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Abstract

Polysaccharides are polymers of long chains of monosaccharide units linked via glycosidic bonds. Starch, cellulose, chitin and their derivatives, such as chitosan, are examples of polysaccharides. Chitin is the second most common natural polysaccharide in the world (after cellulose). Chitin and chitosan are amino polysaccharides. Chitosan is often obtained by chemical, or sometimes enzymatic, deacetylation of chitin. These compounds are increasingly being modified to the nanometric scale. New engineering nanomaterials show better chemical, biological, mechanical, thermal, electrical and sorption properties than the primary materials. In this paper, the methods of chitosan nanomaterials synthesis and their adsorption properties of metal cations are discussed. As it is shown, the selected chitosan nanomaterials have promising adsorption properties of metal cations.

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... The results of these processes are presented in Figure 1. The method of chitosan obtained from chitin is known in the literature [29][30][31]. ...
... Subsequently, chitin was converted to chitosan via c deacetylation (oil bath on a magnetic stirrer with mechanical stirring; 50% NaO 1:30; 130 °C; 3h), the sample was rinsed to neutral and dried to dryness mass (80 ° The results of these processes are presented in Figure 1. The method of chitosan from chitin is known in the literature [29][30][31]. ...
... 12 of 19 hydrophilic chitosan was not incorporated into the PUR chains, but the particles were stuck with PUR. Li et al. also investigated PUR foams for oil spill cleanup [31]. Their results presented the water sorption capacity in the range from 51% to 141%. ...
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Water sustainability is becoming a major concern for Canadians. Governments are actually considering various water initiatives to establish recommendations on water governance and policies to ensure the sustainability of water supply for people and industries. The pulp and paper industry is a major user of water. Implementation of such water initiatives will force them to move further towards closed-cycle papermaking. Advanced wastewater treatment methodologies will be mandatory to reduce fresh water consumption with minimum detrimental effects on papermaking operations and paper quality. Adsorption experiments were carried out using electrospun chitosan (CS)/polyethylene oxide (PEO) nanofibres to investigate adsorption of copper (II) ions from aqueous solutions. A central composite design (CCD) was used to investigate the influence of temperature, copper concentration, and adsorbent mass on adsorption efficiency. An optimal adsorption of 94.7% was obtained by using 75. mg of nanofibres in 200. min at pH 5.5 and a temperature of 55.7. °C with initial copper concentration of 100. ppm.
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In this work, samples of chitosan obtained in different conditions were characterized by molecular weight distribution, using Gel Permeation Chromatography (GPC), in two different solvents. It was observed that the increase in the number of deacetylation steps promotes a increase in the degree of deacetylation followed by a decrease in the average of molecular weight and polydispersion. The GPC curves obtained for chitosan samples in the two solvents used (CH3COOH 0.30 mol/dm(3) CH3CONa 0.20 mol/dm(3) and CH3COOH 0.10 mol/dm(3) - NaCl 0.20 mol/dm(3)) showed small difference in elution volume, but significant changes in the average molecular weight (M-n and M-w) and polydispersion that, in agree with the values of Huggins constant, present evidences of chitosan aggregates formation in the second solvent.
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Chitosan of different degrees of deacetylation have been prepared from chitin. Pyrolysis-mass spectra of these chitosan samples in the ion source of a mass spectrometer were examined to check for a correlation with the degree of deacetylation, as represented by the amine content. The results indicate that as the degree of deacetylation increases, the peak ratios 80:60, 67:60 and 80:42 increase to a limit, representing the limit of deacetylation of chitin. The 80 and 67 fragments originate from the d-glucosamine moiety of the polymer and the 60 and 42 fragments from the N-ethyl-d-glucosamine moiety. For chitin, the predicted values of these ratios are expected to be low when compared to chitosan, and this is borne out by the experimental data.
