scholarly journals Chemical Structures of Adhesive and Interphase Parts in Sucrose/Citric Acid Type Adhesive Wood-Based Molding Derived from Japanese Cedar (Cryptomeria japonica)

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4224
Author(s):  
Daisuke Ando ◽  
Kenji Umemura
Keyword(s):  
Citric Acid ◽  
Quantum Coherence ◽  
Japanese Cedar ◽  
Wood Adhesive ◽  
Hydroxyl Groups ◽  
Molding Process ◽  
Chemical Structures ◽  
Glycosidic Bonds ◽  
Acid Type ◽  
Adhesive Effect

In sucrose/citric acid based wood adhesive, the detailed bonding mechanism has still been unknown. Here, we investigated the detailed chemical structures of this adhesive wood (Japanese cedar)-based molding by using heteronuclear single quantum coherence–nuclear magnetic resonance (HSQC-NMR). NMR peaks associated with the furan-type structure appeared, suggesting that the furan compound was formed from sucrose and converted to a furan polymer during the adhesive process and that some of the furan structures in the polymers were ester-bonded with citric acid. The secondary forces between the furan polymers and wood components were thought to contribute to the adhesive effect. In our analysis of the interphase structure, primary hydroxyl groups of both polysaccharides and of lignin substructures were found to be esterified with citric acid. Additionally, some of the glycosidic bonds in polysaccharides were cleaved during the acidic condition produced by citric acid. The above results provided evidence of the polymerization of sucrose-derived 5-HMF, the esterification of wood components, and the degradation of polysaccharides during the molding process. Citric acid functioned as a clamp between the obtained furan polymer and the wood components. The sucrose/citric acid based wood adhesive can be defined as a hybrid-type wood adhesive, involving both secondary forces and chemical bonding interactions.

scholarly journals Bond Structures between Wood Components and Citric Acid in Wood-Based Molding

Polymers ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 58
Author(s):  
Daisuke Ando ◽  
Kenji Umemura
Keyword(s):  
Citric Acid ◽  
Chemical Bonding ◽  
Quantum Coherence ◽  
Japanese Cedar ◽  
Wood Adhesive ◽  
Hydroxyl Groups ◽  
Nmr Analysis ◽  
Correlation Peak ◽  
Primary Hydroxyl ◽  
Molding Condition

Citric acid-based wood adhesive is considered a chemical-bonding wood adhesive. However, the detailed structures of the bonds between wood components and citric acid remain unknown. Here, we examine the chemical bonding structures between citric acid and wood by heteronuclear single quantum coherence-nuclear magnetic resonance (HSQC-NMR) analysis of wood-based molding using Japanese cedar (Cryptomeria japonica) and citric acid. In the HSQC-NMR spectrum of the wood molding, some esterified C/H correlation peaks appeared. The primary hydroxyl groups of polysaccharides, such as cellulose and galactoglucomannan, and the primary hydroxyl groups of the β-O-4 and β-5 substructures in lignin were found to be esterified with citric acid. In contrast, the secondary hydroxyl groups, except for xylan, barely reacted because of the steric hindrance. Additionally, the C/H correlation peak volumes of the reducing ends of mannan and xylan in the anomeric region increased after molding. It was clarified that the glycosidic bonds in the hemicelluloses were cleaved under the acidic molding condition with citric acid. The HSQC-NMR analysis revealed that the esterification of hemicellulose and lignin, and degradation of hemicellulose, proceeded under the molding condition. These results will promote understanding of the adhesive mechanism of citric acid-based wood adhesive and of the properties of the molding.

