Kuenenia to water quality. By combining with iron‑carbon, the rapid modification of mixed sludge was achieved, and the iron‑carbon micro-electrolysis coupled denitrification anaerobic ammonia oxidation process was established, which provides a certain reference value for treating industrial wastewater.

The mechanism and prospect of exogenous promoters enhancement Anammox at low temperatures: a review

The anaerobic ammonium oxidation (Anammox) process has revolutionized nitrogen removal in wastewater treatment with its exceptional cost-effectiveness and carbon-neutral characteristics. Nevertheless, the intrinsic psychrophilic sensitivity of anaerobic ammonium-oxidizing bacteria (AnAOB), particularly their rapid metabolic suppression below 15 °C, poses a critical bottleneck for sustainable implementation in cold-climate regions. Recent advancements in exogenous stimulation strategies offer promising solutions to this challenge, with particular emphasis on iron supplementation and cryogenic activity regulators (CARs) due to their non-invasive operational compatibility and mechanistic versatility. This review provides a comprehensive analysis of the operational performance, functional enzyme activity, and microbial abundance associated with the use of iron and CARs as exogenous promoters in low-temperature Anammox system. Building upon current limitations in single-factor approaches, the dual-modulation strategy integrating iron-chelated CARs complexes are proposed, which leverages the complementary benefits of iron-mediated metabolic activation and CARs-induced cryoprotection, potentially enabling year-round Anammox operation under low temperatures. This mechanistic-to-applied review provides critical insights for advancing Anammox implementation in circular economy-driven wastewater infrastructures under climate change scenarios.

Enhancing anammox granular sludge for mainstream anammox process by adding iron-loaded diatomite: Performance and intrinsic mechanism

Iron-loaded diatomite (Fe-DE) was developed as the innovative material to enhance anammox granular sludge (AnGS) and mainstream anammox performance. By adding Fe-DE with the Fe:DE ratio of 1:20 and the dosage of 3 g/L, the start-up period of mainstream anammox process was shortened from 29 d to 17 d and its nitrogen removal rate was increased from 0.234 kg N/(m3·d) to 0.437 kg N/(m3·d). AnGS generated more hydrophobic functional groups and redox substances, forming the robust particle structure and improving the electron transfer of anammox reaction. In addition, the key genes PleC, PleD and TrpE/G, related to quorum sensing, increased from 502.69, 91.18 and 18.25 CPM to 532.84, 103.66 and 19.96 CPM. The key genes hzs and hdh related to anammox process also increased by 30.76% and 24.26%. As a result, formation of AnGS was promoted and the enrichment level of Candidatus Brocadia was improved. This study provides a novel insight into the development of innovative material for enhancing mainstream anammox process.

Unraveling the resistance mechanism of anammox granular sludge to iron nanoparticles

Iron nanoparticles (FeNPs) generated from industrial activities could end up into the sewer system, and potentially affect wastewater treatment processes. The impact of FeNPs on anammox process is getting increasing attention. However, the resistance mechanism of anammox granular sludge (AnGS) to FeNPs has not been fully elucidated. The current study investigated the metabolic and morphological response of AnGS to acute and chronic FeNPs exposure. Results showed that nitrogen removal efficiencies were elevated at 1-4 mM FeNPs concentrations compared to 0-0.5 mM FeNPs. Extracellular protein and tyrosine-like and tryptophan-like fluorophore secretions of AnGS were stimulated by FeNPs, which largely contributed to the adsorption of FeNPs on AnGS surface. FeNPs exposure triggered higher necrotic fraction of AnGS compared with no FeNPs condition. Highly absorbed particles appeared inside the bacterial cells of AnGS, soft X-ray imaging illustrated that anammox bacteria maintained intact cellular and anammoxosome structures whereas non-anammox bacterial structures were damaged under FeNPs exposure. Anammox bacterial abundance increased from 4.84% to 20.64%, when FeNPs concentrations increased from 0 mM to 4 mM, and anammoxosome membrane ensured anammox bacterial metabolism under FeNPs exposure. This study extended fundamental understanding of AnGS resistance mechanisms to FeNPs.

Nano-micro materials regulated biocatalytic metabolism for efficient environmental remediation: Fine engineering the mass and electron transfer in multicellular environments

The escalating energy and environmental crises have spurred significant research interest into developing efficient biological remediation technologies for sustainable contaminant and resource conversion. Integrating engineered nano-micro materials (NMMs) with these biocatalytic processes offers a promising approach to improve the microbial performance for environmental remediation. Core to such material-enhanced hybrid biocatalysis systems (MHBSs) is the rational regulation of metabolic processes with the assistance of NMMs, where a fine engineered mass and electron transfer is beneficial for the improved biocatalytic activity. However, the specific mechanisms of those NMMs-enhanced microbial metabolisms are normally overlooked. Here, we review the recent progress in MHBSs, focusing primarily on the mass/electron transfer regulation strategies for an enhanced microbial behavior. Specifically, the NMMs-regulated mass and electron transfer in extracellular, interfacial, and intracellular environment are summarized, where the patterns of diverse microbiological response are discussed thoroughly. Notably, fine modifications of cell interfaces and intracellular compartments by NMMs could even endow the biohybrids with new metabolic functions beyond their natural capabilities. Further, we also emphasize the importance of matching the various metabolic demands of biosystems with the diverse properties of NMMs to achieve efficient environmental remediation through a coordinated regulation strategy. Finally, major challenges and opportunities for the future development and practical implementation of MHBSs for environment remediation practices are given, aiming to provide future system design guidelines for attaining desirable biological behaviors.

The concentration of Lithium in water resources: A systematic review, meta-analysis and health risk assessment

The presence of trace elements such as lithium (Li) in water resources in the long term can endanger consumers' health. Several studies have been conducted on Li concentration in water sources; hence, this study attempted to retrieve studies using a systematic search. The search was conducted in Web of Sciences, Embase, PubMed, and Scopus databases from 1 January 2010 to 15 January 2023. Li concentration was meta-analyzed based on the type of water resources and countries subgroups in the random effects model (REM) statistical analysis. In addition, health risk assessment in different age groups was calculated using the target hazard quotient (THQ). This study included 76 papers with 157 data reports in our meta-analysis. The overall pooled concentration of Li was 5.374 (95 % CI: 5.261-5.487 μg/L). The pooled concentration of Li in groundwater (40.407 μg/L) was 14.53 times surface water (2.785 μg/L). The highest water Li content was attributed to Mexico (2,209.05 μg/L), Bolivia (1,444.05 μg/L), Iraq (1,350 μg/L), and Argentina (516.39 μg/L). At the same time, the lowest water Li content was associated with Morocco (1.20 μg/L), Spain (0.46 μg/L), and India (0.13 μg/L). THQ due to Li in water resources in consumers of Iraq, Mexico, South Africa, Afghanistan, Bolivia, Portugal, Malawi, South Korea, Nepal, South Korea, Argentina, and the USA was higher than 1 value. Therefore, continuous monitoring of Li concentration in water sources and reducing Li concentration, especially in groundwater water, using new water treatment processes in these countries are recommended.

Unraveling the synergistic promotion mechanism of Fe0 coupling phragmites australis biomass for nitrogen removal in coastal wetland: From low to moderate salinities

The simulated coastal constructed wetlands supplemented with Fe0 and phragmites australis (P.A) biomass (CW-M) were constructed to improve nitrogen removal under different salinities (0-15‰). Results showed that the denitrification performance of CW-M were improved significantly, with the higher NO3--N removal of 72-94% and lower N2O emission flux, when compared with mono-P.A biomass(CW-bio), mono-Fe0 system (CW-Fe) and control system. The nitrogen removal showed a trend of first increasing (0‰-7‰) and then decreasing (7‰-15‰) with the highest NO3--N removal of 94% and enhanced removal efficiency of 41% in CW-M. Fe0 and P.A biomass coupling could reduce the stress of salinity on denitrification. Batch experiments have demonstrated that Fe0 and P.A biomass could mutually stimulate more total organic carbon and total iron (TFe) release as electron donors for denitrification. Meanwhile, appropriate salinity could also promote the release of TFe. The typical heterotrophic denitrifying genera Bacillus and iron autotrophic denitrifying genera Thermomonas have the highest proportion in CW-M, with 21.83% and 0.10%, respectively. Fe0 and P.A biomass adding simultaneously promoted the carbon and iron metabolism, further enhancing the nitrogen metabolism process. The joint enhancement of autotrophic and heterotrophic denitrification contributes to NO3--N removal in CW-M for treating saline, low C/N wastewater in coastal wetlands.

