scholarly journals Free Volume and Water Sorption by Cellulose Esters

Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2644
Author(s):  
Anatoly E. Chalykh ◽  
Ivan I. Bardyshev ◽  
Tatiana F. Petrova
Keyword(s):  
Cellulose Acetate ◽  
Water Vapour ◽  
Sorption Capacity ◽  
Water Sorption ◽  
Hydroxyl Groups ◽  
High Humidity ◽  
Cellulose Ethers ◽  
Sorption Model ◽  
Cellulose Esters ◽  
Oh Groups

The results ofthe sorption properties of cellulose acetate (CA) with different degrees of substitution (SD) are summarised. It has been shown that the sorption capacity of CA in water vapour decreases naturally with increasing content of acetate groups in monomeric units of cellulose ethers. The experimental isotherms are analysed according to the double sorption model. Hydrate numbers of hydroxyl and acetate groups were determined. The paired parameters of the Flory–Huggins interaction were calculated. It is shown that the decrease of the Langmuir component is due to the replacement of hydroxyl groups by ester groups, whose local sorption capacity by water vapour is lower than the sorption capacity of OH groups. In the area of high humidity, there is an increase in vacancy sizes due to plasticisation of the sorbents.

scholarly journals Improving Functional Properties of Cassava Starch-Based Films by Incorporating Xanthan, Gellan, or Pullulan Gums

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Mayra Sapper ◽  
Pau Talens ◽  
Amparo Chiralt
Keyword(s):  
Water Vapour ◽  
Sorption Capacity ◽  
Functional Properties ◽  
Water Sorption ◽  
Cassava Starch ◽  
Water Vapour Permeability ◽  
Gellan Gum ◽  
Partial Substitution ◽  
Vapour Permeability ◽  
Starch Films

The effect of the partial substitution of cassava starch in edible films for 10 and 20 wt% of gellan, xanthan, or pullulan gums was analysed in films obtained by casting. The tensile properties, barrier capacity to water vapour, and oxygen and water sorption isotherms of the samples were analysed. The blend of starch with gellan gum was effective to reduce the moisture sorption capacity of starch films while reducing water vapour permeability, enhancing the film strength and resistance to break and preserving films against starch retrogradation throughout the storage time. Xanthan gum improved the tensile behaviour of the starch films, but did not reduce their water sorption capacity and water vapour permeability. Pullulan did not notably improve the functional properties of the starch films. Gellan gum at 10 and 20 wt% in the blend could be used to obtain starch films with more adequate properties for food packaging purposes.

scholarly journals Development of Highly Efficient, Glassy Carbon Foam Supported, Palladium Catalysts for Hydrogenation of Nitrobenzene

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1172
Author(s):  
Ádám Prekob ◽  
Mahitha Udayakumar ◽  
Gábor Karacs ◽  
Ferenc Kristály ◽  
Gábor Muránszky ◽  
...  
Keyword(s):  
Zeta Potential ◽  
Glassy Carbon ◽  
Palladium Nanoparticles ◽  
Palladium Catalysts ◽  
Sucrose Solution ◽  
Supported Catalyst ◽  
Carbon Foam ◽  
Hydroxyl Groups ◽  
Polyurethane Elastomers ◽  
Oh Groups

Glassy carbon foam (GCF) catalyst supports were synthesized from waste polyurethane elastomers by impregnating them in sucrose solution followed by pyrolysis and activation (AC) using N2 and CO2 gas. The palladium nanoparticles were formed from Pd(NO3)2. The formed palladium nanoparticles are highly dispersive because the mean diameters are 8.0 ± 4.3 (Pd/GCF), 7.6 ± 4.2 (Pd/GCF-AC1) and 4.4 ± 1.6 nm (Pd/GCF-AC2). Oxidative post-treatment by CO2 of the supports resulted in the formation of hydroxyl groups on the GCF surfaces, leading to a decrease in zeta potential. The decreased zeta potential increased the wettability of the GCF supports. This, and the interactions between –OH groups and Pd ions, decreased the particle size of palladium. The catalysts were tested in the hydrogenation of nitrobenzene. The non-treated, glassy-carbon-supported catalyst (Pd/GCF) resulted in a 99.2% aniline yield at 293 K and 50 bar hydrogen pressure, but the reaction was slightly slower than other catalysts. The catalysts on the post-treated (activated) supports showed higher catalytic activity and the rate of hydrogenation was higher. The maximum attained aniline selectivities were 99.0% (Pd/GCF-AC1) at 293 K and 98.0% (Pd/GCF-AC2) at 323 K.