Diffusion coefficients and viscosities of organic aerosol components through equilibrium and non-equilibrium molecular dynamics simulations

2021 ◽  
Author(s):  
Katerina S. Karadima ◽  
Vlasis G. Mavrantzas ◽  
Spyros N. Pandis
Keyword(s):  
Molecular Dynamics ◽  
Functional Groups ◽  
Organic Compounds ◽  
Diffusion Coefficients ◽  
Amorphous Solid ◽  
Good Effect ◽  
Hydroxyl Groups ◽  
Chemical Structures ◽  
Organic Particles ◽  
Non Equilibrium

<p>Organic aerosols have been typically considered to be liquid, with equilibration between gas and aerosol phase assumed to be reached within seconds. However, Virtanen et al. (Nature, 2010) suggested that particles in amorphous solid state may also occur in the atmosphere implying that mass transfer between the atmospheric particulate and gas phases may be much slower than initially thought. Experimentally, the direct measurement of the diffusion coefficients of different compounds inside atmospheric organic particles is challenging. Thus, an indirect approach is usually employed, involving viscosity measurements and then estimation of diffusion coefficients via the Stokes-Einstein equation, according to which the diffusion coefficient is inversely proportional to the medium viscosity. However, the corresponding diffusion estimates are highly uncertain, especially for highly viscous aerosols which is the most important case. Molecular simulation methods, such as molecular dynamics (MD), can be an alternative method to determine directly the diffusion rates and the viscosity of the constituents of atmospheric organic particles. MD also provides detailed information of the exact dynamics and motion of the molecules, thus offering a deeper understanding on the underlying mechanisms and interactions.</p><p>In the present work, we use equilibrium and non-equilibrium MD simulations to estimate the viscosity and diffusion coefficients of bulk systems of representative organic compounds with different chemical structures and physicochemical characteristics. Hydrophilic and hydrophobic compounds representative of primary and secondary oxidized organic products and of primary organic compounds emitted by various sources are considered. The viscosity and self-diffusion coefficients calculated by our simulations are in good agreement with available experimentally measured values. Our results confirm that the presence of carboxyl and hydroxyl groups in the molecule increases the viscosity. The number of carboxyl and hydroxyl groups, in particular, seems to have a good effect on diffusivity (the diffusivity decreases as the number of these functional groups increase), and to a lesser extent on the viscosity. We also discuss the role of the hydrogen bonds formed between these functional groups.</p>

scholarly journals Cd(II) Adsorption on Different Modified Rice Straws under FTIR Spectroscopy as Influenced by Initial pH, Cd(II) Concentration, and Ionic Strength

2019 ◽  
Vol 16 (21) ◽  
pp. 4129
Author(s):  
Shuai Wang ◽  
Wanhong Li ◽  
Xinhua Yin ◽  
Nan Wang ◽  
Shuai Yuan ◽  
...  
Keyword(s):  
Citric Acid ◽  
Ionic Strength ◽  
Ion Exchange ◽  
Adsorption Capacity ◽  
Rice Straw ◽  
Ph Value ◽  
Sorption Process ◽  
Oh Groups ◽  
Chemical Structures ◽  
Adsorption Amount

Rice straw is a kind of low-cost biosorbent. Through mechanical crushing, pyrolysis, incineration, and citric acid (CA) modification, it could be converted to rice straw powder (Sp), biochar (Sb), ash (Sa), and modified rice straw (Ms) accordingly. Using rice straw as an adsorbent, the influence of pH value (2, 4, and 9), initial Cd(II) concentration (0, 200, and 800 mg/L), and ionic strength (0, 0.2, to 0.6 mg/L) on the adsorption capacity for Cd(II) were examined with three replicates, and the relevant mechanisms were explored using Fourier transform infrared (FTIR) technology. Results showed that the modifications could improve the adsorption capacity of Cd(II) by changing their chemical structures. The products (Sb and Sa) of the pyrolysis and incineration of rice straw contained fewer hydroxyl and alkyl groups, but more Si–O groups. Citric acid modification removed a portion of silica in rice straw, increased its carboxylic content, and made more –OH groups exposed. Compared with Sp, Sb, Sa, and Ms were more likely to act as π donors in the Cd(II) sorption process and exhibited more carboxyl binding. The bands of C = C, –O–CH3, and the O–H, carboxyl, Si–O–Si or Si–O groups were involved in the Cd(II) sorption process. The adsorption amount of Cd(II) by the four adsorbents increased with the increase in the pH value of the solution and the initial Cd(II) concentration. Affected by pH in a solution, ion exchange, surface complexation, and precipitation were the major adsorption mechanisms. Further, under the influence of the initial Cd(II) concentration, electrostatic attraction played a leading role. With no interference by ionic strength, all the adsorbents had the greatest adsorption amount of Cd(II), and the intensity of O–H vibration was also the weakest; ion exchange was the most important mechanism in this process. Regardless of the influencing factors, Sa, with the greatest specific surface area, had an absolute advantage in the adsorption capacity of Cd(II) over Sp, Sb, and Ms.

