Influences and mechanisms of nanofullerene on the horizontal transfer of plasmid-encoded antibiotic resistance genes between E. coli strains

• Sub-inhibitory levels of nC₆₀ promote conjugative transfer of ARGs. • nC₆₀ can induce ROS generation, oxidative stress and SOS response. • nC₆₀ can increase cell membrane permeability and alter gene expression. • Results provide evidence of nC₆₀ promoting antibiotic resistance dissemination. The spread and development of antibiotic resistance globally have led to severe public health problems. It has been shown that some non-antibiotic substances can also promote the diffusion and spread of antibiotic resistance genes (ARGs). Nanofullerene (nC₆₀) is a type of nanomaterial widely used around the world, and some studies have discovered both the biological toxicity and environmental toxicity of nC₆₀. In this study, cellular and molecular biology techniques were employed to investigate the influences of nC₆₀ at sub-minimum inhibitory concentrations (sub-MICs) on the conjugation of ARGs between the E. coli strains. Compared with the control group, nC₆₀ significantly increased the conjugation rates of ARGs by 1.32‒10.82 folds within the concentration range of 7.03‒1800 mg/L. This study further explored the mechanism of this phenomenon, finding that sub-MICs of nC₆₀ could induce the production of reactive oxygen species (ROS), trigger SOS-response and oxidative stress, affect the expression of outer membrane proteins (OMPs) genes, increase membrane permeability, and thus promote the occurrence of conjugation. This research enriches our understanding of the environmental toxicity of nC₆₀, raises our risk awareness toward nC₆₀, and may promote the more rational employment of nC₆₀ materials.     

Enhanced activation of peroxymonosulfate by CNT-TiO2 under UV-light assistance for efficient degradation of organic pollutants

CNT-TiO₂ composite is used to activate PMS under UV-light assistance. Superior performance is due to the enhanced electron-transfer ability of CNT. SO₄•⁻, •OH and ¹O₂ play key roles in the degradation of organic pollutants. In this work, a UV-light assisted peroxymonosulfate (PMS) activation system was constructed with the composite catalyst of multi-walled carbon nanotubes (CNT) - titanium dioxide (TiO₂). Under the UV light irradiation, the photoinduced electrons generated from TiO₂ could be continuously transferred to CNT for the activation of PMS to improve the catalytic performance of organic pollutant degradation. Meanwhile, the separation of photoinduced electron-hole pairs could enhance the photocatalysis efficiency. The electron spin resonance spectroscopy (EPR) and quenching experiments confirmed the generation of sulfate radical (SO₄•⁻), hydroxyl radical (•OH) and singlet oxygen (¹O₂) in the UV/PMS/20%CNT-TiO₂ system. Almost 100% phenol degradation was observed within 20 min UV-light irradiation. The kinetic reaction rate constant of the UV/PMS/20%CNT-TiO₂ system (0.18 min⁻¹) was 23.7 times higher than that of the PMS/Co₃O₄ system (0.0076 min⁻¹). This higher catalytic performance was ascribed to the introduction of photoinduced electrons, which could enhance the activation of PMS by the transfer of electrons in the UV/PMS/CNT-TiO₂ system.     

Electro-catalytic activity of CeOx modified graphite felt for carbamazepine degradation via E-peroxone process

•CeO_x/GF-EP process had the better degradation efficiency than GF-EP process. •CeO_x/GF-EP process had the flexible application in the pH range from 5.0 to 9.0. •CeO_x could enhance surface hydrophilicity and reduce the charge-transfer resistance. •The interfacial electron transfer process was revealed. E-peroxone (EP) was one of the most attractive AOPs for removing refractory organic compounds from water, but the high energy consumption for in situ generating H₂O₂ and its low reaction efficiency for activating O₃ under acidic conditions made the obstacles for its practical application. In this study, cerium oxide was loaded on the surface of graphite felt (GF) by the hydrothermal method to construct the efficient electrode (CeO_x/GF) for mineralizing carbamazepine (CBZ) via EP process. CeO_x/GF was an efficient cathode, which led to 69.4% TOC removal in CeO_x/GF-EP process with current intensity of 10 mA in 60 min. Moreover, CeO_x/GF had the flexible application in the pH range from 5.0 to 9.0, TOC removal had no obvious decline with decrease of pH. Comparative characterizations showed that CeO_x could enhance surface hydrophilicity and reduce the charge-transfer resistance of GF. About 5.4 mg/L H₂O₂ generated in CeO_x/GF-EP process, which was 2.1 times as that in GF-EP process. The greater ozone utility was also found in CeO_x/GF-EP process. More O₃ was activated into hydroxyl radicals, which accounted for the mineralization of CBZ. An interfacial electron transfer process was revealed, which involved the function of oxygen vacancies and Ce³⁺/Ce⁴⁺ redox cycle. CeO_x/GF had the good recycling property in fifth times’ use.     