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Article
Of late, the most bountiful natural biopolymer chitin and chitosan have become cynosure of all party because of an unusual combination of biological activities plus mechanical and physical properties. However applications of chitin are limited due to its inherent insoluble and intractable nature. Chitosan, alkaline hydrolytic derivative of chitin has better solubility profile, less crystallinity and is amenable to chemical modifications due to presence of functional groups as hydroxyl, acetamido, and amine. The chemical modification of chitosan is of interest because the modification would not change the fundamental skeleton of chitosan, would keep the original physicochemical and biochemical properties and finally would bring new or improved properties. In view of rapidly growing interest in chitosan its chemical aspects and chemical modification studies is reviewed. The several chemical modifications such as oligomerization, alkylation, acylation, quternization, hydroxyalkylation, carboxyalkylation, thiolation, sulfation, phosphorylation, enzymatic modifications and graft copolymerization along with many assorted modifications have been carried out. The chemical modification affords a wide range of derivatives with modified properties for specific end use applications in diversified areas mainly of pharmaceutical, biomedical and biotechnological fields. Assorted modifications including chitosan hybrids with sugars, cyclodextrin, dendrimers, and crown ethers have also emerged as interesting multifunctional macromolecules. The versatility in possible modifications and applications of chitosan derivatives presents a great challenge to scientific community and to industry. The successful acceptance of this challenge will change the role of chitosan from being a molecule in waiting to a lead player.
Article
An economical and accurate determination of degree of acetylation (DA) for highly acetylated chitin has always been a challenge for researchers dealing with chitin and chitosan. A new protocol for the first derivative UV method using concentrated phosphoric acid as a solvent for highly acetylated chitin was developed in this study. The solvent was proposed based on thorough investigation of the effects of associated reactions including chain degradation, monomer dehydration, and oxazolinium ion formation. The reproducibility and performance of the new protocol was evaluated using commercial samples and the results showed the DA values of both chitin and chitosan could be determined accurately by a single analytical technique in less than 3h.
Article
Organosoluble derivatives of chitin were prepared and used as precursors for regioselective and quantitative chemical modifications. Based on these precursors, various sugar groups could be introduced to prepare nonnatural branched chitins and chitosans. With a view to establishing a new route to facile modifications, reactivity of β-chitin was examined and confirmed to be much higher than that of ordinary α-chitin. The resulting chitin derivatives were evaluated in terms of affinity for solvents, lysozyme susceptibility, and antimicrobial activity, and the effects of substituents were discussed.
Article
Creation of affordable materials for constant release of silver ions in water is one of the most promising ways to provide microbially safe drinking water for all. Combining the capacity of diverse nanocomposites to scavenge toxic species such as arsenic, lead, and other contaminants along with the above capability can result in affordable, all-inclusive drinking water purifiers that can function without electricity. The critical problem in achieving this is the synthesis of stable materials that can release silver ions continuously in the presence of complex species usually present in drinking water that deposit and cause scaling on nanomaterial surfaces. Here we show that such constant release materials can be synthesized in a simple and effective fashion in water itself without the use of electrical power. The nanocomposite exhibits river sand-like properties, such as higher shear strength in loose and wet forms. These materials have been used to develop an affordable water purifier to deliver clean drinking water at US $2.5/y per family. The ability to prepare nanostructured compositions at near ambient temperature has wide relevance for adsorption-based water purification.
Article
Viscosity-average relative molecular masses have been determined for a series of chitosans having the same relative molecular mass and relative molecular mass distribution but differing extents of N-acetylation. The results obtained show that the same viscometric constants in the Mark-Houwink equation [η] = Km ·Ma are applicable to chitosans over the range between 0 and 40% N-acetylation Comparison of literature values for number- and weight-avepge rela-tive molecular masses Mn, and Mw, with the viscosity-average relative molecular mass M, values calculated using the related viscosity data and each of the three sets of viscometric constants that have been proposed for chitosan, confirms that the most accurate values currently available are km = 1,81 · cm−3 · 10−1 and a = 0,93, using 0,l M acetic acid/0,2M NaCl as solvent.
