جستجوی مقالات مرتبط با کلیدواژه "لیگنین" در نشریات گروه "مهندسی شیمی، نفت و پلیمر"

In this research, it was aimed to investigate the production of a sizing agent based on lignin extracted from the soda black liquor. The crude lignin was subjected to a chemical modification process, i.e., sulfomethylation, in order to improve its reactivity ratio and to increase its solubility in water. Unmodified/ sulfomethylated lignin were mixed with starch and then, applied on the test liner papers by surface. The SEM micrograph of the treated papers surface indicated capability of soda lignin to fill the pores and to prepare for a homogeneous film on the paper surface. The roughness increased by 20 % in case of a paper treated with unmodified lignin. The lightness decreased for the paper sized with unmodified lignin compared to the control paper. The results indicated the positive effect of the chemical modification and or starch usage in improvement of the lightness and yellowness. The optical density measurement indicated higher relative values for lignin-based solutions either unmodified or modified ones.

Hypothesis: Nanofibrous yarns produced from twisted strings of electrospun polymers like nylon showed acceptable mechanical properties as sutures. Using biopolymers such as lignin with interesting properties like biocompatibility, antioxidant, anti-bacterial, and drug delivery ability in the form of nanofibrous yarns could improve suture yarn properties. Nanofibrous yarns containing lignin could be used as biocompatible drug delivery suture yarn when having an acceptable strength.

Nylon nanofibrous yarn, nylon-lignin-polyethylene oxide (N/L/P) hybrid nanofibrous yarn and its drug-loaded form were produced using the electrospinning method. The electrospinning conditions were optimized and the mechanical properties of the produced yarn were compared to a nanofibrous nylon yarn. The strength of knotted hybrid yarn (square knot and surgeon knot) with three different twist levels was examined and compared with each other. The presence of lignin and drug in N/L/P nanoyarn was proved using FTIR spectroscopy. The morphology of the produced yarn, its rupture mechanism, and degradation are studied by FESEM microscopy. The degradation rate of yarn was examined in a phosphate buffer medium. Drug delivery properties and drug release mechanisms are also investigated by loading a drug in N/L/P nanoyarn.   

Statistical comparison between N/L/P and nylon nanofibrous yarn showed that there is no significant difference in their strength. The rupture test showed that the hybrid nanoyarn has a two-stage rapture compared to the single-stage rapture of nylon nanoyarn. The hybrid yarn showed a degradation percentage of 46.13% in 60 min, while the drug release from the drug-loaded yarn was about 97% after 4 h. In conclusion, the results showed that the N/L/P nanofibrous yarn can be used as a drug delivery suture with good mechanical strength and a proper drug release profile for a short period of time.

Activated carbon is a porous absorbent with reasonable specific surface area, pore volume, and pore size distribution for many applications such as adsorption. This material is obtained from various natural sources of carbon. Due to increasing demand for activated carbon, the economical precursors have been highly noticed. In the meanwhile, black liquor, industrial residue from Lignin Kraft process in paper factories, has high amount of carbon which can be used as an appropriate and cheap precursor for activated carbon production, and make high value added.

In this study, at first, lignin was extracted from black liquor, prepared from Iran wood & paper industries-Chouka factory, under defined conditions and investigation of pH effect, and then, powdered carbon was synthesized from extracted lignin using chemical activation method by phosphoric acid chemical agent. To consider the effects of activation temperature parameter on activated carbon structure, including specific surface area, pore volume, and pore size distribution, three activation temperature of 400, 500 and 600 ⁰C in impregnation ratio of 2 were investigated. To study the physical and morphological properties of sensitized absorbents, they were analyzed by BET, SEM, and FTIR methods.

The results confirmed that the highest amount of lignin with a similar structure to the degraded lignin was recovered at pH = 2. Investigation of the effect of activation temperature parameter suggested that the activation temperature of 500 °C can be a reasonable temperature for the synthesis of high specific surface area activated carbon and increasing the temperature above 500 °C is not effective. Among these sensitized adsorbents, the activated carbon sensitized in activation temperature of 500 ⁰C showed the highest specific surface area and the pore volume of 1573.31 m2/g and 0.89 cm3/g respectively, which exhibits the high potential of this precursor as activated carbon adsorbent.

