scholarly journals pH-Dependent Gelation of a Stiff Anionic Polysaccharide in the Presence of Metal Ions

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 868 ◽  
Author(s):  
Andrey V. Shibaev ◽  
Dmitry A. Muravlev ◽  
Aleksandra K. Muravleva ◽  
Vladimir V. Matveev ◽  
Anatoly E. Chalykh ◽  
...  
Keyword(s):  
Metal Ions ◽  
Freeze Fracture ◽  
Industrial Applications ◽  
Cross Linking ◽  
Chromium Ions ◽  
Transmission Electron ◽  
Wide Range ◽  
Carboxylic Groups ◽  
Wide Ph Range ◽  
Ph Range

Cross-linking of polysaccharides by metal ions provides polymer gels highly required by industrial applications. In this article, we study the rheological properties and microstructure of solutions of a stiff anionic polysaccharide xanthan cross-linked by chromium (III) ions, and we demonstrate that their properties are highly sensitive to the preparation pH. Stable gels are obtained in a wide range of pH from 2.4 to 7.8. The maximum elastic modulus is observed for the gels made at pH 6.3, and by freeze-fracture transmission electron microscopy it is shown that they are characterized by the most dense network structure. However, out of this pH interval, no gelation is observed. At low pH (< 2.4) it is due to high protonation of carboxylic groups of xanthan preventing their interaction with chromium ions, and to the disappearance of oligomeric ions, which are effective in cross-linking. At high pH (> 7.8) the absence of gelation is caused by the transformation of reactive chromium ions into insoluble chromium hydroxide. At the same time, for the gels initially formed at pH 6.3, subsequent change of pH to strongly acidic (1.4) or basic (8.9) medium does not affect appreciably their properties, meaning that chromium cross-links are stable once they are formed. These observations open a reliable route to produce polysaccharide gels with required mechanical properties in a wide pH range where they initially cannot be prepared. It is also shown that the increase of pH to 6.3 of the initially ungelled solution prepared at pH 1.5 results in gelation. This effect offers a facile way for delayed gelation of polysaccharides, which is especially required by oil industry.

A novel fluorescent probe for Hg2+ detection in a wide pH range and its application in living cell imaging

2018 ◽  
Vol 10 (46) ◽  
pp. 5554-5558 ◽  
Author(s):  
Jing Xu ◽  
Honglin Li ◽  
Yanchi Chen ◽  
Bing Yang ◽  
Qingcai Jiao ◽  
...  
Keyword(s):  
Amino Acids ◽  
Metal Ions ◽  
Fluorescent Probe ◽  
Living Cell ◽  
Cell Imaging ◽  
Enhanced Fluorescence ◽  
Wide Ph Range ◽  
Ph Range ◽  
Living Cell Imaging

A novel fluorescent probe (XL-1) exhibited over 50-fold enhanced fluorescence in the presence of Hg2+ and no interference could be produced by other metal ions, anions and amino acids.

scholarly journals Ion Exchange Properties of a Terpolymer Resin Derived from 2, 4-Dihydroxybenzaldehyde, Oxamide and Formaldehyde

2009 ◽  
Vol 6 (3) ◽  
pp. 639-650 ◽  
Author(s):  
M. V. Tarase ◽  
W. B. Gurnule ◽  
A. B. Zade
Keyword(s):  
Hydrochloric Acid ◽  
Ion Exchange ◽  
Metal Ions ◽  
Metal Ion ◽  
Polymer Sample ◽  
Equilibrium Method ◽  
Wide Ph Range ◽  
Ph Range ◽  
Exchange Properties

Terpolymer resins (2,4-DHBOF) were synthesized by the condensation of 2,4-dihydroxybenzaldehyde and oxamide with formaldehyde in the presence of hydrochloric acid as catalyst, proved to be selective chelation ion exchange terpolymer resins for certain metals. Chelation ion exchange properties of these polymers were studied for Fe+3, Cu+2, Hg+2, Cd+2, Co+2, Zn+2, Ni+2and Pb+2ions. A batch equilibrium method was employed in the study of the selectivity of the distribution of a given metal ions between the polymer sample and a solution containing the metal ion. The study was carried out over a wide pH range and in a media of various ionic strengths. The polymer showed a higher selectivity for Fe+3, Cd+2and Co+2ions than for Cu+2, Hg+2, Zn+2, Ni+2and Pb+2ions.

