Catalyst-free contact-electro-catalytic H2O2 synthesis via simple combination of a poly(tetrafluoroethylene) stir bar and ultrasound.

Herein, we present a catalyst-free contact-electro-catalytic method for synthesizing hydrogen peroxide (H2O2) by combining continuous agitation with a poly(tetrafluoroethylene) (PTFE) stir bar and ultrasonication. A high H2O2 production rate of 256.6 µM h-1 is achieved under ambient conditions without adding particle catalysts and sacrificial agents, which is competitive with recent advancements in redox technology. Eco-friendliness, convenience and efficiency make this process a promising alternative method for H2O2 synthesis.

O2-Independent H2O2 Production via Water-Polymer Contact Electrification.

Hydrogen peroxide (H2O2), as a critical green chemical, has received immense attention in energy and environmental fields. The ability to produce H2O2 in earth-abundant water without relying on low solubility oxygen would be a sustainable and potentially economic process, applicable even to anaerobic microenvironments, such as groundwater treatment. However, the direct water to H2O2 process is currently hindered by low selectivity and low production rates. Herein, we report that poly(tetrafluoroethylene) (PTFE), a commonly used inert polymer, can act as an efficient triboelectric catalyst for H2O2 generation. For example, a high H2O2 production rate of 24.8 mmol gcat-1 h-1 at a dosage of 0.01 g/L PTFE was achieved under the condition of pure water, ambient atmosphere, and no sacrificial agents, which exceeds the performance of state-of-the-art aqueous H2O2 powder catalysts. Electron spin resonance and isotope experiments provide strong evidence that water-PTFE tribocatalysis can directly oxidize water to produce H2O2 under both anaerobic and aerobic conditions, albeit with different synthetic pathways. This study demonstrates a potential strategy for green and effective tribocatalytic H2O2 production that may be particularly useful toward environmental applications.

Impacts of dissolved organic matter on the aggregation and photo-dissolution of cadmium pigment nanoparticles in aquatic systems.

Cadmium pigments are a group of inorganic pigments used in consumer products. The aggregation behavior and photo-dissolution process of cadmium pigment nanoparticles in aquatic systems control their environmental fate, which is largely unknown. Herein, we investigated the influence of dissolved organic matter (DOM) on the aggregation behavior and photo-dissolution process of CdS nanoparticles in aquatic systems. Bare CdS nanoparticles are prone to aggregation in both NaCl and CaCl2 solutions. DOM can remarkably increase the colloidal stability of CdS nanoparticles owing to the steric hindrance and enhanced electrostatic repulsion. With 10 mg/L Suwannee River natural organic matter (SRNOM), the colloidal stability of CdS nanoparticles is significantly enhanced in NaCl solutions (i.e., the critical coagulation concentration, CCCNa, is 707.2 mM). Suwannee River humic acid (SRHA) has a stronger stabilization effect than SRNOM due to its higher molecular weight and aromaticity. The Ca2+ cations can induce charge neutralization and structural compacting of DOM corona, efficiently reducing the colloidal stability of CdS nanoparticles. The CCCCa is 10.8 mM and 14.9 mM with 10 mg/L SRNOM and SRHA, respectively. Upon solar irradiation, the presence of a low concentration of SRNOM (3 mg/L) can enhance the photo-dissolution of CdS nanoparticles and the consequent Cd2+ leaching. This is caused by the facilitated electron transfer from CdS nanoparticles to O2 induced by SRNOM corona, leading to better electron-hole separation. However, a high concentration of SRNOM inhibited the photo-dissolution of CdS nanoparticles due to the strong inner filter effect and the scavenging of phototransients. The colloidal stability of SRNOM-coated CdS nanoparticles increases in NaCl but decreases in CaCl2 solutions after irradiation owing to the oxidation of SRNOM corona. Our results highlight the decisive role of DOM in the environmental fate of cadmium pigments.

