The present study is devoted to the vertical distribution of potentially toxic elements (PTEs) in the peat profiles of the northern taiga, which depend on endogenous processes, external inputs, geochemical barriers, and are also influenced by fires. Based on the obtained results, elements were distributed within the soil profile into two distinct groups. The first group predominantly concentrates in the lower horizons and includes zinc (Zn), nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe), chromium (Cr), vanadium (V), titanium (Ti), and magnesium (Mg). The second group is primarily found in the peat layer and comprises mercury (Hg), copper (Cu), lead (Pb), cadmium (Cd), Zn, Ni, Mn, aluminum (Al), V, barium (Ba), strontium (Sr), calcium (Ca), and arsenic (As). The plant biomass, in particular that of pine and birch wood, plays a significant role in the deposition of PTEs. The key geochemical barriers that immobilize PTEs include humic acids, sulfur-containing compounds, and iron oxides and hydroxides, which form stable associations with these elements under reducing conditions. Special attention is paid to the fire events: ash resulting from fires is a source of alkaline and alkaline earth elements (potassium (K), Ca), as well as Mn, V, Ni, Cd, Pb, and Cu. Statistically significant spatial differences in PTE content were observed between the studied soil pits, likely attributable to meteorological factors influencing the atmospheric transport of elements from fires. Manganese exhibits high mobility and a downward distribution pattern, while Cu and Pb remain associated with and immobilized by organic matter. Overall, the study highlights the complex, multifactorial nature of the formation of the geochemical structure of peat ecosystems.
This study presents a regional survey of treated and untreated water sources in the Seridó Ocidental region of Paraíba, Brazil. A single-sampling campaign was conducted to evaluate chemical, microbiological, and radiological parameters against national standards. High concentrations of sodium (up to 5000 mg L-1), chloride (up to 1579 mg L-1), calcium (up to 105 mg L-1), and magnesium (up to 124 mg L-1) were observed, exceeding recommended limits and affecting taste and hardness. Turbidity in untreated water reached up to 105 NTU, about 20 times the permissible limit. Nitrate levels reached 34 mg N-NO3- L-1 (26% non-compliance), and lead concentrations up to 0.026 mg L-1 were found, both exceeding regulatory limits. Activity concentrations of 226Ra (up to 1.28 Bq L-1) and 228Ra (up to 1.20 Bq L-1) in some untreated sources also exceeded standards, associated with local geochemical conditions such as uranium- and thorium-rich minerals and high salinity. Calculated annual effective doses for children aged 1 to 10 years exceeded the WHO reference value of 0.1 mSv in several cases, indicating a need for further assessment and management. These results highlight the need for continuous monitoring and targeted interventions to ensure safe water in vulnerable semi-arid regions.
Pesticide use in extensive agriculture generates complex exposures for wildlife, however, early-life effects in reptiles remain underexplored. In this study, we evaluated whether embryonic exposure at manufacturer-recommended concentration for field use: glyphosate (GLY at 1 and 2%), 2,4-D (at 0.06 and 0.12%), chlorantraniliprole (CAP at 0.015 and 0.03%), imidacloprid (IMI at 0.1 at 0.2%) and three mixtures at the lowest concentrations (M1: GLY+2,4-D; M2: CAP + IMI; M3: M1+M2) disrupt lipid metabolism, lipoperoxidation and corticosterone levels in Caiman latirostris hatchlings. Hatching success declined under 2,4-D 0.06%, CAP 0.03%, and IMI 0.2%. Residual yolk showed alterations in polyunsaturated fatty acids, together with yolk-cholesterol and α-tocopherol depletion, particularly under CAP 0.03% and in the complex mixtures M1, M2, and M3. Changes in plasma lipid profiles, hepatic aminotransferase activities as well as alteration of NADPH-producing gene expression in blood were observed in M2 and M3. Higher lipoperoxidation levels were observed at the highest concentration across single compounds and in M1 and M3; whereas corticosterone increased in 2,4-D 0.12%. These findings demonstrate that early life stages of caimans are highly sensitive to these xenobiotics, affecting lipid metabolism and associated physiological processes. Moreover, mixtures induced stronger and more complex responses than single compounds, leading to metabolic disruption during early development. Our findings highlight the importance of evaluating realistic agrochemical mixtures to better assess their ecological risk.
