Mechanism of birnessite-promoted oxidative dissolution of antimony trioxide

2020 ◽  
Vol 17 (4) ◽  
pp. 345 ◽  
Author(s):  
Jun Shan ◽  
Xintong Ding ◽  
Mengchang He ◽  
Wei Ouyang ◽  
Chunye Lin ◽  
...  
Keyword(s):  
Release Rate ◽  
Dissolution Mechanism ◽  
Antimony Trioxide ◽  
Oxidative Dissolution ◽  
Reaction Solution ◽  
Initial Stage ◽  
Geochemical Cycle ◽  
Alkaline Conditions ◽  
Toxic Hazard ◽  
Neutral Conditions

Environmental contextThe release of antimony and its compounds to the environment can present a toxic hazard for humans. We evaluated the use of birnessite to dissolve antimony trioxide and found that birnessite accelerated the dissolution process, and ~50% of the oxidised antimony was absorbed. The results can help evaluate the bioavailability of antimony in the environment. AbstractThe most important naturally occurring forms of antimony (Sb) are the ore mineral stibnite (Sb2S3) and its principal weathering product antimony trioxide (Sb2O3). Moreover, most Sb is released into the environment as Sb2O3 from manufacturing, formulations, processing, and the use and disposal of Sb products. In this study, birnessite (δ-MnO2) was employed to promote Sb2O3 dissolution. The Sb2O3 dissolution rate accelerated from ~2% to >99% after 9 days of reaction, and more than 98% of the dissolved SbIII was oxidised into SbV in the presence of birnessite. The birnessite-promoted oxidative dissolution mechanism of Sb2O3 was studied through experiments on the effects of the reaction time and pH. The release rate of Sb in the aqueous phase at the initial stage (335.4 μmol L−1 day−1, pH 6.5) was much higher than that at the late stage (13.28 μmol L−1 day−1, pH 6.5), and when the pH increased from 4.7 to 8.0, the Sb release rate decreased from 351.2 μmol L−1 day−1 to 257.7 μmol L−1 day−1. The dissolution promotion effects of birnessite on Sb2O3 were the most evident under acidic and neutral conditions (the percentages of dissolved Sb2O3 under acidic and neutral conditions were 98.3% and 100.0% after 9 days of reaction). Not all of the produced SbV was released in the reaction solution because ~50% of it was adsorbed by birnessite, and the amount of Sb adsorbed increased with increasing pH. Therefore, alkaline conditions are shown to reduce the release of SbV by inhibiting Sb2O3 dissolution (86.7%) and enhancing SbV adsorption. These results could help clarify the geochemical cycle and fate of Sb in the environment.

scholarly journals Factors influencing dissolution of carbonaceous materials in liquid Fe–Mn

2020 ◽  
Vol 27 (10) ◽  
pp. 1153-1162
Author(s):  
Hamideh Kaffash ◽  
Merete Tangstad
Keyword(s):  
Dissolution Mechanism ◽  
Carbonaceous Materials ◽  
Resistance Furnace ◽  
Metal Interface ◽  
Dissolution Rates ◽  
Factors Affecting ◽  
Carbon Dissolution ◽  
Initial Stage ◽  
Ash Layer ◽  
Solid Liquid

Abstract Carbon dissolution from four types of metallurgical cokes and graphite was investigated by using immersion rods in a resistance furnace to clarify the influence of factors governing the rate of carbon dissolution from carbonaceous materials into Fe–Mn melts at 1550 °C. The factors studied were the microstructure of carbonaceous materials, roughness, porosity and the wettability between carbonaceous materials and the melt. Carbon/metal interface was characterised by scanning electron microscopy accompanied with energy-dispersive X-ray spectrometry to investigate the formation of an ash layer. The results showed that coke E had the highest dissolution rate. Surface roughness and porosity of the carbonaceous materials seemed to be dominant factors affecting the dissolution rates. Further, crystallite size did not have a significant effect on the dissolution rates. Solid/liquid wettability seemed to affect the initial stage of dissolution reaction. The dissolution mechanism was found to be both mass transfer and interfacial reactions.

scholarly journals Glucosylceramide Contained in Koji Mold-Cultured Cereal Confers Membrane and Flavor Modification and Stress Tolerance to Saccharomyces cerevisiae during Coculture Fermentation

2015 ◽  
Vol 81 (11) ◽  
pp. 3688-3698 ◽  
Author(s):  
Kazutaka Sawada ◽  
Tomoya Sato ◽  
Hiroshi Hamajima ◽  
Lahiru Niroshan Jayakody ◽  
Miyo Hirata ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Acetic Acid Bacteria ◽  
Yeast Cells ◽  
Membrane Properties ◽  
Yeast Culture ◽  
Content Type ◽  
Initial Stage ◽  
Alkaline Conditions ◽  
Metabolic Interactions ◽  
Alkali Tolerance