scholarly journals Selective removal of silicic acid by a gallic-acid modified resin

2019 ◽  
Vol 9 (4) ◽  
pp. 431-441
Author(s):  
Shuqin Bai ◽  
Jue Han ◽  
Cong Du ◽  
Wei Ding
Keyword(s):  
Adsorption Capacity ◽  
Gallic Acid ◽  
Silicic Acid ◽  
Adsorption Mechanism ◽  
Adsorption Process ◽  
Selective Adsorption ◽  
Hydroxyl Groups ◽  
Acid Type ◽  
The Common ◽  
Common Anion

Abstract To remove silicic acid from aqueous solutions, a novel gallic acid-type resin (GA-type resin) was prepared by a grafting method. The effects of the adsorption capacity, pH and presence of NaCl, NaNO3, Na2SO4, and NaCO3 salts on the silicic acid removal were studied. The GA-type resin adsorbs monosilicic acid, silicate ions, and polymeric silicic acid. The adsorption capacity of 4.64–4.94 mg/g was achieved in a short adsorption time (Qm of 8.99 mg/g) and is 30–40 times larger than that of the OH-type resin. The silicic acid removal efficiency was almost unaffected by the pH and common anions when the common anion and silicic acid contents were similar, proving the GA-type resin exhibits an excellent performance for selective adsorption of silicic acid. The Temkin isotherm model can well describe the adsorption process, which is chemical adsorption, and indicates that the adsorption heat decreases with the increasing adsorption amount. The adsorption mechanism of silicic acid on the GA-type resin involves dehydration condensation reactions of the hydroxyl groups in silicic acid and gallic acid. The GA-type resin can be efficiently regenerated and reused after treatment with an HCl solution.

scholarly journals Exploring the Antioxidant Features of Polyphenols by Spectroscopic and Electrochemical Methods

Antioxidants ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 523 ◽  
Author(s):  
Berta Alcalde ◽  
Mercè Granados ◽  
Javier Saurina
Keyword(s):  
Antioxidant Activities ◽  
Reference Electrode ◽  
Principal Component ◽  
Trolox Equivalent Antioxidant Capacity ◽  
Hydroxyl Groups ◽  
Antioxidant Power ◽  
Chemical Structures ◽  
Trolox Equivalent ◽  
Ferric Reducing Antioxidant Power ◽  
Comprehensive Study

This paper evaluates the antioxidant ability of polyphenols as a function of their chemical structures. Several common food indexes including Folin-Ciocalteau (FC), ferric reducing antioxidant power (FRAP) and trolox equivalent antioxidant capacity (TEAC) assays were applied to selected polyphenols that differ in the number and position of hydroxyl groups. Voltammetric assays with screen-printed carbon electrodes were also recorded in the range of −0.2 to 0.9 V (vs. Ag/AgCl reference electrode) to investigate the oxidation behavior of these substances. Poor correlations among assays were obtained, meaning that the behavior of each compound varies in response to the different methods. However, we undertook a comprehensive study based on principal component analysis that evidenced clear patterns relating the structures of several compounds and their antioxidant activities.

