scholarly journals Influence of pH and Contaminant Redox Form on the Competitive Removal of Arsenic and Antimony from Aqueous Media by Coagulation

Minerals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 574 ◽  
Author(s):  
Muhammad Ali Inam ◽  
Rizwan Khan ◽  
Du Ri Park ◽  
Babar Aijaz Ali ◽  
Ahmed Uddin ◽  
...  
Keyword(s):  
Binary System ◽  
Quaternary System ◽  
Aqueous Media ◽  
Single System ◽  
Redox Species ◽  
Wide Ph Range ◽  
Alkaline Conditions ◽  
Ft Ir ◽  
Ph Range ◽  
Removal Of Arsenic

In most countries, arsenic (As) and antimony (Sb) are regulated pollutants, due to their significant impacts on the environment and human health. Iron-based (Fe) coagulants play a fundamental role in the removal of both elements from aqueous media. This study aims to investigate the competitive removal of As and Sb in relation to Fe solubility. Coagulation experiments were conducted in synthetic water under various pH and contaminant loading, using ferric chloride (FC) as a coagulant. In the single system, the pentavalent species significantly reduced the Fe solubility and thereby enhanced the mobility of As and Sb under these environmental conditions. The coexistence of pentavalent and trivalent species in the binary system considerably decreases the Fe solubility at acidic conditions while enhancing the dissolution under alkaline conditions, thus affecting the overall removal of both species. The presence of four redox species in the quaternary system decreases the Fe solubility remarkably over a wide pH range, with better Sb removal, as compared to As under similar conditions. The adsorption study of the single system showed a decrease in As(V) adsorption capacity at higher concentration, while in the binary system, the Sb(III) showed strong adsorption potential, compared to other species. In the quaternary system, the presence of all four redox species has a synergistic effect on total Sb adsorption, in comparison to the total As. Furthermore, the results of Fourier transform infrared (FT-IR) analysis of FC composite contaminant flocs confirm that the combined effect of charge neutralization and inner sphere complexation might be a possible removal mechanism. These findings may facilitate the fate, transport and comparative removal of redox species in the heterogeneous aquatic environment.

2´-carboxy-3-keto-D-arabinitol 1,5-bisphosphate, the six-carbon intermediate of the ribulose bisphosphate carboxylase reaction

1986 ◽  
Vol 313 (1162) ◽  
pp. 397-407 ◽  
Keyword(s):  
Metal Ion ◽  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Bisphosphate Carboxylase ◽  
Wide Ph Range ◽  
Alkaline Conditions ◽  
Divalent Metal Ion ◽  
Ph Range ◽  
Short Time ◽  
Hydrolysis Of

The six-carbon intermediate of the ribulose 1,5-bisphosphate (RuBP) carboxylase reaction, 2'-carboxy-3-keto-D-arabinitol 1,5-bisphosphate (CKABP), was prepared enzymatically by quenching the reaction with acid after a short time ( ca 12 ms). Over a wide pH range (4-11), GKABP undergoes a slow ( t 1/2 = 1 h), pH-independent decarboxylation. No detectable decomposition of CKABP occurs over a six-week period at — 80 °C. The decarboxylation of CKABP is acid-catalysed and is also catalysed by deactivated enzyme lacking the activator carbamate-divalent metal ion complex. Decarboxylation is accompanied by β-elimination of the C-1 phosphate from the 2,3-enediolate. Under alkaline conditions (pH >11) CKABP undergoes hydrolysis. Non-enzymatic hydrolysis of the intermediate is also accompanied by β-elimination of the C-1 phosphate (presumably from the aci-acid of the upper glycerate 3-phosphate) and the formation of pyruvate. Fully activated enzyme catalyses the complete hydrolysis of CKABP to glycerate 3-phosphate, although enzymic hydrolysis of CKABP is limited by an event not on the direct path of carboxylation. Carbon-13 NMR analysis of [2',3- 13 C]CKABP indicates that it exists in solution predominantly (> 85%) as the C-3 ketone. In contrast, borohydride trapping of CKABP formed from [3- 18 O]RuBP indicates that the intermediate exists on the enzyme predominantly (> 94%) as the hydrated C-3 gem-diol. In solution, the hydration of the C-3 ketone of CKABP proceeds slowly ( k = 2.5 x 10 -3 s -1 ). The enzymatic hydration of CKABP must proceed at least as fast as k cat ( ca. 5 s -1 ) or at least 2000 times faster than the hydration of CKABP in solution.

scholarly journals Tuning the Properties of High Molecular Weight Chitosans to Develop Full Water Solubility Within a Wide pH Range

