Chitosan Template Research Articles

Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water

Magnetic nanoparticles impregnated chitosan beads (MICB) synthesized by using chitosan template was investigated for uptake capacity of arsenic in batch studies. The adsorption isotherm could be better described by the Langmuir model than the Freundlich model. The Langmuir maximum capacity of the MICB was calculated to be 35.7 mg/g for As(V), and 35.3 mg/g for As(III) at pH 6.8, respectively, which was reasonably good compared with that of other granular adsorbents reported previously. The effects of various factors such as adsorbent dose, pH, contact time, arsenic concentration and co-existing anions on arsenic removal were systematically studied. Furthermore, the as-prepared adsorbent showed an excellent arsenic removal performance in real underground water. A distinct advantage of this adsorbent was that the adsorbent could readily be isolated from solutions by application of an external magnetic field. The study of adsorption mechanism indicated that the hydroxyl groups on the adsorbent surface were involved in arsenic adsorption.

Biotemplated synthesis of highly stable calcium-based sorbents for CO2 capture via a precipitation method

The alternation between uptake and release of CO2 by CaO sorbents is a promising method for removal of CO2 from a hot gas stream. The main drawback of this method is the deterioration of CO2 capture capacity following multiples cycles. In the present study, CaO sorbents with a high CO2 capture capacity and improved stability were prepared using chitosan as biotemplate via a simple precipitation method. Effects of mass ratio of chitosan to Ca2+ (0.125:1–2.5:1) on physical properties of the CaO sorbents as well as their CO2 capture performance were investigated. The cyclic CO2 capture performance of the CaO sorbents derived from chitosan template has been compared with that of CaO templated on a synthetic polymer (SDS), a hybrid of chitosan and SDS, and a non-templated CaO sorbent. The variation of chitosan to Ca2+ ratios was found to drastically change both the morphology and size of the CaCO3 products. CaCO3 particles homogeneously amalgamated with the chitosan matrix at a ratio of chitosan to Ca2+ of 0.125:1–0.75:1. With a yet higher ratio of 0.75:1, larger amount of chitosan molecule could incorporate into the CaCO3 particles, but a phase separation was also observed. SDS was found to act as a template for the formation of large CaCO3 particles with a spherical shape. CO2 uptake activity and stability were found to depend on both surface area and shape of the synthetic CaO materials. The CaO sorbent derived from chitosan template exhibited a higher CO2 uptake activity and stability than the other CaO sorbents. The CaO prepared in the presence of chitosan to Ca2+ ratio of 0.75:1 achieved the highest CO2 uptake of 83.75% in the first cycle and retained an excellent carbonation conversion of 57.78% after 20 consecutive test cycles. This finding indicates that the CaO derived from chitosan template constitutes a feasible option as a CO2 sorbent due to its potentially low costs, environmentally benign nature, and elevated CO2 capture capacity.

Preparation of High Performance LiFePO4/C Cathode Materials by Using Polymer Templates

This work reported a solid-state method to prepare LiFePO4/C composite cathode materials by using chitosan and polystyrene sphere (denoted as PSS) as templates. The characteristic properties of the composite cathode materials were examined by micro-Raman spectroscopy, XRD, SEM, EA, CV and EIS. The CR 2032 coin cell was used to investigate the electrochemical performance at various rates. It was found that the specific discharge capacity of LiFePO4/C composite cathode materials with chitosan template and PSS template were 141 and 146 mAh g-1 at 0.1C rate, respectively. However, the specific discharge capacities of LiFePO4/C composite cathode materials with 10%PSS template were 143, 140, 134, 113, 106 and 88 mAh g-1 at 0.2, 0.5, 1, 3, 5 and 10C rates, respectively. The results also showed that the current efficiency is ca. 95-98%. In summary, the as-prepared LiFePO4/C composite material by using polymer template can be a good candidate for Li ion battery applications.

Cr-substitution effect on the structural and magnetic properties of nano-sized NiFe2O4 prepared via novel chitosan route

Nano-crystalline Cr-substituted nickel ferrites; NiFe2−xCrxO4 (x=0.0–1.0) were prepared using chitosan template method. Differential thermal analysis–thermogravimetric measurements revealed the complete combustion of the gel precursor at 220°C. X-ray diffraction (XRD) of the as-prepared precursors exhibited the presence of secondary phases besides the entire ferrites. XRD of the calcined precursors at 500°C indicated single-phase cubic spinel structure for all the prepared samples. The lattice parameter are slightly changed with increasing Cr-content while the particle size and X-ray density gradually decreases. Vibrating sample magnetometer measurements confirmed that Cr-substitution caused a decrease in the saturation magnetization while increasing coercivity. The higher magnetizations obtained compared with other methods in literature enhances using of chitosan as a template for the preparation of other systems. The relatively high coercivity values suggested higher demagnetization magnetic field of the investigated samples. The expected chitosan complexation mechanism as well as the auto-combustion reaction were discussed. A proper cation distribution of the investigated system was suggested through structural data and was confirmed by magnetization studies.

