Structural analysis of lignite-derived humic acid and its microscopic interactions with heavy metal ions in aqueous solution.

Understanding heavy metal environmental behavior with humic acid (HA) is critical. There is currently a lack of information on the control of its structure organization on its reactivity to metals. The difference in HA structures under non-homogeneous conditions is critical for revealing its micro-interaction with heavy metals. The heterogeneity of HA was reduced using the fractionation method in this study, the chemical properties of HA fractions were analyzed using py-GC/MS, and the structural units of HA were proposed. Pb2+ was used as a probe to investigate the difference in the adsorption capacity of HA fractions. The microscopic interaction of structures with heavy metal was investigated and validated by structural units. The results show that as molecular weight increased, the oxygen content and the number of aliphatic chains decreased, but the opposite was true for aromatic and heterocyclic rings. The adsorption capacity for Pb2+ was as follows: HA-1 > HA-2 > HA-3. According to the linear analysis of the influencing factors of maximum adsorption capacity and possibility factors, the adsorption capacity was positively correlated with the contents of acid groups, carboxyl groups, phenolic hydroxyl groups, and the number of aliphatic chains. The phenolic hydroxyl group and the aliphatic-chain structure have the greatest impact. Therefore, structural differences and the number of active sites play an important role in adsorption. The binding energy of HA structural units to Pb2+ was calculated. It was found that the chain structure is easier to bind to heavy metals than aromatic rings, and the affinity of-COOH to Pb2+ is greater than that of -OH. These findings can help improve the adsorbent design.

Exosomal miR-370-3p increases the permeability of blood-brain barrier in ischemia/reperfusion stroke of brain by targeting MPK1.

Ischemia/reperfusion (I/R) damage induced by stroke poses a serious hazard to human life, while mechanism of blood-brain barrier (BBB) dysfunction is still unknown. To imitate stroke induced ischemia conditions in vivo, the rat model of cerebral I/R damage was created by middle cerebral artery occlusion (MCAO). In vitro, the rat microvascular endothelial cell line bEND.3 was subjected to oxygen-glucose deprivation/reperfusion (OGD/R). Evans blue was used to evaluate the permeability of the blood-brain barrier (BBB). To evaluate gene expression at the mRNA and protein levels, researchers used real-time PCR and western blotting. Infarct volume and BBB permeability were considerably higher in cerebral (I/R) animals than in the Sham group. Exosomal miR-370-3p expression was shown to be higher in the brains of I/R injured rats and OGD/R treatment bEND.3. The BBB permeability was considerably increased when miR-370-3p was downregulated in OGD/R pretreated bEND.3. miR-370-3p regulates MAPK1 expression by targeting it. In bEND.3, OGD/R therapy increased BBB permeability substantially. OGD/R was inhibited by miR-370-3p mimic transfection, while miR-370-3p mimic was abolished by co-transfection with MAPK1 overexpression lentivirus. In cerebral I/R damage, exosomal miR-370-3p targets MAPK1 and aggregates BBB permeability.

Oxidation of Congo red by Fenton coupled with micro and nanobubbles.

Dye wastewater is a kind of refractory organic wastewater. Fenton coupled with micro-nano bubbles (MNBs+FT) was used for the degradation of Congo red (CR), aiming at simplifying the organic pollutants degradation process and reducing the cost of the process. The optimum condition of Fenton alone, the outlet pressure of the cavitation process and different combinations on the degradation of CR dye wastewater were discussed in this study. The results showed that the degradation of CR (100 mg/L) could reach 94.4% by using the MNBs+FT at the pH of 7, which was 72% higher than that using Fenton oxidation alone and 79% higher than that using MNBs alone. Based on the same degradation efficiency, the traditional Fenton process alone required 8 times the dose of oxidants of these combination systems, and the synergy coefficient of MNBs+FT was up to 2.44. ESR analysis indicated that ·OH was the predominant active species during the degradation of CR and MNBs+FT improved the utilization efficiency of H2O2 and produced more ·OH. Besides, the MNBs+FT could extend the pH range of the high-efficiency oxidation reaction, and it could also keep a high degradation rate under neutral conditions, which eliminated the process of adjusting the pH and reduced the anti-corrosion requirements of the equipment. According to the economic analysis results, the total cost of treatment for the MNBs/FT was about 13% of the cost of only the Fenton process. This study provides a reference for the application of MNBs+FT systems in full-scale dye wastewater treatment.