2020 ◽  
Author(s):  
Anderson Fiamingo ◽  
Sergio Paulo Campana Filho ◽  
Osvaldo Novais Oliveira Junior
Keyword(s):  
Molecular Weight ◽  
Biomedical Applications ◽  
Random Distribution ◽  
Water Solubility ◽  
Aqueous Media ◽  
Degree Of Polymerization ◽  
Molecular Weights ◽  
H Nmr ◽  
Wide Ph Range ◽  
Ph Range

<p>The preparation of chitosans soluble in physiological conditions has been sought for years, but so far solubility in non-acidic aqueous media has only been achieved at the expense of lowering chitosan molecular weight. In this work, we applied the multistep ultrasound-assisted deacetylation process (USAD process) to β-chitin and obtained extensively deacetylated chitosans with high molecular weights (Mw ≥ 1,000,000 g mol<sup>-1</sup>). The homogeneous <i>N</i>-acetylation of a chitosan sample resulting from three consecutive USAD procedures allowed us to produce chitosans with a high weight average degree of polymerization (DPw ≈ 6,000) and tunable degrees of acetylation (DA from 5 to 80%). <i>N</i>-acetylation was carried out under mild conditions to minimize depolymerization, while preserving a predominantly random distribution of 2-amino-2-deoxy-D-glucopyanose (<i>GlcN</i>) and 2-acetamido-2-deoxy-D-glucopyanose (<i>GlcNAc</i>) units. This close to random distribution, inferred with deconvolution of nuclear magnetic resonance (<sup>1</sup>H NMR) spectra, is considered as responsible for the solubility within a wide pH range. Two of the highly <i>N</i>-acetylated chitosans (DA ≈ 60 % and ≈ 70 %) exhibited full water solubility even at neutral pH, which can expand the biomedical applications of chitosans. </p>

scholarly journals Synthesis of water-soluble chitosan for biomedical applications

2015 ◽  
Vol 18 (3) ◽  
pp. 170-180
Author(s):  
Anh Thi Tram Tu ◽  
Huy Thuc Ha
Keyword(s):  
Drug Delivery ◽  
Molecular Weight ◽  
Iron Oxide ◽  
Biomedical Applications ◽  
Drug Delivery Systems ◽  
Water Soluble ◽  
Oxide Nanoparticles ◽  
Wide Ph Range ◽  
Ft Ir ◽  
Ph Range

Highly deacetylated chitosan (CS) reacted with anhydride acetic (Ac2O) to produce chitosan with various degree of deacetylation (DDA) depending on the CS/Ac2O ratios. The structure of products was characterized by FT-IR, 1H NMR, 13C NMR, and the molecular weight was identified by GPC. The DDA of products decreases as the CS/Ac2O ratio increases. The products with less than 80 % DDA were soluble in water with a wide pH range. The water-soluble chitosan can be used in many biomedical applications such as manufacturing drug delivery systems or functionalized iron oxide nanoparticles.

A sensitive detection of Cr(vi) in wide pH range using polyethyleneimine protected silver nanoclusters

2016 ◽  
Vol 8 (28) ◽  
pp. 5684-5689 ◽  
Author(s):  
Na Xu ◽  
Quan Zhu ◽  
Xiang-Yue Kong ◽  
Lei Meng
Keyword(s):  
Fluorescence Probe ◽  
Silver Nanoclusters ◽  
Sensitive Detection ◽  
Trace Level ◽  
Wide Ph Range ◽  
Alkaline Conditions ◽  
Ph Range

A sensitive fluorescence probe of polyethyleneimine protected silver nanoclusters (AgNCs@PEI) was proposed for the detection of trace level of Cr(vi) in both acidic and alkaline conditions.

scholarly journals A Comparison Study on Fluorescence Properties of Formononetin and Ononin

2021 ◽  
Author(s):  
Jinjin Cao ◽  
Fang Lv ◽  
Ting Liu ◽  
Luchen Niu ◽  
Bocong Han ◽  
...  
Keyword(s):  
Fluorescence Enhancement ◽  
Alkaline Condition ◽  
Excitation Wavelength ◽  
Comparison Study ◽  
Spectral Difference ◽  
Experimental Conditions ◽  
Pyrone Ring ◽  
Wide Ph Range ◽  
Alkaline Conditions ◽  
Ph Range