Nanoscale zero-valent iron alleviated horizontal transfer of antibiotic resistance genes in soil: The important role of extracellular polymeric substances

Extracellular polymeric substances (EPS) are tightly related to the horizontal gene transfer (HGT) of antibiotic resistance genes (ARGs), but often neglected in soil. In this study, nanoscale zero-valent iron (nZVI) was utilized for attenuation of ARGs in contaminated soil, with an emphasis on its effects on EPS secretion and HGT. Results showed during soil microbe cultivation exposed to tetracycline, more EPS was secreted and significant increase of tet was observed due to facilitated HGT. Notably, copies of EPS-tet accounted for 71.39 % of the total tet, implying vital effects of EPS on ARGs proliferation. When co-exposed to nZVI, EPS secretion was decreased by 38.36-71.46 %, for that nZVI could alleviate the microbial oxidative stress exerted by tetracycline resulting in downregulation of genes expression related to the c-di-GMP signaling system. Meanwhile, the abundance of EPS-tet was obviously reduced from 7.04 to 5.12-6.47 log unit, directly causing decrease of total tet from 7.19 to 5.68-6.69 log unit. For the reduced tet, it was mainly due to decreased EPS secretion induced by nZVI resulting in inhibition of HGT especially transformation of the EPS-tet. This work gives an inspiration for attenuation of ARGs dissemination in soil through an EPS regulation strategy.

Feasibility of simultaneous optimization of Anammox start-up and nitrogen removal performance by intermittent dosing of nanoscale zero-valent iron

The long acclimation period and sensitivity to environmental conditions of Anammox are the bottlenecks for its promotion and application. An innovative strategy was adopted to accelerate functional microbial enhancement and improve nitrogen removal performance by inoculating cryopreserved Anammox sludge and activated sludge with intermittent dosing of nanoscale zero-valent iron (nZVI). The acclimation time was shortened by 76 days with nitrogen removal efficiency (NRE) reaching up to 91.07 %. Anammox, NDFO (nitrate/nitrite-dependent Fe(II) oxidation), Feammox (Fe(III) reduction coupled with anaerobic ammonium oxidation) and abiotic reactions were coupled in the system with nZVI, contributing to 69.79 %, 15.14 %, 9.84 % and 0.25 % of nitrogen removal, respectively. Further microbial analysis demonstrated significant enrichment of functional microorganisms, such as Candidatus Jettenia, Acidovorax and Comamonas. High-efficient nitrogen removal was attribute to the increase of functional genes involved in Anammox, electronic transfer, heme C synthesis and iron metabolism. This work provides an inspiring idea for the mainstream Anammox application.

Metagenomic unveils the promotion of mainstream PD-anammox process at lower nZVI concentration and inhibition at higher dosage

The partial-denitrification-anammox (PdNA) process exhibits great potential in enabling the simultaneous removal of NO3--N and NH4+-N. This study delved into the impact of exogenous nano zero-valent iron (nZVI) on the PdNA process. Adding 10 mg L-1 of nZVI increased nitrogen removal efficiency up to 83.12 % and maintained higher relative abundances of certain beneficial bacteria. The maximum relative abundance of Candidatus Brocadia (1.6 %), Candidatus Kuenenia (1.5 %), Ignavibacterium (1.3 %), and Azospira (1.2 %) was observed at 10 mg L-1 of nZVI. However, the greatest relative abundance of Thauera (1.3 %) was recorded under 50 mg L-1. Moreover, applying nZVI selectively enhanced the abundance of NO3--N reductase genes. So, keeping the nZVI concentration at 10 mg L-1 or below is advisable to ensure a stable PdNA process in mainstream conditions. Considering nitrogen removal efficiency, using nZVI in the PD-anammox process could be more cost-effective in enhancing its adoption in industrial and mainstream settings.

Enhancing collaboration of anammox with heterotrophic microbes mediated selectively by iron of different valences: Activities balance, metabolic mechanism, and functional genes regulation

The partial denitrification/anammox (PD/A) process is receiving increasing attention due to its cost-effectiveness advantages. However, effective strategies to alleviate organic matter inhibition and promote anammox activity have been proven to be a big challenge. This study investigated the effects of three types of iron (nano zero-valent iron (nZVI), Fe(II), and Fe(III)) on the PD/A process. It is worth noting that nZVI of 5-50 mg/L and Fe(III) of 5-120 mg/L promoted both PD and anammox activity. Long-term intermittent addition of nZVI (50 mg/L) resulted in a nitrogen removal efficiency of 98.2% in the mixotrophic PD/A system driven by iron and organic matter. The contribution of anammox for nitrogen removal reached as high as 93.8%. The organic carbon demand decreased due to the external electron donor provided by nZVI for PD. Multiple Fe-N metabolic pathways, primarily involving ammonia oxidation by Fe(III) and nitrate reduction by nZVI, play a crucial role in facilitating nitrogen transformation. Conversely, the direct addition of 30-120 mg/L Fe (II) resulted in a significant decrease in pH to below 5.0 and severe inhibition of PD and anammox activity. Following prolonged operation in the presence of nZVI, it was demonstrated that there is an enhancing effect on robust nitrite production for anammox. This was accompanied by a remarkable up-regulation of genes encoding nitrate reductase and iron-transporting proteins dominated by Thauera. Overall, this study has provided an efficient approach for advanced nitrogen removal through organic- and iron-driven anammox processes.

Emerging biotechnological applications of anaerobic ammonium oxidation

Anaerobic ammonium oxidation (anammox) is an energy-efficient method for nitrogen removal that opens the possibility for energy-neutral wastewater treatment. Research on anammox over the past decade has primarily focused on its implementation in domestic wastewater treatment. However, emerging studies are now expanding its use to novel biotechnological applications and wastewater treatment processes. This review highlights recent advances in the anammox field that aim to overcome conventional bottlenecks, and explores novel and niche-specific applications of the anammox process. Despite the promising results and potential of these advances, challenges persist for their real-world implementation. This underscores the need for a transition from laboratory achievements to practical, scalable solutions for wastewater treatment which mark the next crucial phase in the evolution of anammox research.

Fluoride in Raw Rice (Oryza sativa): a Global Systematic Review and Probabilistic Health Risk Assessment

Rice (Oryza sativa) is one of the essential staple foods highly consumed globally, with nearly 40% to 45% of the global population estimated to consume rice. Therefore, consumable rice should have low levels of harmful elements. This study investigates fluoride (F¯) content in raw rice (uncooked rice) and evaluates Probabilistic Health Risk Assessment (PHRA) through Monte Carlo simulation (MCS) due to the consumption of F¯ enriched rice. The literature review reveals that limited studies have been conducted on the investigation of F¯ in raw rice. The fluoride (F¯) concentration in raw rice varies across the studied countries, indicating the need for additional studies to facilitate a more accurate comparison. The F¯ content in raw rice varied among the studied countries, making it difficult to definitively state that the concentration of F¯ in one country is higher. However, the concentration of F¯ in raw rice in India is notably elevated. This study also highlighted the importance of investigating the F¯ content in raw rice. The study will be highly helpful for policymakers to formulate guidelines for water used for irrigation.

Formation of iron-rich encrustation layer on anammox granules for high load stress resistance: Performance, advantages, and mechanisms

Anaerobic ammonia oxidation (anammox) is a cost-effective technology but its performance can be seriously inhibited by high load stress. This study has created an innovative iron-rich encrustation layer (IEL) on the surface of anammox granules (AnGS) through the addition of a certain amount of nano zero-valent iron. The IEL was formed through the aggregation of a gel network and the binding of iron species with extracellular polymeric substances (EPS), resulting in a significant increase in settling ability, EPS secretion, and heme content. Metagenomic analysis indicated a notable rise in the functional genes associated with nitrogen andiron metabolism in IEL AnGS. Under high load stress, the ammonia removal performance of AnGS without IEL severely declined. In contrast, IEL AnGS exhibited excellent ammonia removal efficiency of over 90%. The IEL served as a protective barrier for AnGS, effectively mitigating the strong shear forces, thereby enhancing their resistance to high load stress.