Lignin-based adsorbents are one of the common materials for removal of heavy metal ions in wastewater treatment and the adsorption of metals extracted in mines. Therefore, it seems that industrial lignin and its carboxymethylated derivative are able to adsorb zinc and copper cations from aqueous solutions under different operating conditions.

Firs, industrial lignin was carboxymethylated by reacting with sodium chloroacetate. After carboxymethylation of lignin, the characterization tests including FTIR spectroscopy, 1H NMR spectroscopy, acid-base titration, pHpzc (pH point of zero charge) and zeta potential tests were performed. Concentration of ions in aqueous solutions was determined by atomic adsorption technique.

The results of structural characterization tests showed that the reaction of lignin with sodium chloroacetate removed the aromatic hydroxyl groups of lignin, while the concentration of carboxyl groups increased. Thus, it was found that lignin was carboxymethylated successfully. The results of zinc (II) and copper (II) ions adsorption showed that the maximum adsorption of copper ion in comparison with zinc ion occurs in the presence of the modified industrial lignin adsorbent at a pH close to 4. The kinetic study results showed that the adsorption of both ions follows a pseudo second-order model. In the isotherm studies, the Sips model showed the best performance for both the industrial and modified lignin samples. Maximum adsorption capacities for the zinc and copper ions by carboxymethylated lignin were observed to be 0.25 and 0.37 mmol/g, respectively, showing a significant improvement in comparison with unmodified kraft lignin. However, selectivity of the copper ion decreased in contrast. This improvement could be mainly attributed to the significant increase in active sites on carboxymethylated lignin.

The ever-increasing regulations within the adhesives industry and the continuous demand for more sustainability, have led to the development of environmentally more suitable alternatives to petroleum-based pressure-sensitive adhesives (PSAs). This review provides an overview of the current strategies and methods to develop sustainable, acrylic PSAs derived from renewable resources, such as vegetable oil, lignin, carbohydrates and terpenes. Herein, we emphasize some of the key concepts in the literature within the past decades, which paved the way to the current focus of improving the adhesive properties by employing the full array of natural building blocks. In this context, some recent strategies that give tailor-made adhesive properties to PSAs are also discussed, in view of the desired application. With this critical insight on the large set of research efforts in the context of biosourced acrylic PSAs, we aim to provide a guide for new researchers in this highly emerging field

Lignin is a reinforcing filler with properties such as abundantannually renewable, low weight, high biological efficiency, and wide ecological adaptability. These properties are causedincreasing attention from researchers and become an alternative to carbon black in the rubber industry. in this paper, we try to briefly review the lignin. In this regard,initially, the chemical structure of lignin and its structuresareconsidered. it is obvious from the application and process point that this polymer has little tendency to spread in the rubber matrix due to polar functional group and so it will not appear as agglomeration in rubber compoundand thereforewon’t be as reinforcing filler. There have been studies in order to solve this problem and improved the reinforcing properties of lignin. These include modifying the mixing process, increasing the interfacial bonding strength between lignin and the rubber, formation of nano structure with lignin and use of hybrid technologies with other filler.Here some of these methods and the effects of lignin on its curing, mechanical and thermal properties are summarized.

In this research, catalytic hydrodeoxygenation process of anisole derived from lignin is investigated over Pt/Al2O3 catalyst at 573-673 K, 8-14 bar and space velocity of 3-20 (ganisole/gcatalyst*h), in the presence of hydrogen as one of the reactants, using a fixed-bed tubular reactor. The main reaction classes during catalytic conversion of anisole are hydrogenolysis, hydrodeoxygenation, dehydration and transalkylation. During this process, anisole initially converts to phenol through hydrogenolysis reaction. Afterwards, phenol derivatives including: 2-methyl phenol, 2,4-di methyl phenol, 2,3,5,6-tetra methyl phenol are generated via alkylation and trans-alkylation reactions. Benzene is formed through hydrodeoxygenation (HDO) reaction. More over hexa-methylbenzene is formed via alkylation and HDO reactions. Reactions network and kinetic constants are determined using products selectivity and anisole conversion data. According to achieved results, phenol, 2-methyl phenol and benzene are primary products of HDO process. Furthermore, based on kinetic calculations, formation of benzene is not a first-order reaction. Formation of phenol, 2,4,6-tri methyl phenol, 2,6-di methyl phenol, 2-methyl phenol, hexamethyl benzene and 2,3,5,6-tetra methyl phenol are first-order reactions, and the activation energy for their formation are 25.3 kJ/mol, 40.2 kJ/mol, 43.4 kJ/mol, 55.4 kJ/mol, 70.1 kJ/mol and 93.6 kJ/mol respectively.