基于席夫碱反应合成氮掺杂的碳活化PMS降解双酚A

基于石墨相氮化碳(g-C3N4)的热聚合形成过程和席夫碱反应,本文将尿素和2-萘甲醛作为前驱体,经一步热聚合反应制备了氮掺杂的碳材料(NCN-x),并以其作为催化剂活化过一硫酸盐(PMS)来降解双酚A(BPA).在催化剂特性研究部分,利用SEM、XRD、FTIR以及XPS对其表面形貌、结构与元素组成进行分析.结果 表明...     

Toward better understanding vacuum ultraviolet–iodide induced photolysis via hydrogen peroxide formation,iodine species change,and difluoroacetic acid degradation

• UV/VUV/I^– induces substantial H₂O₂ and IO₃^– formation, but UV/I^– does not. • Increasing DO level in water enhances H₂O₂ and iodate productions. • Increasing pH decreases H₂O₂ and iodate formation and also photo-oxidation. • The redox potentials of UV/VUV/I^– and UV/VUV changes with pH changes. • The treatability of the UV/VUV/I^– process was stronger than UV/VUV at pH 11.0. Recently, a photochemical process induced by ultraviolet (UV), vacuum UV (VUV), and iodide (I^–) has gained attention for its robust potential for contaminant degradation. However, the mechanisms behind this process remain unclear because both oxidizing and reducing reactants are likely generated. To better understand this process, this study examined the evolutions of hydrogen peroxide (H₂O₂) and iodine species (i.e., iodide, iodate, and triiodide) during the UV/VUV/I^– process under varying pH and dissolved oxygen (DO) conditions. Results show that increasing DO in water enhanced H₂O₂ and iodate production, suggesting that high DO favors the formation of oxidizing species. In contrast, increasing pH (from 6.0 to 11.0) resulted in lower H₂O₂ and iodate formation, indicating that there was a decrease of oxidative capacity for the UV/VUV/I^– process. In addition, difluoroacetic acid (DFAA) was used as an exemplar contaminant to verify above observations. Although its degradation kinetics did not follow a constant trend as pH increases, the relative importance of mineralization appeared declining, suggesting that there was a redox transition from an oxidizing environment to a reducing environment as pH rises. The treatability of the UV/VUV/I^– process was stronger than UV/VUV under pH of 11.0, while UV/VUV process presented a better performance at pH lower than 11.0.     

Removing ammonia from air with a constant pH,slightly acidic water spray wet scrubber using recycled scrubbing solution

Slightly acidic solutions are a practical means of removing ammonia from air Scrubbed NH₃ accumulates in solution as NH₄⁺ and should be an excellent fertilizer Increased air velocity decreased NH₃ removal and increased NH₄⁺ collection Previous research on wet scrubbers has only studied highly acidic scrubbing solutions because of their high ammonia capture efficiencies; however, the high acidity created practical problems. Lower acidity solutions would reduce corrosion, maintenance, and cost; however, designers may need to use strategies for increasing scrubber effectiveness, such as using lower air velocities. The objective of this study was to determine if a spray scrubber with slightly acidic and higher pH scrubbing solution (pH from 2 to 8) could effectively remove NH₃ from NH₃ laden air (such as animal building exhaust air), and also collect this valuable resource for later use as a fertilizer. A bench-scale spray wet scrubber treated 20 ppmv NH₃/air mixture in a countercurrent contact chamber. First, the solution pH was varied from 2 to 8 while maintaining constant air velocity at 1.3 m·s⁻¹. Next, air velocity was increased (2 and 3 m·s⁻¹) while solution pH remained constant at pH6. At 1.3 m·s⁻¹, NH₃ removal efficiencies ranged between 49.0% (pH8) and 84.3% (pH2). This study has shown that slightly acidic scrubbing solutions are a practical means of removing ammonia from air especially if the scrubber is designed to increase collisions between solution droplets and NH₃ molecules. The NH₃ removed from the air was held in solution as NH₄⁺ and accumulates over time so the solution should be an excellent fertilizer.     