Controllable integration of nano zero-valent iron into MOFs with different structures for the purification of hexavalent chromium-contaminated water: Combined insights of scavenging performance and potential mechanism investigations

This work combined the stability of the porous structure of metal-organic frameworks with the strong reducibility of nano zero-valent iron, for the controllable integration of NZVI into MOFs to utilize the advantages of each component with enhancing the rapid decontamination and scavenging of Cr(VI) from wastewater. Hence, four kinds of MOFs/NZVI composites namely ZIF67/NZVI, MOF74/NZVI, MIL101(Fe)/NZVI, CuBTC/NZVI, were prepared for Cr(VI) capture. The results indicated that the stable structure of ZIF67, MOF74, MIL101(Fe), CuBTC, was beneficial for the dispersion of NZVI that could help more close contact between MOFs/NZVI reactive sites and Cr(VI), subsequently, MOFs/NZVI was proved to be better scavengers for Cr(VI) scavenging than NZVI alone. The Cr(VI) capture achieved the maximum adsorption capacity at pH ~ 4.0, which might be due to the participation of more H+ in the reaction and better corrosion of NZVI at lower pH. Mechanism investigation demonstrated synergy of adsorption, reduction and surface precipitation resulted in enhanced Cr(VI) scavenging, and Fe(0), dissolved and surface-bound Fe(II) were the primary reducing species. The findings of this investigation indicated that the as-prepared composites of ZIF67/NZVI, MOF74/NZVI, MIL101(Fe)/NZVI, CuBTC/NZVI, with high oxidation resistance and excellent reactivity, could provide reference for the decontamination and purification of actual Cr(VI)-containing wastewater.

Recovery strategies and mechanisms of anammox reaction following inhibition by environmental factors: A review

Anaerobic ammonium oxidation (anammox) is a promising biological method for treating nitrogen-rich, low-carbon wastewater. However, the application of anammox technology in actual engineering is easily limited by environmental factors. Considerable progress has been investigated in recent years in anammox restoration strategies, significantly addressing the challenge of poor reaction performance following inhibition. This review systematically outlines the strategies employed to recover anammox performance following inhibition by conventional environmental factors and emerging pollutants. Additionally, comprehensive summaries of strategies aimed at promoting anammox activity and enhancing nitrogen removal performance provide valuable insights into the current research landscape in this field. The review contributes to a comprehensive understanding of restoration strategies of anammox-based technologies.

Surface Modification of Polyurethane Sponge with Zeolite and Zero-Valent Iron Promotes Short-Cut Nitrification

Partial nitrification-Anammox (PN-A) is a cost-effective, environmentally friendly, and efficient method for removing ammonia (NH4+-N) pollutants from water. However, the limited accumulation of nitrite (NO2--N) represents a bottleneck in the development of PN-A processes. To address this issue, this study developed a composite carrier loaded with nano zero-valent iron (nZVI) and zeolite to enhance NO2--N accumulation during short-cut nitrification. The modified composite carrier revealed electropositive, hydrophilicity, and surface roughness. These surface characteristics correlate positively with the carrier's total biomass adsorption capacity; the initial adsorption of microorganisms by the composite carrier was increased by 8.7 times. Zeolite endows the carrier with an NH4+-N adsorption capacity of 4.50 mg/g carrier. The entropy-driven ammonia adsorption process creates an ammonia-rich microenvironment on the surface of the carrier, providing effective inhibition of nitrite-oxidizing bacteria (NOB). In tests conducted with a moving bed biofilm reactor and a sequencing batch reactor, the composite carrier achieved a 95% NH4+-N removal efficiency, a NO2--N accumulation efficiency of 78%, and a doubling in total nitrogen removal efficiency. This composite carrier enhances NO2--N accumulation by preventing biomass washout, inhibiting NOB, and enriching PN-A functional bacteria, suggesting its potential for large-scale, stable PN-A applications.

Quorum sensing bacteria improve microbial networks stability and complexity in wastewater treatment plants

Quorum-sensing bacteria (QSB) are crucial factors for microbial communication, yet their ecological role in wastewater treatment plants (WWTPs) remains unclear. Here, we developed a method to identify QSB by comparing 16S rRNA gene sequences. QSB in 388 activated sludge samples collected from 130 WWTPs across China primarily were identified as rare taxa and conditionally rare taxa. A co-occurrence network shared by all sludge communities revealed that QSB exhibited higher average clustering coefficient (0.46) than non-QSB (0.15). Individual sludge networks demonstrated that quorum sensing microbiomes were positively correlated with network robustness and network complexity, including average clustering coefficient and link density. We confirmed that QSB keystones and QSB nodes have a positive impact on network complexity by influencing network modularity through a structural equation model. Meanwhile, QSB communities directly contributed to maintaining network robustness (r = 0.29, P < 0.05). Hence, QSB play an important role in promoting network complexity and stability. Furthermore, QSB communities were positively associated with the functional composition of activated sludge communities (r = 0.33, P < 0.01), especially the denitrification capacity (r = 0.45, P < 0.001). Overall, we elucidated the ecological significance of QSB and provided support for QS-based regulation of activated sludge microbial communities.

Steroid hormones in surface water resources in China: systematic review and meta-analysis and probabilistic ecological risk assessment

A Search was conducted in international databases including Scopus, PubMed, Embase, and Web of Science from 10 January 2005 to 15 January 2023. The risk quotient (RQ) of Estrone (E1), 17β-E2 (E2), and Estriol (E3) on the surface water resources of China was calculated by Monte Carlo Simulation (MCS) technique. The rank order of steroid hormones based on pooled (weighted average) concentration in surface water was E3 (2.15 ng/l) > E2 (2.01 ng/l) > E1 (1.385 ng/l). The concentration of E1 in Dianchi lake (236.50.00 ng/l), 17β-E2 in Licun river (78.50 ng/l), and E3 in Dianchi lake (103.1 ng/l) were higher than in other surface water resources in China. RQ related to E1, 17β-E2 and E3 in 68.00%, 88.89% and 3.92% of surface water resources were high ecological risk, respectively. Therefore, carrying out source control plans for steroid hormones in surface water sources should be conducted continuously.

Mechanistic insight into the aggregation ability of anammox microorganisms: Roles of polarity, composition and molecular structure of extracellular polymeric substances

The chemical characteristics of extracellular polymeric substances (EPS) of anammox bacteria (AnAOB) play a crucial role in the rapid enrichment of AnAOB and the stable operation of wastewater anammox processes. To clarify the influential mechanisms of sludge EPS on AnAOB aggregation, multiple parameters, including the polarity distribution, composition, and molecular structure of EPS, were selected, and their quantitative relationship with AnAOB aggregation was analyzed. Compared to typical anaerobic sludge (anaerobic floc and granular sludge), the anammox sludge EPS exhibited higher levels of tryptophan-like substances (44.82-56.52 % vs. 2.57-39.81 %), polysaccharides (40.02-53.49 mg/g VSS vs. 30.22-41.69 mg/g VSS), and protein structural units including α-helices (20.70-23.98 % vs. 16.48-19.32 %), β-sheets (37.43-42.98 % vs. 25.78-36.72 %), and protonated nitrogen (Npr) (0.065-0.122 vs. 0.017-0.061). In contrast, it had lower contents of β-turns (20.95-27.39 % vs. 28.17-39.04 %). These biopolymers were found to originate from different genera of AnAOB. Specifically, the α-helix-rich proteins were mainly derived from Candidatus Kuenenia, whereas the extracellular proteins related to tryptophan and Npr were closely associated with Candidatus Brocadia. Critically, these EPS components could drive anammox aggregation through interactions. Substantial amounts of tryptophan-like substances facilitated the formation of β-sheet structures and the exposure of internal hydrophobic clusters, which benefited the anammox aggregation. Meanwhile, extracellular proteins with high Npr content played a pivotal role in the formation of mixed protein-polysaccharide gel networks with the electronegative regions of polysaccharides, which could be regarded as the key component in the maintenance of anammox sludge stability. These findings provide a comprehensive understanding of the multifaceted roles of EPS in driving anammox aggregation and offer valuable insights into the development of EPS regulation strategies aimed at optimizing the anammox process.

