Electrocatalytic reduction of COsub.2 to valuable chemicals can alleviate the energy crisis, and solve the greenhouse effect. The key is to develop non-noble metal electrocatalysts with high ...activity, selectivity, and stability. Herein, bimetallic metal organic frameworks (MOFs) materials (BiZn-MOF, BiSn-MOF, and BiIn-MOF) were constructed by coordinating the metals Zn, In, Sn, and Bi with the organic ligand 3-amino-1H-1,2,4-triazole-5-carboxylic acid (Hsub.2atzc) through a rapid microwave synthesis approach. The coordination centers in bimetallic MOF catalyst were regulated to optimize the catalytic performance for electrochemical COsub.2 reduction reaction (COsub.2RR). The optimized catalyst BiZn-MOF exhibited higher catalytic activity than those of Bi-MOF, BiSn-MOF, and BiIn-MOF. BiZn-MOF exhibited a higher selectivity for formate production with a Faradic efficiency (FE = 92%) at a potential of −0.9 V (vs. RHE, reversible hydrogen electrode) with a current density of 13 mA cmsup.−2. The current density maintained continuous electrolysis for 13 h. The electrochemical conversion of COsub.2 to formate mainly follows the *OCHO pathway. The good catalytic performance of BiZn-MOF may be attributed to the Bi-Zn bimetallic coordination centers in the MOF, which can reduce the binding energies of the reaction intermediates by tuning the electronic structure and atomic arrangement. This study provides a feasible strategy for performance optimization of bismuth-based catalysts.
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Besides acidic environments, pyrite oxidation also occurs in circumneutral environments, such as well-buffered marine and estuarine sediments and salt marshes where low-molecular-weight organic acids ...(LMWOAs) (e.g., citrate and oxalate) prevail. However, the production of hydroxyl radicals (OH) from pyrite oxidation by oxygen (O2) in these circumneutral environments is poorly understood. In this study, OH production was measured during the abiotic oxidation of pyrite by O2 under circumneutral conditions. A pyrite suspension (50g/L pyrite) that was buffered at pH 6–8 was exposed to air for oxygenation in the dark. Benzoate (20mM) was added into the suspension to trap OH. At pH 7, the cumulative OH reached 7.5μM within 420min in the absence of LMWOAs, whereas it increased to 14.8, 12 and 11.2μM in the presence of 1mM ethylenediaminotetraacetate, citrate and oxalate, respectively. When the citrate concentration, which serves as a LMWOAs model, was increased from 0.5 to 5mM, the cumulative OH increased from 10.3 to 27.3μM within 420min at pH 7. With the decrease in pH from 8 to 6, the cumulative OH increased from 2.1 to 23.3μM in the absence of LMWOAs, but it increased from 8.8 to 134.9μM in the presence of 3mM citrate. The presence of LMWOAs enhanced the OH production from pyrite oxidation under circumneutral conditions.
In the absence of LMOWAs, OH is produced mostly from the oxidation of adsorbed Fe(II) by O2. In the presence of citrate, OH production is attributed mainly to the oxidation of Fe(II)-citrate− by O2 and secondarily to the oxidation of H2O on surface-sulfur defects. The acceleration of pyrite oxidation by Fe(III)-citrate increases OH production. Fe(II)-citrate− is generated mainly from the complexation of adsorbed Fe(II) by citrate and the reduction of Fe(III)-citrate, and the generation is suppressed by the oxidation of adsorbed Fe(II). Fe(III)-citrate is generated predominantly from Fe(II)-citrate− oxidation. Most soluble Fe3+ that is produced from pyrite oxidation hydrolyzes to Fe(III) hydroxide. Kinetic models that were developed according to the proposed mechanisms identified the relative importance of each reaction for OH production. Using the kinetic model, the oxidation efficiencies of the redox-active substances that react with OH at different reaction-rate constants were estimated in the presence of 1mM citrate. This study presents on the overlooked role of LMWOAs in enhancing OH production from pyrite oxidation by O2 in pyrite-rich circumneutral environments, such as marine and estuarine sediments and salt marshes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The oxidation of fossil fuels produces billions of tons of anthropogenic carbon dioxide (CO2) emissions from stationary and nonstationary sources per annum, contributing to global warming. The ...natural carbon cycle consumes a portion of CO2 emissions from the atmosphere. In contrast, substantial CO2 emissions accumulate, making it the largest contributor to greenhouse gas emissions and causing a rise in the planet's temperature. The Earth's temperature was estimated to be 1 °C higher in 2017 compared to the mid-twentieth century. A solution to this problem is CO2 storage in underground formations, abundant throughout the world. Millions of tons of CO2 are stored underground into geological formations annually, including deep saline aquifers. However, these geological formations have minute concentrations of organic material, significantly influencing the CO2 containment security, fluid dynamics, and storage potential. Examining the wetting characteristics and influencing parameters of geological formations is pertinent to understanding the supercritical CO2 behavior in rock/brine systems. Wettability is an important parameter governing the ability of injected CO2 to displace formation water and determine the containment security and storage capacity. Previously, many studies have provided comprehensive overviews of CO2-wettability depending on various factors, such as pressure, temperature, salinity, formation type, surfactants, and chemicals. However, mineral surfaces in these wettability studies are chemically cleaned, and natural geological storage conditions are anoxic (containing organic molecules) where reductive conditions ensue. A severe gap exists in the literature to comprehend the effects of organic material for determining the CO2 storage capacities and how this effect can be reversed using nanomaterial for increased CO2 storage potential. Therefore, we conducted a thorough literature review to comprehend the recent advances in rock/CO2/brine and rock/oil/brine systems containing organic material in different geo-storage formations. We also present recent advances in anoxic rock/CO2/brine and rock/oil/brine systems that have employed nanomaterial for wettability reversal to be more water-wet. This comprehensive review is divided into four parts: 1) reviewing CO2 emissions and geological systems, 2) recent advances in direct quantitative experimental procedures in anoxic rock/CO2/brine systems and effects of organic contaminations on experimental methodology and their controls, 3) effects of organics and nanomaterial in rock/CO2/brine and rock/oil/brine systems, and 4) the future outlook of this study.