scholarly journals Organic/Inorganic Superabsorbent Hydrogels Based on Xylan and Montmorillonite

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Shuang Zhang ◽  
Ying Guan ◽  
Gen-Que Fu ◽  
Bo-Yang Chen ◽  
Feng Peng ◽  
...  
Keyword(s):  
Compressive Modulus ◽  
Cross Linking ◽  
Swelling Properties ◽  
Ph Values ◽  
Swelling Capacity ◽  
Wide Ph Range ◽  
Grafting Copolymerization ◽  
Ph Range ◽  
Influence Of Ph ◽  
Superabsorbent Hydrogels

The unique organic/inorganic superabsorbent hydrogels based on xylan and inorganic clay montmorillonite (MMT) were prepared via grafting copolymerization of acrylic acid (AA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) withN,N-methylenebisacrylamide (MBA) as a cross-linking agent and potassium persulfate (KPS) as an initiator. The effect of variables on the swelling capacity of the hydrogels, such as the weight ratios of MMT/xylan, MBA/xylan, and AMPS/AA, was systematically optimized. The results indicated that the superabsorbent hydrogels comprised a porous cross-linking structure of MMT and xylan with side chains that carry carboxylate, carboxamide, and sulfate. The hydrogels exhibit the high compressive modulus (E), about 35–55 KPa, and the compression strength of the hydrogels increased with an increment of the MMT content. The effect of various cationic salt solutions (LiCl, CaCl2, and FeCl3) on the swelling has the following order: Li+> Ca2+> Fe3+. Furthermore, the influence of pH values on swelling behaviors showed that the superabsorbent composites retained around 1000 g g−1over a wide pH range of 6.0–10.0. The xylan-based hydrogels with the high mechanical and swelling properties are promising for the applications in the biomaterials area.

Dynamic Light Scattering and Zeta Potential Studies of Ceria Nanoparticles

2018 ◽  
Vol 278 ◽  
pp. 112-120 ◽  
Author(s):  
Ishaq Yusuf Habib ◽  
N.T.R.N. Kumara ◽  
Chee Ming Lim ◽  
Abdul Hanif Mahadi
Keyword(s):  
Average Particle Size ◽  
Nanoparticle Synthesis ◽  
Average Particle ◽  
Wide Range ◽  
Isoelectric Points ◽  
Wide Ph Range ◽  
Electrolyte Mixture ◽  
Oxide Nanoparticle ◽  
Ph Range ◽  
Adsorption Desorption

A Cerium (IV) oxide nanoparticle (nanoceria) is widely used in different applications such as biomedicine and catalysis due to its unique structural, morphological and catalytic properties. In this report, the dispersion of nanoceria in both aqueous and non-aqueous (methanol and ethanol) media were studied. Adsorption-desorption processes were observed upon addition of different classes of surfactants such as citric acid (CA), cetrimonium bromide (CTAB) and diethanolamine (DEA). Stable dispersions were obtained in both aqueous, non-aqueous and electrolyte assisted media with the overall mechanism being hydrolysis, dissolution and adsorption. XRD, FE-SEM, FTIR and DLS have been used in the present study to characterize the nanoceria and to quantitatively analyze their average particle size distributions in a unique electrolyte mixture of (0.1 M NaOH/ 65% HNO3:H2O, 1:1 v/v) which has not been reported previously. The surface charge study was carried out across a wide pH range between 1.4 – 9.6 and the isoelectric points (IEP) with respect to 15 ml H2O and 50 ml H2O dispersed phases occurred at a pH of about 6.5 and 6.7 respectively. The present study could be useful in a wide range of applications including nanoparticle synthesis, stabilization, and adsorption of toxic materials, biomedical and pharmaceutical.