Enhancement of hydrogenotrophic methanogenesis for methane production by nano zero-valent iron in soils

Nanoscale zero-valent iron (nZVI) is attracting increasing attention as the most commonly used environmental remediation material. However, given the high surface area and strong reducing capabilities of nZVI, there is a lack of understanding regarding its effects on the complex anaerobic methane production process in flooded soils. To elucidate the mechanism of CH4 production in soil exposed to nZVI, paddy soil was collected and subjected to anaerobic culture under continuous flooding conditions, with various dosages of nZVI applied. The results showed that the introduction of nZVI into anaerobic flooded rice paddy systems promoted microbial utilization of acetate and carbon dioxide as carbon sources for methane production, ultimately leading to increased methane production. Following the introduction of nZVI into the soil, there was a rapid increase in hydrogen levels in the headspace, surpassing that of the control group. The hydrogen levels in both the experimental and control groups were depleted by the 29th day of culture. These findings suggest that nZVI exposure facilitates the enrichment of hydrogenotrophic methanogens, providing them with a favorable environment for growth. Additionally, it affected soil physicochemical properties by increasing pH and electrical conductivity. The metagenomic analysis further indicates that under exposure to nZVI, hydrogenotrophic methanogens, particularly Methanobacteriaceae and Methanocellaceae, were enriched. The relative abundance of genes such as mcrA and mcrB associated with methane production was increased. This study provides important theoretical insights into the response of key microbes, functional genes, and methane production pathways to nZVI during anaerobic methane production in rice paddy soils, offering fundamental insights into the long-term fate and risks associated with the introduction of nZVI into soils.

Sponge iron strengthens the activity of anammox biofilm under low nitrogen conditions in a two-stage fixed-bed biofilm reactor

Strengthening the activity competitiveness of anaerobic ammonium oxidation (anammox) bacteria (AnAOB) under low nitrogen conditions is indispensable for mainstream anammox application. This study demonstrates that sponge iron addition (42.8 g/L) effectively increased apparent AnAOB activity and extracellular polymeric substance (EPS) production of low load anammox biofilms cultivated under low (influent of 60 mg N/L) and even ultra-low (influent of 10 mg N/L) nitrogen conditions. In-situ batch tests showed that after sponge iron addition the specific AnAOB activity in the low and ultra-low nitrogen systems further increased to 1.18 and 0.47 mmol/g VSS/h, respectively, with an apparent growth rate for AnAOB of 0.011 ± 0.001 d-1 and 0.004 ± 0.001 d-1, respectively. The averaged EPS concentration of anammox biofilm in both low (from 35.84 to 71.05 mg/g VSS) and ultra-low (from 44.14 to 57.59 mg/g VSS) nitrogen systems increased significantly, while a higher EPS protein/polysaccharide ratio, which was positively correlated with AnAOB activity, was observed in the low nitrogen system (3.54 ± 0.34) than that in the ultra-low nitrogen system (1.82 ± 0.10). In addition, Candidatus Brocadia was detected as dominant AnAOB in the anammox biofilm under the low (12.2 %) and ultra-low (24.7 %) nitrogen condition. Notably, the genus Streptomyces (26.3 %), capable for funge-like codenitrification, increased unexpectedly in the low nitrogen system, but not affecting the nitrogen removal performance. Therefore, using sponge iron to strengthen AnAOB activity under low nitrogen conditions is feasible, providing support for mainstream anammox applications.

Statistical computational optimization approach for photocatalytic-ozonation decontamination of metronidazole in aqueous media using CuFe2O4/SiO2/ZnO nanocomposite

The increasing use of pharmaceuticals and the ongoing release of drug residues into the environment have resulted in significant threats to environmental sustainability and water safety. In this sense, developing a robust and easy-recovered magnetic nanocomposite with eminent photocatalytic activity is very imperative for detoxifying pharmaceutical compounds. Herein, a systematic study was conducted to investigate the photocatalytic ozonation for eliminating metronidazole (MET) from aqueous media utilizing the CuFe2O4/SiO2/ZnO heterojunction under simulated sunlight irradiation. The composite material was fabricated by a facile hydrothermal method and diagnosed by multiple advanced analytical techniques. Modelling and optimization of MET decontamination by adopting the central composite design (CCD) revealed that 90 % of MET decontamination can be achieved within 120 min of operating time at the optimized circumstance (photocatalyst dose: 1.17 g/L, MET dose: 33.20 mg/L, ozone concentration: 3.99 mg/min and pH: 8.99). In an attempt to scrutinize the practical application of the CuFe2O4/SiO2/ZnO/xenon/O3 system, roughly 56.18% TOC and 73% COD were removed under the optimized operational circumstances during 120 min of degradation time. According to the radical quenching experiments, hydroxyl radicals (HO•) were the major oxidative species responsible for the elimination of MET. The MET degradation rate maintained at 83% after seven consecutive runs, manifesting the efficiency of CuFe2O4/SiO2/ZnO material in the MET removal. Ultimately, the photocatalytic ozonation mechanism over the CuFe2O4/SiO2/ZnO heterojunction of the fabricated nanocomposites was rationally proposed for MET elimination. In extension, the results drawn in this work indicate that integrating photocatalyst and ozonation processes by the CuFe2O4/SiO2/ZnO material can be applied as an efficient and promising method to eliminate tenacious and non-biodegradable contaminants from aqueous environments.

Iron-modified carriers accelerate biofilm formation and resist anammox bacteria loss in biofilm reactors for partial denitrification-anammox

The slow formation of anammox biofilms presents a bottleneck for resolving anammox bacterial loss and achieving stable performance in biofilm-based partial denitrification-anammox (PD-A) processes. This study utilized iron-modified (K1/Fe3O4 NPs) carriers, which were prepared and used for the first time in PD-A processes. Parallel moving bed biofilm reactors (MBBRs) indicated that iron-modified carriers facilitated the formation of biofilms at a faster rate than K1 carriers, consequently improving the nitrogen removal performance of the process by over 40 %. 16S rDNA analysis showed that anammox bacteria were approximately four times more abundant in the iron-modified carrier biofilm than in the K1 carrier biofilm. XPS and zeta potential analysis suggested that the improved microbial affinity of the iron-modified carrier surface caused this. As a result, the iron-modified carriers facilitated the formation of anammox biofilms and enhanced PD-A performance.

Biosynthesis cobalt-doped nickel nanoparticles and their toxicity against disease

The nanostructures have the great potential for novel medical and drug delivery applications. In present paper a green approach for the preparation of pure nickel oxide (NiO) and 5% cobalt-doped NiO (Co╫NiO) nanoparticles (NPs) by using Prosopis fracta extract have been study. The product of Co╫NiO NPs was proved through the PXRD, Raman, UV-Vis, FESEM, and EDX analyses. The results of XRD, EDX, and UV-Visible spectra displayed well doped cobalt in NiO NP. The particle sizes of Co╫NiO NPs were observed to be about 80 nm. The MTT test results for the cytotoxicity of Co╫NiO NPs on breast cancer cells (MCF-7) affirmed the stronger impact of doped NiO-NPs on cancer cells compared to NiO NPs. Thus, it is indicated that the doping process on NiO NPs caused an increase in its inhibitory effect against MCF-7 cells. RESEARCH HIGHLIGHTS: Cobalt-doped NiO nanoparticles were prepared using ecofriendly synthesis method and their cytotoxicity studied against MCF-7 cells.