Nowadays, In order to reduce environmental footprint, polymer industry has started to develop new materials based on natural resources. Two kinds of biobased polymers can be developed. The first one corresponds to macromolecular structures existing in nature as cellulose, lignin, starch, alginate and so-on that most of them are probably the ones that derived from well-established cellulosic industries. Nevertheless, the thermal stability of these rich in oxygen structures are limited, they release relatively little heat during burning and are often able to char. Other biobased polymers are made up of molecules synthesized from natural resources. Not only polymers but also all additives used to modify their properties can be biobased to meet sustainable development. Intensive research is devoted to develop flame retardant biobased polymers from various raw resources. These flame retardant biobased polymers can be used directly as they are, alone or as a component of a more complex system. This is especially true when the molecules are phosphorus-rich as DNA or phytic acid or charring as lignin. All the efforts reviewed in this paper, show that a major objective is to develop 100 % biobased materials suitable for applications requiring high flame retardancy level. Different biomolecules from the cellulosic industry are also the most promising in flame retardancy.

Lignin is the second most abundant polymer in the world after cellulose. Therefore, characterization of the structure and functional groups of lignin in order to assess its potential applications in various technical fields has become a necessity. One of the major problems related to the characterization of lignin is the lack of well-defined protocols and standards. In this paper, systematic studies have been done to characterize the structure and functional groups of lignin quantitatively using different techniques such as elemental analysis, titration and 1H NMR and FTIR techniques. Lignin as a black liquor was obtained from Choka Paper Factory and it was purified before any test. The lignin was reacted with α-bromoisobutyryl bromide to calculate the number of hydroxyl and methoxyl moles. Using 1H NMR spectroscopic method on α-bromoisobutyrylated lignin (BiBL) in the presence of a given amount of N,N-dimethylformamide (DMF) as an internal standard, the number of moles of hydroxyl and methoxyl groups per gram of lignin was found to be 6.44 mmol/g and 6.64 mmol/g, respectively. Using aqueous titration, the number of moles of phenolic hydroxyl groups and carboxyl groups of the lignin were calculated as 3.13 mmol/g and 2.84 mmol/g, respectively. The findings obtained by 1H NMR and elemental analysis indicated to phenyl propane unit of the lignin with C9 structural formula as C9 HAl 3.84HAr2.19S0.2O0.8(OH)1.38(OCH3)1.42. Due to poor solubility of the lignin in tetrahydrofuran (THF), acetylated lignin was used in the GPC analysis, by which number-average molecular weight of the lignin was calculated as 992 g/mol.

In the recent decades, many articles have been published on the development of lignin and mostly related to the chemical modification of lignin.The direct use of lignin often leads to the synthesis and production of low-value added materials. Hence, chemical modification of lignin not only increases its activity in the reactions but also represents a fine dispersion in the polymer materials. Chemical structure of lignin contains phenyl propane units, originating from three aromatic alcohol precursors of p-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol. The main uses of lignin can be classified into two different methods. In the first method, without chemical modification, lignin is directly incorporated into a polymer matrix to give new or improved properties. In the second method, a large range of polymer materials is synthesized via chemical modification of the lignin. Chemical modification of the lignin has been studied frequently for various purposes. Lignin modification through reaction with formaldehyde, epichlorohydrin, phenol, propylene oxide, propylene carbonate, polyethylene glycol and synthesis of lignin-based copolymers are among reactions studied in the literature. However, this article has been restricted to the discussion on chemical modification of lignin and its use as a source of monomer in the polymerization process.

