Search Results (2,882)

Despite extensive work on FeOCl-based photocatalysts, few studies have explored rare-earth (Ce) doping to simultaneously tune bandgap, suppress charge recombination, and enhance visible light-driven persulfate (PS) activation for the degradation of emerging contaminants. This study synthesized FeOCl/Ce composite photocatalysts via a partial pyrolysis method and systematically characterized their physicochemical properties. The results show that Ce doping significantly lowers the bandgap energy of the photocatalyst, enhances its visible light absorption ability, and effectively suppresses the recombination of photogenerated electron–hole pairs, thereby markedly improving photocatalytic performance under visible light. Analyses including XRD, EDS, XPS, and FT-IR confirm that Ce is incorporated into the FeOCl matrix and modulates the radial growth behavior of FeOCl without altering its intrinsic crystal structure. Morphological observations reveal that FeOCl/Ce exhibits a uniform nanosheet layered structure, with larger particles formed by the aggregation of smaller nanosheets. The nitrogen adsorption–desorption isotherm of FeOCl/Ce shows characteristics of Type IV with a relatively small BET surface area. The broadened optical absorption edge of FeOCl/Ce and the results of PL spectra and I-T curves further confirm its enhanced visible light absorption capacity and reduced electron–hole recombination compared to pure FeOCl. At an initial caffeine (CAF) concentration of 10 μM, FeOCl/Ce dose of 0.5 g/L, PS concentration of 1 mM, and initial pH of 5.06, the FeOCl/Ce-catalyzed PS system under visible light irradiation can degrade 91.2% of CAF within 30 min. An acidic environment is more favorable for CAF degradation, while the presence of SO₄²⁻, Cl⁻, and NO₃⁻ inhibits the process performance to varying degrees, possibly due to competitive adsorption on the photocatalyst surface or quenching of reactive species. Cyclic stability tests show that FeOCl/Ce maintains good catalytic performance over multiple runs. Mechanistic analysis indicates that ^•OH and holes are the dominant reactive species for CAF degradation, while PS mainly acts as an electron acceptor to suppress electron–hole recombination. Overall, the FeOCl/Ce photocatalytic system demonstrates high efficiency, good stability, and visible light responsiveness in CAF degradation, with potential applications for removing CAF and other emerging organic pollutants from aquatic environments. Full article

β-blockers are among the most widely prescribed cardiovascular drugs and are increasingly recognised as emerging pollutants due to their persistence, continuous release into aquatic environments, and potential toxicological effects on aquatic organisms. Their removal in conventional wastewater treatment plants is often inefficient, highlighting the need for biological remediation strategies. This study aimed to identify bacterial strains with the highest potential for the biotransformation of β-blockers. Therefore, we isolated and characterised bacterial strains capable of transforming two commonly used β-blockers—propranolol and metoprolol. The strains BB2 and BB3, which were able to transform propranolol and metoprolol, respectively, were identified as Raoultella terrigena and Stenotrophomonas terrae, respectively. BB2 showed broad metabolic versatility, utilising a wide range of carbon sources, whereas BB3 exhibited limited substrate utilisation. Antibiotic resistance profiling further distinguished the strains, with BB2 resistant across multiple antibiotic classes and BB3 largely sensitive. Co-metabolic assays demonstrated that supplementation with specific carbon and nitrogen sources markedly enhanced β-blocker removal, increasing propranolol biotransformation from 5% to 50% and metoprolol from 4% to 36%. These findings demonstrate the bioremediation potential of newly isolated strains and emphasise the importance of aligning microbial metabolic traits with nutrient conditions to improve pharmaceutical removal in wastewater treatment systems. Full article

