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.

Synthesis, Applications and Swelling Properties of Poly (Sodium Acrylate-Coacrylamide) Based Superabsorbent Hydrogels

2019 ◽  
Vol 41 (4) ◽  
pp. 668-668
Author(s):  
Saud Hashmi Saud Hashmi ◽  
Saad Nadeem Saad Nadeem ◽  
Zahoor Awan Zahoor Awan ◽  
Adeel ur Rehman Adeel ur Rehman ◽  
Ahsan Abdul Ghani Ahsan Abdul Ghani
Keyword(s):  
Rate Constant ◽  
Polymeric Materials ◽  
Water Soluble ◽  
Ion Concentration ◽  
Copolymer Composition ◽  
Swelling Properties ◽  
Swelling Capacity ◽  
Swelling Rate ◽  
Crosslinker Concentration ◽  
Superabsorbent Hydrogels

Superabsorbent hydrogels constitute a group of polymeric materials with three-dimensional network structure, which can swell to absorb an enormous amount of water or aqueous solutions. This property enables various commercial applications of hydrogels such as water holding capability in agriculture and superabsorbent material for baby diapers. Several novel superabsorbent hydrogels based on acrylic acid-co-acrylamide copolymers were synthesized under variation of copolymer compositions through free radical polymerization. N,N’methylenebisacrylamide (MBA) was used as a water soluble crosslinker and potassium persulphate (KPS) as an initiator. Effect of varying the copolymer composition, change in crosslinker concentration, and effect of environmental parameters (pH, temperature, and ion concentration) on both swelling capacity and swelling rate were examined. These gel shows maximum swelling at neutral pH-7, whereas increasing salt concentration in water decrease the swelling capacity. It was found interesting that an increase in crosslinker concentration from 0.020% to 0.16%, the swelling capacity decreases up to 70% while the swelling rate increases from 0.007g water/g dry hydrogel sec to 0.024g water/g dry hydrogel sec, respectively because there is a compromise exists between entropic spring forces between network connection points and the hydrostatic pressure of the water diffusing into the gels. Dynamic swelling curve obtained were fitted to the three different kinetic models namely Peleg’s kinetic model, pseudo 1st order as proposed by Lagergen and pseudo 2nd order kinetics. All these models provided a good agreement with the experimental data; However on the bases of statistical parameters (RMSE, R2 and X2) the Peleg’s model was selected as the most appropriate model for this study. Analyzing rate constant for Peleg’s models at different swelling temperatures disclosed that increasing temperature could only increase the swelling rate without affecting the swelling capacity of the hydrogels. Experimental values for rate constant k1 of Peleg’s model at different temperature shows a sharp decrease from 0.57545 at 30 oC to 0.1535 at 75 oC that contemplated the rate of swelling at 75 oC was 65% faster than that of 30 oC. The diffusion mechanisms in hydrogels were proven to be tailorable by increasing cross-linker concentration and temperature, leading towards the Fickian type diffusion behavior. The synthesized superabsorbent hydrogels were also tested for water retention applications in agriculture.

Influence of pH on the Absorption and Fluorescence Spectra of 6,7-Dihydroxycoumarin in Aqueous Solution

1982 ◽  
Vol 37 (3) ◽  
pp. 262-265 ◽  
Author(s):  
Jerzy Grzywacz ◽  
Stanisława Taszner
Keyword(s):  
Aqueous Solution ◽  
Fluorescence Spectra ◽  
Singlet State ◽  
Ph Value ◽  
Emission Spectra ◽  
Excited Singlet ◽  
Acid Base ◽  
Wide Ph Range ◽  
Ph Range ◽  
Influence Of Ph

Abstract Absorption and emission spectra of 6,7-dihydroxycoumarin [6,7-DHC] in aqueous solution over a wide pH range are reported. The absorption spectra proved to be strongly sensitive to the pH-value of the solution, whereas the emission spectra change in this range only insignificantly. An interpretation is attempted on the basis of the differences of the acid-base properties of the 6,7-DHC molecule in its ground and excited singlet state. For this purpose the pKa's and pKax's values have been calculated. It has been stated that in the excited state the phototautomer form is very unlikely.

Über die Wechselwirkung des Vanadyl(IV)-Kations mit Nucleobasen / Interaction of the Vanadyl(IV) Cation with Nucleic Bases

1993 ◽  
Vol 48 (12) ◽  
pp. 1845-1847 ◽  
Author(s):  
P. A. M. Williams ◽  
S. B. Etcheverry ◽  
E. J. Baran
Keyword(s):  
The Other ◽  
Ph Values ◽  
Nucleic Bases ◽  
Wide Ph Range ◽  
Ph Range ◽  
Oxygen Donors

The interaction of VO2+ with the nucleic bases adenine, guanine, cytosine, thymine and uracil has been investigated spectrophotometrically in a wide pH-range and with metal to base ratios 1:1 and 1:10. Adenine, guanine and uracil interact with the cation at pH-values >5, but whereas adenine apparently coordinates through Natoms, the other two bases seem to be coordinated through oxygen donors.

scholarly journals Chemoenzymatic synthesis of the pH responsive surfactant octyl β-D-glucopyranoside uronic acid