Understanding phosphate (PO43-) transport during anaerobic treatment is essential for improving nutrient removal from municipal landfill leachate. This study tested the hypothesis that the Generalized Fulazzaky (GF) equations can quantitatively distinguish external, internal, and global mass-transfer processes and identify the dominant rate-controlling resistance governing PO43- removal in anaerobic systems. A laboratory-scale up-flow anaerobic sludge blanket (UASB) reactor equipped with a gas-liquid-solid separator was operated under mesophilic conditions (38 °C) for 197 d to treat municipal landfill leachate. During the initial operating stage, PO43- removal was limited because the anaerobic sludge (ANS) was still acclimating and granule development was incomplete. As the biomass matured and the influent PO43- concentration increased from 5.02 to 10.93 mg L-1, the removal efficiency improved from 25.25% to 57.79%. Linear GF analysis showed an excellent fit (R2 = 0.9929), enabling determination of the β and B parameters for kinetic simulation. The global mass-transfer factor closely followed the internal mass-transfer factor, whereas the external mass-transfer factor remained consistently lower, indicating that external mass-transfer resistance governed overall PO43- removal under the investigated conditions. Analysis of the C/N/P ratio further demonstrated the coupling between nutrient availability, ANS development, and phosphate transport. These findings provide new mechanistic insight into PO43- biosorption in anaerobic systems and demonstrate that the GF framework is a useful mechanistic tool for interpreting nutrient mass-transfer behavior in laboratory-scale UASB reactors, providing a basis for future pilot-scale validation.
The integration of molecular colorimetric sensors with smartphone-assisted image analysis and machine learning has emerged as a next-generation sensing paradigm for environmental diagnostics. Herein, we report an artificial intelligence (AI)-integrated chemosensing platform based on a norbornene-appended rhodamine derivative (RhB-NBE) for the sequential monitoring of Fe3+ and arsenic species [As(V)/As(III))] in aqueous media. The probe was synthesized through a Schiff base condensation reaction and fully characterized using NMR, X-ray, and other spectroscopic techniques. RhB-NBE exhibited highly selective and instantaneous recognition of Fe3+ over competing metal ions, including Fe2+, through a spirolactam ring-opening mechanism that generated a discrete colorimetric response. The resulting RhB-NBE + Fe3+ ensemble served as a secondary sensing platform for arsenite and arsenate via a cation-displacement process, producing a visible color transition from pink to colorless with a low detection limit of 2 nM (below the World Health Organization critical limit). Practical applicability was demonstrated using portable paper-based sensing strips, and successful quantification of arsenic species in environmental water samples with excellent recovery values. Despite the rapid advancement of AI-assisted chemical sensing, integration of machine learning with colorimetric arsenic detection remains largely unexplored due to challenges in sensor reproducibility, image standardization, and reliable concentration classification. Herein, we combine a selective colorimetric chemosensor with AI-based image analytics for rapid field monitoring. Smartphone images were analyzed using GNB, SVM, and CNN models trained on 1000 RGB datasets; SVM achieved 97.0% accuracy for equipment-free arsenic screening.
The increasing resistance of the yellow fever mosquito, Aedes aegypti, to conventional larvicides underscores the critical need for novel vector control strategies. This work investigates the intrinsic larvicidal activity of free-thiol derivatives (3-mercaptopropionic acid (MPA) and cysteamine (CA)) and evaluates how their specific functional groups (carboxylic acid and amine) govern molecular interactions within the larval digestive system. The free MPA and CA compounds exhibited remarkable larvicidal efficacy against fourth-instar (L4) larvae, presenting LC50 values of 18.34 ± 0.68 mg L-1 and 8.26 ± 0.58 mg L-1, respectively. Ingestion assays revealed that spatial nanoprobe distribution is strictly regulated by the larval intestinal pH gradient and ligand pKa. While negatively charged CdTe-MPA maintained broad colloidal stability across the midgut, CdTe-CA underwent charge neutralization in the alkaline central midgut, triggering localized colloidal deposition at neutral-to-acidic boundaries. Both probes showed strong affinity for chitinous structures, compromising gut homeostasis. This study provides mechanistic proof of concept that surface-charge tailoring can exploit vector physiology for targeted pest control.