Calcium-Modified Fe3O4 Nanoparticles Encapsulated in Humic Acid for the Efficient Removal of Heavy Metals from Wastewater.

Ca-modified Fe3O4 nanoparticles encapsulated in humic acid (HA-Ca/Fe3O4) were produced using a co-precipitation method. Furthermore, the adsorption performance of HA-Ca/Fe3O4 as well as the effect of coexisting ions and mechanisms were evaluated. A good description of the adsorption process was given using pseudo-second-order kinetic and Langmuir models. The adsorption capacities of HA-Ca/Fe3O4 for Pb2+, Cu2+, and Cd2+ were 208.33, 98.33, and 99.01 mg g-1, respectively. The 0.02-0.1 times concentrations in alkali and alkaline-earth metals promoted Pb2+ and Cd2+ adsorption; however, any concentration of alkali and alkaline-earth metals inhibited Cu2+-ion adsorption, probably owing to the differences in ionic radii between the interfering and heavy-metal ions. Pb2+, Cu2+, and Cd2+ removal using HA-Ca/Fe3O4 occurred via ion exchange, complexation of O-containing functional groups, mineral precipitation, and π-electron coordination. A method was proposed to calculate the contribution of these mechanisms to the adsorption process. In practice, HA-Ca/Fe3O4 can remove 99% Pb2+ and 91% Cu2+ and Cd2+ from real wastewater samples. Following five adsorption-desorption cycles, HA-Ca/Fe3O4 adsorption capacity did not change significantly. The aforementioned results indicated that HA-Ca/Fe3O4 presented a good potential in removing heavy metals in wastewater.

Characteristics of Moisture Transfer and Surface Crack Development of a Single Lignite Particle Driven by Humidity Difference.

The research on moisture transfer characteristics and surface crack development of a single lignite particle (SLP) driven by humidity difference is helpful to achieve a better understanding of the fragmentation characteristics of lignite during the moisture transfer process. This is of great significance to the safe operation of a drying system. The characteristics of moisture transfer within SLP driven by humidity difference were studied in different stages. Six drying equations commonly used in the literature were selected to describe the moisture transfer behavior. The apparent diffusion coefficient (D eff) of moisture in each stage was calculated to compare the driving forces of moisture transfer in different stages. The surface crack rate (CR) was used to quantitatively analyze the fragmentation characteristics of SLP caused by moisture transfer. The results showed that the moisture transfer process of SLP driven by humidity difference can be divided into three stages, and stage I is the main moisture removal stage. The larger the particle size, the longer the stage I, while less moisture is removed in this stage. A logarithmic drying equation best simulates the moisture transfer process of SLP. The larger the particle size, the larger the D eff value in each stage. The driving force of moisture transfer in stage I is the largest, which is the opposite of a thermal drying process. CR for SLP has experienced a rapid increase - stable at the highest value - rapid decrease - stable during the moisture transfer process driven by the humidity difference.

Bacterial strain for bast fiber crops degumming and its bio-degumming technique.

The research and development of bio-degumming technology is under a slow progress due to the shortage of proper efficient bacterial strains and processes. A degumming bacterial strain-Pectobacterium wasabiae (PW)-with broad-spectrum degumming abilities was screened out in this study. After the fermentation for 12 h, the residual gum contents of kenaf bast, ramie bast, hemp bast, flax bast, and Apocynum venetum bast were all lower than 15%. This bacterial strain could realize the simultaneous extracellular secretion of pectinase, mannase, and xylanase with the maximum enzyme activity levels of 130.25, 157.58, and 115.24 U/mL, respectively. The optimal degumming conditions of this bacterial strain were as follows: degumming time of 12 h, bath ratio of 1:10, temperature of 33 °C, and inoculum size of 2%. After the bio-degumming through this bacterial strain, the COD in wastewater was below 4000 mg/L, which was over 60% lower than that in boiling-off wastewater generated by chemical degumming. This technology achieves higher efficiency, higher quality, and lower pollution.