In this work, we present a gettering technique for multicrystalline silicon (mc-Si) by combining a nanowire structure with thermal treatment under nitrogen in an infrared lamp furnace. The silicon nanowires were elaborated using the Silver Nanoparticles Chemical Etching (Ag-NPsCE) technique. The optimal conditions for achieving effective gettering were determined based on the minority carrier lifetime (τ_eff) measurements. The results show τ_eff as a function of the gettering temperature and etching time, both before and after the removal of Ag nanoparticles using HNO₃. In both cases, the surface was identically treated with a 10% HF dip immediately prior to the carrier lifetime measurements. The highest τ_eff value, prior to Ag removal, was obtained after an etching duration of 3 min and was 6 µs at an excess carrier density Δn = 1 × 10¹⁴ cm⁻³. Moreover, τ_eff improves after silver removal. Therefore, removing Ag atoms using an aqueous HNO₃ solution is necessary to prevent this issue. Following Ag nanoparticle removal, τ_eff further increases, reaching 19 µs at a gettering temperature of 850 °C. Similarly, the electrical conductivity (ρ) and carrier mobility (μ) improve significantly after gettering, where the resistivity increases from 5.5 Ω·cm for the reference mc-Si to 1.9 Ω·cm, and the mobility rises from 122 cm²·V⁻¹·s⁻¹ to 253 cm²·V⁻¹·s⁻¹ after nanowire-based gettering at 850 °C. Overall, this method provides a scalable, practical, and cost-effective route to optimize mc-Si for high-performance photovoltaic applications. Full article

The Água Forte (AF) stream located in the Southern Alentejo region (Portugal), is a tributary of the Roxo river. The AF stream has acid mining drainage (AMD) traits, which contributes to the degradation of the river’s water quality and the adjacent soils. The use of ecological floating beds (EFBs) is an eco-rehabilitation strategy for polluted waters. This work aimed to evaluate the application of EFBs at real-scale as a water treatment system for the AF stream. Thus, three EFB, planted with Vetiveria zizanioides (3.3 m²·unit⁻¹; density 40.5 plants·m⁻²), were placed on the stream. The water quality was monitored monthly, upstream (Inlet) and downstream (Outlet) of EFBs, from May 2020 to November 2021. With the use of the EFBs, the pH remained acidic, and the other main parameters showed average removal rates of around: 8% organic matter; 7% sulphates; 4% chlorides; 18% nitrogen, 30% copper, 29% zinc, 53% iron, and 10% manganese. Inlet and Outlet mass loads correlations showed high removal diversity. For the parameters under analysis, during the treatment period, the removal efficiency showed high variability due to the hydraulic conditions. The higher removal efficiencies were obtained for low-hydraulic retention times, except for heavy metals. Overall, EFBs showed some potential, but their efficiency was variable, highlighting the need for optimization under variable hydraulic conditions. Full article

Wastewater nitrogen pollution is a serious environmental problem, and traditional treatment techniques are frequently constrained by their high energy requirements and operational complexity. The anaerobic ammonium oxidation (anammox) process combined with membrane bioreactor (MBR) technology (anammox-MBR) offers a practical and energy-efficient solution for the sustainable removal of nitrogen, further enhanced by its potential to minimize emissions of nitrous oxide (N₂O), a potent greenhouse gas with a global warming potential nearly 300 times that of carbon dioxide. This review outlines the most recent advancements in anammox-MBR systems, highlighting their ability to achieve nitrogen removal efficiencies of more than 70–90% and, in integrated systems with reverse osmosis, to recover up to 75% of the inflow as high-quality reusable water. Significant advancements such as high-rate activated sludge coupling, reverse osmosis integration, microaeration methods, and membrane surface modifications have decreased membrane fouling, accelerated startup times, and enhanced system stability. Despite these achievements, there are still issues that hinder widespread use, such as membrane fouling exacerbated by hydrophobic anammox metabolites, sensitivity to low temperatures (≤10 °C), and the persistent challenge of suppressing nitrite-oxidizing bacteria (NOB), which compete for the essential nitrite substrate. To enable cost-effective, energy-efficient, and environmentally sustainable large-scale applications, future research directions will focus on creating cold-tolerant anammox strains, advanced anti-fouling membranes, and AI-driven process optimization. Full article