Shale gas activities can release trace elements and naturally occurring radionuclides into aquatic environments, yet the long-term impact of low-intensity contamination events remains poorly constrained. This study investigates a localized geochemical anomaly observed in river sediments collected in 2021 near a documented shale-gas-related spill and waste disposal area in the Kennebecasis River watershed. Sediment cores and associated porewaters were collected to assess the distribution, potential sources, and mobility of uranium (U), barium (Ba), and radium-226 (226Ra). Results reveal localized enrichment of U and Ba near the disposal site. Elemental and radionuclide activity ratios (238U/226Ra, Th/U, Ba/Ca, and 226Ra/Ca), together with contaminant spatial distributions, are consistent with an anthropogenic source potentially associated with shale-gas-related waste disposal. Early diagenetic processes appear to promote contaminant release into porewaters, whereas transfer to the overlying water column remains limited. Distribution coefficients (Kd) and diffusive flux estimates suggest greater mobility of uranium relative to radium. Present-day diffusive flux estimates indicate limited contaminant removal by molecular diffusion. Assuming that current concentration gradients remained broadly stable through time, diffusion would account for only a few percent of the current contaminant inventory, generally less than 8%, over a 15-year period. This estimate should be regarded as a conceptual scenario rather than a reconstruction of actual attenuation history. These results highlight the value of sediment geochemistry and radionuclide tracers for identifying localized environmental anomalies potentially associated with shale-gas-related activities. Future work should include sediment dating and direct characterization of buried waste materials and associated leachates to strengthen source attribution and constrain links with the documented 2006 event.
Over the past three decades, the Tapajós River Basin, Brazilian Amazon, has become a major setting for investigating chronic environmental mercury (Hg) exposure, predominantly associated with dietary methylmercury (MeHg) intake through fish consumption. This critical review synthesizes Hg research conducted between 1990 and 2026, tracing scientific progress from contamination sources to human exposure, health effects, biological susceptibility, and emerging environmental health challenges. Early studies identified artisanal and small-scale gold mining, the remobilization of legacy Hg through biogeochemical processes, and fish consumption as central components linking environmental Hg sources to human exposure. Subsequent investigations expanded this evidence by examining health effects, biological susceptibility, nutritional interactions, and multiple environmental stressors. Although Hg concentrations in piscivorous fish have remained persistently elevated, biomonitoring studies suggest a gradual decline in Hg exposure in some communities, potentially reflecting changes in dietary patterns, socioeconomic conditions, sampling characteristics, and study locations.Despite major advances in characterizing contamination and exposure, less progress has been achieved in understanding long-term health consequences. Most epidemiological studies remain descriptive or cross-sectional, limiting causal inference and characterization of exposure-response relationships. Neurological, sensory, visual, and motor alterations remain the most consistently reported outcomes, yet uncertainties persist regarding causality, individual susceptibility, and mechanisms underlying variability among exposed populations. The contrasting findings of the Faroe Islands and Seychelles longitudinal cohorts illustrate these challenges.Recent studies increasingly recognize that Hg toxicity is shaped by complex exposomes involving selenium (Se), co-exposure to lead (Pb) and other contaminants, nutritional transition, infectious diseases, climate change, and social determinants of health. Future progress will require adequately powered longitudinal cohorts, population-specific reference values, biomarkers of exposure, effect and susceptibility, and integration of multi-omics, exposome, and One Health approaches to strengthen causal inference and improve environmental health policies for Amazonian populations.
The advancement of ozonation for wastewater treatment requires a thorough understanding of transformation processes affecting emerging contaminants such as pharmaceuticals and personal care products (PPCPs). This study investigates the degradation products of umifenovir (Arbidol) during aqueous ozonation. Using HPLC-ESI-HRMS, 23 primary (intermediate) transformation products were identified, their structures proposed, and degradation pathways established. The highest product diversity occurred at neutral pH due to reactions involving both molecular ozone and hydroxyl radicals. Initial transformation pathways include sulfide group oxidation with thiophenol moiety elimination, and indole ring oxidation followed by debromination. Under excess ozonation, GC-HRMS and mixed-mode (WAX/WCX) HPLC-HRMS revealed over 42 low-molecular-weight deep degradation products. Most arise from parent molecule transformation (e.g., trimethylamine or thiophenol) and subsequent oxidation. In addition to expected products, side radical reactions such as chlorination and dealkylation were observed. The bromine atom in umifenovir enabled HPLC-ICP-MS quantification of bromine-containing transformation products without individual standards. Umifenovir is rapidly removed from the reaction medium; however, persistent intermediate and deep transformation products remain even under excess ozonation. These findings highlight the need for advanced analytical methods for transformation product identification and for evaluating ozonation efficiency based on product formation rather than parent compound removal alone.
