جستجوی مقالات مرتبط با کلیدواژه "کایتوزان" در نشریات گروه "جنگلداری"

In this study, efficient hybrid hydrogels as drug delivery platforms were synthesized using Kraft lignin, a biopolymer obtained from the alkaline paper industry, chitosan and glutaraldehyde as a crosslinker. The ratio of lignin was an important variable factor of this study and its effect on morphology and mechanical properties were studied. The characteristics such as compressive property, swelling capacity, drug release, degradation time, and SEM imaging of the hydrogels of chitosan and chitosan/ lignin with different amount of lignin were investigated. Also, paracetamol drug was selected as a drug model. The results showed that the glutaraldehyde crosslinker can effectively create a crosslinked structure, so that the durability and stability of the hydrogels in the desired conditions is up to 15 days for the pure chitosan sample and 11 days for the lignin chitosan sample, respectively. Although the shortest shelf life (5 days) corresponds to the highest amount of lignin, which was a shorter period of time, but it gives enough time for the drug to be completely released. The results showed that although the hydrogel structure is weakened by increasing the percentage of lignin, the drug was released faster with the increasing of lignin, which can be considered as a factor for changing the release rate of drug according to the intended application. The highest amount of release was observed in hydrogels with the highest amount of lignin, so that in the first two hours, its amount was about six times higher than that of pure chitosan hydrogel.

chitin and chitosan, as the most abundant amino-polysaccharide in nature, have characteristics such as biocompatibility, low toxicity, and biodegradability. These unique specifications have resulted in chitin and chitosan attracting a lot of attention because of the high potential for producing valuable products. Chitosan has many uses in the agricultural industry and wood preservation, such as pesticides and insecticides, as well as in biomedical applications, including the use in the pharmaceutical industry as a drug release, and can also be used as drug carriers. The purpose of this article is to extract highly purified chitosan with high de-acetylation degree from shrimp shells.

In this study, the extraction and characterization of chitosan from the shrimp shell (Litopenaeus vannamei) was investigated. For this purpose, chitosan was extracted by chemical method including mineralization (with 4% HCl concentration), protein degradation (with 4% NaOH concentration), and deacetylation (with 60% NaOH concentration). Also, nano-chitosan was prepared by ionic gelation method. A series of parameters were studied, which included the degree of deacetylation, molecular weight, pH and solubility. Also, FTIR spectroscopy, FESEM scanning electron microscopy, Zeta potential, X-ray diffraction spectroscopy (EDX) and X-ray diffraction (XRD) were used.

The results of FTIR test on chitin and chitosan extracted from shrimp shell showed that the removal of protein and mineral materials was appropriate with the use of hydrochloric acid, sodium hydroxide. The high degree of deacetylation of chitosan in this study (87%) had a significant effect on the proper solubility and low viscosity of chitosan. The solubility of chitosan in acetic acid was 86%. The molecular weight of the chitosan extracted was 110 kDa. With this molecular weight, chitosan can be used well in the pharmaceutical industry. According to chitosan XRD patterns in previous studies, the peaks obtained in XRD patterns in this study confirmed the semi-crystalline structure of chitosan. Due to the change in the level of chitosan seen in FESEM images, it can be due to the purification of chitosan. The FESEM test confirms nano-chitosan with diameter range of 100 to 150 nm.

From the results of this study, it can be concluded that using the chitosan extraction method in this research, highly purified chitosan with high de-acetylation degree can be obtained. With increasing degree of deacetylation, the solubility of chitosan has increased, and this degree of deacetylation has had a significant effect on improving molecular weight (Low molecular weight). As a result of the study of the role of solubility of chitosan in the vicinity of acetic acid, it becomes obvious that the solubility of the chitosan and the size of the nano-chitosan particles depend on the solution pH. The produced chitosan can be used in wide variety of application mainly in pharmaceutical industry.