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•Earth's temperature is continuously rising due to anthropogenic CO2 emissions, which is the main cause of global warming.•An effective solution to control global warming is to capture and store CO2 emissions in underground formations.•CO2-wettability determines residual and structural trapping potential in geo-storage formations.•Natural geo-storage formations have the presence of organic acids which substantially alter the wettability to CO2-wet.•The effect of organic acids on CO2-wettability can be reversed by the injection of nanofluids in geo-storage formations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Six new polyene carboxylic acids named serpentemycins E-J (1-6), together with three known analogs (7-9), were isolated from the fermentation medium of Streptomyces sp. TB060207, which was isolated ...from arid soil collected from Tibet, China. The structures of the new compounds were elucidated mainly on the basis of HR-ESI-MS and NMR spectroscopic analyses. The inhibitory activities of compounds 1-9 against NO production in LPS-activated RAW264.7 cells were evaluated. Compound 9 has an inhibition rate of 87.09% to 60.53% at concentrations ranging from 5.0 to 40.0 µM.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Testing a number of N-omega-(purin-6-yl)aminoalkanoyl derivatives of 7,8-difluoro-3,4-dihydro-3-methyl-2H-1,4benzoxazine in a panel of nine tumor cell lines has shown that the studied compounds ...exhibit high cytotoxic activity, especially against 4T1 murine mammary carcinoma, COLO201 human colorectal adenocarcinoma, SNU-1 human gastric carcinoma, and HepG2 human hepatocellular carcinoma cells. Synthesis and study of structural analogs of these compounds made it possible to find that the presence of both a difluorobenzoxazine fragment and a purine residue bound via a linker of a certain length is crucial for the manifestation of the cytotoxic activity of this group of compounds. The study of the effect of the most promising compound on the cell cycle of the human tumor cell lines, the most sensitive and least sensitive to cytotoxic action (MDA-MB-231 breast adenocarcinoma and COLO201 colorectal adenocarcinoma, respectively), allows us to conclude that this compound is an inhibitor of DNA biosynthesis. The found group of purine conjugates may be of interest in the design of new antitumor agents.
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46.
Organocatalysis for depolymerisation Jehanno, Coralie; Pérez-Madrigal, Maria M; Demarteau, Jeremy ...
Polymer chemistry,
01/2019, Volume:
1, Issue:
2
Journal Article
Peer reviewed
Open access
Polymeric materials have been accumulating in the environment for decades as a result of the linear way of consuming plastics. Unfortunately, the current approaches followed to treat such a large ...amount of plastic waste, mainly involving physical recycling or pyrolysis, are not efficient enough. Recently, chemical degradation has emerged as a long-term strategy towards reaching completely sustainable cycles where plastics are polymerised, depolymerised, and then re-polymerised with minimal changes in their quantity or final properties. Organocatalysts, which are promising "green" substitutes for traditional organometallic complexes, are able to catalyse depolymerisation reactions yielding highly pure small molecules that are adequate for subsequent polymerisations or other uses. Moreover, by varying several reaction parameters (
e.g.
solvent, temperature, concentration, co-catalyst,
etc.
), the depolymerisation products can be tuned in innumerable possibilities, which further evidences the versatility of depolymerisation. In this review, we highlight the recent advances made by applying organocatalysts, such as organic bases, organic acids, and ionic compounds, to chemically degrade the most commonly used commercial polymers. Indeed, organocatalysis is envisaged as a promising tool to reach a circular and environmentally friendly plastic economy.
Chemical recycling of plastics offers a green method to deal with plastic waste. In this review, we highlight the recent advances made by applying organocatalysts to chemically degrade polymers as a promising tool to reach a circular plastic economy.