Heavy metal (HM) toxicity has become one of the major environmental concerns in recent years. In this study, we investigate the adsorption-based approach for the detection and removal of heavy metal ions (HMIs) from wastewater applications. Density functional theory (DFT) calculations are used to systematically investigate pristine γ-graphyne (γ-GY) and transition-metal-decorated γ-graphyne (TM/γ-GY) as efficient adsorbents for Hg, As, and Pb removal under implicit solvation conditions. Pristine γ-GY exhibits adsorption of Hg, As, and Pb with adsorption energies of -1.17 eV, -2.21 eV, and -3.46 eV, respectively. Transition metal doping enhances adsorption performance via strengthened TM-C interactions, increased electron transfer, enhanced stability, and electronic structure tuning. Re/γ-GY and Os/γ-GY show exceptionally strong adsorption for As and Pb (-4.81 and -4.30 eV, respectively), while Mn/γ-GY offers balanced adsorption for all HMIs. TM doping reduces the γ-GY band gap from 0.37 eV to below 0.15 eV in several systems, enhancing both electrical conductivity and adsorption sensitivity. Sensitivity analysis shows that Re/γ-GY achieves ∼100% sensitivity toward As, while Mn/γ-GY and Os/γ-GY selectively respond to Hg with >90% sensitivity. Adsorption capacity calculations show that pristine γ-GY exhibits a Hg uptake of 1043 mg g-1, while TM doping enhances As and Pb capacities to 237 mg g-1 and 984 mg g-1 on Mn/γ-GY, respectively. Through a descriptor-guided framework incorporating adsorption selectivity, sensitivity, and adsorption capacity, Mn/γ-GY attains the highest overall performance score (0.72), making it the most promising adsorbent for multi-contaminant heavy metal removal.
Evaluating regional and seasonal air pollution variability is essential for monitoring tropical environments. This study evaluated regional and seasonal variations in fine particulate matter (PM2.5) and ground-level ozone (O3) across five regions of Malaysia using daily atmospheric and meteorological observations from 2018 to 2023 from the Department of Environment (DOE), complemented by ERA5 reanalysis variables (boundary layer height, solar radiation, and cloud cover). Multiple Linear Regression (MLR) and Extreme Gradient Boosting (XGBoost) were compared, while Shapley Additive Explanations (SHAP) were applied to interpret driver importance and nonlinear relationships. Kruskal-Wallis and Dunn post hoc tests identified regional and seasonal differences in both pollutants. PM2.5 varied spatially with (χ2 = 3239.530, p < 0.001) and seasonally (χ2 = 477.837, p < 0.001). O3 varied geographically with (χ2 = 2173.607, p < 0.001) and seasonally (χ2 = 69.579, p < 0.001). XGBoost outperformed MLR, achieving R2 = 0.576 and RMSE = 4.87 μg m-3 for PM2.5, and R2 = 0.543 and RMSE = 3.4 ppb for O3, with skill varying by region and season and increasing to R2 = 0.85 when persistence was included. SHAP analysis showed that PM2.5 variability was associated with combustion-related tracers and meteorological factors, whereas O3 was more strongly associated with humidity and temperature, with humidity exerting greater influence during the Northeast Monsoon. These suggest that air pollution variability across Malaysia is governed by interactions between emission patterns and meteorological conditions, emphasizing the importance of season-specific evaluation, explainable machine learning, and regional assessment for policy development.