scholarly journals Adjustment of Hydrophobic Properties of Cellulose Materials

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1241
Author(s):  
Michael Ioelovich
Keyword(s):  
Ester Group ◽  
Hydroxyl Groups ◽  
Chemical Methods ◽  
Hydrophobic Properties ◽  
Cellulose Esters ◽  
Cellulose Modification ◽  
Polar Groups ◽  
Polar Substituents ◽  
Hydrolysis Of ◽  
Cellulose Materials

In this study, physicochemical and chemical methods of cellulose modification were used to increase the hydrophobicity of this natural semicrystalline biopolymer. It has been shown that acid hydrolysis of the initial cellulose increases its crystallinity, which improves hydrophobicity, but only to a small extent. A more significant hydrophobization effect was observed after chemical modification by esterification, when polar hydroxyl groups of cellulose were replaced by non-polar substituents. The esterification process was accompanied by the disruption of the crystalline structure of cellulose and its transformation into the mesomorphous structure of cellulose esters. It was found that the replacement of cellulose hydroxyls with ester groups leads to a significant increase in the hydrophobicity of the resulting polymer. Moreover, the increase of the number of non-polar groups in the ester substituent contributes to rise in hydrophobicity of cellulose derivative. Depending on the type of ester group, the hydrophobicity increased in the following order: acetate < propionate < butyrate. Therefore, tributyrate cellulose (TBC) demonstrated the most hydrophobicity among all studied samples. In addition, the mixed ester, triacetobutyrate cellulose (TAB), also showed a sufficiently high hydrophobicity. The promising performance properties of hydrophobic cellulose esters, TBC and TAB, were also demonstrated.

Adsorption of Benzene from Aqueous Solution Using Base Modified Expanded Perlite

2012 ◽  
Vol 622-623 ◽  
pp. 1779-1783
Author(s):  
Richard Appiah-Ntiamoah ◽  
Xuan Thang Mai ◽  
Francis W.Y. Momade ◽  
Hern Kim
Keyword(s):  
Zeta Potential ◽  
Adsorption Capacity ◽  
Linear Regression Analysis ◽  
Basic Medium ◽  
Maximum Adsorption Capacity ◽  
Hydroxyl Groups ◽  
Expanded Perlite ◽  
Oh Groups ◽  
Base Solution ◽  
Ph Range

In this study, the adsorption capacity of expanded perlite (EP) for benzene at low concentrations in water was investigated after EP was treated with sodium hydroxide (NaOH). IR spectra used to characterize the modified EP showed that there was no bonding between NaOH and the hydroxyl groups on the surface of EP. However, the NaOH provided a basic medium for negatively charged surface oxide ions (-SO-) to form on EP. This fact was corroborated by pH readings of the modification solution. This reduced in pH from 10 to 9 at the end of the reaction which indicated that the hydroxyl OH- groups on the EP underwent deprotonation and hence releases H+ into the solution, and also positive sites on EP adsorbed OH- ions from the base solution. Mahir et al. in their paper Zeta potential of unexpanded and expanded perlite samples in various electrolyte media confirmed that EP has no isoelectric point and exhibits negative zeta potential in the pH range of 2-11. The surface oxides (-SO-) were believed to have given EP it adsorptive potential. Adsorption isotherm values correlated reasonably well with the Langmuir isotherm model and it parameters (qo and K) were obtained using linear regression analysis. A maximum adsorption capacity (qo) value of 19.42 mg/g was achieved.

scholarly journals THE LOCATION OF THE XANTHATE GROUPS IN PARTLY SUBSTITUTED CELLULOSE XANTHATES

1957 ◽  
Vol 35 (12) ◽  
pp. 1522-1533 ◽  
Author(s):  
E. P. Swan ◽  
C. B. Purves
Keyword(s):  
Cellulose Acetate ◽  
Chlorine Dioxide ◽  
Methyl Esters ◽  
Lead Tetraacetate ◽  
Degree Of Substitution ◽  
Hydroxyl Groups ◽  
Primary Position ◽  
Standard Methods ◽  
The Third ◽  
Almost All