Efficient inhibition of cyanobacteria M. aeruginosa growth using commercial food-grade fumaric acid.

The control of cyanobacteria blooms is a global challenge. Here, we reported the efficient inhibition of M. aeruginosa by fumaric acid (FA), an intermediate metabolite of the tricarboxylic acid cycle. FA showed strong algicidal activity with an inhibition rate of 90.5% on the 8th day at a dose of 40 mg/L. The presence of FA caused severe membrane damage, as suggested by the fluorescence flow cytometry and morphology analysis. FA inhibited the formation of chlorophyll a, interrupting the photosynthesis system. It also induced oxidative stress in cells. Principal component analysis of the indicators suggested that the FA-treated sample had a significantly different inhibitory pattern than the acid-treated sample. Thus, the inhibitory effect was not solely caused by the pH effect. Untargeted metabolomic analysis revealed that 31 metabolites were differentially expressed in response to FA stress, which were mainly involved in the metabolite processes and the membranes. A commercial food-grade FA was able to inhibit the growth of M. aeruginosa similar to the analytical-grade FA. Our results suggest that FA can be potentially an efficient and low-risk chemical for inhibiting M. aeruginosa growth, which may find future applications in cyanobacteria bloom control.

Prediction of hydrophobic organic compound partition to algal organic matter through the growth cycle of Microcystis aeruginosa.

Algal organic matter (AOM) is an important source for the dissolved organic matter (DOM) pool in aquatic systems, particularly in eutrophic waters. In this study, we reported the dynamic pattern of AOM hydrophobicity during the growth cycle of Microcystis aeruginosa using the partition coefficients of AOM in the aqueous two-phase system (KATPS) as a simple quantitative measure. AOM hydrophobicity had significant and non-monotonic changes during the growth cycle. It increased in the lag and early exponential phases, then decreased in the late exponential and stationary phases, and rebounded in the decline phase. AOM hydrophobicity determined using the resin fractionation, SUVA254, and nuclear magnetic resonance methods shared similar non-monotonic pattern. Nevertheless, the correlations among these indicators were poor. The partition behavior of polycyclic aromatic hydrocarbons and chlorobenzenes to AOM was assessed based the KATPS dataset and the two-phase system (TPS) model. The TPS model showed good prediction power for the partition behavior of AOM with an RMSE of 0.23, suggesting that it was applicable to AOM from Microcystis aeruginosa. Our results indicate that algae activity will influence the overall hydrophobicity of the DOM pool depending on the growth phase, resulting in changes in the bioavailability of hydrophobic organic compounds in aquatic systems.

[Effects of butylphthalide on H2S/CBS pathway in hippocampal and amygdala and learning and memory ability in chronic alcoholism rats].

Objective: To investigate the effects of butylphthalide (NBP) on learning and memory related ability, hydrogen sulfide (H2S) content in hippocampus and amygdala, cystathionine-ß-synthase (CBS) expression and mitochondrial ATPase activity in rats with chronic alcoholism. Methods: Ninety SD male rats were randomly divided into three groups: normal control group (NC), model group (M) and butylphthalide remedy group (BR). Except for the control group, the water solution containing 6% (v/v) alcohol was used as the sole source of drinking water in the other two groups. After 14 days of feeding, the butylphthalide remedy group was injected with NBP intraperitoneally at the dose of 5 mg/kg once a day for 14 consecutive days, and the remaining two groups were injected with the same dose of normal saline. The control group subsequently used the Morris water maze method to observe and record the animals after entering the water. The time required for the underwater platform, their strategies and their swimming trajectories could analyze and infer the animal's ability to learn and remember. H2S concentration, CBS expression and mitochondrial ATPase activity in hippocampus and amygdale were dectected. Results: Compared with NC group, the latency period and swimming distance of M group were increased, the content of H2S and the mean optical density of CBS in hippocampus and amygdala were increased, and the activity of mitochondrial ATPase in hippocampus and amygdala was decreased significantly (P＜0. 01) . Compared with the M group, the latency period and swimming distance of learning and memory performance of BR group were decreased, the content of H2S and the mean optical density of CBS in hippocampus and amygdala were decreased, and the activity of mitochondrial ATPase in hippocampus and amygdala was increased significantly (P＜0. 01) . Conclusion: NBP can alleviate the effect of ethanol on learning and memory in rats, which may be related to the effect of NBP on the concentration of H2S and the expression of CBS in the amygdala of hippocampus and the increase of ATPase activity.