Titanium(IV) hydrate based on chitosan template for defluoridation from aqueous solution

A cost effective bio-adsorbent, titanium(IV) hydrate based on chitosan template (Ti-CHI), was synthesized using Ti(SO4)2 and chitosan for defluoridation from aqueous solutions. The Ti-CHI material was characterized using FTIR, SEM with EDX, XRD, XPS and Zeta potential. The adsorption kinetics of fluoride onto Ti-CHI followed pseudo-second-order and intra-particle diffusion models. The Ti-CHI was effective for defluoridating systems with low fluoride concentrations (4.52mg/L), exhibiting a 87.50% removal rate and permitting a residual fluoride concentration (0.55mg/L). The most stable pH range for fluoride removal was from 4 to 9. After combining the results of pH effects, FTIR and Zeta potential, the NH groups and TiOH groups were revealed as the fluoride adsorption sites on Ti-CHI. In addition, the carbonate ions present in the aqueous solutions adversely impact the fluoride adsorption. The Langmuir, Freundlich, and Langmuir–Freundlich models were used to illustrate the isotherms of the adsorption process. The adsorption of fluoride onto Ti-CHI fits the Langmuir and Langmuir–Freundlich isotherm models well. The maximum adsorption capacity for fluoride on the Ti-CHI was 16.12mg/g. Thermodynamic studies revealed that the adsorption process was spontaneous.

Magnetic binary oxide particles (MBOP): A promising adsorbent for removal of As (III) in water

Magnetic binary oxide particles (MBOP) synthesized using chitosan template has been investigated for uptake capacity of arsenic (III). Batch experiments were performed to determine the rate of adsorption and equilibrium isotherm and also effect of various rate limiting factors including adsorbent dose, pH, optimum contact time, initial adsorbate concentration and influence of presence cations and anions. It was observed that uptake of arsenic (III) was independent of pH of the solution. Maximum adsorption of arsenic (III) was ∼99% at pH 7.0 with dose of adsorbent 1 g/L and initial As (III) concentration of 1.0 mg/L at optimal contact time of 14 h. The adsorption equilibrium data fitted well to Langmuir and Freundlich isotherm. The maximum adsorption capacity of adsorbent was 16.94 mg/g. With increase in concentration of Ca 2+, Mg 2+ from 50 mg/L to 600 mg/L, adsorption of As (III) was significantly reduced while for Fe 3+ the adsorption of arsenic (III) was increased with increase in concentration. Temperature study was carried out at 293 K, 303 K and 313 K reveals that the adsorption process is exothermic nature. A distinct advantage of this adsorbent is that adsorbent can readily be isolated from sample solutions by application of an external magnetic field. Saturation magnetization is a key factor for successful magnetic separation was observed to be 18.78 emu/g which is sufficient for separation by conventional magnate.

Size control of nanostructured silica using chitosan template and fractal geometry: effect of chitosan/silica ratio and aging temperature

The uses of low cost, renewable, environmentally friendly chitosan biopolymer as the structural template to control the size of silica particles in the range of nanometer scales are attractive for their practical industrial applications. In this paper, the nanostructured silica was synthesized using sodium silicate as the silica source and chitosan as the template under mild conditions. Effects of chitosan/silica ratio and aging temperature on the formation and the control of nanostructured silica was investigated by using thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), N2-sorption measurement, and transmission electron microscopy (TEM). It was found that the silica products were composed of the aggregates of primary silica nanoparticles and nanostructured silica units. At low aging temperature, the size of nanostructured silica was decreased when increasing the chitosan/silica ratio from 0.1 to 0.4. In contrast, the reverse trend was observed at the chitosan/silica ratio of higher than 0.4. The increase of aging temperature led to the formation of larger primary silica nanoparticles and nanostructured silica, and also promoted the formation of silica/chitosan composites. The fractal dimension calculated using modified FHH method found the linear correlation at two different regimes which might reflect the aggregates of silica products at different length scales.

Chitosan based mesoporous Ti–Al binary metal oxide supported beads for defluoridation of water

In the present study, the performance of Ti–Al binary metal oxide supported beads using chitosan template was studied for fluoride removal from drinking water. The adsorbent was synthesized by precipitation method and characterized using FTIR, SEM, XRD and BET. The higher surface area of the synthesized adsorbent 323.83 m 2/g results in a much higher fluoride removal capacity Q max = 2.22 mg g −1 as compared to bare chitosan. Pore size of beads is 42.97 Å, suggesting mesoporous nature of adsorbent. Material works very effectively at all pH except at pH greater than 9. The presence of carbonate and bicarbonate ions showed significant decline in the fluoride removal capacity of adsorbent. The experimental data fitted well to Langmuir adsorption model. The kinetic studies indicate that the system follows the pseudo-second-order and intra-particle diffusion model. Thermodynamic study reveals that the fluoride adsorption by Ti–Al binary metal oxide supported beads is an exothermic and spontaneous process. Alum appears to be the promising regeneration media showing 80% regeneration. The applicability of the adsorbent for fluoride removal was tested in field water collected from the Dhar district in Madhaya Pradesh, India.