A sensitive colorimetric method is described for the determination of the activity of alkaline phosphatase (ALP). It is based on the regulation of the oxidase-mimicking activity of MnO.sub.2 ...nanosheets. In the absence of ALP, MnO.sub.2 nanosheets are capable of catalyzing the oxidation of the colorless substrate 3,3',5,5'-tetramethylbenzidine (TMB) by oxygen to form a blue oxidized product (TMB Ox) with an absorption peak at 652 nm. In the presence of ALP and its substrate ascorbic acid-2-phosphate, the latter is hydrolyzed to form ascorbic acid (AA). AA triggers the decomposition of MnO.sub.2 nanosheets by reducing MnO.sub.2 to Mn.sup.2+, thereby weakening the enzyme mimicking activity of the MnO.sub.2 nanosheets and causing a drop in absorbance. The drop in absorbance at 652 nm is related to the ALP activity in the range from 0.05-10 m-units per mL (mU·mL.sup.-1), and the detection limit is 0.05 mU·mL.sup.-1. The method was applied to the determination of ALP in spiked calf serum samples and gave satisfactory results.
The identification of unstable metabolites of ellagitannins having ortho-quinone structures or reactive carbonyl groups is important to clarify the biosynthesis and degradation of ellagitannins. Our ...previous studies on the degradation of vescalagin, a major ellagitannin of oak young leaves, suggested that the initial step of the degradation is regioselective oxidation to generate a putative quinone intermediate. However, this intermediate has not been identified yet. In this study, young leaves of Quercus dentata were extracted with 80% acetonitrile containing 1,2-phenylenediamine to trap unstable ortho-quinone metabolites, and subsequent chromatographic separation afforded a phenazine derivative of the elusive quinone intermediate of vescalagin. In addition, phenylenediamine adducts of liquidambin and dehydroascorbic acid were obtained, which is significant because liquidambin is a possible biogenetic precursor of C-glycosidic ellagitannins and ascorbic acid participates in the production of another C-glycosidic ellagitannin in matured oak leaves.
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BACKGROUND AND AIM: Recycled sources of phosphorus (P), such as struvite extracted from wastewater, have potential to substitute for more soluble manufactured fertilisers and help reduce the ...long-term threat to food security from dwindling finite reserves of phosphate rock (PR). This study aimed to determine whether struvite could be a component of a sustainable P fertiliser management strategy for arable crops. METHODS: A combination of laboratory experiments, pot trials and mathematical modelling of the root system examined the P release properties of commercial fertiliser-grade struvite and patterns of P uptake from a low-P sandy soil by two different crop types, in comparison to more soluble inorganic P fertilisers (di-ammonium phosphate (DAP) and triple super phosphate (TSP)). RESULTS: Struvite had greatly enhanced solubility in the presence of organic acid anions; buckwheat, which exudes a high level of organic acids, was more effective at mobilising struvite P than the low level exuder, spring wheat. Struvite granules placed with the seed did not provide the same rate of P supply as placed DAP granules for early growth of spring wheat, but gave equivalent rates of P uptake, yield and apparent fertiliser recovery at harvest, even though only 26 % of struvite granules completely dissolved. Fertiliser mixes containing struvite and DAP applied to spring wheat have potential to provide both optimal early and late season P uptake and improve overall P use efficiency. CONCLUSIONS: We conclude that the potential resource savings and potential efficiency benefits of utilising a recycled slow release fertiliser like struvite offers a more sustainable alternative to only using conventional, high solubility, PR-based fertilisers.
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BFBNIB, DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NMLJ, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Aesculus hippocastanum L., also known as horse chestnut, is an ornamental tree whose seeds are mostly discarded in landfills in the regions where they are grown. However, recent studies have shown ...that these seeds can be a source of interesting compounds for several industries. This work aimed to chemically characterize horse chestnut seeds at the level of compounds recognized for their wide bioactivity, i.e., organic acids, including phenolic compounds, using chromatographic methodologies (UFLC-DAD and LC-DAD-ESI/MSn). In addition, the bioactivity of these seeds was evaluated by in vitro methodologies, seeking to relate the respective (bio)activity to the compounds present in the endocarp (husk), seed coat (skin), and peeled seed (pulp). The antioxidant activity (lipid peroxidation inhibition and oxidative haemolysis inhibition), antibacterial potential (against Gram-positive and Gram-negative bacteria) and cytotoxicity (in human tumour cell lines and porcine liver primary cells) were evaluated. Kaempferol-O-pentoside-O-hexoside-O-hexoside was the main phenolic identified in the pulp. At the same time, (-)-epicatechin and β-type (epi)catechin dimer were the major phenolics present in husk and skin, respectively. In general, A. hippocastanum extracts presented antioxidant and antibacterial potential, without toxicity up to the maximal tested dose. Overall, these findings anticipate potential applications of A. hippocastanum seeds in food- or pharmaceutical-related uses.
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