ABSTRACTIn nature, different microorganisms create communities through their physiochemical and metabolic interactions. Many fermenting microbes, such as yeasts, lactic acid bacteria, and acetic acid bacteria, secrete acidic substances and grow faster at acidic pH values. However, on the surface of cereals, the pH is neutral to alkaline. Therefore, in order to grow on cereals, microbes must adapt to the alkaline environment at the initial stage of colonization; such adaptations are also crucial for industrial fermentation. Here, we show that the yeastSaccharomyces cerevisiae, which is incapable of synthesizing glucosylceramide (GlcCer), adapted to alkaline conditions after exposure to GlcCer from koji cereal cultured withAspergillus kawachii. We also show that various species of GlcCer derived from different plants and fungi similarly conferred alkali tolerance to yeast. Although exogenous ceramide also enhanced the alkali tolerance of yeast, no discernible degradation of GlcCer to ceramide was observed in the yeast culture, suggesting that exogenous GlcCer itself exerted the activity. Exogenous GlcCer also increased ethanol tolerance and modified the flavor profile of the yeast cells by altering the membrane properties. These results indicate that GlcCer fromA. kawachiimodifies the physiology of the yeastS. cerevisiaeand demonstrate a new mechanism for cooperation between microbes in food fermentation.

Reactivity Comparison of Different Ni(II)-Pyrites during Oxidative Dissolution under Acidic and pH-Neutral Conditions

2019 ◽  
Vol 3 (6) ◽  
pp. 1096-1108 ◽  
Author(s):  
Zong-Sheng Liang ◽  
Bao-Dong Song ◽  
Yong-Ling Liu ◽  
Yong Liu ◽  
Hai-Tao Ren ◽  
...  
Keyword(s):  
Oxidative Dissolution ◽  
Neutral Conditions

scholarly journals Formulation of More Efficacious Curcumin Delivery Systems Using Colloid Science: Enhanced Solubility, Stability, and Bioavailability

Molecules ◽  
2020 ◽  
Vol 25 (12) ◽  
pp. 2791 ◽  
Author(s):  
Bingjing Zheng ◽  
David Julian McClements
Keyword(s):  
Water Solubility ◽  
Biological Activities ◽  
Anticancer Activities ◽  
Potential Health ◽  
Colloid Science ◽  
Enhanced Solubility ◽  
Alkaline Conditions ◽  
Low Toxicity ◽  
Neutral Conditions ◽  
Bioactive Constituent

Curcumin is a bioactive constituent isolated from turmeric that has historically been used as a seasoning, pigment, and herbal medicine in food. Recently, it has become one of the most commonly studied nutraceuticals in the pharmaceutical, supplement, and food areas because of its myriad of potential health benefits. For instance, it is claimed to exhibit antioxidant, anti-inflammatory, antimicrobial, antiparasite, and anticancer activities when ingested as a drug, supplement, or food. Toxicity studies suggest that it is safe to consume, even at relatively high levels. Its broad-spectrum biological activities and low toxicity have meant that it has been widely explored as a nutraceutical ingredient for application in functional foods. However, there are several hurdles that formulators must overcome when incorporating curcumin into commercial products, such as its low water solubility (especially under acidic and neutral conditions), chemical instability (especially under neutral and alkaline conditions), rapid metabolism by enzymes in the human body, and limited bioavailability. As a result, only a small fraction of ingested curcumin is actually absorbed into the bloodstream. These hurdles can be at least partially overcome by using encapsulation technologies, which involve trapping the curcumin within small particles. Some of the most commonly used edible microparticles or nanoparticles utilized for this purpose are micelles, liposomes, emulsions, solid lipid particles, and biopolymer particles. Each of these encapsulation technologies has its own benefits and limitations for particular product applications and it is important to select the most appropriate one.

Hydrothermal Synthesis of Nanostructured TiO2 Particles and Characterization of Their Photocatalytic Antimicrobial Activity

2008 ◽  
Vol 8 (2) ◽  
pp. 878-886 ◽  
Author(s):  
Beril K. Erdural ◽  
Alp Yurum ◽  
Ufuk Bakir ◽  
Gurkan Karakas
Keyword(s):  
Sol Gel ◽  
Time Lag ◽  
Alkaline Treatment ◽  
Antimicrobial Activities ◽  
Distilled Water ◽  
Bacterial Inactivation ◽  
Sem Images ◽  
Alkaline Conditions ◽  
Aqueous Conditions ◽  
Neutral Conditions