2019 ◽  
Vol 104 (3) ◽  
pp. 1055-1062 ◽  
Author(s):  
Ngoc T. N. Ngo ◽  
Carl Grey ◽  
Patrick Adlercreutz
Keyword(s):  
Substrate Concentration ◽  
Uronic Acid ◽  
Catalyst System ◽  
Low Ph ◽  
Chemoenzymatic Synthesis ◽  
Ph Responsive ◽  
Ph Values ◽  
Wide Ph Range ◽  
Carboxyl Derivative ◽  
Ph Range

AbstractMethodology was developed to expand the range of benign alkyl glycoside surfactants to include also anionic types. This was demonstrated possible through conversion of the glycoside to its carboxyl derivative. Specifically, octyl β-D-glucopyranoside (OG) was oxidised to the corresponding uronic acid (octyl β-D-glucopyranoside uronic acid, OG-COOH) using the catalyst system T. versicolor laccase/2,2,6,6-tetramethylpiperidinyloxy (TEMPO) and oxygen from air as oxidant. The effects of oxygen supply methodology, concentrations of laccase, TEMPO and OG as well as reaction temperature were evaluated. At 10 mM substrate concentration, the substrate was almost quantitatively converted into product, and even at a substrate concentration of 60 mM, 85% conversion was reached within 24 h. The surfactant properties of OG-COOH were markedly dependent on pH. Foaming was only observed at low pH, while no foam was formed at pH values above 5.0. Thus, OG-COOH can be an attractive low-foaming surfactant, for example for cleaning applications and emulsification, in a wide pH range (pH 1.5–10.0).

Influence of pH on hexavalent chromium reduction by Fe(II) and sulfide compounds

2015 ◽  
Vol 72 (1) ◽  
pp. 22-28 ◽  
Author(s):  
Juan Chen ◽  
Ri Chen ◽  
Mei Hong
Keyword(s):  
Reduction Process ◽  
Single Species ◽  
Batch Experiments ◽  
Chromium Reduction ◽  
Promoting Effect ◽  
Ph Values ◽  
Ph Dependent ◽  
Ph Range ◽  
Influence Of Ph ◽  
Sulfide Species

Abstract Batch experiments were conducted to investigate the influence of pH on Cr(VI) reduction with Fe(II), sulfide and mixtures of Fe(II) and sulfide at pH 3.0–12.0. The results showed that Fe(II) could reduce Cr(VI) with a high removal of nearly 100% in the pH range of 3.0–9.0, while the reduction of Cr(VI) decreased to approximately 60% considering the oxygenation of Fe(II) at pH 12.0. The reaction between Cr(VI) and sulfide, however, was largely pH dependent. H2S was the main sulfide species with the Cr(VI) removal of ∼80% at pH < 7.0, while sulfide mainly existed in the forms as HS− or S2− at pH ≥ 7.0, which had very limited removal of Cr(VI) (no more than 10%). The Cr(VI) removal by the mixtures of Fe(II) and sulfide was also compared with the sum of separate ones at different pH values. The sum of Cr(VI) removal by single Fe(II) and S(-II) was similar to that by the mixtures at pH 3.0–5.0 and pH 12.0, while the removal of Cr(VI) by the mixtures was observed to be more effective than the sum of the single-species removals at pH 7.0–9.0; the promoting effect was primarily attributed to the catalysis of ferric ion generated during the reduction process.

Reactions of β-Sulphato-ethylsulphone Crosslinking Agent with Wool

1992 ◽  
Vol 62 (6) ◽  
pp. 309-316 ◽  
Author(s):  
B. M. Smith ◽  
P. L. Spedding ◽  
M. S. Otterburn ◽  
D. M. Lewis
Keyword(s):  
Hplc Analysis ◽  
Crosslinking Agent ◽  
Cross Linking ◽  
Chemical Crosslinking ◽  
The Novel ◽  
Burst Strength ◽  
Ph Values ◽  
Wool Fibers ◽  
Ph Range ◽  
Original Strength

In Part I of our study of the application to wool of the novel chemical crosslinking agent, 2-chloro-4,6-di(-aminobenzene-4-β-sulphato-ethylsulphone)-1,3,5-triazine (XLC), HPLC analysis showed the compound to have good substantivity for wool fibers when applied from boiling aqueous dyebaths in the pH range 3 to 6. In Part II, various solubility and swelling tests have been used to determine whether XLC introduces additional crosslinks into the fiber. The extent of crosslinking depends on the application pH: there is little crosslinking at pH values up to 4, but extensive cross-linking occurs when the compound is applied at pH 5 and 6. Studies on the wet burst strength of XLC treated fabrics indicate that the compound can limit the damage caused to wool by boiling aqueous treatments. For fabrics treated with XLC at pH 6, the compound preserves the original strength of the fabric. Although these results indicate that XLC treatment of wool introduces crosslinks into wool fibers, the mechanism and morphological sites of reaction with wool require further study.