Performance and kinetics of iron-based oxygen carriers reduced by carbon monoxide for chemical looping combustion

Chemical looping combustion is a promising technology for energy conversion due to its low-carbon, high-efficiency, and environmental-friendly feature. A vital issue for CLC process is the development of oxygen carrier, since it must have sufficient reactivity. The mechanism and kinetics of CO reduction on iron-based oxygen carriers namely pure Fe₂O₃ and Fe₂O₃ supported by alumina (Fe₂O₃/Al₂O₃) were investigated using thermo-gravimetric analysis. Fe₂O₃/Al₂O₃ showed better reactivity over bare Fe₂O₃ toward CO reduction. This was well supported by the observed higher rate constant for Fe₂O₃/Al₂O₃ over pure Fe₂O₃ with respective activation energy of 41.1±2.0 and 33.3±0.8 kJ·mol⁻¹. The proposed models were compared via statistical approach comprising Akaike information criterion with correction coupled with F-test. The phase-boundary reaction and diffusion control models approximated to 95% confidence level along with scanning electron microscopy results; revealed the promising reduction reactions of pure Fe₂O₃ and Fe₂O₃/Al₂O₃. The boosting recital of iron-based oxygen carrier support toward efficient chemical looping combustion could be explained accurately through the present study.     

Enhanced triallyl isocyanurate (TAIC) degradation through application of an O3/UV process: Performance optimization and degradation pathways

• UV/O₃ process had higher TAIC mineralization rate than O₃ process. • Four possible degradation pathways were proposed during TAIC degradation. • pH impacted oxidation processes with pH of 9 achieving maximum efficiency. • CO₃^2– negatively impacted TAIC degradation while HCO₃^– not. • Cl^– can be radicals scavenger only at high concentration (over 500 mg/L Cl^–). Triallyl isocyanurate (TAIC, C₁₂H₁₅N₃O₃) has featured in wastewater treatment as a refractory organic compound due to the significant production capability and negative environmental impact. TAIC degradation was enhanced when an ozone(O₃)/ultraviolet(UV) process was applied compared with the application of an independent O₃ process. Although 99% of TAIC could be degraded in 5 min during both processes, the O₃/UV process had a 70%mineralization rate that was much higher than that of the independent O₃ process (9%) in 30 min. Four possible degradation pathways were proposed based on the organic compounds of intermediate products identified during TAIC degradation through the application of independent O₃ and O₃/UV processes. pH impacted both the direct and indirect oxidation processes. Acidic and alkaline conditions preferred direct and indirect reactions respectively, with a pH of 9 achieving maximum Total Organic Carbon (TOC) removal. Both CO₃^2– and HCO₃^– decreased TOC removal, however only CO₃^2– negatively impacted TAIC degradation. Effects of Cl^– as a radical scavenger became more marked only at high concentrations (over 500 mg/L Cl^–). Particulate and suspended matter could hinder the transmission of ultraviolet light and reduce the production of HO· accordingly.     

Impact of anthropogenic heat emissions on meteorological parameters and air quality in Beijing using a high-resolution model simulation

• The Large scale Urban Consumption of energY model was updated and coupled with WRF. • Anthropogenic heat emissions altered the precipitation and its spatial distribution. • A reasonable AHE scheme could improve the performance of simulated PM_2.5. • AHE aggravated the O₃ pollution in urban areas. Anthropogenic heat emissions (AHE) play an important role in modulating the atmospheric thermodynamic and kinetic properties within the urban planetary boundary layer, particularly in densely populated megacities like Beijing. In this study, we estimate the AHE by using a Large-scale Urban Consumption of energY (LUCY) model and further couple LUCY with a high-resolution regional chemical transport model to evaluate the impact of AHE on atmospheric environment in Beijing. In areas with high AHE, the 2-m temperature (T₂) increased to varying degrees and showed distinct diurnal and seasonal variations with maxima in night and winter. The increase in 10-m wind speed (WS₁₀) and planetary boundary layer height (PBLH) exhibited slight diurnal variations but showed significant seasonal variations. Further, the systematic continuous precipitation increased by 2.1 mm due to the increase in PBLH and water vapor in upper air. In contrast, the precipitation in local thermal convective showers increased little because of the limited water vapor. Meanwhile, the PM_2.5 reduced in areas with high AHE because of the increase in WS₁₀ and PBLH and continued to reduce as the pollution levels increased. In contrast, in areas where prevailing wind direction was opposite to that of thermal circulation caused by AHE, the WS₁₀ reduced, leading to increased PM_2.5. The changes of PM_2.5 illustrated that a reasonable AHE scheme might be an effective means to improve the performance of PM_2.5 simulation. Besides, high AHE aggravated the O₃ pollution in urban areas due to the reduction in NO_x.     