Cluster defects in gibbsite nanoplates grown at acidic to neutral pH

Nanoscale ◽  
2021 ◽  
Author(s):  
Sebastian Mergelsberg ◽  
Mateusz Dembowski ◽  
Mark E Bowden ◽  
Trent R Graham ◽  
Micah P Prange ◽  
...  
Keyword(s):  
Growth Mechanism ◽  
Industrial Applications ◽  
Mineral Phase ◽  
Neutral Ph ◽  
Wide Ph Range ◽  
Ph Range

Gibbsite [α-Al(OH)3] is the solubility limiting phase for aluminum across a wide pH range, and it is a common mineral phase with many industrial applications. But the growth mechanism of...

scholarly journals Characterization and Antibacterial Mode of a Novel Bacteriocin with Seven Amino Acids from Lactobacillus plantarum in Guizhou Salted Radish

2016 ◽  
Vol 8 (10) ◽  
pp. 120 ◽  
Author(s):  
Meizhong Hu ◽  
Lijuan Dang ◽  
Haizhen Zhao ◽  
Chong Zhang ◽  
Yingjian Lu ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Cell Membrane ◽  
Lactobacillus Plantarum ◽  
Foodborne Pathogens ◽  
Transmission Electron ◽  
Wide Range ◽  
Probiotic Lactic Acid Bacteria ◽  
Probiotic Food ◽  
Ph Range

<p>Traditional Chinese fermented vegetables are excellent probiotic food with probiotic lactic acid bacteria that are benefical to the health. A novel bacteriocin with molecular weight, 825 Da was found successfully from Lactobacillus plantarum 163, which was isolated from Guizhou salted radish. The complete amino acid sequence was speculated as YVCASPW based on the mass spectrometry, and was named as bacteriocin 163-1. The bacteriocin 163-1 was highly thermostable and stability over a broad pH range (pH 3-6), sensitive to protease K and pepsin, and exhibited a wide range of antimicrobial activity not only against lactic acid bacteria (LAB) but also against other foodborne pathogens including Gram-positive and Gram-negative bacteria. Bacteriocin 163-1 could disrupt the cell membrane of bacteria. The observations of the transmission electron microscopy and laser confocal microscopy on the cell membrane of Escherichia coli and Staphylococcus aureus showed that bacteriocin 163-1 could result in forming pores on the cell membrane and then cytolysis of the bacteria. The new bacteriocin with broad-spectrum antibacterial activity will be useful in preservation of vegetable, fruit and food as well agricultural bio-controlling.</p>

Preparation and Analysis of Magnetic Nanoparticles Used as Highly Active Catalysts over a Wide pH Range

2012 ◽  
Vol 424-425 ◽  
pp. 1057-1061
Author(s):  
Wei Wang ◽  
Tie Long Li ◽  
Ying Liu
Keyword(s):  
Magnetic Nanoparticles ◽  
Precipitation Method ◽  
Fe3o4 Magnetic Nanoparticles ◽  
Ph Adjustment ◽  
Highly Active ◽  
Wide Range ◽  
Iron Leaching ◽  
Wide Ph Range ◽  
Ph Range ◽  
Co Precipitation

In this work, Fe3O4 magnetic nanoparticles with high peroxidase-like catalytic activity and spontaneous pH adjustment ability were successfully prepared by co-precipitation method followed by appropriate thermal treatment. Key synthesis factors were identified and adjusted to tailor the crystallinity, chemical composition and then catalytic property. The crystal structure and Fe (II) content of the catalyst strongly affected its degradation efficiency. Phenol was completely removed by the optimal magnetic nanoparticles under a wide range of pH from 3.0 to 8.0. Additionally, this catalyst exhibited low iron leaching, good reusability and excellent potential to eliminate various organic pollutants from waste water. The reaction mechanism was discussed in terms of the formation of HO• and O2•−/HO2• radicals.

Cartap wastewater treatment by a microwave-induced catalytic oxidation procedure over Ce/Co/γ-Al2O3

2021 ◽  
Vol 11 (11) ◽  
pp. 1856-1865
Author(s):  
Kaixuan Liu ◽  
Fang Lian ◽  
Guoqi Wang ◽  
Jiaru Dai ◽  
Xuepeng Tian ◽  
...  
Keyword(s):  
Catalytic Oxidation ◽  
Oxidative Degradation ◽  
Degradation Process ◽  
Reaction Rates ◽  
Catalyst Design ◽  
Electron Microscopies ◽  
Transmission Electron ◽  
Wide Ph Range ◽  
Ph Range ◽  
Novel Catalyst