The adsorptive removal of tetracycline (TC) in aqueous solution, a widely used antibiotic, was investigated using activated carbon derived from cotton textile waste. The valorization of textile waste provides a sustainable strategy that not only reduces the growing accumulation of discarded textiles but also supports a circular economy by transforming waste into efficient adsorbent materials for the removal pharmaceutical contaminants. This dual environmental and economic benefit underscores the novelty and significance of using cotton-based activated carbons in wastewater treatment. In this study, cotton textile waste was utilized as a raw material for the preparation of adsorbents via pyrolysis under nitrogen at 600 °C followed by chemical modification with H₂SO₄ solutions (1, 2, and 3 M). The sulfuric-acid modified-carbons (SMCs) were characterized by BET surface area analysis, FTIR spectroscopy and SEM imaging. Batch adsorption experiments were carried out to evaluate the effects of key operational parameters including contact time, initial TC concentration and solution pH. The results showed that the material treated with 2 M H₂SO₄ displayed the highest adsorption performance, with a specific surface area of 700 m²/g and a pore volume of 0.352 m³/g. The pH has a great influence on TC adsorption; the adsorbed amount increases with the initial TC concentration from 5 to 100 mg/L and the maximum adsorption capacity (74.02 mg/g) is obtained at pH = 3.8. The adsorption behavior was best described by Freundlich isotherm and pseudo-second-order kinetic models. This study demonstrates that low-cost and abundantly available material, such as cotton textile waste, can be effectively repurposed effective adsorbents for the removal of pharmaceutical pollutants from aqueous media. Full article

This study addresses the challenges of efficiency and cost in traditional sulfur hexafluoride (SF₆) degradation methods and the throughput limitations of common plasma technologies, with the aim of promoting sustainable treatment of potent greenhouse gases. A method of premixing SF₆ with plasma media before entering the plasma discharge region was employed to systematically investigate the effects of three atmospheres—nitrogen, air, and hydrogen—on the degradation efficiency, product distribution, and energy efficiency of SF₆. An experimental setup was constructed, and Gibbs free energy minimization simulations were conducted to analyze the degradation performance under different conditions. The results show that the premixed gas injection method achieves a degradation removal efficiency of over 99.84% when the SF₆ flow rate is lower than 4 slm, which is significantly better than the staged mixing method. When the discharge current increases from 40 A to 100 A, the degradation effect of SF₆ improves significantly, but the improvement becomes marginal when the current is further increased to 120 A. Compared with nitrogen, air and hydrogen atmospheres can effectively enhance the degradation removal rate, with the air atmosphere achieving the highest energy yield of 271 g/kWh. This research reveals the regulatory mechanism of medium components on SF₆ degradation, providing a theoretical basis for the sustainable, full-process treatment of industrial-scale reactors and contributing to the mitigation of greenhouse gas emissions. Full article