Microbially driven Fe-N cycle: Intrinsic mechanisms, enhancement, and perspectives

The iron‑nitrogen (FeN) cycle driven by microbes has great potential for treating wastewater. Fe is a metal that is frequently present in the environment and one of the crucial trace elements needed by microbes. Due to its synergistic role in the microbial N removal process, Fe goes much beyond the essential nutritional needs of microorganisms. Investigating the mechanisms behind the linked Fe-N cycle driven by microbes is crucial. The Fe-N cycle is frequently connected with anaerobic ammonia oxidation (anammox), nitrification, denitrification, dissimilatory nitrate reduction to ammonium (DNRA), Feammox, and simultaneous nitrification denitrification (SND), etc. Although the main mechanisms of Fe-mediated biological N removal may vary depending on the valence state of the Fe, their similar transformation pathways may provide information on the study of certain element-microbial interactions. This review offers a thorough analysis of the facilitation effect and influence of Fe on the removal of nitrogenous pollutants in various biological N removal processes and summarizes the ideal Fe dosing. Additionally, the synergistic mechanisms of Fe and microbial synergistic N removal process are elaborated, covering four aspects: enzyme activity, electron transfer, microbial extracellular polymeric substances (EPS) secretion, and microbial community interactions. The methods to improve biological N removal based on the intrinsic mechanism were also discussed, with the aim of thoroughly understanding the biological mechanisms of Fe in the microbial N removal process and providing a reference and thinking for employing Fe to promote microbial N removal in practical applications.

Degradation of reactive red 198 dye from aqueous solutions by combined technology advanced sonofenton with zero valent iron: Characteristics/ effect of parameters/kinetic studies

Dyes are one of the most common contaminants in industrial effluents, whose continuous release into the environment has become an increasing global concern. In this work, nanoparticles of zero-valent iron (NZVI) were synthesized using the chemical regeneration method ،and were utilized for the first time as a catalyst in the advanced Sono-Nano-Fenton hybrid method for the decomposition of Reactive Red 198 (RR198). The properties of zero-valent iron nanoparticles were analyzed using SEM and XRD. The effect of pH, initial dye concentration, nanoparticle dosage, zero-valent iron and H2O2 concentration on the decomposition efficiency of Red Reactive 198 was investigated. Comparing the efficiency of Reactivate 198 dye degradation in Sonolysis, Sono-NZVI, Sono-H2O2 and Sono-Nano Fenton processes showed that 97 % efficiency was achieved by the Sono-Nano Fenton process in 60 min. The kinetics of the removal process showed that this process follows pseudo-first-order kinetics and the Langmuir-Hinshelwood model. The results indicate that the effectiveness of the ultrasonic process in removing resistant organic pollutants such as dyes increases tremendously with the synergy of the Fenton process.

Synthesis and characterization of titanium dioxide nanoparticles from Bacillus subtilis MTCC 8322 and its application for the removal of methylene blue and orange G dyes under UV light and visible light

Over the last decade there has been a huge increase in the green synthesis of nanoparticles. Moreover, there is a continuous increase in harnessing the potential of microorganisms for the development of efficient and biocompatible nanoparticles around the globe. In the present research work, investigators have synthesized TiO2 NPs by harnessing the potential of Bacillus subtilis MTCC 8322 (Gram-positive) bacteria. The formation and confirmation of the TiO2 NPs synthesized by bacteria were carried out by using UV-Vis spectroscopy, Fourier transforms infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDX/EDS). The size of the synthesized TiO2 NPs was 80-120 nm which was spherical to irregular in shape as revealed by SEM. FTIR showed the characteristic bands of Ti-O in the range of 400-550 cm-1 and 924 cm-1 while the band at 2930 cm-1 confirmed the association of bacterial biomolecules with the synthesized TiO2 NPs. XRD showed two major peaks; 27.5° (rutile phase) and 45.6° (anatase phase) for the synthesized TiO2 NPs. Finally, the potential of the synthesized TiO2 NPs was assessed as an antibacterial agent and photocatalyst. The remediation of Methylene blue (MB) and Orange G (OG) dyes was carried out under UV- light and visible light for a contact time of 150-240 min respectively. The removal efficiency for 100 ppm MB dye was 25.75% and for OG dye was 72.24% under UV light, while in visible light, the maximum removal percentage for MB and OG dye was 98.85% and 80.43% respectively at 90 min. Moreover, a kinetic study and adsorption isotherm study were carried out for the removal of both dyes, where the pseudo-first-order for MB dye is 263.269 and 475554.176 mg/g for OG dye. The pseudo-second-order kinetics for MB and OG dye were 188.679 and 1666.667 mg/g respectively. In addition to this, the antibacterial activity of TiO2 NPs was assessed against Bacillus subtilis MTCC 8322 (Gram-positive) and Escherichia coli MTCC 8933 (Gram-negative) where the maximum zone of inhibition in Bacillus subtilis MTCC 8322 was about 12 mm, and for E. coli 16 mm.

Potential role of AgNPs within wastewater in deteriorating sludge floc structure and settleability during activated sludge process: Filamentous bacteria and quorum sensing

Excellent sludge floc structure and settleability are essential to maintain the process stability and excellent effluent quality during the activated sludge process. The underlying effect of silver nanoparticles (AgNPs) within wastewater on sludge floc structure and settleability is still unclear. The potential role of AgNPs in promoting filamentous bacterial proliferation and deteriorating sludge floc structure and settleability based on quorum sensing (QS) were investigated in this study. The results indicated that N-acyl homoserine lactose (AHL) concentration sharply increased from 23.56 to 108.41 ng/g VSS in the sequencing batch reactor with 1 mg/L AgNPs. AgNPs strengthened communication between filamentous bacteria, which triggered the filamentous bacterial QS system involving the synthetic gene hdtS and sensing genes traR and lasR. Filamentous bacterial proliferation was promoted by the triggered QS via positively regulating its cell cycle progression including chromosomal replication and divisome formation. In addition, extracellular protein production was obviously increased from 43.56 to 97.91 mg/g VSS through QS by regulating arginine and tyrosine secretion during filamentous bacterial proliferation under 1 mg/L AgNPs condition, which led to an increase in the negative charge and hydrophily at the cell surface. AgNPs resulted in an obvious increase in the surface energy barrier (WT) between bacteria. The change in the physicochemical properties of extracellular polymeric substance (EPS) induced by QS among filamentous bacteria obviously inhibited bacterial aggregation between filamentous bacteria and floc-forming bacteria under AgNPs condition, thus resulting in serious deterioration of the sludge floc structure and settleability. This study provided new insights into the microcosmic mechanism for the effect of AgNPs on sludge floc structure and settleability.

Roles and regulation of quorum sensing in anaerobic granular sludge: Research status, challenges, and perspectives

Anaerobic granular sludge (AnGS) has a complex and important internal microbial communication system due to its unique microbial layered structure. As a concentration-dependent communication system between bacterial cells through signal molecules, QS (quorum sensing) is widespread in AnGS and exhibits great potential to regulate microbial behaviors. Therefore, the universal functions of QS in AnGS have been systematically summarized in this paper, including the influence on the metabolic activity, physicochemical properties, and microbial community of AnGS. Subsequently, the common QS-based AnGS regulation approaches are reviewed and analyzed comprehensively. The regulation mechanism of QS in AnGS is analyzed from two systems of single bacterium and mixed bacteria. This review can provide a comprehensive understanding of QS functions in AnGS systems, and promote the practical application of QS-based strategies in optimization of AnGS treatment process.

Microbial synthesis of titanium dioxide nanoparticles and their importance in wastewater treatment and antimicrobial activities: a review

Nanotechnology (NT) and nanoparticles (NPs) have left a huge impact on every field of science today, but they have shown tremendous importance in the fields of cosmetics and environmental cleanup. NPs with photocatalytic effects have shown positive responses in wastewater treatment, cosmetics, and the biomedical field. The chemically synthesized TiO2 nanoparticles (TiO2 NPs) utilize hazardous chemicals to obtain the desired-shaped TiO2. So, microbial-based synthesis of TiO2 NPs has gained popularity due to its eco-friendly nature, biocompatibility, etc. Being NPs, TiO2 NPs have a high surface area-to-volume ratio in addition to their photocatalytic degradation nature. In the present review, the authors have emphasized the microbial (algae, bacterial, fungi, and virus-mediated) synthesis of TiO2 NPs. Furthermore, authors have exhibited the importance of TiO2 NPs in the food sector, automobile, aerospace, medical, and environmental cleanup.