Abstract In this work, reasons for the spectral difference between two isoflavones, Formononetin (F) and ononin (FG), are explained in the viewpoint of molecular structure through a comparison study of the fluorescence features of the two. The fluorescence enhancement of FG in hot alkaline condition is reported for the first time. For F, there was almost no fluorescence under acidic conditions, but when pH>5, its fluorescence began to increase with increasing pH due to the proton ionization of 7-OH. In the range of pH 9.3-12.0, the anion form of F produced a fairly strong and stable fluorescence with maximum excitation wavelength (λex) of 334 nm and emission wavelength (λem) of 464 nm, its fluorescence quantum yield (Yf) was measured to be 0.042. And for FG, its aqueous solution fluoresced weakly in a wide pH range until it was placed under hot alkaline conditions, which was presumed to the cleavage reaction of the γ-pyrone ring in FG by observing a significant fluorescence at λex / λem =288 / 388nm, and Yf was determined to be 0.020. The fluorescence sensitization methods of F and FG both exhibit low limits of detection (2.60 ng·mL-1, 9.30 ng·mL-1) and wide linear ranges (0.0117-1.86 μg·mL-1, 0.0146-2.92μg·mL-1). Although the structural relationship between F and FG is glycoside and aglycone, FG cannot be translated to F by glucoside hydrolysis under hot alkaline condition, the fluorescence enhancement mechanisms of the two are essentially different. The fluorescence difference between the two under different experimental conditions lays the foundation for future fluorescence quantitative analysis.

scholarly journals Stability of gamma-valerolactone under pulping conditions as a basis for process optimization and chemical recovery

Cellulose ◽  
2021 ◽  
Author(s):  
Marianna Granatier ◽  
Inge Schlapp-Hackl ◽  
Huy Quang Lê ◽  
Kaarlo Nieminen ◽  
Leena Pitkänen ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Treatment Time ◽  
Reaction Times ◽  
Chemical Recovery ◽  
Wide Ph Range ◽  
Alkaline Conditions ◽  
Naoh Solution ◽  
Hydroxyvaleric Acid ◽  
Ph Range ◽  
Spent Liquor

AbstractThis study focuses on the investigation of the extent of the γ-valerolactone (GVL) hydrolysis forming an equilibrium with 4-hydroxyvaleric acid (4-HVA) in aqueous solutions over a wide pH range. The hydrolysis of a 50 wt% GVL solution to 4-HVA (3.5 mol%) was observed only at elevated temperatures. The addition of sulfuric acid (0.2 × 10–5 wt% to 6 wt%) at elevated temperatures (150–180 °C) and reaction times between 30 and 180 min caused the formation of 4 mol% 4-HVA. However, with decreasing acidity, the 4-HVA remained constant at about 3 mol%. The hydrolysis reactions in alkaline conditions were conducted at a constant time (30 min) and temperature (180 °C) with the variation of the NaOH concentration (0.2 × 10–6 wt% to 7 wt%). The addition of less than 0.2 wt% of NaOH resulted in the formation of less than 4 mol% of sodium 4-hydroxyvalerate. A maximum amount of 21 mol% of 4-HVA was observed in a 7 wt% NaOH solution. The degree of decomposition after treatment was determined by NMR analysis. To verify the GVL stability under practical conditions, Betula pendula sawdust was fractionated in 50 wt% GVL with and without the addition of H2SO4 or NaOH at 180 °C and a treatment time of 120 min. The spent liquor was analyzed and a 4-HVA content of 5.6 mol% in a high acidic (20 kg H2SO4/t wood) and 6.0 mol% in an alkaline (192 kg NaOH/t wood) environment have been determined.

scholarly journals Montmorillonite of the Ohlanlynske deposit and magnetic composites based on it — sorbents for water purification from 137Cs and 90Sr

2021 ◽  
Vol 20 ◽  
pp. 73-80
Author(s):  
S. O. Kobets ◽  
Keyword(s):  
Water Purification ◽  
Natural Waters ◽  
Liquid Radioactive Waste ◽  
Aqueous Media ◽  
Langmuir Equation ◽  
Magnetic Composites ◽  
Natural Minerals ◽  
Magnetic Sorbents ◽  
Wide Ph Range ◽  
Ph Range

A comparative study on the extraction of 137Cs and 90Sr from aqueous media using magnetic composites obtained on the basis of bentonite from the Ohlanlynske deposit and magnetite was carried out. It is shown that magnetic composites based on a natural mineral — bentonite rock, isolated montmorillonite in the Na-form, impurities — clinoptilolite and cristobalite, as well as natural minerals without magnetite, efficiently sorb 137Cs and 90Sr in a wide pH range (3.7–9). Despite the fact that magnetite in the composition of composites practically does not affect the efficiency of purification of aqueous media, but acts as only a magnetoactive component, composites are quite promising sorbents for purifying of large volumes of radioactively contaminated waters due to the possibility of removing water purification sludge using an external magnetic field. It has been established that the highest sorption properties are possessed by magnetic sorbents obtained on the basis of clinoptilolite — for 137Cs, and the Na-form of montmorillonite — for 90Sr. The values of their limiting adsorption by the indicated composites, calculated using the Langmuir equation, are 43.3 and 40.6 mg/g, respectively. It is shown that among the macrocomponents (Na+ , K+ , Ca2+), Ca2+ ions have the greatest influence on the efficiency of purification of natural waters and liquid radioactive waste containing 137Cs and 90Sr radionuclides.