Microwave-assisted catalytic technology is potentially promising in the application of water treatment due to its merits of high reaction rates, simple equipment and operations. In case of the cartap wastewater rarely studied, the easy transformation of cartap into metabolites could induce higher toxicity. This study aimed to develop a novel catalyst Ce/Co/γ-Al2O3 to dispose cartap effectively. The catalyst was prepared by loading Ce and Co on the surface of the support Al2O3, followed by characterization with X-ray diffraction, scanning and transmission electron microscopies. Based on the treatment results, the microwave-induced catalytic oxidation procedure over Ce/Co/γ-Al2O3 could decompose the contaminants efficiently and fast in the case of a low oxidant dosage and a wide pH range. Under the conditions of pH of 5, microwave power of 450 W, catalyst dosage of 0.7 g and hydrogen peroxide dosage of 0.2 mL, the activity of Ce/Co/γ-Al2O3 catalyst could reach up to 86.08%. Importantly, the Ce/Co/γ-Al2O3 catalyst displayed excellent stability after using for 6 times in the degradation process. This work paved a new way for the effective catalyst design for efficient microwave-induced oxidative degradation.

scholarly journals Facile Production of a Fenton-Like Photocatalyst by Two-Step Calcination with a Broad pH Adaptability

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 676
Author(s):  
Siyang Ji ◽  
Yanling Yang ◽  
Xing Li ◽  
Hang Liu ◽  
Zhiwei Zhou
Keyword(s):  
Rhodamine B ◽  
Photoelectron Spectroscopy ◽  
Active Oxygen Species ◽  
Oxygen Species ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Wide Ph Range ◽  
Calcination Method ◽  
Ph Range

A novel heterogeneous Fenton-like photocatalyst, Fe-doped graphitic carbon nitride (Fe-g-C3N4), was produced by facile two-step calcination method. This Fe–g–C3N4 catalyzed rhodamine B degradation in the presence of H2O2 accompanied with visible light irradiation. transmission electron microscopy(TEM), x-ray diffraction (XRD), FT-IR, x-ray photoelectron spectroscopy (XPS), and photoluminescence fluorescent spectrometer (PL) characterization analysis methods were adopted to evaluate the physicochemical property of samples. It can be observed that the Fe-g-C3N4 exhibited excellent photocatalytic Fenton-like activity at a wide pH range of 3–9, with rhodamine B(RhB) degradation efficiency up to 95.5% after irradiation for 45 min in the presence of 1.0 mM H2O2. Its high activity was ascribed to the formation of Fe–N ligands in the triazine rings that accelerated electron movement driving the Fe(III)/Fe(II) redox cycle, and inhibited photo-generated electron hole re-combinations for continuous generation of reactive oxygen species by reactions between Fe(II) and H2O2. The main active oxygen species were hydroxyl radicals, followed by superoxide radicals and hole electrons. This produced catalyst of Fe–g–C3N4 shows excellent reusability and stability, and can be a promising candidate for decontamination of wastewater.

scholarly journals Metal Chelates of Petunidin Derivatives Exhibit Enhanced Color and Stability

Foods ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 1426
Author(s):  
Peipei Tang ◽  
M. Monica Giusti
Keyword(s):  
Metal Ion ◽  
Bathochromic Shift ◽  
Color Stability ◽  
Metal Chelates ◽  
Dependent Manner ◽  
Metal Chelation ◽  
Wide Range ◽  
Wide Ph Range ◽  
Ph Range ◽  
Dose Dependent

Anthocyanins with catechol (cyanidin) or pyrogallol (delphinidin) moieties on the B-ring are known to chelate metals, resulting in bluing effects, mainly at pH ≤ 6. Metal interaction with petunidin, an O-methylated anthocyanidin, has not been well documented. In this study, we investigated metal chelation of petunidin derivatives in a wide pH range and its effects on color and stability. Purple potato and black goji extracts containing >80% acylated petunidin derivatives (25 μM) were combined with Al3+ or Fe3+ at 0 μM to 1500 μM in buffers of pH 3–10. Small metal ion concentrations triggered bathochromic shifts (up to ~80nm) at an alkaline pH, resulting in vivid blue hues (hab 200°–310°). Fe3+ caused a larger bathochromic shift than Al3+, producing green colors at pH 8-9. Generally, metal ions increased the color stability and half-life of petunidin derivatives in a dose-dependent manner, particularly at pH 8. Petunidin derivative metal chelates produced a wide range of colors with enhanced stability.

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