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In order to select an ideal chitosan (CS) species as a material for implantation vehicle to control drug release in the body, the relationship between physicochemical characteristics (including molecular weight, degree of deacetylation, and viscosity) and functional properties (including ability to form spherical gel, control of drug release from CS gel, and biodegradation of CS) was investigated for various CS. The ease of spherical gel formation in aqueous amino acid solution or aqueous solution containing metal ions was affected mainly by viscosity of the CS solution. Drug diffusion rate from the CS gel was controlled by density of the gel matrix structure, which was governed by viscosity of the CS solution prior to gelation. Biodegradation of CS tended to vary with degree of deacetylation. However, linear relationships for these trends were not observed, and the possibility that characteristics other than CS molecular weight, degree of deacetylation, and viscosity of the CS solution, such as distribution of acetamide groups in the CS molecule affect functional properties of CS, was also indicated. These observations demonstrate that CS functions are affected by various CS characteristics and that investigation of individual CS characteristics is important for the selection of the appropriate CS as a material for drug delivery vehicles.
Article
Metal cations can be adsorbed by chelation on amine groups of chitosan in near neutral solutions. In the case of metal anions, the sorption proceeds by electrostatic attraction on protonated amine groups in acidic solutions. However, the presence of ligands and the pH strongly control sorption performance (sorption isotherm) and the uptake mechanism (changing the speciation of the metal may result in turning the chelation mechanism into the electrostatic attraction mechanism). Several examples are discussed with precious metals (Pd, Pt), oxo-anions (Mo, V) and heavy metals (Cu, Ag). Sorption performance (equilibrium uptake but also kinetics) is also strictly controlled by other structural parameters of the polymer (degree of deacetylation, crystallinity for example) that control swelling and diffusion properties of chitosan. The identification of the limiting steps of the sorption process helps in designing new derivatives of chitosan. Diffusion properties may be improved by physical modification of chitosan (manufacturing gel beads, decreasing crystallinity). Selectivity can be enhanced by chemical modification (grafting, for example, sulfur compounds). Several examples are discussed to demonstrate the versatility of the material. This versatility allows the polymer to be used under different forms (from water soluble form, to solid form, gels, fibers, hollow fibers …) for polymer-enhanced ultrafiltration and sorption processes. These interactions of metal ions with chitosan can be used for the decontamination of effluents, for the recovery of valuable metals but also for the development of new materials or new processes involving metal-loaded chitosan. Several examples are cited in the design of new sorbing materials, the development of chitosan-supported catalysts, the manufacturing of new materials for opto-electronic applications or agriculture (plant disease treatment …).
Article
Nonflocculating and chiral-nematic self-ordering were observed in cellulose microcrystals suspensions in nonpolar solvents. Initial suspensions of cellulose microcrystals were prepared by acid hydrolysis. The homogeneous dispersion of cellulose microcrystals and microfibrils in a number of polymer solutions and melts was studied.
Book
This fourth edition of the book provides readers with a detailed explanation of PLM, enabling them to gain a full understanding and the know-how to implement PLM within their own business environment. This new and expanded edition has been fully updated to reflect the numerous technological and management advances made in PLM since the release of the third edition in 2014, including chapters on both the Internet of Things and Industry 4.0. The book describes the environment in which products are ideated, developed, manufactured, supported and retired before addressing the main components of PLM and PLM Initiatives. These include product-related business processes, product data, product data management (PDM) systems, other PLM applications, best practices, company objectives and organisation. Key activities in PLM Initiatives include Organisational Change Management (OCM) and Project Management. Lastly, it addresses the PLM Initiative, showing the typical steps and activities of a PLM project or initiative. Enhancing readers’ understanding of PLM, the book enables them to develop the skills needed to implement PLM successfully and achieve world-class product performance across the lifecycle. .
Article
Chitin and chitosan-derivatives have gained wide attention as effective biosorbents due to low cost and high contents of amino and hydroxyl functional groups which show significant adsorption potential for the removal of various aquatic pollutants. In this review, an extensive list of chitin- and chitosan-derivatives from vast literature has been compiled and their adsorption capacities for various aquatic pollutants as available in the literature are presented. This paper will give an overview of the principal results obtained during the treatment of water and wastewater utilizing chitin and chitosan-derivatives for the removal of: (a) metal cations and metal anions; (b) radionuclides; (c) different classes of dyes; (d) phenol and substituted phenols; (e) different anions and other miscellaneous pollutants. The review provides a summary of recent information obtained using batch studies and deals with the various adsorption mechanisms involved. It is evident from the literature survey that chitin- and chitosan-derivatives have shown good potential for the removal of various aquatic pollutants. However, still there is a need to find out the practical utility of such developed adsorbents on commercial scale.