Note: Influence of pH on the Extraction Yield and Functional Properties of Macadamia (Macadamia Integrofolia) Protein Isolates

2004 ◽  
Vol 10 (4) ◽  
pp. 263-267 ◽  
Author(s):  
P. S. Bora ◽  
D. Ribeiro
Keyword(s):  
Functional Properties ◽  
Extraction Yield ◽  
Emulsifying Properties ◽  
Alkaline Ph ◽  
Protein Isolates ◽  
Ph Values ◽  
Macadamia Nut ◽  
Isoelectric Ph ◽  
Ph Range ◽  
Influence Of Ph

Three protein isolates from de-fatted macadamia nut kernel flour were prepared by extraction at acidic (pH2.0), neutral (pH7.2 with 0.2M phosphate buffer containing 0.5MNaCl) and alkaline (pH12.0) conditions. Extraction at pH2.0 solubilised nearly 52.0% of the proteins present in defatted macadamia flour, while extraction with buffer (pH7.2) and alkaline pH (12.0) solubilised about 83.0% of proteins. The yield of isoelectrically precipitated protein from acidic extract (pH2.0, isolate A) was about 65.2% and from neutral (isolate B) and alkaline extracts (isolate C) was slightly over 83.0% which accounted for 33.7, 69.1 and 69.4% of the proteins present in defatted flour. The protein content of the isolates was 80.1, 92.1 and 92.0% in A, B and C isolates respectively. The functional properties of these isolates were significantly different. Isolate A presented better solubility at pH below isoelectric pH, isolate C at pH above isoelectric pH and isolate B intermediate solubility at the pH range studied. Isolate B showed best water and oil absorption capacities followed by isolate C and least by isolate A. For each isolate, the emulsifying properties were also significantly different at different pH values.

Influence of pH and Incubation Time on Ochratoxin A Production by Aspergillus carbonarius in Culture Media

2005 ◽  
Vol 68 (7) ◽  
pp. 1435-1440 ◽  
Author(s):  
A. ESTEBAN ◽  
M. L. ABARCA ◽  
M. R. BRAGULAT ◽  
F. J. CABAÑES
Keyword(s):  
Ochratoxin A ◽  
Culture Media ◽  
Aspergillus Carbonarius ◽  
Yeast Autolysate ◽  
Initial Ph ◽  
Wide Ph Range ◽  
Ph Range ◽  
Incubation Temperatures ◽  
Influence Of Ph ◽  
Czapek Yeast Autolysate Agar

The effect of pH (2 to 10) and temperature (15 and 30°C) on growth and production of ochratoxin A (OTA) of six strains of Aspergillus carbonarius was studied in two culture media: Czapek yeast autolysate agar and yeast extract sucrose agar. Isolates were selected by their different source and different reported ability to produce OTA. Regardless of the initial pH or the temperature tested, Czapek yeast autolysate agar has been shown to be the best culture medium for OTA production by A. carbonarius. In this medium, OTA was produced from pH 2 to 10 at the two incubation temperatures tested. The results obtained show the ability of A. carbonarius to not only grow but also produce OTA over a wide pH range at high or low temperatures. This may help explain why this species is considered the main OTA source in some substrata.

Morphogenesis-Associated/Dissociated Production of Epothilone in Wild Sorangium Cellulosum Strains

2011 ◽  
Vol 343-344 ◽  
pp. 951-957
Author(s):  
Xin Li Liu ◽  
Lin Zhao ◽  
Wei Hu ◽  
Yue Zhong Li
Keyword(s):  
Fruiting Body ◽  
Fruiting Bodies ◽  
Sorangium Cellulosum ◽  
Strongly Coupled ◽  
High Ph ◽  
Ph Values ◽  
Wide Ph Range ◽  
Ph Range

To investigate the characters ofSorangiumstrains and the approaches for improving the production of epothilone, correlation of epothilone production and morphogenesis was studied in strains So0157-2, So0007-3andSo0003-3. On lean medium, So0157-2 could produce epothilones in a wide pH range (5.0-12.0), but formed fruiting bodies at high pH values (9.0-14.0). Formation of fruiting body did not affect the yield of epothilones in So0157-2. In So0007-3 and So0003-3, producing of epothilone was strongly coupled with the process of morphogenesis. It suggests that reduction of the association between morphogenesis and epothilone producing would prominently improve the epothilone production.

Rational design of porous binary Pt-based nanodendrites as efficient catalysts for direct glucose fuel cells over a wide pH range

2017 ◽  
Vol 7 (13) ◽  
pp. 2819-2827 ◽  
Author(s):  
Kamel Eid ◽  
Yahia H. Ahmad ◽  
Siham Y. AlQaradawi ◽  
Nageh K. Allam
Keyword(s):  
Catalytic Activity ◽  
Oxidation Reaction ◽  
Rational Design ◽  
Glucose Oxidation ◽  
Room Temperature ◽  
Ph Values ◽  
Wide Ph Range ◽  
One Step ◽  
Ph Range ◽  
Glucose Oxidation Reaction

Porous binary PtPd, AuPt, PtCu, and PtNi nanodendrites prepared by a facile one-step reduction under ultrasonic irradiation at room temperature, exhibited a substantial catalytic activity towards glucose oxidation reaction at different pH values relative to a commercial Pt/C catalyst.

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