Nanostructured titania particles were synthesized by using hydrothermal processing and the photocatalytic antimicrobial activities were characterized. Both sol–gel synthesized and commercial TiO2 (anatase) samples were processed with two step hydrothermal treatments, under alkaline and neutral conditions. Scanning Electron Microscope (SEM) images showed that alkaline treatment yields nanofibers and lamellar structured particles from the commercial anatase and sol–gel synthesized samples respectively. Further treatment of nanofibers and nanostructured lamellar particles with distilled water results with crystal growth and the formation of nano structured bipyramidal crystalline particles. The photocatalytic antimicrobial activities of the samples were determined against Escherichia coli under irradiation. It was observed that the samples treated under alkaline conditions have improved activity than the original anatase samples. Limited activity and resulting time lag in bacterial inactivation were observed for hydrothermally treated samples with distilled water. However, a post treatment comprising the UV irradiation in aqueous conditions enhanced the photocatalytic activity.

Removal of odorant dimethyl disulfide under alkaline and neutral conditions in biotrickling filters

2012 ◽  
Vol 66 (8) ◽  
pp. 1641-1646 ◽  
Author(s):  
L. Arellano-García ◽  
A. González-Sánchez ◽  
H. Van Langenhove ◽  
A. Kumar ◽  
S. Revah
Keyword(s):  
Main Product ◽  
Dimethyl Disulfide ◽  
Continuous Treatment ◽  
Batch Experiments ◽  
Reduced Sulfur Compounds ◽  
Biotrickling Filters ◽  
Bacterial Consortia ◽  
Low Concentrations ◽  
Alkaline Conditions ◽  
Neutral Conditions

The aim of this paper was to evaluate the performance of biotrickling filters (BTFs) for treating low concentrations of dimethyl disulfide (DMDS), using different bacterial consortia adapted to consume reduced sulfur compounds under alkaline (pH ≈ 10) or neutral (pH ≈ 7) conditions. Solubility experiments indicated that the partition of DMDS in neutral and alkaline mineral media was similar to the value with distilled water. Respirometric assays showed that oxygen consumption was around ten times faster in the neutrophilic as compared with the alkaliphilic consortium. Batch experiments demonstrated that sulfate was the main product of the DMDS degradation. Two laboratory-scale BTFs were implemented for the continuous treatment of DMDS in both neutral and alkaline conditions. Elimination capacities of up to 17 and 24 gDMDS m−3 h−1 were achieved for the alkaliphilic and neutrophilic reactors with 100% removal efficiency after an initial adaptation and biomass build-up.

Kinetics and Mechanism of Photopromoted Oxidative Dissolution of Antimony Trioxide

2014 ◽  
Vol 48 (24) ◽  
pp. 14266-14272 ◽  
Author(s):  
Xingyun Hu ◽  
Linghao Kong ◽  
Mengchang He
Keyword(s):  
Kinetics And Mechanism ◽  
Antimony Trioxide ◽  
Oxidative Dissolution

scholarly journals Enhanced effects of reducing agent on oxalate chelated Fe(II) catalyzed percarbonate system for benzene degradation

2021 ◽  
Author(s):  
Xiaori Fu ◽  
Xinyan Wei ◽  
Wei Zhang ◽  
Wupeng Yan ◽  
Peng Wei ◽  
...  
Keyword(s):  
Hydroxylamine Hydrochloride ◽  
Reducing Agent ◽  
Sodium Ascorbate ◽  
High Concentration ◽  
H2o2 Decomposition ◽  
Benzene Degradation ◽  
Benzene Removal ◽  
Alkaline Conditions ◽  
Negative Effect ◽  
Neutral Conditions

Abstract The addition of hydroxylamine hydrochloride (HAH), ascorbic acid (ASC), sodium ascorbate (SAS) to the OA-Fe(II)/SPC system could promote the generation of HO• by accelerating Fe(II)/Fe(III) recycles and H2O2 decomposition. The enhancement of HAH on HO• generation surpasses ASC and SAS in the OA-Fe(II)/SPC system. The generation of O2•− was also enhanced by HAH, ASC and SAS, and more significant promotion of O2•− generation was observed with ASC and SAS addition. More effective benzene removal was achieved in an OA-Fe(II)/SPC system with suitable HAH, ASC and SAS addition, compared to the parent system. Excessive HAH, ASC or SAS had a negative effect on benzene removal. Results of scavenger tests showed that HO• is indeed the dominant free radical for benzene removal in every system, but the addition of HAH, ASC and SAS increased the contribution of O2•− to benzene degradation. HAH, ASC and SAS enhanced OA-Fe(II)/SPC systems could be well utilized to acidic and neutral conditions, while HCO3−, high concentration of HA and alkaline conditions were not favorable to benzene removal. Moreover, the addition of HAH, ASC and SAS are conducive to benzene removal in actual groundwater, and HAH was the optimal reducing agent for the enhancement of the OA-Fe(II)/SPC system.

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