scholarly journals Efficient Synthesis and Characterization of Some Novel Nitro-Schiff Bases and Their Complexes of Nickel(II) and Copper(II)

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Hossein Naeimi ◽  
Mohsen Moradian
Keyword(s):  
Schiff Base ◽  
Schiff Base Complexes ◽  
Synthesis And Characterization ◽  
Planar Geometry ◽  
Hydroxyl Groups ◽  
Spectroscopic Techniques ◽  
Spectral Techniques ◽  
Chemical Structures ◽  
Ft Ir

Synthesis and characterization of some new Schiff base ligands derived from various diamines and nitrosalicylaldehyde and their complexes of Ni(II) and Cu(II) are reported. Several spectral techniques such as UV-Vis, FT-IR, and NMR spectra were used to identify the chemical structures of the reported ligands and their complexes. The ligands are found to be bound to the metal atom through the oxygen atoms of the hydroxyl groups and nitrogen atoms of imine groups, which is also supported by spectroscopic techniques. The results obtained by FT-IR and NMR showed that the Schiff base complexes of transition metal (II) have square-planar geometry.

Lignin-Polyphenol Interaction in Azobe (Lophira alata) Heartwood. A Study on Milled Wood Lignin (MWL) and Klason Residues

Holzforschung ◽  
1999 ◽  
Vol 53 (5) ◽  
pp. 519-524 ◽  
Author(s):  
Werner Lange ◽  
Oskar Faix
Keyword(s):  
Cell Wall ◽  
Degradation Products ◽  
Oxidation Products ◽  
Hydroxyl Groups ◽  
Milled Wood Lignin ◽  
Permanganate Oxidation ◽  
Methods Of Determination ◽  
Step Procedure ◽  
Acid Type

Summary Findings about anomalous high Klason residues of azobe (Lophira alata) heartwood prompted a search for methods of determination of non lignin-type polyphenols in lignin preparations. A four step procedure was performed: (1) ethylation of milled wood lignins (MWLs) from azobe and beech heartwood, (2) permanganate oxidation, (3) methylation, and (4) GC analysis of the oxidation products. Besides the well known degradation products of hemipinic, iso-hemipinic, and meta-hemipinic acid type, methyl-3,4-diethoxy-benzoate (compound I) has also been detected among the oxidation products. The oxidation of beech MWL gave rise only to 0.4 mol % of I but azobe MWL yielded the remarkably high amount of 10.7 mol % of I. As lignins do not contain two adjacent aromatic hydroxyl groups, we concluded that I is of polyflavonoid origin. Hence the extraordinarily high Klason residues of azobe heartwood can be rationalized with large amounts of acid insoluble polyphenols which are an integral part of the azobe cell wall and which is also closely associated to MWLs. Ethylation followed by KMnO4 oxidation is an effective tool to detect polyflavonoids in lignins.

scholarly journals Wet extrusion molding of wood powder with hydroxy-propylmethyl cellulose and with citric acid as a crosslinking agent

BioResources ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. 2314-2325
Author(s):  
Xiangyu Tao ◽  
Hiroshi Nonaka
Keyword(s):  
Citric Acid ◽  
Crosslinking Agent ◽  
Three Dimensional ◽  
Heating Time ◽  
Wood Powder ◽  
Molding Process ◽  
Natural Substances ◽  
Biomass Materials ◽  
Wet Extrusion ◽  
Derivatives Of