Catalytic oxidation of CO over Pt/Fe3O4 catalysts: Tuning O2 activation and CO adsorption

• Strong metal-support interaction exists on Pt/Fe₃O₄ catalysts. • Pt metal particles facilitate the formation of oxygen vacancies on Fe₃O₄. • Fe₃O₄ supports enhance the strength of CO adsorption on Pt metal particles. The self-inhibition behavior due to CO poisoning on Pt metal particles strongly impairs the performance of CO oxidation. It is an effective method to use reducible metal oxides for supporting Pt metal particles to avoid self-inhibition and to improve catalytic performance. In this work, we used in situ reductions of chloroplatinic acid on commercial Fe₃O₄ powder to prepare heterogeneous-structured Pt/Fe₃O₄ catalysts in the solution of ethylene glycol. The heterogeneous Pt/Fe₃O₄ catalysts achieved a better catalytic performance of CO oxidation compared with the Fe₃O₄ powder. The temperatures of 50% and 90% CO conversion were achieved above 260°C and 290°C at Pt/Fe₃O₄, respectively. However, they are accomplished on Fe₃O₄ at temperatures higher than 310°C. XRD, XPS, and H₂-TPR results confirmed that the metallic Pt atoms have a strong synergistic interaction with the Fe₃O₄ supports. TGA results and transient DRIFTS results proved that the Pt metal particles facilitate the release of lattice oxygen and the formation of oxygen vacancies on Fe₃O₄. The combined results of O₂-TPD and DRIFTS indicated that the activation step of oxygen molecules at surface oxygen vacancies could potentially be the rate-determining step of the catalytic CO oxidation at Pt/Fe₃O₄ catalysts. The reaction pathway involves a Pt-assisted Mars-van Krevelen (MvK) mechanism.     

Contributions of adsorption,bioreduction and desorption to uranium immobilization by extracellular polymeric substances

● EPS immobilizes U(VI) via adsorption, bioreduction and desorption. ● This work provides a framework to quantify the three immobilization processes. ● The non-equilibrium adsorption of U follows pseudo-second-order kinetics. ● The equilibrium adsorption of U followed Langmuir and Freundlich isotherms. Hexavalent uranium (U(VI)) can be immobilized by various microbes. The role of extracellular polymeric substances (EPS) in U(VI) immobilization has not been quantified. This work provides a model framework to quantify the contributions of three processes involved in EPS-mediated U(VI) immobilization: adsorption, bioreduction and desorption. Loosely associated EPS was extracted from a pure bacterial strain, Klebsiella sp. J1, and then exposed to H₂ and O₂ (no bioreduction control) to immobilize U(VI) in batch experiments. U(VI) immobilization was faster when exposed to H₂ than O₂ and stabilized at 94% for H₂ and 85% for O₂, respectively. The non-equilibrium data from the H₂ experiments were best simulated by a kinetic model consisting of pseudo-second-order adsorption (k_a = 2.87 × 10⁻³ g EPS·(mg U)⁻¹·min⁻¹), first-order bioreduction (k_b = 0.112 min⁻¹) and first-order desorption (k_d = 7.00 × 10⁻³ min⁻¹) and fitted the experimental data with R² of 0.999. While adsorption was dominant in the first minute of the experiments with H₂, bioreduction was dominant from the second minute to the 50^th min. After 50 min, adsorption was negligible, and bioreduction was balanced by desorption. This work also provides the first set of equilibrium data for U(VI) adsorption by EPS alone. The equilibrium experiments with O₂ were well simulated by both the Langmuir isotherm and the Freundlich isotherm, suggesting multiple mechanisms involved in the interactions between U(VI) and EPS. The thermodynamic study indicated that the adsorption of U(VI) onto EPS was endothermic, spontaneous and favorable at higher temperatures.     