Article
Chitosan-Fe(0) nanoparticles (chitosan-Fe(0)) were prepared using nontoxic and biodegradable chitosan as a stabilizer. Batch experiments were conducted to evaluate the influences of initial Cr(VI) concentration and other factors on Cr(VI) reduction on the surface of the chitosan-Fe(0). The overall disappearance of Cr(VI) may include both physical adsorption of Cr(VI) onto the chitosan-Fe(0) surface and subsequent reduction of Cr(VI) to Cr(III). The rate of reduction of Cr(VI) to Cr(III) can be expressed by a pseudo-first-order reaction kinetics. The rate constants increase with the increase in temperature and iron loading but decrease with the increase in initial Cr(VI) concentration and pH. The apparent activation energy is found to be 33 kJ mol(-1), which is characteristic of a chemically controlled reaction. Characterization with high-resolution X-ray photoelectron spectroscopy reveals that after the reaction, relative to Cr(VI) and Fe(0), Cr(III) and Fe(III) are the predominant species on the surface of chitosan-Fe(0). Chitosan has also been found to inhibit the formation of Fe(III)-Cr(III) precipitation due to its high efficiency in chelating the Fe(III) ions. This study demonstrates that chitosan-Fe(0) has the potential to become an effective agent for in situ subsurface environment remediation.
Article
Magnetic chitosan nanocomposites have been synthesized on the basis of amine-functionalized magnetite nanoparticles. These nanocomposites can be removed conveniently from water with the help of an external magnet because of their exceptional properties. The nanocomposites were applied to remove heavy metal ions from water because chitosan that is inactive on the surface of the magnetic nanoparticles is coordinated with them. The interaction between chitosan and heavy metal ions is reversible, which means that those ions can be removed from chitosan in weak acidic deionized water with the assistance of ultrasound radiation. On the basis of the reasons referred to above, synthesized magnetic chitosan nanocomposites were used as a useful recyclable tool for heavy metal ion removal. This work provides a potential platform for developing a unique route for heavy metal ion removal from wastewater.
Article
Chitosan microspheres having good spherical geometry and a smooth surface were prepared by the glutaraldehyde cross-linking of an aqueous acetic acid dispersion of chitosan in paraffin oil using dioctyl sulphosuccinate as the stabilizing agent. Microspheres having different degrees of swelling were made by varying the cross-linking density. Microspheres were prepared by incorporating theophylline, aspirin or griseofulvin. Drug incorporation efficiencies exceeding 80% could be achieved for these drugs. In-vitro release studies of these drugs were carried out in simulated gastric and intestinal fluids at 37 degrees C. It was observed that the drug release rates were influenced by the cross-linking density, particle size and initial drug loading in the microspheres.
Article
An enzyme which hydrolyzes the acetamido groups of N-acetylglucosamine residues in chitin was partially purified from Mucor rouxii. The enzyme deacetylates also N-acetylchitooligoses, whereas it is inactive toward bacterial cell wall peptidoglycan, N-acetylated heparin, a polymer of N-acetylgalactosamine, di-N-acetylchitobiose, or N-acetylglucosamine. The enzyme shows a pH optimum of 5.5 and is markedly inhibited by acetate. The occurrence of this enzyme accounts for the formation of chitosan in fungi.
