Effect of Clay Minerals on Carbonate Precipitation Induced by Cyanobacterium Synechococcus sp.

Carbonate precipitation induced by cyanobacteria is an important factor in lacustrine fine-grained carbonate rock genesis. As key components of these rocks, clay minerals play an important role in aggregating cyanobacteria. However, the formation mechanism of fine-grained carbonate under the effect of clay minerals is unclear. In this study, we investigated carbonate precipitation by Synechococcus cells under the influence of clay minerals. The results showed that clay minerals can accelerate Synechococcus aggregation, and the aggregation rate of the kaolinite group was significantly higher than that of montmorillonite. The aggregate size and Synechococcus cell content increased with an increase in clay minerals, resulting in increasing organic matter and carboxyl content in the aggregates. Due to the high affinity between carboxyl and Ca2+, the presence of Synechococcus sp. could improve the Mg/Ca molar ratio in the microenvironment of aggregates, which is conducive to aragonite precipitation. Thus, aragonite 5 to 10 µm in size precipitated when Synechococcus and clay minerals coexisted, whereas low-magnesium calcite (15 to 60 µm) was the main carbonate only in the presence of Synechococcus. This study provides important insights into the mechanisms of microbial-induced carbonate precipitation under the effect of clay minerals, which might offer theoretical support for the genesis of fine-grained lacustrine carbonate. IMPORTANCE The biogenesis of lacustrine fine-grained carbonates is of great significance to the exploitation of shale oil. Clay minerals are an important component of lacustrine fine-grained sedimentary rocks, which is conductive to the aggregation and settlement of cyanobacteria. We investigated the precipitation of carbonate induced by Synechococcus sp. with the addition of kaolinite and montmorillonite. The pH and calcium carbonate saturation of the environment increased under the effect of cyanobacteria photosynthesis. The aggregation of cyanobacteria cells increased the Mg/Ca molar ratio of the microenvironment, creating a favorable condition for the precipitation of aragonite, which was similar in size to the micritic calcite of fine-grained sedimentary rocks. This study provides theoretical support for the genesis of fine-grained carbonates.

The metabolism of pyrene by a novel Altererythrobacter sp. with in-situ co-substrates: A mechanistic analysis based on pathway, genomics, and enzyme activity.

Using co-substrates to enhance the metabolic activity of microbes is an effective way for high-molecular-weight polycyclic aromatic hydrocarbons removal in petroleum-contaminated environments. However, the long degradation period and exhausting substrates limit the enhancement of metabolic activity. In this study, Altererythrobacter sp. N1 was screened from petroleum-contaminated soil in Shengli Oilfield, China, which could utilize pyrene as the sole carbon source and energy source. Saturated aromatic fractions and crude oils were used as in-situ co-substrates to enhance pyrene degradation. Enzyme activity was influenced by the different co-substrates. The highest degradation rate (75.98%) was achieved when crude oil was used as the substrate because strain N1 could utilize saturated and aromatic hydrocarbons from crude oil simultaneously to enhance the degrading enzyme activity. Moreover, the phthalate pathway was dominant, while the salicylate pathway was secondary. Furthermore, the Rieske-type aromatic cyclo-dioxygenase gene was annotated in the Altererythrobacter sp. N1 genome for the first time. Therefore, the co-metabolism of pyrene was sustained to achieve a long degradation period without the addition of exogenous substrates. This study is valuable as a potential method for the biodegradation of high-molecular-weight polycyclic aromatic hydrocarbons.

P-cresol degradation through Fe(III)-EDDS/H2O2 Fenton-like reaction enhanced by manganese ion: Effect of pH and reaction mechanism.

P-cresol is a highly toxic phenolic pollutant in coal chemical wastewater. The effective removal of p-cresol is of great significance to the ecological environment. In this study, the degradation of p-cresol by the Fe(III)-EDDS/H2O2 Fenton-like reaction modified by Mn2+ was investigated. The results showed that the removal rate of p-cresol could be significantly increased by the addition of Mn2+ under neutral and weakly alkaline conditions (pH 6.5-8.5). Acidic conditions (pH 3.5) were not conducive to the Fenton-like reaction. This is because a neutral or weakly alkaline environment is conducive to Mn2+-EDDS complex formation, which can produce O2·- to accelerate the reduction of Fe(III), and the efficiency of p-cresol degradation through a Fenton-like reaction catalyzed by the Fe(III)-EDDS complex is significantly improved. In addition, the degradation of EDDS through ·OH was reduced by O2·-, which maintained and stabilized the Mn2+-EDDS complex and Fe(III)-EDDS complex. Under neutral conditions, the optimal dosage of Fe(III) is 0.7 mM, and the optimal molar ratios are EDDS/Fe(III) = 1: 1, Mn2+/Fe(III) = 1: 1, and H2O2/Fe(III) = 15: 1. The addition of free radical clearance isopropanol and CHCl3 proved that ·OH was the main active substance in the p-cresol degradation process.

Nitrogen-Dopped Ordered Mesoporous Carbon Anchored Pd Nanoparticles for Solvent Free Selective Oxidation of Benzyl Alcohol to Benzaldehyde by Using O2.