Phosphorus (P) transport in riparian wetland systems is strongly influenced by hydrological events and interactions with suspended solids, yet association with its speciation and coupling with contaminant transport remain unclear. Here, we investigated P dynamics using high-frequency time-series sampling during five storm events in a riparian-wetland located on the Savannah River Site, South Carolina. Total P was fractionated into dissolved and particulate forms, with particulate P further separated into four operationally defined species identified by sequential extraction techniques. Total P was dominated by particulate P (>85%), with storm-driven increases primarily associated with elevated suspended solids. Marked shifts in P speciation occurred between early and late stormflow stages. Early-stage samples were enriched in reactive particulate P (e.g., exchangeable- and Fe-bound P), whereas late-stage samples contained higher proportions of occluded P and phosphate. These patterns corresponded to changes in particle composition, with early samples associated with Fe/organic matter (OM)-rich flocs and late samples contributed by less reactive mineral particles and aggregates. Strong correlations between P partitioning coefficients and solid-phase Fe and Mn highlight the likely central role of Fe-rich particles in regulating P transport. Significant correlations between stream P and uranium (U), one of key contaminants on the site, indicate their co-variation transport via shared associations with reactive suspended solids, suggesting that P may serve as an indicator of contaminant-associated particle transport under the studied conditions. Overall, storm-driven formation and mobilization of Fe/OM-rich particulates play an important role in regulating P speciation and transport in riparian-wetland systems.
Microplastics (<5 mm) are widespread environmental contaminants, with increasing human exposure through ingestion, inhalation, and dermal contact. Their presence in terrestrial, aquatic, and atmospheric systems, along with detection in human tissues such as blood, lungs, placenta, and the gastrointestinal tract, highlights their bioavailability and potential health risks. Owing to their small size, high surface-area-to-volume ratio, and surface reactivity, microplastics can interact with biological molecules and cells, raising concerns about their role in disease development. This review presents a mechanistic perspective on microplastic-induced carcinogenesis. Microplastics can enter the body via multiple routes and disrupt cellular homeostasis by inducing oxidative stress, chronic inflammation, mitochondrial dysfunction, and genotoxicity. These effects contribute to genomic instability and dysregulation of key signaling pathways, including NF-κB, MAPK, and PI3K/Akt, which are associated with tumor initiation and progression. Additionally, microplastics act as "Trojan horse" carriers, facilitating the transport of co-contaminants such as heavy metals, persistent organic pollutants, and microbial agents, thereby enhancing their bioavailability and toxicity. The combined effects of microplastics and associated toxicants amplify oxidative stress, inflammatory responses, and epigenetic alterations, promoting a pro-tumorigenic environment. Despite growing evidence, significant knowledge gaps remain regarding long-term exposure, the behavior of nanoplastics in biological systems, and their direct link to cancer. This review emphasizes the need for integrated and interdisciplinary research to better understand microplastic-associated carcinogenesis and to support effective risk assessment and regulatory strategies.
The blow fly Lucilia sericata is a species of major medical and veterinary importance, functioning both as a causative agent of myiasis and as a beneficial organism in maggot debridement therapy. Increasing resistance to conventional insecticides highlights the need for alternative compounds targeting fundamental physiological processes. In this study, we investigated the insecticidal and physiological effects of 2,6-dimethylphenol (2,6-DMP), a lipophilic phenolic compound, with particular emphasis on its impact on cuticular lipid homeostasis and immune cell integrity. Topical application of 2,6-DMP significantly reduced larval survival and, more prominently, suppressed adult emergence to 5-20% of control levels, indicating disruption of metamorphosis beyond acute toxicity. Dose-response analysis revealed similar median lethal doses (LD50) for larvae and adults (∼1.85-1.95 μg/mg body mass), suggesting comparable susceptibility across developmental stages. Gas chromatography-mass spectrometry demonstrated pronounced, stage-specific remodeling of cuticular free fatty acids (FFAs). In larvae, exposure induced a strong, dose-dependent accumulation of long-chain FFAs, particularly C16:0 and C18:1. In contrast, adults exhibited a biphasic response: sublethal exposure resulted in a >3-fold increase in total FFAs, whereas lethal exposure caused near-complete lipid depletion. Cholesterol was consistently depleted in all treated groups. Principal component analysis confirmed that variation in lipid profiles was driven primarily by changes in total FFA abundance and sterol composition. In parallel, hemocyte analysis revealed clear immunotoxic effects, including reduced granulocyte abundance, impaired aggregation, and progressive morphological disruption in both in vivo and in vitro models. Collectively, these findings demonstrate that disruption of lipid homeostasis contributes to the physiological and immunotoxic effects of 2,6-DMP in L. sericata. Beyond revealing a potential mode of insecticidal action, our findings raise concerns about the potential ecotoxicological impact of 2,6-DMP as an environmental contaminant, particularly with respect to non-target insects, and identify lipid homeostasis as a sensitive mechanistic endpoint for environmental risk assessment.