This study presented the successful synthesis of a visible light responsive Z-scheme BiTmDySbO₇/BiEuO₃ heterojunction photocatalyst (BBHP) via the hydrothermal method, exhibiting outstanding removal efficiency for degrading the metronidazole (MNZ) in wastewater. The BBHP exhibited exceptional photocatalytic activity during the degradation process of the MNZ which was a widely detected pharmaceutical pollutant in aquatic environments. The key to the high photocatalytic activity of the BBHP was the formation of a Z-scheme photogenerated carrier transport channel which existed between BiTmDySbO₇ and BiEuO₃ within the heterojunction structure. This innovative structural design was experimentally confirmed for enhancing the separation efficiency of the photogenerated charge carriers significantly, thereby, the efficient photocatalytic activity of the BBHP was promoted. After visible light irradiation for 130 min, the BBHP achieved a removal efficiency of 99.56% for degrading MNZ and a mineralization rate of 98.11% for removing the total organic carbon (TOC) concentration. In contrast to a single photocatalyst, the removal rate of the MNZ by using the BBHP was 1.14 times that by using the BiEuO₃, 1.26 times that by using the BiTmDySbO₇, and 2.65 times that by using the nitrogen-doped TiO₂ (N-T) under visible light irradiation. The mineralization rate for removing the TOC concentration during the degradation process of the MNZ by using the BBHP was 1.17 times that by using the BiEuO₃, 1.29 times that by using the BiTmDySbO₇, and 2.86 times that by using the N-T under visible light irradiation. The photocatalytic degradation process of the MNZ by using the BBHP followed first-order kinetics model, concurrently, a dynamics rate constant of 0.0345 min⁻¹ was obtained. Furthermore, the BBHP demonstrated excellent stability and durability in accordance with multiple cyclic degradation experiments. According to the capturing radicals experiments and the electron paramagnetic resonance test experiments, it was determined that the hydroxyl radicals (•OH) and the superoxide anions (•O₂⁻) played key role during the photocatalytic degradation process of the MNZ by using the BBHP under visible light irradiation. Finally, the intermediate products that were produced during the degradation process of the MNZ were analyzed by using liquid chromatography-mass spectrometer, as a result, a potential degradation pathway for the MNZ was proposed. Overall, this study could provide valuable references for future research on composite photocatalysts and effectively maintain the safety and sustainable utilization of water resource. Full article

This study aimed to evaluate the effects of different light wavelengths on nitrogen removal efficiency and microbial community dynamics in a bacterial–algal biofilm reactor (BABR) within recirculating aquaculture systems (RASs). Four RAS units were operated under red, blue, red–blue (1:1), and white light, and their performance in nitrogen transformation, microbial community composition, extracellular polymeric substances (EPSs), and gene abundance was systematically assessed. The results showed that red light markedly improved ammonia removal and overall nitrogen transformation stability, particularly under high nitrogen loading, by enabling faster recovery and suppressing nitrite accumulation. Microbial analyses revealed that red light enriched key algae (e.g., Scenedesmus) and functional bacteria (e.g., Bosea and Nitrospirota), supporting efficient nitrification and denitrification. Furthermore, gene annotation demonstrated that red light enhanced the abundance of photosynthetic proteins and nitrogen metabolism pathways, including biofilm formation, quorum sensing, and amino acid biosynthesis. Collectively, these findings highlight red light as a promising regulatory factor for enhancing biofilm-based nitrogen removal in RASs, providing a theoretical basis for light-assisted aquaculture wastewater treatment. Full article

Nitrogen oxides (NO_x) are major atmospheric pollutants, and their escalating emissions, driven by rapid economic development and urbanization, pose a severe threat to both the ecological environment and human health. Conventional denitrification technologies are often hampered by high costs, significant energy consumption, and stringent operational conditions, making them increasingly inadequate in the face of tightening environmental regulations. In this context, photocatalytic technology, particularly systems based on graphitic carbon nitride (g-C₃N₄), has garnered significant research interest for NO_x removal due to its visible-light responsiveness, high stability, and environmental benignity. To advance the performance of g-C₃N₄, numerous modification strategies have been explored, including morphology control, elemental doping, defect engineering, and heterostructure construction. These approaches effectively broaden the light absorption range, enhance the separation efficiency of photogenerated electron-hole pairs, and improve the adsorption and conversion capacities for NO_x. Notably, constructing heterojunctions between g-C₃N₄ and other materials (e.g., metal oxides, noble metals, metal–organic frameworks (MOFs)) has proven highly effective in boosting catalytic activity and stability. Furthermore, the underlying photocatalytic mechanisms, encompassing the generation and migration pathways of charge carriers, the redox reaction pathways of NO_x, and the influence of external factors like light intensity and reaction temperature, have been extensively investigated. From an application perspective, g-C₃N₄-based photocatalysis demonstrates considerable potential in flue gas denitrification, vehicle exhaust purification, and air purification. Despite these advancements, several challenges remain, such as limited solar energy utilization, rapid charge carrier recombination, and insufficient long-term stability, which hinder large-scale implementation. Future research should focus on further optimizing the material structure, developing greener synthesis routes, enhancing catalyst stability and poison resistance, and advancing cost-effective engineering applications to facilitate the practical deployment of g-C₃N₄-based photocatalytic technology in air pollution control. Full article

