“…It is because the phenylpropane units are most likely to be attacked in the chemical reactions of lignin. In this study, the phenolic groups presented in both kraft and soda lignins was determined by UV spectroscopy and 13 C NMR [10, 12]. Figure 5 shows the UV spectra of kraft lignin and soda lignin in neutral solution and alkaline solution which was a dioxane-water solution (9:1, v/v) and pH 12 NaOH solution respectively.…”
Section: Resultsmentioning
confidence: 99%
“…This indicates that the initial crystal cell structure of TiO 2 is maintained and no other crystalline by-products are formed even after the formation of lignin/TiO 2 composite. Since lignin is amorphous in nature and lack of ordered structure [10, 12], the XRD diffractograms of both composites did not show any diffraction peak that can be referred to lignin.Fig. 8XRD diffractograms of a SL/TiO2-1.0 and b KL/TiO2-1.0 composites…”
Section: Resultsmentioning
confidence: 99%
“…Since lignin is difficult to dissolve in most deuterated solvents [12], acetylation was done to enhance the results of the analysis. 1.0 g of lignin, 7.5 mL pyridine and 7.5 mL acetic anhydride were mixed in 250 mL conical flask and stirred for 24 h at room temperature.…”
Section: Methodsmentioning
confidence: 99%
“…1 [10]. It can be extracted from different biomass materials such as oil palm ligocellulosic waste, and kenaf through soda, kraft, ethanol or other pulping processes [10, 12]. The composition and properties of lignin vary for different pulping processes, types, and parts of plants.Fig.…”
Titanium dioxide (TiO
2
) is added in sunscreens due to its ability to absorb ultraviolet (UV) light. However, upon irradiation of UV light, reactive oxygen species particularly hydroxyl radical which can damage human skin will be generated. In this study, lignin/TiO
2
composites were employed to quench the hydroxyl radicals generated by the TiO
2
. The lignin was extracted from oil palm empty fruit bunch (OPEFB) via kraft and soda pulping processes. The kraft lignin composite was labelled as KL/TiO
2
whereas the soda lignin composite was labelled as SL/TiO
2
. The lignins and the composites were characterized by FTIR, UV spectroscopy,
13
C NMR, SEM, EDX, and XRD. The relative hydroxyl radical production of composites and TiO
2
were compared through photo-oxidation of coumarin to 7-hydroxycoumarin as a test medium. The effect of types and amounts of lignin used were studied. The KL/TiO
2
composite showed the least radical production due to higher phenolic hydroxyl content of kraft lignin. The activity of the hydroxyl radicals will be quenched when it abstract hydrogen atoms from the phenolic hydroxyl groups.
“…It is because the phenylpropane units are most likely to be attacked in the chemical reactions of lignin. In this study, the phenolic groups presented in both kraft and soda lignins was determined by UV spectroscopy and 13 C NMR [10, 12]. Figure 5 shows the UV spectra of kraft lignin and soda lignin in neutral solution and alkaline solution which was a dioxane-water solution (9:1, v/v) and pH 12 NaOH solution respectively.…”
Section: Resultsmentioning
confidence: 99%
“…This indicates that the initial crystal cell structure of TiO 2 is maintained and no other crystalline by-products are formed even after the formation of lignin/TiO 2 composite. Since lignin is amorphous in nature and lack of ordered structure [10, 12], the XRD diffractograms of both composites did not show any diffraction peak that can be referred to lignin.Fig. 8XRD diffractograms of a SL/TiO2-1.0 and b KL/TiO2-1.0 composites…”
Section: Resultsmentioning
confidence: 99%
“…Since lignin is difficult to dissolve in most deuterated solvents [12], acetylation was done to enhance the results of the analysis. 1.0 g of lignin, 7.5 mL pyridine and 7.5 mL acetic anhydride were mixed in 250 mL conical flask and stirred for 24 h at room temperature.…”
Section: Methodsmentioning
confidence: 99%
“…1 [10]. It can be extracted from different biomass materials such as oil palm ligocellulosic waste, and kenaf through soda, kraft, ethanol or other pulping processes [10, 12]. The composition and properties of lignin vary for different pulping processes, types, and parts of plants.Fig.…”
Titanium dioxide (TiO
2
) is added in sunscreens due to its ability to absorb ultraviolet (UV) light. However, upon irradiation of UV light, reactive oxygen species particularly hydroxyl radical which can damage human skin will be generated. In this study, lignin/TiO
2
composites were employed to quench the hydroxyl radicals generated by the TiO
2
. The lignin was extracted from oil palm empty fruit bunch (OPEFB) via kraft and soda pulping processes. The kraft lignin composite was labelled as KL/TiO
2
whereas the soda lignin composite was labelled as SL/TiO
2
. The lignins and the composites were characterized by FTIR, UV spectroscopy,
13
C NMR, SEM, EDX, and XRD. The relative hydroxyl radical production of composites and TiO
2
were compared through photo-oxidation of coumarin to 7-hydroxycoumarin as a test medium. The effect of types and amounts of lignin used were studied. The KL/TiO
2
composite showed the least radical production due to higher phenolic hydroxyl content of kraft lignin. The activity of the hydroxyl radicals will be quenched when it abstract hydrogen atoms from the phenolic hydroxyl groups.
“…In this case, lignin is partially or completely used as substitute to phenol in the resin formulation. 34 To make lignin appropriate to be used as adhesives for wood panels, several properties of lignin must be considerate, being its chemical heterogeneity is a limiting factor. 35 In general, the lignin is isolated from the lignocellulosic biomass using different chemical processes, aiming to solubilize and precipitate this polymer, but during these processes the lignin structure is strongly affected, e.g., reducing its molecular weight and functional groups, such as phenol content.…”
The efficient use of renewable resources has become a driving force for the worldwide industry aiming to improve the competitiveness. Considering the available natural raw materials, the lignin present in the lignocellulosic biomass such as trees, is the unique natural polymer that presents aromatic rings in its constitution. In this way, this review details the structure of native lignin as well as the technical lignin, including information on the characteristics that this polymer must have for the most promissory applications as feedstock for bioproducts. Approximately 50 million tons of lignin are produced worldwide annually, of which 98% to 99% is incinerated to produce energy and steam in the pulp mills. Only a small fraction of the lignin, derived mainly from the sulfite pulp mill is recovered commercially in a biorefinery concept. There are many opportunities for producing high value-added products from technical lignin, mainly considering the pulp mills growing, and environmental restrictions using non-renewable raw materials. The currently trend have shown that technical lignin sources may also be used as feedstock for phenol derived products, technical carbons, fuels, and adhesives. On the other hand, there are some technological hurdles must be overcome to make these uses feasible.
The valorization of lignin to replace phenol is significant in the production of phenolic resins. However, a great challenge is to produce lignin‐based resin (LR) with a suitable viscosity and high substitution rate of lignin to phenol. In this study, LRs were produced using hardwood technical lignin derived from the pulping industry. Structural analysis of the LRs indicated that the unsubstituted para and ortho carbon atoms of the aromatic ring influenced the curing temperature and activation energy of the resins. The curing kinetics and thermal decomposition study implied that urea and methylene groups in cured LRs were significant factors that affected the thermal stability negatively. The prepared LRs showed desirable features if used as adhesives to make plywood. This is the first approach in which a substitution rate of up to 65 % is achieved for low‐reactive‐site hardwood lignin, which provides a solution to the challenge of the simultaneous realization of the high addition of lignin and the adaptive viscosity of resins.
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