Water reuse is a key pillar of circular economy strategies, particularly in water-scarce regions, by preserving freshwater resources and supporting agricultural production. Current regulations promote the use of reclaimed water for irrigation, placing wastewater treatment plants (WWTPs) at the center of this transition. However, emerging risks related to antibiotic-resistant bacteria (ARB) and antibiotic-resistance genes (ARGs) challenge the safety of reuse as these determinants may persist after treatment. This study evaluated the effectiveness of ozonation, sodium hypochlorite, UV-C irradiation, and membrane bioreactor (MBR) systems in reducing ARGs in effluents from the Region of Murcia (Spain) across five sampling campaigns between 2023 and 2024. Metagenomic sequencing identified ARGs associated with 17 antibiotic classes, with macrolide-, β-lactam-, and tetracycline-ARGs dominating. Total ARG abundance was lower in treated effluents than in influents, with the greatest percentage reduction in MBR system, although based on only two effluent samples. Selected macrolide-, sulfonamide-, tetracycline- and β-lactam-ARGs nevertheless remained detectable after treatment, with distinct gene-specific profiles among the wastewater-reclamation systems. Effluent samples differed in the taxonomic composition of ARG-carrying reads and in the detection of ARGs putatively co-localized on mobilome associated contigs. These findings show that total ARG reduction alone does not fully characterize wastewater-reclamation performance because substantial decreases in total ARG burden were accompanied by different residual resistome profiles. Combining ARG abundance, identity, potential hosts, and genomic context enables a fuller assessment of reclaimed-water treatment. These metagenomic associations indicate potential persistence and mobility but do not constitute direct evidence of horizontal gene transfer or quantitative environmental risk.
Agricultural intensification has increased pesticide inputs into freshwater ecosystems worldwide, yet pesticide risk assessments still rely largely on toxicity data from standard Northern Hemisphere model organisms. This may limit the biogeographical representativeness of acute SSD-derived hazard benchmarks. We evaluated the acute toxicity of lambda-cyhalothrin and ammonium glufosinate using three native Pampean freshwater species: Hyalella curvispina, Boana pulchella, and Cnesterodon decemmaculatus. Acute toxicity values (96-h LC50) were integrated into Species Sensitivity Distributions (SSDs) to estimate acute HC5 values, assess regional sensitivity, and characterize hazard under reported exposure scenarios. Lambda-cyhalothrin was markedly more toxic than ammonium glufosinate. Hyalella curvispina was the most sensitive species, with 96-h LC50 values of 0.25 μg/L for lambda-cyhalothrin and 1.07 mg/L for ammonium glufosinate. For lambda-cyhalothrin, the acute SSD yielded an HC5 of 0.0052 μg/L, and the highest reported concentration for Pampean streams (0.56 μg/L) exceeded both the LC50 of H. curvispina and the community-level acute hazard benchmark, resulting in an HQcommunity of 107.0. In contrast, reported ammonium glufosinate concentrations remained below acute lethal thresholds and yielded HQ values below unity, although the SSD showed greater uncertainty due to limited taxonomic coverage. Sensitivity analyses showed that adding Pampean taxa changed HC5 point estimates in a compound-specific manner, highlighting that the influence of native species depends on their position within each SSD and on database composition. Overall, these results indicate a robust acute hazard signal for lambda-cyhalothrin under peak exposure scenarios, whereas ammonium glufosinate represents a preliminary screening-level vulnerability signal. The study highlights the need to expand South American toxicity datasets and incorporate chronic, sublethal, and temporally resolved exposure information.