Influence of phosphate on deposition and detachment of TiO2 nanoparticles in soil

We examined influence of phosphate on transport of TiO₂ NPs in soil. Deposition was reduced at higher pH and by adsorption of phosphate in soil. Release was more for NPs initially deposited at higher pH. Release was more for NPs initially deposited in the presence of phosphate. Surface roughness and charge heterogeneity play a role in the deposition/ release. The widespread use of TiO₂ nanoparticles (NPs) makes inevitable their release into the soil. Phosphate is also widespread within soil, and is likely copresent with TiO₂ NPs. However, the influence of phosphate on deposition/release— and thereby on transport— of TiO₂ NPs in soil is yet to be elucidated. In this study we conducted saturated column experiments to systematically examine the transport of TiO₂ NPs in soil amended with phosphate at different ionic strengths (ISs) (1, 10, 100 mmol/L NaCl) and pHs (4 and 9). Results show that the deposition of TiO₂ NPs decreased with decreasing IS, increasing pH, and when soil absorbed phosphate. These observations are qualitatively in agreement with Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy calculations, because the repulsive energy barrier is larger and secondary minimum depth is smaller at a lower IS, higher pH, and in the presence of phosphate. Accordingly, both primary- and secondary-minimum deposition were inhibited. Interestingly, although the deposition was less at higher pH and in the presence of phosphate, the subsequent spontaneous detachment and detachment by reduction of solution IS in these cases were greater. In addition, the presence of phosphate in the solution can cause a small quantity of attached TiO₂ NPs to detach, even without perturbations of physical and chemical conditions. Our study was the first to investigate the influence of phosphate on detachment of TiO₂ NPs and the results have important implication for accurate prediction of fate and transport of TiO₂ NPs in subsurface environments.     

Micro-analysis of nitrogen transport and conversion inside activated sludge flocs using microelectrodes

To investigate the nitrogen transport and conversion inside activated sludge flocs, micro-profiles of O₂, NH₄⁺, NO₂^–, NO₃^–, and pH were measured under different operating conditions. The flocs were obtained from a laboratory-scale sequencing batch reactor. Nitrification, as observed from interfacial ammonium and nitrate fluxes, was higher at pH 8.5, than at pH 6.5 and 7.5. At pH 8.5, heterotrophic bacteria used less oxygen than nitrifying bacteria, whereas at lower pH heterotrophic activity dominated. When the ratio of C to N was decreased from 20 to 10, the ammonium uptake increased. When dissolved oxygen (DO) concentration in the bulk liquid was decreased from 4 to 2 mg·L^-1, nitrification decreased, and only 25% of the DO influx into the flocs was used for nitrification. This study indicated that nitrifying bacteria became more competitive at a higher DO concentration, a higher pH value (approximately 8.5) and a lower C/N.     

Singlet molecular oxygen—mediated photooxidation of monochloro and mononitrophenols. A kinetic study

A kinetic and mechanistic study on the aerobic dye sensitized photooxidation of the mono—nitro and chlorophenols was carried out. A singlet molecular oxygen mechanism operates in the photooxidation. Solvent and substituent effects, suggest the intermediacy of a complex with partial charge transfer character, as has been postulated for other phenols.

Chemical (reactive) and physical interactions of the substrates with singlet molecular oxygen were discriminated. Quantum yields for photooxidation (higher for the chlorophenols) range from 3 × 10^‐2 to 2 × 10^‐3, as measured by substrate or oxygen consumption. These values indicate the viability of a singlet molecular oxygen photooxidation as a way for the degradation of nitro and chlorophenol environmental contaminants.     