Paper recycling has been greatly developed as a suitable approach to use waste paper and as a huge source of cellulose fibers in recent years. Regarding to the structural characteristics of these fibers, which differ largely from those virgin fibers; the first and most important challenge of their application is to modify them for reusing in papermaking industry. It seems that if these fibers are repeatedly used, their applicability will reduce. Although the impact of recycling number for these type of fibers on the paper properties has always been taken into consideration, but there are not many reports available in the literature review. Recent studies show that layer-by-layer technique is a good way for modifying the cellulose fibers characteristics and improving its quality. In this technique, cellulosic fibers and counter-ionic particles are placed in an interaction media. During the interaction, ionic particles are absorbed by fibers surface mainly via electrostatic absorption. Thus, the fibers network strength would improve considerably. Therefore, in current study, the Kraft paper recovered three times at first. The possibility of modifying of three times recovered Kraft fibers has been investigated using layer-by-layer technique in order to develop the bonding potential of the fibers. Kraft fibers were first recycled three times. Then, the three times recycled fibers were treated by 1 % cationic chitosan and 1 % anionic carboxyl methyl cellulose (CMC), based on the oven dry (OD) weight of fibers, by using layer-by-layer method. The treatment was applied to form one, two and three double layers of pair polymers on the fiber surface. To form a consecutive double layers, 500 ml of fiber suspension with consistency of about 0.6 % was mixed with chitosan and CMC solutions for 10 minutes by using dynamic drainage jar (DDJ) machine. Paper sheets with base weight of about 80±5 g/m2 were prepared from the pulp samples and their characteristics were evaluated according to TAPPI standard methods. In addition, SEM micrographs were prepared from the papers to evaluate the changes in the structure of the fiber surface. The alternate variation of zeta potential confirmed the formation of chitosan and CMC layers on the surface of Kraft recycled fibers. The evaluation of paper strengths showed that the fibers bonding has been developed by treating the three times recycled Kraft fibers with layer-by-layer method, through absorbing of these two strength-enhancing polymers. Meanwhile, paper apparent density, tensile index, internal bonding, and tensile energy absorption have significantly increased. However, the bending stiffness of the paper has shown a significant decrease due to the increased in paper density (decrease in thickness). In addition, based on SEM results there was a clear difference between the surface of treated and untreated fibers, which indicated the absorption of polymers, leading to the development of bonds between the fibers, and paper strength. It can be concluded that it is possible to modify the bonding-ability of three times recycled Kraft fibers by using layer-by-layer technique. This method can be applied to assemble multilayers of chitosan and CMC polymers on the fiber surfaces, to improve the strength properties of the resulting paper.

Increasing the application of tissue papers and its competitive market, particularly in respect to the water absorbency and wet strength, is important and utilization of necessary chemicals especially bio-based ones, for required specification is extensive. Therefore, the aim of this is to focuses on the bio-based chemical and its efficiency. Effects of the chitosan biopolymer compared to the common synthetic polyamide epichlorohydrin (PAE)on the wet and dry strengths, whiteness, brightness and water absorbency of handsheets prepared from deinked pulp of mixed office waste paper were carried out at 0.5, 0.75 and 1% addition levels of the wet strengths agents. SEM images proved the sedimentation of additives and higher advent of chitosan fibers than PAE. Higher dry tensile, burst and wet tensile strengths, lower rate and content of water absorption of treatment with chitosan were determined mainly caused due to creation of cross links among the paper ingredients during the drying. Due to the high similarity between the cellulose and chitosan and also plenty of amine and hydroxyl functional groups of the chitosan, the bonding increased while water uptake sites decreased. Extensive bonding resulted in lower flexibility and higher bending stiffness, which was higher in PAE than chitosan treatments at 0.5%. In spite of declining trend, variations in whiteness (111%) and brightness (86%) of chitosan reinforced handsheets were insignificant. Generally, 0.5% of the chitosan compared to 1% of PAE, provided higher strengths values and minimum reduction in water absorption (~10%) and optical properties while higher flexibility donated to the paper. Also an improvement in the wet strengths of the fibrous network could be resulted in better machine runnability.