Chameleon-like Anammox Bacteria for Surface Color Change after Suffering Starvation

Bacteria are often exposed to long-term starvation during transportation and storage, during which a series of enzymes and metabolic pathways are activated to ensure survival. However, why the surface color of the bacteria changes during starvation is still not well-known. In this study, we found black anammox consortia suffering from long-term starvation contained 0.86 mmol gVSS-1 cytochrome c, which had no significant discrepancy compared with the red anammox consortia (P > 0.05), indicating cytochrome c was not the key issue for chromaticity change. Conversely, we found that under starvation conditions cysteine degradation is an important metabolic pathway for the blackening of the anammox consortia for H2S production. In particular, anammox bacteria contain large amounts of iron-rich nanoparticles, cytochrome c, and other iron-sulfur clusters that are converted to produce free iron. H2S combines with free iron in bacteria to form Fe-S compounds, which eventually exist stably as FeS2, mainly in the extracellular space. Interestingly, FeS2 could be oxidized by air aeration, which makes the consortia turn red again. The unique self-protection mechanism makes the whole consortia appear black, avoiding inhibition by high concentrations of H2S and achieving Fe storage. This study expands the understanding of the metabolites of anammox bacteria as well as the bacterial survival mechanism during starvation.

Z. AL-bonsrulah H. Optimization of oil industry wastewater treatment system and proposing empirical correlations for chemical oxygen demand removal using electrocoagulation and predicting the system's performance by artificial neural network

The alarming pace of environmental degradation necessitates the treatment of wastewater from the oil industry in order to ensure the long-term sustainability of human civilization. Electrocoagulation has emerged as a promising method for optimizing the removal of chemical oxygen demand (COD) from wastewater obtained from oil refineries. Therefore, in this study, electrocoagulation was experimentally investigated, and a single-factorial approach was employed to identify the optimal conditions, taking into account various parameters such as current density, pH, COD concentration, electrode surface area, and NaCl concentration. The experimental findings revealed that the most favorable conditions for COD removal were determined to be 24 mA/cm2 for current density, pH 8, a COD concentration of 500 mg/l, an electrode surface area of 25.26 cm2, and a NaCl concentration of 0.5 g/l. Correlation equations were proposed to describe the relationship between COD removal and the aforementioned parameters, and double-factorial models were examined to analyze the impact of COD removal over time. The most favorable outcomes were observed after a reaction time of 20 min. Furthermore, an artificial neural network model was developed based on the experimental data to predict COD removal from wastewater generated by the oil industry. The model exhibited a mean absolute error (MAE) of 1.12% and a coefficient of determination (R2) of 0.99, indicating its high accuracy. These findings suggest that machine learning-based models have the potential to effectively predict COD removal and may even serve as viable alternatives to traditional experimental and numerical techniques.

Advanced multifunctional nano-lipid carrier loaded gel for targeted delivery of 5-flurouracil and cannabidiol against non-melanoma skin cancer

Non-melanoma skin cancer is one of the most common malignancies reported around the globe. Current treatment therapies fail to meet the desired therapeutic efficacy due to high degree of drug resistance. Thus, there is prominent demand in advancing the current conventional therapy to achieve desired therapeutic efficacy. To break the bottleneck, nanoparticles have been used as next generation vehicles that facilitate the efficient interaction with the cancer cells. Here, we developed combined therapy of 5-fluorouracil (5-FU) and cannabidiol (CBD)-loaded nanostructured lipid carrier gel (FU-CBD-NLCs gel). The current investigation has been designed to evaluate the safety and efficacy of developed 5-Flurouracil and cannabidiol loaded combinatorial lipid-based nanocarrier (FU-CBD NLCs) gel for the effective treatment of skin cancer. Initially, confocal microscopy study results showed excellent uptake and deposition at epidermal and the dermal layer. Irritation studies performed by IR camera and HET cam shows FU-CBD NLCs was much more tolerated and less irritant compared to conventional treatment. Furthermore, gamma scintigraphy evaluation shows the skin retention behavior of the formulation. Later, in-ovo tumor remission studies were performed, and it was found that prepared FU-CBD NLCs was able to reduce tumor volume significantly compared to conventional formulation. Thus, obtained results disclosed that permeation and disposition of 5-FU and CBD into different layers of the skin FU-CBD NLCs gel could be more potential carrier than conventional gel. Furthermore, prepared formulation showed greater tumor remission, better survival rate, reduction in tumor number, area, and volume with improved biochemical profile. Thus, prepared gel could serve as a promising formulation approach for the skin cancer treatment.

UV and solar-based photocatalytic degradation of organic pollutants from ceramics industrial wastewater by Fe-doped ZnS nanoparticles

UV and solar-based photocatalytic degradation of 2,4-dichlorophenol (2,4-DCP) as an organic contaminant in ceramics industry wastewater by ZnS and Fe-doped ZnS NPs was the focus of this research. Nanoparticles were prepared using a chemical precipitation process. The cubic, closed-packed structure of undoped ZnS and Fe-doped ZnS NPs was formed in spherical clusters, according to XRD and SEM investigations. According to optical studies, the optical band gaps of pure ZnS and Fe-doped ZnS nanoparticles are 3.35 and 2.51 eV, respectively, and Fe doping increased the number of carriers with high mobility, improved carrier separation and injection efficiency, and increased photocatalytic activity under UV or visible light. Doping of Fe increased the separation of photogenerated electrons and holes and facilitated charge transfer, according to electrochemical impedance spectroscopy investigations. Photocatalytic degradation studies revealed that in the present pure ZnS and Fe-doped ZnS nanoparticles, 100% treatment of 120 mL of 15 mg/L phenolic compound was obtained after 55- and 45-min UV-irradiation, respectively, and complete treatment was attained after 45 and 35-min solar light irradiation, respectively. Because of the synergistic effects of effective surface area, more effective photo-generated electron and hole separation efficiency, and enhanced electron transfer, Fe-doped ZnS demonstrated high photocatalytic degradation performance. The study of Fe-doped ZnS's practical photocatalytic treatment capability for removing 120 mL of 10 mg/L 2,4-DCP solution made from genuine ceramic industrial wastewater revealed Fe-doped ZnS's excellent photocatalytic destruction of 2,4-DCP from real industrial wastewater.

Solar light driven enhanced photocatalytic treatment of azo dye contaminated water based on Co-doped ZnO/ g-C3N4 nanocomposite

The current research concentrated on the Co-precipitation synthesis of g-C3N4 (CN), ZnO, ZnO/CN, and Co-doped ZnO/CN nanocomposite, as well as the solar light enhanced photocatalytic treatment of Reactive Red 120 (RR120) from genuine wool textile effluent. The 3D flower-like structure of Co-doped ZnO distributed on the surface of CN thin sheets, according to structural studies employing XRD and SEM examinations Electrochemical experiments exhibited that the Co-doped ZnO/CN nanocomposite has a large electroactive surface area. The optical band-gap values of CN, ZnO, ZnO/CN, and Co-doped ZnO/CN nanocomposites were 2.68, 3.13, 2.38, and 2.23 eV, respectively, according to optical characterizations. The synergistic effects and heterojunction produced by Co-doped ZnO and CN can be linked to the narrow gap in nanocomposites. After 75, 60, 50, and 40 min of exposure to solar light, photocatalytic degradation assays for 250 mL of 20 mg/L RR120 solution in the presence of CN, ZnO, ZnO/CN, and Co-doped ZnO/CN nanocomposites demonstrated 100% dye treatment. The applicability of photocatalysts for decolorization of 250 mL of 10 mg/L RR120 prepared from actual wool textile wastewater was investigated, and the results showed that Co-doped ZnO/CN nanocomposites for treatment of RR120 from actual wool textile wastewater were highly efficient at photocatalytic degradation.