The white rot fungi can produce different isoenzymes of extracellular oxidases such as lignin peroxidase, manganese peroxidase and laccase having ability to decompose lignin. Because of the non-specific nature of peroxidases produced by lignin-degrading system of white rot fungi, they can be used for degradation of a wide range of toxic and carcinogenic materials including industrial dyes. Laboratory studies on the ability and physiology of lignolytic system of white rot fungi demonstrated that it is promising to use these fungi for wastewater treatment of those companies which produce and consume industrial dyes. For large-scale treatment of wastewater containing dyes, it is necessary to immobilize these fungi on suitable carries in bioreactors. In this article, considering the metabolic and physiological characteristics of white rot fungi and their lignolytic system, the previous studies carried out on the degradation of dye wastewater using these fungi in free or immobilized form have been mentioned and their perspective has been also presented.

Lignin is the second most abundant natural polymer after cellulose in the world; and as a cheap, non-toxic and biodegradable material, it is a good alternative to the petroleum-based polyols. Despite researchers’ efforts to identify the structure of lignin, there are many problems which hinder lignin to be accepted as an appropriate monomer and a competitive alternative to the monomers derived from the crude oil for synthesis of polymers such as polyurethane. One of the major problems related to identification of the lignin structure is lack of well-defined protocols and standard. In this paper, a systematic study has been performed to quantitatively identify the functional groups present in the lignin structure using different techniques such as 1H NMR, 13C NMR, 31P NMR, 19F NMR and UV-VIS spectroscopies and titration. The advantages and limitations of each method havealso been discussed. Moreover, the molecular weight and thermal properties of lignin have been determined by a variety of methods.

According to environmental issues and limited fossil resources، the use of renewable and biodegradable resources has been considered very important. Forest biomass is the most abundant source of renewable and carbon-rich organic matter on land that has a desirable potential as raw material for a wide variety of industrial and domestic products، including paper، lumber، chemicals and advanced materials such as fuel and biodegradable polymers. By-products obtained from bio-refinery lignocellulosic biomass include hemicelluloses derivatives (furfural، xylitol، biodegradable polymers and polymeric paper strength) and lignin derivatives (turpentine، tall oil and raw material for production of plastic & binder) are remarkable. These products can be manufactured with pulp and paper or dissolving pulp from lignocellulosic resources. So one of the important goals in biorefinery is to create value-added in black liquor from lignocellulosic materials cooking in pulp mills، which in addition، in production of pulp and paper there are also some byproducts as well. Finally، biorefinery has provided an economic opportunity to enhance the economic strength in this industry.

During the past decade, the use of plant fibers for reinforcing biocomposite material has attracted many researchers. The lignin content of the fibers reduces the mechanical properties of the resulting biocomposites, thus the lignin content is reduced by chemical treatments. In this research, the effective factors in the process of lignin reduction, including hydrogen peroxide and sodium hydroxide content, and temperature of the medium and the retention time, were optimized to prepare fiber with lowest amount of lignin and with highest tensile strength. The experiments were performed based on "central composite rotatable design" using four independent factors, each at five levels. A second degree polynomial was used to define a function relating the dependent and independent variables. The experimental data and the predicted data by the models were highly correlated (R2 <0. 98). The optimization results indicated that the optimized level for hydrogen peroxide and sodium hydroxide were 4. 5% and 5. 7%، wt. The optimum medium temperature and retention time were 41. 9ºC and 16. 8 h, respectively. At the optimized values of the independent variables, the lignin content and the tensile strength of the fibers were 10. 23% ww and 220. 08 MPa, respectively.

The lignocelluloses fibers are produced in nature and by various agricultural activities. These materials are used in textile, paper and agricultural industries. The lignin content of these fibers causes browning and brittleness in the products made from them. In industries, the fibers are treated by various chemical treatments to reduce their lignin and hemicellulose content, as these are the main hydrophobic factors. In this research, the date palm fibers were treated using 1) sodium hydroxide and 2) sodium hydroxide and hydrogen peroxide. The physical, mechanical and chemical properties of the treated fibers were compared with untreated fibers. The results indicated that the color of the treated fibers were lighter than the untreated fibers. The static friction of the two groups of treated fibers reduced by 29 and 60%, respectively. The diameters of the treated fibers were also reduced by about 22%. The mean ultimate tensile strengths of the treated fibers were 75.1 and 91.2 MPa. The chemical and FTIR analysis of the fibers indicated a significant reduction in the hemicellulose and lignin content of the treated fibers. The TGA test on the fibers showed the treated fibers had higher temperatures both for starting and end of degradation.