To address the issues of zero-valent iron Fe(0) passivation and limited nitrogen and phosphorus removal in constructed wetlands (CWs), this study investigated the enhancement effect of two carbon materials—activated carbon (AC) obtained through high-temperature pyrolysis and biochar (BC) obtained through low-temperature pyrolysis—when coupled with Fe(0). Four systems were set up: control (CW-C), Fe(0) alone (CW-Fe), Fe(0) with AC (CW-FeAC), and Fe(0) with BC (CW-FeBC). Evaluations covered wastewater treatment performance, microbial community structure, and functional gene abundance. Results showed that iron–carbon coupling significantly improved nitrogen and phosphorus removal, with the CW-FeAC system performing best, achieving 58% total nitrogen (TN) and 90% total phosphorus (TP) removal. This enhancement was attributed to AC’s high conductivity, which strengthened iron–carbon micro-electrolysis, accelerated Fe(0) corrosion, and enabled continuous Fe²⁺/Fe³⁺ release, supplying electrons for denitrification and phosphorus precipitation. Microbial analysis indicated that iron–carbon coupling markedly reshaped community structure, enriching key genera such as Thiobacillus (33.8%) and Geobacter (12.5%) in CW-FeAC. Functional gene analysis further confirmed higher abundances of denitrification (napA/narG→nirS→nosZ) and iron metabolism genes (feoA/feoB), suggesting enhanced nitrogen-iron cycling. This study clarifies the mechanisms by which iron–carbon coupling improves nitrogen and phosphorus performance in CWs and highlights the superiority of AC over BC in facilitating electron transfer and functional microorganism enrichment, providing a basis for the design of enhanced CW systems treating low-carbon-nitrogen-ratio wastewater, such as secondary effluent or lightly polluted surface water. Full article

This study assessed the effects of tetracycline (TC) on growth of Lemna aoukikusa and Spirodela polyrhiza under batch conditions. The duckweeds were exposed to a range of 0.0–5.0 mg L⁻¹ of TC for 7 days in a medium containing 10 mg L⁻¹ total nitrogen (TN) and 1 mg L⁻¹ total phosphorus (TP). The relative growth rate (RGR) of each species was determined from the frond area measurement using image analysis. The EC₅₀ values as the TC concentrations causing a 50% reduction in RGR, were 4.4 mg L⁻¹ for L. aoukikusa and 0.65 mg L⁻¹ for S. polyrhiza. At 5.0 mg L⁻¹ TC, TP removal decreased to 60% in the L. aoukikusa culture and 77% in the S. polyrhiza culture, compared to 85–91% and 96%, respectively, under lower TC exposure. Nevertheless, TN and TP removals were not significantly impaired at TC concentrations found in swine wastewater. The TC removals were 76–94% for the L. aoukikusa culture and 68–91% for the S. polyrhiza culture, which were attributed to adsorption and plant uptake. These findings highlight the feasibility of duckweed-based stabilization ponds for simultaneous antibiotic attenuation and nutrient removal. Full article