Directed regulation of anammox communities based on exogenous siderophores for highly efficient nitrogen removal

It is expected that the quicker domestication of anaerobic ammonia oxidation (anammox) communities and the enhancement of their nitrogen transformation capability can be achieved through targeted regulation of anammox communities. Iron cast a vital role in the growth and metabolism of anammox bacteria. Specific siderophores offer promising prospects for the targeted regulation of anammox communities by facilitating the efficient utilization of iron. Two siderophores-enterobactin and putrebactin-exclusively for Ca. Brocadia and Ca. Kuenenia were developed to specifically regulate anammox communities towards different directions, respectively. Anammox communities in the reactors evoluted targetedly towards Ca. Brocadia-dominated communities and Ca. Kuenenia-dominated communities, respectively, leading to a maximum increase in community nitrogen removal capacity by 84.64±0.55% and 210.26±0.57%, respectively, under different nitrogen concentrations. It was indicated that siderophores could regulate anammox communities by redistributing iron resources in a targeted manner based on the analyses of transcriptome and proteome. This study provides novel insights into the rational selection and utilization of exogenous siderophores as an effective implement to manipulate anammox communities and create communities with high nitrogen removal ability fleetly.

The ability of twisted nanographene for removal of Pb2+, Hg2+ and Cd2+ ions from wastewater: Computational study

CONTEXT

Heavy metal ion removal from wastewater has become a global concern due to its extensive negative effects on human health and the environment. The density functional theory is employed to investigate the possibility of removing Pb2+, Hg2+, and Cd2+ ions from wastewater using nano-graphene. Researchers have shown that NG can efficiently remove heavy metals from media. Additionally, it was shown that the adsorption of Pb2+, Hg2+, and Cd2+ ions might reduce the large pristine NG (HOMO-LUMO) gap.

METHODS

HSE06 may accurately represent NG electrical characteristics. The DFT-D3 method was also used to account for Van der Waals interactions in the present study. The results demonstrated that charge transfer and binding energy remained greater in cation-NG systems with greater electron transfer rates. Pb2+, Hg2+, and Cd2+ adsorption results indicated that Egap was significantly reduced by 68%, 15%, and 21%, respectively. The Pb2+@NG complex exhibited the strongest oscillator strength. This may be explained by the enormous occupation number difference between the 2px orbital of the C atoms and the 6 s orbital of the Pb2+ cations. The greater Ebin value of Pb2+@NG is consistent with the increased predicted redshifts (199 nm). DFT (hybrid functional HSE06) studies that rely on time showed that the relevant complexes have "ligand-to-metal charge transfer" excitations. In general, it was found that Pb2+@NG had the greatest k value, binding energy, redshifts, and charge transfer rate among the complexes. The theoretical insights of this study may influence experimental efforts to identify NG-based compounds that are effective and efficient at removing pollutants from wastewater.

Characterization and synthesis of new adsorbents with some natural waste materials for the purification of aqueous solutions

In this study, hexavalent chromium Removal from aqueous environments was investigated by using polyaniline composites with some natural waste materials. Batch experiments were used, and some parameters such as contact time, pH and adsorption isotherms were determined for the best composite with the highest removal efficiency. Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR) spectroscopy, and X-ray Diffraction (XRD) were used to characterize the composites. According to the results, the polyaniline/walnut shell charcoal/PEG composite outperformed other composites and showed the highest chromium removal efficiency of 79.22%. Polyaniline/walnut shell charcoal/PEG has a larger specific surface area of 9.291 (m²/gr) which leads to an increase in its removal efficiency. For this composite, the highest removal efficiency was obtained at the pH = 2 and 30 min contact time. The maximum calculated adsorption capacity was 500 mg/g.

Mitigating mechanism of nZVI-C on the inhibition of anammox consortia under long-term tetracycline hydrochloride stress: Extracellular polymeric substance properties and microbial community evolution

In this study, activated carbon-loaded nano-zero-valent iron (nZVI-C) composites were added to anaerobic ammonium oxidation bacteria (AnAOB) to overcome the inhibition of tetracycline hydrochloride (TCH). Results showed that 500 mg L^-1 nZVI-C effectively mitigated the long-term inhibition of 1.5 mg L^-1 TCH on AnAOB and significantly improved the total nitrogen removal efficiency (TNRE) (from 65.27% to 86.99%). Spectroscopic analysis revealed that nZVI-C increased the content of N-H and CO groups in EPS, which contributed to the adsorption of TCH. The accumulation of humic acid-like substances in EPS was also conducive to strengthening the extracellular defense level. In addition, TCH-degrading bacteria (Clostridium and Mycobacterium) were enriched in situ, and the abundance of Ca. Brocadia was significantly increased (from 10.69% to 18.59%). Furthermore, nZVI-C increased the abundance of genes encoding tetracycline inactivation (tetX), promoted mineralization of TCH by 90%, weakening the inhibition of TCH on microbial nitrogen metabolism. nZVI-C accelerated the electron consumption of anammox bacteria by upregulating the abundance of electron generation genes (nxrA, hdh) and providing electrons directly.

Efficient cobalt hydroxide nanosheets for enhanced electrochemical sensing of Hg (II) ion

A sensitive electrochemical device was suggested via the modification of a simple graphite rod electrode (GRE) with cobalt hydroxide (Co(OH)₂) nanosheets. After closed circuit process on the modified electrode, the anodic stripping voltammetry (ASV) technique was used for measuring of Hg(II). In optimal experimental conditions, the suggested assay depicted a linear response over a broad range in the range 0.25-30 μg L^-1, with the lowest detection limit of 0.07 μg L^-1. Besides good selectivity, the sensor also indicated excellent reproducibility with a relative standard deviation (RSD) value of 2.9%. Moreover, the Co(OH)₂-GRE showed satisfactory sensing performance in real water samples with appropriate recovery values (96.0-102.5%). Additionally, possible interfering cations were examined, but no significant interference was found. By taking some merits such high sensitivity, remarkable selectivity and good precision, this strategy is expected to provide an efficient protocol for the electrochemical measuring of toxic Hg(II) in environmental matrices.

An ultra-small fluorescence zero-valent iron nanoclusters selectively kill gram-positive bacteria by promoting reactive oxygen species generation

A list of the most dangerous bacteria that are multiple-drug resistance has been published by WHO, among which are various Gram-positive bacteria related with serious healthcare and community-associated infection. An effort is called for developing new strategies to combat the resistance, and nanomaterial-based approaches provide an ideal potential to mitigate the antimicrobial resistance as an alternative to antibiotics. Nanoscale zero-valent iron particles exhibited a good antimicrobial activity by triggering Fenton reaction, however, no zero-valent iron nanoclusters are developed as antimicrobial medical materials. In this work, a novel ultra-small zero-valent iron nanoclusters (usZVIN) was synthesized by one-step reduction in aqueous solutions, which exhibited bright red fluorescence at 616 nm. Interestingly, the usZVIN displayed an excellent selectively antibacterial activity against Gram-positive bacteria, and little effects on Gram-negative bacteria. The killing efficiency of usZVIN against S. aureus can reach 100 % with a concentration of 40 μg mL^-1 after 1 h incubation, whereas there is no killing effect of usZVIN against E.coli even with a concentration of 900 μg mL^-1 for 4 h. The antimicrobial mechanism of usZVIN was demonstrated to be the intracellular reactive oxygen species (ROS) production triggered by usZVIN due to its excellent peroxidase-like activity. Collectively, our findings suggested that usZVIN is a good medical-material candidate for fighting against Gram-positive bacterial infections, especially when we need leave beneficial Gram-negative bacteria intact.