Article
A polymeric delayed-release protein delivery system was investigated with albumin as a model drug. The polysaccharide chitosan was reacted with sodium alginate in the presence of calcium chloride to form microcapsules with a polyelectrolyte complex membrane. Variables believed to be important for membrane formation were examined; these included reaction time, chitosan molecular weight, alginate concentration, chitosan concentration, and solution pH. An alginate-chitosan reaction time, in the range of 10 to 45 min, had no effect on the release of albumin. Increasing the alginate concentration, however, resulted in a decreased rate of release of albumin (from 37% release at 4 h with 1.5% alginate to 20% release with 2.5% alginate). Another key variable was the chitosan molecular weight. The molecular weight of chitosan was varied from 1.25 x 10(6) to 0.25 x 10(6) through a nitrite oxidation reaction with sodium nitrite. Decreasing the molecular weight increased the release of albumin (from 37% release at 4 h with high molecular weight chitosan to 77% release with low molecular weight chitosan). The pH of the extracapsular environment was found to affect the release of albumin significantly (15% release over 24 h at a pH 3.0 and 73% release at pH 8.0). Capsules produced with high molecular weight chitosan and a combination of high and low molecular weight chitosan gave the best results for reducing elution of albumin in the first 4 h and increasing elution in the following 20 h.
Article
Microspheres of chitosan crosslinked with three different crosslinking agents viz, glutaraldehyde, sulphuric acid and heat treatment have been prepared to encapsulate diclofenac sodium (DS). Chitosan microspheres are produced in a w/o emulsion followed by crosslinking in the water phase by one of the crosslinking methods. Encapsulation of DS has been carried out by soaking the already swollen crosslinked microspheres in a saturated solution of DS. Microspheres are further characterized by FTIR, x-RD and SEM. The in-vitro release studies are performed in 7.4 pH buffer solution. Microspheres produced are spherical and have smooth surfaces, with sizes ranging between 40-230 microm, as evidenced by SEM. The crosslinking of chitosan takes place at the free amino group in all the cases, as evidenced by FTIR. This leads to the formation of imine groups or ionic bonds. Polymer crystallinity increases after crosslinking, as determined by x-RD. The method adopted for drug loading into the microspheres is satisfactory, and up to 28-30% w/w loading is observed for the sulphuric acid-crosslinked microspheres, whereas 23-29 and 15-23% of loadings are obtained for the glutaraldehyde (GA)- and heat-crosslinked microspheres, respectively. Among all the systems studied, the 32% GA crosslinked microspheres have shown the sloxvest release i.e. 41% at 420 min, and a fastest release of 81% at 500 min is shown by heat crosslinking for 3 h. Drug release from the matrices deviates slightly from the Fickian process.
Chitin, chitosan, oligosaccharides and their derivatives biological activities and applications
  • K Se-Kwon
Se-Kwon K; (2011) Chitin, chitosan, oligosaccharides and their derivatives biological activities and applications. CRC Press Taylor & Francis Group, Boca Raton.
Starch, chitin and chitosan based composites and nanocomposites
  • M S Thomas
  • R R Koshy
  • S K Mary
  • S Thomas
  • L A Pothan
Thomas MS, Koshy RR, Mary SK, Thomas S, Pothan LA; (2019) Starch, chitin and chitosan based composites and nanocomposites. Springer, Switzerland. DOI: 10.1007/978-3-030-03158-9
Chitozan wszechstronny polimer ze źródeł odnawialnych. Wydawnictwo Naukowo-Techniczne
  • M Mucha
Mucha M; (2010) Chitozan wszechstronny polimer ze źródeł odnawialnych. Wydawnictwo Naukowo-Techniczne, Polska.
Enzymic preparation of acid-free-water-soluble chitosan
  • A V Ilyina
  • V E Tikhonov
  • A I Albulov
  • V P Varlamov
Ilyina AV, Tikhonov VE, Albulov AI, Varlamov VP; (2000) Enzymic preparation of acid-free-water-soluble chitosan. Process Biochem, 35, 563-568. DOI: 10.1016/S0032-9592(99)00104-1 DOI: 10.15259/PCACD.25.004
Improved method for IR determination for the degree of N-acetylation of chitosan
  • A Baxter
  • A Dillon
  • Kda Taylor
  • Gaf Roberts
Baxter A, Dillon A, Taylor KDA, Roberts GAF; (1992) Improved method for IR determination for the degree of N-acetylation of chitosan. Int J Biol Macromol, 14(3), 166-169. DOI: 10.1016/S0141-8130(05)80007-8