Adsorption of direct yellow brown D3G from aqueous solution using loaded modified low-cost lignite: Performance and mechanism.

Low-cost lignite-based, copper-containing adsorbents (Cu-raw) were developed through a simple ultrasonic impregnation protocol for enhanced adsorption of direct yellow brown D3G (DYB) from aqueous solutions while treating copper-containing wastewater. The adsorbent was characterized by X-ray diffraction (XRD), scanning electron microscopy-energy dispersion spectroscopy (SEM-EDS), Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The adsorption isotherms and kinetics were studied, and the factors that affect the adsorption, such as adsorbent dosage and solution pH, were investigated. The results showed that DYB adsorption was highly pH dependent and the isotherm of adsorption could be well described by the Langmuir-Freundlich model and the maximum DYB adsorption capacity was estimated to be 369 mg/g at 25°C. The electrostatic and chelating interactions were the main interfacial interaction mechanism, and the synergetic removal performance of lignite toward cationic metal ions and anionic dye was shown. The kinetic data were well fitted to the pseudo-second-order equation, indicating that chemical sorption was the rate-limiting step. The findings reported in this work highlight the potential of using lignite as an effective low-cost adsorbent for the removal of organic pollutants from wastewater.

Water Clusters in Lignite and Desorption Energy Calculation by Density Functional Theory.

The interaction of water and hydrophilic sites with hydroxyl, carboxyl, and multiple oxygen-containing functional groups (OFGs) in lignite molecules was studied by density functional theory. The adsorption of water molecules on the lignite surface initially resulted in the formation of hydrogen bond-driven stable rings by three to four water molecules, followed by the formation of three-dimensional water clusters like a ″patchwork″. Aqueous layer thickness obtained from the water cluster size was 0.4-0.6 nm, which was consistent with the experimental data. Thus, pore-filling water beyond this range was less affected by the OFGs on the surface. Calculation of the adsorption energy predicts that the water clusters were primarily formed in the hydrophilic sites with three OFGs (site 1, including a carbonyl group, an alcoholic hydroxyl group and an etheroxy group in tetrahydropyran), then in COOH, and in O-H. For isolated hydroxyl groups, the interaction between the hydroxyl group and water molecules was weaker than that between the water molecules. When the water cluster was located at the hydrophilic sites with two or more OFGs, the adsorption energy of lignite-water interaction was higher than that of water-water interaction. Investigating the thermodynamics of the adsorption process at a molecular scale will help in understanding both drying and resorption process of dried lignite during industrial production.

Inhaled Methane Protects Rats Against Neurological Dysfunction Induced by Cerebral Ischemia and Reperfusion Injury: PI3K/Akt/HO-1 Pathway Involved.

BACKGROUND AND AIMS: Cerebral ischemia and reperfusion (I/R) could produce excess reactive oxygen species (ROS), which in turn induce neurological dysfunction and inflammation in cerebral tissues. This study was designed to study the effect of methane on cerebral I/R injury. METHODS: Fifty Sprague-Dawley (SD) rats were used to induce an animal model of cerebral I/R injury. Methane was mixed with air to achieve a final concentration of 2.2%. Rats started to inhale methane-air mixture after ischemia and continued it during the reperfusion. The neurological deficits, malondialdehyde (MDA) and tumor necrosis factor-α (TNF-α) in the brain tissue were examined. The protein kinase B (Akt) phosphorylation and heme oxygenase-1 (HO-1) expression was measured by Western Blot. The neurological deficits were re-measured after rats were treated with the HO-1 inhibitor Zinc protoporphyrin IX (ZnPP-IX), phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 and Akt inhibitor triciribine. RESULTS: Cerebral I/R induced neurological deficit, which was significantly decreased by methane. MDA and TNF-α levels were significantly enhanced by cerebral I/R, while methane caused significant reduction of MDA and TNF-α levels. Methane significantly increased Akt phosphorylation and HO-1 expression. The HO-1 inhibitor ZnPP-IX, PI3K inhibitor LY294002 and Akt inhibitor triciribine all significantly abolished the effect of methane on neurological deficit. CONCLUSIONS: This finding suggests the possible application of methane for cerebral I/R injury and PI3K/Akt/HO-1 dependent antioxidant pathway may be involved.