Ce(ΙΙΙ) and La(ΙΙΙ) ions adsorption through Amberlite XAD-7 resin impregnated via CYANEX-272 extractant

The goal of this paper is to investigate the ability of Amberlite XAD-7 (AXAD-7) resin impregnated with CYANEX-272 (di-2,4,4-trimethylpentyl phosphonic acid) to remove cerium (Ce(ΙΙΙ)) and lanthanum (La(ΙΙΙ)) ions from aqueous solutions in the batch scheme. The prepared adsorbent material was determined utilizing FTIR, SEM-EDX, and BET methods. The impact of three individual process variable factors involving feed solution pH (2-6), adsorbent dose (0.05-0.65), and process temperature (15-55 °C) on the simultaneous removal of Ce(ΙΙΙ) and La(ΙΙΙ) ions was evaluated via response surface methodology (RSM) according to the central composite design (CCD). The modeling of Ce(ΙΙΙ) and La(ΙΙΙ) ions adsorption was performed using the quadratic model and was evaluated using a coefficient of determination for both ions. The optimization data revealed that the adsorption amount of Ce(ΙΙΙ) and La(ΙΙΙ) ions removal under optimal conditions were 99.75% and 69.98%, respectively. Equilibrium and kinetic investigations were also conducted to define the removal performance of the calculated adsorbent for Ce(ΙΙΙ) and La(ΙΙΙ) ions removal. Various isotherms models such as Langmuir, Freundlich, Temkin, and Sips were examined at 25 °C to analyze the equilibrium isotherm data. The data revealed that the Sips approach is compatible with the experimental data. The highest adsorption capacity of the resin for Ce(ΙΙΙ) and La(ΙΙΙ) ions were 11.873 mg g^-1 and 7.324 mg g^-1, correspondingly. The kinetic study of the Ce(ΙΙΙ) and La(ΙΙΙ) adsorption process was conducted via pseudo-first-order, pseudo-second-order, and intraparticle diffusion models(IDMs). Based on the data obtained, kinetic data were fitted well to a pseudo-second-order rate correlation. According to the obtained results, the (AXAD-7) resin impregnated with CYANEX-272 performed well in removing both Ce(ΙΙΙ) and La(ΙΙΙ) ions from aqueous solutions with well stability during several adsorption-desorption cycles and well regeneration and excellent metallic ions recovery.

Progresses in lignin, cellulose, starch, chitosan, chitin, alginate, and gum/carbon nanotube (nano)composites for environmental applications: A review

Water sources are becoming increasingly scarce, and they are contaminated by industrial, residential, and agricultural waste-derived organic and inorganic contaminants. These contaminants may pollute the air, water, and soil in addition to invading the ecosystem. Because carbon nanotubes (CNTs) can undergo surface modification, they can combine with other substances to create nanocomposites (NCs), including biopolymers, metal nanoparticles, proteins, and metal oxides. Furthermore, biopolymers are significant classes of organic materials that are widely used for various applications. They have drawn attention due to their benefits such as environmental friendliness, availability, biocompatibility, safety, etc. As a result, the synthesis of a composite made of CNT and biopolymers can be very effective for a variety of applications, especially those involving the environment. In this review, we reported environmental applications (including removal of dyes, nitro compounds, hazardous materialsو toxic ions, etc.) of composites made of CNT and biopolymers such as lignin, cellulose, starch, chitosan, chitin, alginate, and gum. Also, the effect of different factors such as the medium pH, the pollutant concentration, temperature, and contact time on the adsorption capacity (AC) and the catalytic activity of the composite in the reduction or degradation of various pollutants has been systematically explained.

Deciphering the role of granular activated carbon (GAC) in anammox: Effects on microbial succession and communication

Anaerobic ammonium oxidation (anammox) offered an energy-efficient option for nitrogen removal from wastewater. Granular activated carbon (GAC) addition has been reported that improved biomass immobilization, but the role of GAC in anammox reactors has not been sufficiently revealed. In this study, it was observed that GAC addition in an upflow anaerobic sludge blanket (UASB) reactor led to the significantly shortened anammox enrichment time (shortened by 45 days) than the reactor without GAC addition. The nitrogen removal rate was 0.83 kg N/m³/day versus 0.76 kg N/m³/day in GAC and non-GAC reactors, respectively after 255 days' operation. Acyl-homoserine lactone (AHL) quorum sensing signal molecule C8-HSL had comparable concentrations in both anammox reactors, whereas the signal molecule C12-HSL was more pervasive in the reactor containing GAC than the reactor without GAC. Microbial analysis revealed distinct anammox development in both reactors, with Candidatus Brocadia predominant in the reactor that did not contain GAC, and Candidatus Kuenenia predominant in the reactor that contained GAC. Denitrification bacteria likely supported anammox metabolism in both reactors. The analyses of microbial functions suggested that AHL-dependent quorum sensing was enhanced with the addition of GAC, and that GAC possibly augmented the extracellular electron transfer (EET)-dependent anammox reaction.

Biofabrication of Fe3O4 Nanoparticles from Spirogyra hyalina and Ajuga bracteosa and Their Antibacterial Applications

Iron oxide nanoparticles (NPs) have attracted substantial interest due to their superparamagnetic features, biocompatibility, and nontoxicity. The latest progress in the biological production of Fe3O4 NPs by green methods has improved their quality and biological applications significantly. In this study, the fabrication of iron oxide NPs from Spirogyra hyalina and Ajuga bracteosa was conducted via an easy, environmentally friendly, and cost-effective process. The fabricated Fe3O4 NPs were characterized using various analytical methods to study their unique properties. UV-Vis absorption peaks were observed in algal and plant-based Fe3O4 NPs at 289 nm and 306 nm, respectively. Fourier transform infrared (FTIR) spectroscopy analyzed diverse bioactive phytochemicals present in algal and plant extracts that functioned as stabilizing and capping agents in the fabrication of algal and plant-based Fe3O4 NPs. X-ray diffraction of NPs revealed the crystalline nature of both biofabricated Fe3O4 NPs and their small size. Scanning electron microscopy (SEM) revealed that algae and plant-based Fe3O4 NPs are spherical and rod-shaped, averaging 52 nm and 75 nm in size. Energy dispersive X-ray spectroscopy showed that the green-synthesized Fe3O4 NPs require a high mass percentage of iron and oxygen to ensure their synthesis. The fabricated plant-based Fe3O4 NPs exhibited stronger antioxidant properties than algal-based Fe3O4 NPs. The algal-based NPs showed efficient antibacterial potential against E. coli, while the plant-based Fe3O4 NPs displayed a higher zone of inhibition against S. aureus. Moreover, plant-based Fe3O4 NPs exhibited superior scavenging and antibacterial potential compared to the algal-based Fe3O4 NPs. This might be due to the greater number of phytochemicals in plants that surround the NPs during their green fabrication. Hence, the capping of bioactive agents over iron oxide NPs improves antibacterial applications.

The elimination and extraction of organosulfur compounds from real water and soil samples using metal organic framework/graphene oxide as a novel and efficient nanocomposite

In the present work, an efficient metal organic framework/graphene oxide (MOF-801/GO) sorbent was fabricated and employed for the detection of organosulfur pesticides (OSPs) in real samples using gas chromatography-flame photometric detection (GC-FPD). The optimal extraction parameters for the suggested solid-phase extraction (SPE) include sorbent amount (60 mg), extraction solvent (acetonitrile) and extraction time (5 min). The linear dynamic ranges and detection limits for organosulfur pesticides (OSPs) samples under above extraction conditions were ranged from 0.5 to 300 μg L^-1 and 0.1-1.1 μg L^-1, respectively. Moreover, the proposed SPE/GC-FDP method was applied for the analysis of pesticides in different real environmental water and soil samples. The obtained recoveries of the analytes in were between 92.0 and 106.8% and relative standard deviation (RSD) values were lower than 9.2%. The application of the MOF-801/GO as a sorbent in dSPE of OSPs analytes showed to be reliable, fast and sensible methodology for pesticides monitoring in different environmental samples.

Monitoring of COS, SO2, H2S, and CS2 gases by Al24P24 nanoclusters: a DFT inspection

Through utilizing density functional theory (DFT), the current work investigates the potential uses of Al24P24 fullerene for detecting CS2, H2S, SO2, and COS. The interaction order for the stability of these gases was SO2 > H2S > COS > CS2. The moment of electric dipole and molecules' adsorption energy seems correlated. Al24P24 fullerene is regarded as an electronic sensor of the Ф-type for detecting SO2 and CS2. According to the findings, CS2 and SO2 might act as Al24P24 fullerenes when H2S is present. Nevertheless, we cannot presume it to be a COS and H2S sensor of Ф-type. At room temperature, the fullerene of Al24P24 has a quick recovery time of 0.50 μs and 0.17 s in CS2 and SO2 desorption from the surface. It can thus be inferred that it has the ability to function in moist media.