Introducing electron-rich nitrogen atoms to ordered mesoporous carbons (OMC) as supports for noble metal catalysts, not only improves the hydrophilic properties of a mesoporous carbon surface, but also enhances the coordination and binding abilities of metal ion. In the present work, nitrogen-doped ordered mesoporous carbons (NOMCs) were successfully fabricated via a facile hydrothermal self-assembly. The prepared NOMCs were characterized through powder X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption isotherm. The analyses demonstrated that the NOMCs prepared at a pyrolysis temperature of 750°C possessed an ordered 2D hexagonal mesoporous structure, a high graphitization degree, large surface area, and a well-distributed pore size. In particular, NOMCs could anchor Pd nanoparticles uniformly because of the introducing N atoms with strong electronegativity, which were selected as efficient catalysts for the partial oxidation of benzyl alcohol to benzaldehyde. Approximately 24.63% conversion with 85.71% selectivity to benzaldehyde was obtained without using any solvent by molecular O2 oxidation. Most importantly, the TOF value of the catalyst in the reaction system was up to 8698 h-1. After five runs reaction, TOF and selectivity of the catalyst remained essentially same. Hence, the proposed catalyst has a potential engineering application value.

Characterization of cometabolic degradation of p-cresol with phenol as growth substrate by Chlorella vulgaris.

To investigate the potential application of Chlorella vulgaris in the treatment of coal gasification wastewater, the characteristics of phenol and p-cresol cometabolism by Chlorella vulgaris were studied, including phenol degradation, ammonia nitrogen removal, antioxidant enzyme activities, and phenol hydroxylase activity. The results showed that the highest tolerable concentrations of phenol and p-cresol for Chlorella vulgaris were 800 and 400 mg/L, respectively. During cometabolism, phenol at low concentrations (100 mg/L) significantly promoted the degradation of p-cresol. Meanwhile, the removal efficiency of ammonia nitrogen was approximately 60% and was not affected by variations in phenol concentration. Furthermore, the cometabolism of phenol and p-cresol was enhanced by improvement of phenol hydroxylase activity of Chlorella vulgaris after the addition of NaHCO3 as an exogenous nutrient. Therefore, Chlorella vulgaris has a great potential for the biochemical treatment of coal gasification wastewater.

N-doped porous transition metal-based carbon nanosheet networks as a multifunctional electrocatalyst for rechargeable zinc-air batteries.

The development of cost-effective and highly efficient multi-functional oxygen reduction reaction and oxygen evolution reaction catalysts has attracted much research attention due to their great potential applications in many advanced clean energy storage and conversion technologies. Herein, highly efficient N-doped three-dimensional porous Co-Co3O4/C nanosheet network materials have been developed as bifunctional electrocatalysts for rechargeable zinc-air batteries.

Effect of hydroxypropyl-ß-cyclodextrin on the cometabolism of phenol and phenanthrene by a novel Chryseobacterium sp.

Cometabolic degradation is an effective method to remove the polycyclic aromatic hydrocarbons (PAHs) with phenol as growth substrate from coal chemical wastewater (CCW). Unfortunately, the toxicity and low solubility of PAHs always restrict their degradation. In this study, Chryseobacterium sp. H202 was firstly isolated from the aerobic segment of CCW. Then, to improve the cometabolic degradation of PAHs, the effects of hydroxypropyl-ß-cyclodextrin (HPCD) were investigated. Phenanthrene removal was accelerated in the presence of phenol; however, the degradation of phenol was inhibited because of the toxicity of phenanthrene. Addition of 50 mg/L HPCD accelerated the degradation of phenol and effectively improved the phenanthrene removal rate by about 55%. Inclusion of HPCD appeared to increase the apparent solubility and reduce the toxicity of phenanthrene, thereby improving the cometabolic degradation of phenol and phenanthrene. Therefore, HPCD can enhance the degradation of phenanthrene with phenol as the growth substrate during CCW treatment.

Ni(OH)2 Nanoflakes Supported on 3D Ni3 Se2 Nanowire Array as Highly Efficient Electrodes for Asymmetric Supercapacitor and Ni/MH Battery.

Porous Ni(OH)2 nanoflakes are directly grown on the surface of nickel foam supported Ni3 Se2 nanowire arrays using an in situ growth procedure to form 3D Ni3 Se2 @Ni(OH)2 hybrid material. Owing to good conductivity of Ni3 Se2 , high specific capacitance of Ni(OH)2 and its unique architecture, the obtained Ni3 Se2 @Ni(OH)2 exhibits a high specific capacitance of 1689 µAh cm-2 (281.5 mAh g-1 ) at a discharge current of 3 mA cm-2 and a superior rate capability. Both the high energy density of 59.47 Wh kg-1 at a power density of 100.54 W kg-1 and remarkable cycling stability with only a 16.4% capacity loss after 10 000 cycles are demonstrated in an asymmetric supercapacitor cell comprising Ni3 Se2 @Ni(OH)2 as a positive electrode and activated carbon as a negative electrode. Furthermore, the cell achieved a high energy density of 50.9 Wh L-1 at a power density of 83.62 W L-1 in combination with an extraordinary coulombic efficiency of 97% and an energy efficiency of 88.36% at 5 mA cm-2 when activated carbon is replaced by metal hydride from a commercial NiMH battery. Excellent electrochemical performance indicates that Ni3 Se2 @Ni(OH)2 composite can become a promising electrode material for energy storage applications.

The effect of weak acid anions on the selective catalytic wet air oxidation of aqueous ammonia to nitrogen.

In this work, the effect of weak acid anions on the ammonia removal has been extensively studied for the process of selective catalytic wet air oxidation (CWAO) of ammonia to nitrogen. It is found that the presence of weak acid anions can effectively enhance the ammonia conversion and selectivity towards nitrogen. The combination between the weak acid anions and H+ to produce weak acid molecules is responsible for such enhancement. Firstly, the H+ consumption of weak acid anions can increase the NH3 concentration and thus the reactivity of ammonia oxidation, due to the shift to NH3 on the equilibrium of NH4+/NH3. Secondly, the competition combination with H+ between the weak acid anions and NO2- can increase the concentration of NO2- and thus boosts the disproportionation reaction between NH4+ and NO2- to produce nitrogen.