Impact of the Three Gorges Dam on the Quality of Riverine Dissolved Organic Matter.

The Three Gorges Dam (TGD) is the largest hydropower facility in the world, influencing the riverine hydrology and mass flux in the Yangtze River. Little is known about its impact on the riverine dissolved organic matter (DOM) quality. In this work, the water quality and DOM quality for water samples collected from the upstream and downstream sites of TGD were investigated. The presence of TGD significantly affects the quantity and quality of DOM but has no pronounced effect on nutrient concentrations. Upstream DOM had higher concentration but lower average molecular weight and aromaticity than the downstream DOM. The biological processes in the dam reservoir contribute significantly to upstream DOM. In the downstream sites, terrestrial DOM input raises the average molecular weight and aromaticity of the overall DOM pool. These results suggest that TGD will influence not only the mass flux of organic carbon but also its quality and lability, which has both environmental and ecological significance.

Impact of origin and structure on the aggregation behavior of natural organic matter.

The intermolecular interactions of natural organic matter (NOM) play a key role in the fate and transport of organic carbon and pollutants in environmental and engineered systems. In this study, the impact of origin and structure on the aggregation behavior of NOM was investigated in the presence of naturally abundant cations. The physicochemical properties of NOM were quantified using a range of indices. Thermodynamic analysis suggests that the colloidal stability of NOM was mainly determined by its hydrophobicity (i.e., Lewis acid-base interactions). All NOM can be coagulated by Ca2+ owing to the strong cation-NOM interactions, which lead to bridging effect and lower Lewis acid-base interactions. Terrestrial NOM can be coagulated by Mg2+ while aquatic NOM cannot, owing to their different hydrophobicity. The critical coagulation concentrations of tested terrestrial NOM in the presence of Ca2+ (CCC-Ca) were quite similar at 1.94-4.88 mM despite their different structural properties. The CCC-Ca of tested aquatic NOM varied significantly from 46.89 mM to 110.40 mM depending on their structure. The optical indices including E2/E3, FI, and HIX can be potentially used as convenient indicators for assessing the colloidal stability of aquatic NOM for water treatment and risk assessment purposes.

Sunlight-Mediated Lead and Chromium Release from Commercial Lead Chromate Pigments in Aqueous Phase.

Lead chromate pigments are included in a group of the most widely used pigments, which account for 3% of worldwide lead consumption. This study reports the photoactivity of commercial lead chromate pigment (i.e., chrome yellow) under simulated sunlight. It underwent photodissolution in the presence of organic acid and dissolved organic matter in the aqueous phase, releasing Pb(II) and Cr(III). Pb(II) was released more readily than Cr(III) which mainly formed hydroxides and oxides. The photodissolution can be activated by light with a wavelength <514 nm. The reaction is mediated by the reduction of Cr(VI) in the pigment by self-generated electrons. The kinetics were mainly affected by the electron-hole separation efficiency which can be enhanced by electron donors. The reaction rate decreases with increasing solution pH as the photodissolution process consumes protons. The photodissolution of the chrome yellow pigment was further confirmed in a river water sample under natural sunlight, with 11.28% of lead and 2.56% of chromium released in 7 h. This study highlights the importance of considering photochemical processes in risk assessments and regulations of commercial semiconductor pigments, which are currently based on their solubility.