To mitigate global warming and the serious problems incurred by the disposal of petroleum-based plastics, it is important to develop derivatives of biomass materials that can be used as substitutes. To overcome the lack of thermoplasticity of wood, a wet extrusion molding process for wood powder using a cellulose derivative, hydroxypropylmethyl cellulose (HPMC), had been developed. However, this material quickly reabsorbed water, swelled, and disintegrated in liquid. In the present study, a natural organic acid, citric acid, was added and kneaded together with the wood powder, the HPMC, and water. The resultant clay-like material was extruded into a tube-shaped material. The tube was air-dried and heated at 180 °C for 5 min to 30 min to allow crosslinking. By heating 1% citric acid for 30 min, the material avoided disintegrating in water for 60 min. The addition of 3% citric acid with 30 min crosslinking gave the material water resistance in water for 12 h. The degradability in the water was found to be controllable by changing the amount of citric acid and the heating time. This is a novel result because wood can be molded into a practical three-dimensional (3D) biomass composite material using this technology with natural substances without relying on petroleum-based plastics.

scholarly journals Adsorpsi Logam Ni dan Cu pada Limbah Cair Laboratorium Kimia menggunakan Biosorben Batang Jagung Termodifikasi Asam Sitrat

ALCHEMY ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 13
Author(s):  
Eny Yulianti ◽  
RIf'atul Mahmudah ◽  
Ainul Ma'rifah ◽  
Ulal Azmiyani
Keyword(s):  
Citric Acid ◽  
Metal Ions ◽  
Functional Group ◽  
Liquid Waste ◽  
Hydroxyl Groups ◽  
Corn Stalk ◽  
Adsorption Ability ◽  
Chemical Laboratory ◽  
Lactone Group ◽  
Carboxylic Groups

<p class="BodyAbstract">Corn stalk contains 40-50% cellulose, 20-40% hemicellulose, 4-15% lignin which had potential as biosorbent in binding metal ions. In this study, demineralization and modification by adding citric acid (1.5 M and 2 M) of corn stalk were conducted to convert hydroxyl groups into carboxylic. Then, it was analyzed its functional groups using Boehm titration and FTIR. The modified corn stalk was applied directly to chemical laboratory liquid waste which contains multicomponent of heavy metal ions. By modifying the corn stalk, the number of hydroxyl and carboxylic groups increased, but the number of lactone group was constant. The success of the modification was characterized by the appearance of ester uptake at 1734 cm<sup>-1</sup> and increased adsorption ability. The variations in the concentration of citric acid in modification corn stalk showed that biosorbent with addition 1.5 M citric acid had higher in the number of acid site than addition 2 M citric acid to absorb Ni and Cu.</p><p> <br /> Keywords: Corn stalk, citric acid, biosorbent, functional group</p><p class="BodyAbstract"><strong> </strong></p><p class="BodyAbstract"><strong> </strong></p><p>Batang jagung mengandung sekitar 40-50% selulosa, 20-40% hemiselulosa, 4-15% lignin yang berpotensi sebagai biosorben pengikat ion logam. Pada penelitian ini dilakukan demineralisasi dan modifikasi dengan penambahan asam sitrat (1,5 M dan 2 M) untuk mengubah gugus hidroksil pada selulosa membentuk karboksilat. Selanjutnya, dianalisis gugus fungsinya menggunakan titrasi Boehm dan FTIR. Hasil modifikasi diaplikasikan langsung pada limbah cair laboratorium kimia yang mengandung banyak jenis ion logam berat. Biosorben batang jagung setelah dimodifikasi mengalami peningkatan jumlah gugus fungsi hidroksil dan karboksilat, tetapi gugus lakton tetap. Keberhasilan modifikasi ditandai dengan munculnya serapan ester pada 1734 cm<sup>-1 </sup>dan peningkatan kemampuan adsorpsi. Dari hasil variasi konsentrasi asam sitrat diperoleh informasi bahwa biosorben dengan penambahan asam sitrat 1,5 M mempunyai situs asam lebih tinggi dan mempunyai kemampuan adsorpsi terhadap ion logam Ni dan Cu lebih besar dibanding penambahan asam sitrat 2 M.</p><p><span style="text-decoration: line-through;"> </span></p><p>Kata kunci:  Batang jagung, asam sitrat, biosorben, gugus fungsi</p>

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