Visible-light-driven heterostructured g-C3N4/Bi-TiO2 floating photocatalyst with enhanced charge carrier separation for photocatalytic inactivation of Microcystis aeruginosa

• Bi doping in TiO₂ enhanced the separation of photo-generated electron-hole. • The performance of photocatalytic degradation of MC-LR was improved. • Coexisting substances have no influence on algal removal performance. • The key reactive oxygen species were h⁺ and ^•OH in the photocatalytic process. The increase in occurrence and severity of cyanobacteria blooms is causing increasing concern; moreover, human and animal health is affected by the toxic effects of Microcystin-LR released into the water. In this paper, a floating photocatalyst for the photocatalytic inactivation of the harmful algae Microcystis aeruginosa (M. aeruginosa) was prepared using a simple sol-gel method, i.e., coating g-C₃N₄ coupled with Bi-doped TiO₂ on Al₂O₃-modified expanded perlite (CBTA for short). The impact of different molar ratios of Bi/Ti on CBTA was considered. The results indicated that Bi doping in TiO₂ inhibited photogenerated electron-hole pair recombination. With 6 h of visible light illumination, 75.9% of M. aeruginosa (initial concentration= 2.7 × 10⁶ cells/L) and 83.7% of Microcystin-LR (initial concentration= 100 μg/L) could be removed with the addition of 2 g/L CBTA-1% (i.e., Bi/Ti molar ratio= 1%). The key reactive oxygen species (ROSs) in the photocatalytic inactivation process are h⁺ and ^•OH. The induction of the Bi⁴⁺/Bi³⁺ species by the incorporation of Bi could narrow the bandgap of TiO₂, trap electrons, and enhance the stability of CBTA-1% in the solutions with coexisting environmental substances.     

Occurance and control of manganese in a large scale water treatment plant

The continuous variations of dissolved oxygen (DO), manganese (Mn), pH, and their effect on manganese removal by different water treatment processes are investigated. The results show that the declined DO concentration and pH value in the bottom of reservoir results in the increasing release of Mn from sediment to source water. Manganese concentration increased from 0.1 to 0.4 mg·L^-1 under the condition that DO concentration decreased from 12.0 to 2.0 mg·L^-1 in raw water. The different water treatment processes exhibited different efficiency on manganese removal. The processes with recycling of the suspended sludge, low elevation velocity in settling tank and slow filter rate, will benefit the manganese removal. During a high release of manganese in raw water, traditional coagulation-sedimentation and filtration could not completely remove Mn, although granular activated carbon filtration (GAC) had been applied. At that case, preoxidation with chlorine or potassium permanganate (KMnO₄) was necessary to address the high manganese concentration.     

Kinetics of microwave-enhanced oxidation of phenol by hydrogen peroxide

Aqueous solutions of phenol were oxidized by hydrogen peroxide assisted by microwave (MW) irradiation. A simple kinetic model for the overall degradation of phenol in the presence of excess H₂O₂ is proposed in which the degradation rate of phenol is expressed as a linear function of the concentrations of phenol and H₂O₂. A detailed parametric study showed that the degradation rate of phenol increased with increasing [H₂O₂] until saturation was observed. Phenol degradation followed apparent zero-order kinetics under MW radiation or H₂O₂ oxidation. However, after 90 min of irradiation, the observed kinetics shifted to pseudo first order. The overall reaction rates were significantly enhanced in the combined MW/H₂O₂ system, mainly because microwave could accelerate H₂O₂ to generate hydroxyl radical (^·OH) and other reactive oxygen intermediates. The observed synergetic effects of the MW/H₂O₂ process resulted in an increased in the net reaction rate by a factor of 5.75. When hydrogen peroxide is present in a large stoichiometric excess, the time required to achieve complete mineralization is reduced significantly.     

过硫酸钠氧化脱色罗丹明B——影响因素和机理

采用过硫酸钠(PDS)直接氧化和催化活化氧化脱色罗丹明B(RhB),分别考察了PDS剂量、pH、催化剂、Cl-浓度对RhB脱色的影响.结果表明,PDS在无外加催化剂下能够有效脱色RhB,pH越低,脱色率越高;当pH 2.4,PDS用量为3.5 g·L^-1,在120 min内RhB的脱色率可达92%;自由基淬灭实验表明,酸性条件下主要为PDS直接氧化脱色RhB,并存在小部分硫酸根自由基(SO₄4·-)作用.在pH 5.6、pH 8.0条件下,外加活性炭纤维(ACF)、四氧化三铁(Fe₃O₄4)、Fe₃O₄4负载型催化剂(ACF/Fe3O₄4)可促进PDS对RhB脱色;在pH 2.4条件下,外加ACF对RhB脱色的促进作用较小,Fe₃O₄4、ACF/Fe₃O₄4对RhB脱色有一定抑制作用.不同pH和催化剂处理下,低浓度Cl-(0.01、0.04 mO₄l·L^-1)对RhB脱色速率都呈现抑制作用,高浓度Cl-(0.08 mO₄l·L^-1)相对于低浓度Cl-处理都呈促进作用.不同浓度Cl-处理在反应前60 min RhB脱色速率差异较大,而反应120 min后脱色率差异较小.提出Cl-通过调控SO₄4·-脱色RhB途径来影响RhB脱色速率的机理,Cl-竞争消耗SO₄4·-降低RhB脱色速率,但经一系列反应生成的Cl2·-能与RhB快速反应而提高RhB脱色速率;Cl-对RhB的脱色反应速率的影响存在抑制-促进双重机制,且与Cl-浓度相关.研究结果为基于PDS直接氧化和催化氧化处理含盐染料废水的研究和应用提供了一定的理论依据.     