This study presents a cost-effective and accurate method for assessing nitrogen concentration in vermicompost fertilizer using a low-cost TCS3200 color sensor and a K-Nearest Neighbors (KNN) machine learning model. The objective was to evaluate the performance of four different color spaces—RGB, Lab, LCh, and CMYK—identify the most effective feature representation for a multi-class classification task based on accuracy and theoretical robustness to ambient light variations. A total of 2400 data points were collected from a standard chemical test kit and processed. A rigorous 60-fold cross-validation approach was used to determine the optimal model hyperparameters and to ensure the robustness of the findings. The results demonstrate that the model trained on the LCh color space achieved the highest classification accuracy of 0.9708 with an optimal K-value of 6, significantly outperforming Lab (0.9688), RGB (0.9625), and CMYK (0.9583). A detailed analysis of the confusion matrix revealed that the model successfully classified the ‘High’ and ‘Medium’ nitrogen levels with near-perfect accuracy, while minor misclassifications occurred between the ‘Low’ and ‘Trace’ categories (5 Low ⟶ Trace, 6 Trace ⟶ Low). The proposed system offers a practical, robust, and accessible tool for precision agriculture, enabling farmers to make informed decisions regarding fertilization, and directly supporting sustainable agriculture and responsible resource management. The findings indicate that the LCh color space is highly effective for this application, providing a viable solution for the rapid and reliable assessment of vermicompost quality. Most importantly, this inexpensive, on-site system removes the need for costly, time-consuming laboratory analyses, giving farmers and compost users the instantaneous, accurate nitrogen data they need to maximize crop yield, optimize nutrient application, and significantly reduce input costs from overfertilization. Full article

Emerging contaminants such as per- and polyfluoroalkyl substances (PFASs) pose significant challenges for conventional wastewater treatment technologies. Non-thermal plasma (NTP) has gained attention as a promising advanced oxidation process capable of degrading persistent pollutants via hydrated electrons and reactive oxygen/nitrogen species under ambient conditions. This review summarizes recent progress in the application and scale-up of NTP for water treatment, with a focus on reactor configurations, degradation mechanisms, and energy efficiency. Key plasma reactor types—including dielectric barrier discharge, corona discharge, plasma jets, and gliding arc discharge—are evaluated for their suitability in large-scale applications. Pilot-scale studies addressing pharmaceuticals, dyes, and PFASs are reviewed to assess scalability, cost, and operational viability. Although NTP systems consistently achieve >80% contaminant removal, optimizing energy use and maintaining performance across complex water matrices remain critical challenges. Hybrid systems integrating NTP with ozonation, ultrafiltration, or cavitation show potential to improve treatment efficacy and reduce energy demands. Future research priorities include reactor design optimization, contaminant-specific plasma tuning, and technoeconomic analysis to support the translation of NTP technologies from lab-scale innovation to field-scale implementation. Full article

The current paper investigated the potential of oleaginous fungus Rhizopus oryzae B97 for lipid accumulation under varying process variables. The fungal strain was isolated from bread mold and analyzed for its potential to grow on sludge with simultaneous production of microbial lipids. The sludge sample was sourced from the wastewater treatment plant located in Sector I-9, Islamabad. The effects of various process variables, such as pH, temperature, carbon and nitrogen sources, and shaking, on lipid accumulation, cell dry weight (CDW), chemical oxygen demand (COD), and volatile solids (VS) removal were investigated. It was found that glucose and yeast promoted the maximum lipid accumulation. At the same time, the fungal biomass reached its maximum value of up to 64% at 30 °C and at pH 4 (CDW: 28 g/L). These process conditions also improved the sludge treatment efficiency, achieving 68% COD and 55% VS removal in 168 h. FTIR analysis of the accumulated lipids indicated strong characteristic peaks of functional groups associated with fatty acids. The GC-MS analysis confirmed the production of essential FAMEs required in biodiesel production from the corresponding fatty acids, such as oleic acid, palmitic acid, stearic acid, and erucic acid. Operation in a continuous-shaking aerobic batch reactor (CSABR) system under optimum conditions further improved the process efficiency. Overall, the results indicated the competent potential of oleaginous fungus Rhizopus oryzae B97 for lipid-based biofuel production through fatty acid transesterification. Full article