scholarly journals Tuning the Properties of High Molecular Weight Chitosans to Develop Full Water Solubility Within a Wide pH Range

2020 ◽  
Author(s):  
Anderson Fiamingo ◽  
Sergio Paulo Campana Filho ◽  
Osvaldo Novais Oliveira Junior
Keyword(s):  
Molecular Weight ◽  
Biomedical Applications ◽  
Random Distribution ◽  
Water Solubility ◽  
Aqueous Media ◽  
Degree Of Polymerization ◽  
Molecular Weights ◽  
H Nmr ◽  
Wide Ph Range ◽  
Ph Range

<p>The preparation of chitosans soluble in physiological conditions has been sought for years, but so far solubility in non-acidic aqueous media has only been achieved at the expense of lowering chitosan molecular weight. In this work, we applied the multistep ultrasound-assisted deacetylation process (USAD process) to β-chitin and obtained extensively deacetylated chitosans with high molecular weights (Mw ≥ 1,000,000 g mol<sup>-1</sup>). The homogeneous <i>N</i>-acetylation of a chitosan sample resulting from three consecutive USAD procedures allowed us to produce chitosans with a high weight average degree of polymerization (DPw ≈ 6,000) and tunable degrees of acetylation (DA from 5 to 80%). <i>N</i>-acetylation was carried out under mild conditions to minimize depolymerization, while preserving a predominantly random distribution of 2-amino-2-deoxy-D-glucopyanose (<i>GlcN</i>) and 2-acetamido-2-deoxy-D-glucopyanose (<i>GlcNAc</i>) units. This close to random distribution, inferred with deconvolution of nuclear magnetic resonance (<sup>1</sup>H NMR) spectra, is considered as responsible for the solubility within a wide pH range. Two of the highly <i>N</i>-acetylated chitosans (DA ≈ 60 % and ≈ 70 %) exhibited full water solubility even at neutral pH, which can expand the biomedical applications of chitosans. </p>

scholarly journals Stability of Gamma-valerolactone Under Pulping Conditions as a Basis for Process Optimization and Chemical Recovery

2021 ◽  
Author(s):  
Marianna Granatier ◽  
Inge Schlapp-Hackl ◽  
Huy Quang Lê ◽  
Kaarlo Nieminen ◽  
Herbert Sixta
Keyword(s):  
Elevated Temperatures ◽  
Reaction Times ◽  
Chemical Recovery ◽  
Wide Ph Range ◽  
Alkaline Conditions ◽  
Naoh Solution ◽  
Hydroxyvaleric Acid ◽  
The Stability ◽  
Ph Range ◽  
Spent Liquor

Abstract This study investigates the extent of the g-valerolactone (GVL) hydrolysis forming an equilibrium with 4-hydroxyvaleric acid (4-HVA) in aqueous solutions over a wide pH range. The hydrolysis of pure 50 wt% GVL to 4-HVA (3.5 mol%) was observed only at elevated temperatures. The addition of sulfuric acid (0.2×10-5 wt% to 6 wt%) at elevated temperatures (150 – 180°C) and reaction times between 30-180 min caused the formation of 4 mol% 4-HVA but with decreasing acidity, the 4-HVA remained constant at about 3 mol%. The hydrolysis reactions in alkaline conditions were conducted at constant time (30 min) and temperature (180 °C) with variation of the NaOH concentration (0.2×10-6 wt% to 7 wt%). The addition of less than 0.2 wt % of NaOH resulted in the formation of less than 4 mol% of sodium 4-hydroxyvalerate. A maximum amount of 21 mol% of 4-HVA was observed in a 7 wt% NaOH solution. The stability after synthesis was determined by NMR analysis. To verify the GVL stability results obtained under practical conditions, Betula pendula sawdust was fractionated in 50% GVL with and without addition of H2SO4 or NaOH at 180°C and 120 min, and spent liquor was analyzed. The spent liquor contained 5.6 mol% and 6.0 mol% of 4-HVA in a highly acidic (20 kg H2SO4/t wood) and alkaline (192 kg NaOH/ t wood) environment, respectively.

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