Hydroxyapatite (HAp) has garnered considerable attention as an adsorbent for heavy metal removal owing to its favorable surface reactivity and ion-binding capability. Nevertheless, its adsorption performance is strongly governed by surface chemical environments and structural characteristics. In this study, pristine hydroxyapatite (P-HAp), Fe-modified hydroxyapatite (Fe-HAp), and Ti-modified hydroxyapatite (Ti-HAp) were synthesized and systematically evaluated for Mn2+ removal from aqueous solutions. Batch adsorption experiments revealed that metal modification altered the adsorption behavior of the HAp-based materials. The pH-dependent adsorption results showed that Fe-HAp exhibited the highest Mn2+ uptake among the three materials under optimal conditions (pH 5), with adsorption capacities of 13.25, 16.44, and 11.55 mg g-1 for P-HAp, Fe-HAp, and Ti-HAp, respectively. For P-HAp, the Langmuir model provided a better fit. For Fe-HAp and Ti-HAp, the Freundlich model gave higher fitting accuracy at most temperatures, implying that heterogeneous adsorption regions and sites with diverse binding affinities collectively promoted Mn2+ uptake following metal modification. Kinetic analysis revealed that the pseudo-second-order model generally offered a superior fit for all three materials, indicating that surface chemical interactions were central to the adsorption process. Structural and surface characterization confirmed that Fe modification regulated the pore structure and surface chemical environment while preserving the characteristic hydroxyapatite framework. BET analysis demonstrated improved pore characteristics of Fe-HAp, and XPS analysis suggested the involvement of oxygen-containing and phosphate-related surface species during Mn2+ adsorption. Furthermore, DFT calculations indicated that Fe incorporation altered the electronic structure and frontier orbital features of HAp, which may facilitate coordination interactions between Mn2+ and surface oxygen-containing species. Overall, this study demonstrates that metal modification constitutes an effective strategy for tailoring the adsorption properties of HAp-based materials. Fe incorporation improves the adsorption behavior of HAp by modifying structural features and surface chemical environments, thereby boosting Mn2+ removal through synergistic interactions dominated by surface coordination.
Wastewater containing dye pollutants presents a serious environmental challenge in industrial activities. Membrane filtration is a promising treatment method due to its high selectivity and environmental friendliness. Graphene oxide (GO), rich in oxygen-containing functional groups, is commonly incorporated into polyvinyl alcohol (PVA) matrices to improve permeability; however, membrane fouling remains a major limitation. To overcome this issue, Isoreticular Metal-Organic Framework-3 (IRMOF-3), a photocatalytically active material, was incorporated as a self-cleaning additive into PVA/GO membranes. GO was synthesized using a modified Hummer's method, while IRMOF-3 was prepared via precipitation. Composite membranes were fabricated by vacuum filtration on nylon supports and characterized by UV-Vis, FTIR, XRD, SEM-EDX, and UV-Vis DRS. Porosity and pore size were evaluated using the gravimetric method and the Guerout-Elford-Ferry equation. Results confirmed the successful integration of IRMOF-3, producing multifunctional membranes with diverse active sites. IRMOF-3 exhibited an indirect band gap of 2.83 eV. Compared to GO and PVA/GO membranes, PVA/GO/IRMOF-3 membranes showed higher porosity, smaller pore radii, and enhanced rejection stability. Membranes containing 10 mg and 30 mg IRMOF-3 achieved dye rejection rates of 87.75% and 83.72% after five cycles, demonstrating improved performance during repeated UV-assisted filtration-cleaning cycles while maintaining high dye rejection efficiency.
This study presents a comprehensive mechanistic and toxicological investigation into the visible-light-driven degradation of bisphenol A (BPA), 4-bromophenol (4-BP), and sulfamethoxazole (SMX) using template-assisted modified graphitic carbon nitride (MCN) photocatalysts under visible light irradiation. The photocatalysts were synthesized via a one-pot polymerization process using homemade calcium cyanamide (CaCN2) as a template. The prepared MCN nanosheets exhibited significantly enhanced photocatalytic performance, with improved charge separation, reduced sheet grain size, and increased activity, attributed to template-assisted synthesis. The degradation efficiencies of BPA, 4-BP, and SMX were systematically evaluated, demonstrating superior degradation performance. Integrated analytical techniques, including LC-MS/MS, elucidated the degradation pathways, whereas Density Functional Theory (DFT) calculations provided detailed insights into the adsorption mechanisms and molecular descriptors of the pollutants on the photocatalyst surface. Theoretical calculations indicated significant differences in adsorption energy and interaction between the pollutants and MCN, with SMX showing the strongest adsorption but slower degradation kinetics, attributed to its complex structure. Additionally, ecotoxicological assessments using Ecological Structure-Activity Relationship (ECOSAR) predicted a reduction in the toxicity of degradation intermediates, underscoring the broad applicability of MCN in environmental remediation. These findings provide valuable guidance for the rational design of efficient photocatalysts for the degradation of emerging organic pollutants.