Preparation of nZVI embedded modified mesoporous carbon for catalytic persulfate to degradation of reactive black 5

• The MCNZVI is prepared as an interesting material for PS activation. • Graphitized carbon shells facilitate electron transfer from Fe⁰. • The MCNZVI exhibits excellent performance to degrade RB5 by ¹O₂. • The MCNZVI has high stability and reusability in the oxidation system. High-efficiency and cost-effective catalysts with available strategies for persulfate (PS) activation are critical for the complete mineralization of organic contaminants in the environmental remediation and protection fields. A nanoscale zero-valent iron-embedded modified mesoporous carbon (MCNZVI) with a core-shell structure is synthesized using the hydrothermal synthesis method and high-temperature pyrolysis. The results showed that nZVI could be impregnated within mesoporous carbon frameworks with a comparatively high graphitization degree, rich nitrogen doping content, and a large surface area and pore volume. This material was used as a persulfate activator for the oxidation removal of Reactive Black 5 (RB5). The effects of the material dosage, PS concentration, pH, and some inorganic anions (i.e., Cl⁻, SO₄²⁻) on RB5 degradation were then investigated. The highest degradation efficiency (97.3%) of RB5 was achieved via PS (20 mmol/L) activation by the MCNZVI (0.5 g/L). The pseudo-first-order kinetics (k = 2.11 × 10⁻² min⁻¹) in the MCNZVI/PS (0.5 g/L, 20 mmol/L) was greater than 100 times than that in the MCNZVI and PS. The reactive oxygen species (ROS), including ¹O₂, SO₄^·−, HO^·, and ·O₂⁻, were generated by PS activation with the MCNZVI. Singlet oxygen was demonstrated to be the primary ROS responsible for the RB5 degradation. The MCNZVI could be reused and regenerated for recycling. This work provides new insights into PS activation to remove organic contamination.     

Acute toxicity assessment of drinking water source with luminescent bacteria: Impact of environmental conditions and a case study in Luoma Lake,East China

• Acute toxicity assessment was conducted in Luoma lake watershed, East China. • Impacts of environmental factors on the toxicity testing was fully evaluated. • Dissolve oxygen had a weak positive correlation with luminescence inhibition rate. Protecting the quality of lake watersheds by preventing and reducing their contamination is an effective approach to ensure the sustainability of the drinking water supply. In this study, acute toxicity assessment was conducted on the basis of acute bioluminescence inhibition assay using the marine bacterium Vibrio fischeri as the test organism and Luoma Lake drinking water source in East China as the research target. The suitable ranges of environmental factors, including pH value, organic matter, turbidity, hardness, and dissolved oxygen of water samples were evaluated for the toxicity testing of bioluminescent bacteria. The physicochemical characteristics of water samples at the selected 43 sites of Luoma Lake watershed were measured. Results showed that the variations in pH value (7.31–8.41), hardness (5–20 °d) and dissolved oxygen (4.44–11.03 mg/L) of Luoma Lake and its main inflow and outflow rivers had negligible impacts on the acute toxicity testing of V. fischeri. The luminescence inhibition rates ranged from -11.21% to 10.80% at the 43 sites. Pearson’s correlation analysis in the experiment revealed that temperature, pH value, hardness, and turbidity had no correlation with luminescence inhibition rate, whereas dissolved oxygen showed a weak statistically positive correlation with a Pearson correlation coefficient of 0.455 (p<0.05).