Improving the processing and the recycled paper properties is one of permanent concern of papermaking. In this research, the effect of nanochitosan addition on the process and product quality made of writing and printing recycled fiber was investigated. Being nano size and so its capability in access to the space between pulp suspension components and also its probable ability to make electrostatic and hydrogen bonds are the characteristics of nanochitosan. For this purpose, the chitosan nanoparticles were prepared and their size and shape was confirmed with AFM and FE-SEM. Also, the change in FTIR spectrum after conversion of chitosan to nanochitosan was considered and omitting the –NH2 in chitosan and creation of –CONH groups in nanochitosan by polymerization between chitosan and meta acrylic acid were confirmed. In next step, nanochitosan in four levels (0, 0.5, 1, 1.5 and 2% based on oven dry pulp) was used. The results indicated that nanochitosan was successful in increasing the mechanical properties (tensile, burst and tear indices) and process properties (drainage and fines retention) comparing the control treatment (no additive). Moreover, the comparing of nanochitosan and chitosan performance in the same consumption level (1% based on oven dry pulp) showed similar effect on mechanical properties but chitosan had better performance in process properties. Also, both of this polyelectrolyte showed better results on mechanical properties comparing the cationic starch at the same consumption level (1% based on oven dry pulp).

To compensate for some inferior properties of recycled papers, application of processing chemical aids such as chitosan can be quite effective in the wet end section of papermaking. In this study, the performance of chitosan biopolymer, individually or associated with nanobentonite was investigated as wet end additive on recycling process of white cuttings. For this purpose, the performance of this biopolymer at 0.5, 1, 1.5 and 2% (based on oven-dried pulp) were compared in a single polymer system or with nanobentonite. The results revealed that dosing different amounts of chitosan resulted in increasing tensile, tear and burst indices. Moreover, improvement in first pass retention (5 and 10% in single and nanoparticle system, respectively) and drainage (18.75 and 23.5% in the case of single and nanoparticle system, respectively) was observed, while the improvements resulted from nanoparticle system was more prominent according to the wet end parameters. It is noteworthy that increase in strength properties in presence of bentonite nanoparticle was unexpected, and on the other hand the more additive used, the more gains in paper strength properties and processing parameters was detected.

In this research، the effect of pH onthe performance of nanobentonite -chitosan system (as dry strength additives) in hardwood chemi-mechanicalpulp (CMP) was studied. For this purpose، 3 levels of pH (5. 5، 7، 8. 5) and 3 levels of chitosan (0. 75، 1. 25 and 2% - based on oven dried pulp) in constant level of 0. 3 nanobentonite (based on oven dried pulp) were applied. The Atomic Force Microscopy (AFM) imageconfirmed the nano structure of bentonite in thickness dimension at the range of 1-22. 3 nm. The results indicated that nano bentonite – chitosan in all levels of pH caused numerical improvement in tensile،burst and tear indicesand also apparent density in comparison with control sample. Although theeffect of studiedvariables (chitosan dosages and pH levels) on considered properties was statistically significant،but most of treatments were in the same groups according to Duncan grouping. In this research، treatment consisting of 1. 25 chitosan in fixed level of 0. 3 nano bentonite at alkaline pH showed the best results in mentioned properties and statistically had significant difference comparing other treatments. Therefore،it wasintroduced as theselected treatment in this research. It seems that the ratioof chitosanandbentonite nano anion had a great effect on performance ofnanoparticle system. Also the results showed that the performance of system depend on the pH of furnish and the best results was achievedin alkaline condition (pH=8. 5).

Layer-by-Layer self-assembly technique is a novel method in nanothechnology for the modification of the surface properties of solid materials. This paper compares the influence of modification of cotton linter fibers external surfaces via alternate adsorption of positive and negative (chitosan/Cellulose nanofibers) polyelectrolytes. The adsorption of materials on cellulose fibers was analyzed via polyelectrolyte titration. The bonding ability of fibers was improved by polyelectrolyte multilayering (PEM) on the fiber surface visualized using Field-Emission Scanning Electron Microscopy (FESEM). The results showed that apparent density and also bonding ability were significantly improved at second layer، whereas the apparent density and tensile index of the sheet increased by 10% and 76% respectively compared to those of untreated fibers at second layer.