Cellulose sodium xanthates of degree of substitution (D.S.) 0.4 to 0.66 were methylated to xanthate S-methyl esters which were then acetylated completely, the final xanthate D.S. remaining close to the original value. Dexanthation with aqueous chlorine dioxide near pH 4.5 and −5° removed almost all of the S-methyl xanthate groups, but the loss of a few acetyl groups from, and the retention of 1 to 2% of sulphur in, the resulting cellulose acetate could not be avoided. The original xanthate groups were presumably represented in this acetate as unsubstituted hydroxyl groups, and these were located by standard methods involving tosylation–iodination, tritylation, and oxidations with lead tetraacetate. Xanthate groups appeared to occupy the third and sixth, but not the second, position in the cellulose, and 53 to 61% of the substituent was in the sixth or primary position; one sample of viscose was "ripened" before the cellulose sodium xanthate was isolated, and the value was 81%. The results were of a preliminary nature, because severe technical difficulties reduced their reliability.

Water sorption in Nafion® membranes analyzed with an improved dual-mode sorption model—Structure/property relationships

2013 ◽  
Vol 439 ◽  
pp. 1-11 ◽  
Author(s):  
Yongli Li ◽  
Quang Trong Nguyen ◽  
Camille Lixon Buquet ◽  
Dominique Langevin ◽  
Marc Legras ◽  
...  
Keyword(s):  
Water Sorption ◽  
Model Structure ◽  
Structure Property ◽  
Dual Mode ◽  
Sorption Model ◽  
Structure Property Relationships

Proton spin–spin coupling constants and intramolecular hydrogen bonding in bromine derivatives of 1,3-dihydroxybenzene

1976 ◽  
Vol 54 (14) ◽  
pp. 2228-2230 ◽  
Author(s):  
Ted Schaefer ◽  
J. Brian Rowbotham
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Proton Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Derivatives Of

The conformational preferences in CCl4 solution at 32 °C of the hydroxyl groups in bromine derivatives of 1,3-dihydroxybenzene are deduced from the long-range spin–spin coupling constants between hydroxyl protons and ring protons over five bonds. Two hydroxyl groups hydrogen bond to the same bromine substituent in 2-bromo-1,3-dihydroxybenzene but prefer to hydrogen bond to different bromine substituents when available, as in 2,4-dibromo-1,3-dihydroxybenzene. When the OH groups can each choose between two ortho bromine atoms, as in 2,4,6-tribromoresorcinol, they apparently do so in a very nearly statistical manner except that they avoid hydrogen bonding to the common bromine atom.

scholarly journals The Role of Carboxyl and Hydroxyl Groups of Humic Acid in Removing AuCl4- from Aqueous Solution

2017 ◽  
Vol 17 (1) ◽  
pp. 95 ◽  
Author(s):  
Sri Sudiono ◽  
Mustika Yuniarti ◽  
Dwi Siswanta ◽  
Eko Sri Kunarti ◽  
Triyono Triyono ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Humic Acid ◽  
Peat Soil ◽  
Sharp Decrease ◽  
Hydroxyl Groups ◽  
Mixed Solution ◽  
Oh Groups ◽  
Characterization Result ◽  
Ft Ir

Humic acid (HA) extracted from peat soil according to the recommended procedure of the International Humic Substances Society (IHSS) has been tested to remove AuCl4- from aqueous solution. The removal was optimum at pH 2.0 and it was mainly dictated by attachment through hydrogen bonding to unionized carboxyl (–COOH) groups and reduction by the action of the hydroxyl (–OH) groups to gold (Au) metal. The removal of AuCl4- improved after HA was purified through repeated immersion and shaking in a mixed solution containing 0.1 M HCl and 0.3 M HF. When the purification led to the sharp decrease in ash content from 39.34 to 0.85% (w/w) and significant increase in both the –COOH and –OH contents from 3240 to 3487 mmol/kg and from 4260 to 4620 mmol/kg, respectively; the removal of AuCl4- improved from 0.105 to 0.133 mmol/g. This improvement of AuCl4- removal by the purified HA was accompanied by higher ability in reduction to Au metal. The attached AuCl4- on –COOH groups of both crude and purified HAs was qualitatively observed by the characterization result of FT-IR spectroscopy, while the presence of Au metal on the surface of those HAs was verified by the characterization result of XRD.

Sign in / Sign up

Export Citation Format

Share Document