Synthesis of bimodal porous silica from rice husk ash via sol–gel process using chitosan as template

In the present work, rice husk ash was used as a low cost raw material and chitosan was used as a template for the bimodal porous silica (BPS) synthesis. The obtained products exhibited type II isotherm of which revealed the existence of macroporous structures. When the pH of mixture was higher than pH 3, the BPS products with wormhole-like mesopore were formed as the result of the loose agglomeration of silica nanoparticles, and macropore structures were occurred from the chitosan template removal. Depending on the pH of mixtures, the BPS products synthesized with the chitosan template had higher specific surface areas (in the range of 366–627 m 2/g), total pore volumes (0.65–1.70 cm 3/g) and greater thermal stability than those synthesized without the template.

Polymorph Farming of Acetaminophen and Sulfathiazole on a Chip

The aim of this paper is to understand at a given temperature (1) the role of template films, the droplet volume of a saturated sulfathiazole aqueous solution and the solvent on polymorph screening of sulfathiazole on a silicon wafer, and (2) the effect of template films on the acetaminophen crystal face at the template-crystal interface. Template Effect: Spun cast template films of non-annealed chitosan and annealed chitosan at 140 degrees C on silicon wafers were prepared. A 0.01-cm(3) saturated sulfathiazole aqueous solution droplets were deposited on both kinds of chitosan film. Sulfathiazole crystals were produced on those films by evaporation at 25 degrees C. Volume Effect: Different droplet volumes of a saturated sulfathiazole aqueous solution ranging from 0.01 to 0.14 to 2.7 cm(3) were deposited on non-annealed chitosan films. Sulfathiazole crystals were generated on those films by evaporation at 25 degrees C. Solvent Effect: 0.01 cm(3) saturated sulfathiazole methanol solution droplets were deposited on non-annealed chitosan films and sulfathiazole crystals were formed on those films by evaporation at 25 degrees C. The formation pathways of different sulfathiazole crystal polymorphs of the above mentioned effects were analyzed and verified by systematic studies. Template-crystal Interfacial Study: Millimeter-sized acetaminophen crystals were successfully grown on non-annealed chlorosulfonated poly(ethylene) (PE-Chl) and chitosan template films by cooling the saturated acetaminophen aqueous solution from 50 to 25 degrees C in which those template films were immersed. The bonding energies for specific carbons collected by electron spectroscopy for chemical analysis (ESCA) at the acetaminophen crystal surface, together with the molecular interactions between acetaminophen and PE-Chl and between acetaminophen and chitosan in separately prepared solid dispersion film samples detected by Fourier transformed infrared (FTIR) spectroscopy, proved to be useful for identifying the crystal face of acetaminophen essential for its specific intermolecular interactions at the template-crystal interface. Thermodynamically metastable sulfathiazole Form I crystals were reproducibly obtained on the non-annealed chitosan films whereas the stable sulfathiazole Form III crystals were repeatedly formed on the annealed chitosan films. Droplet volumes and solvents were also found responsible for the polymorphic outcome of sulfathiazole in the kinetically driven area of two overlapping metastable zones from two competing polymorphs of Form I and Form III. Thermodynamically stable sulfathiazole Form III crystals were formed on the non-annealed chitosan films instead when the droplet volumes of a saturated sulfathiazole aqueous solution were increased from 0.01 to 0.14 cm(3) and 2.7 cm(3). When the solvent was changed from water to methanol, the thermodynamically stable sulfathiazole Form III crystals were again observed on the non-annealed chitosan films even from the 0.01 cm(3) saturated sulfathiazole methanol solution droplets. Template surfaces were thought to provide specific functional groups to either change the energy barrier for the nuclei formation of the thermodynamically metastable Form I or alter the droplet contact angle and the droplet surface area which was related to the droplet evaporation time. The evaporation time determines the amount of time available for the polymorphic transformation from Form I to Form III. Apparently, droplet volumes could also determine the amount of time needed to reach supersaturation and the amount of time available for a polymorphic transformation from Form I to Form III. In addition, the molecular conformation and viscosity of solvents such as methanol might alter the original nucleation kinetics in water and lead to a more rapid polymorphic transformation from Form I to Form III. Template films of PE-Chl and chitosan were found to be critical for determining the face of a millimeter-sized acetaminophen crystal at the template-crystal interface. The idea of performing polymorph screening on the template film deposited on a chip has opened up a new doorway to examine the roles of: (1) various kinds of drug carrier in the form of a template film, (2) the droplet volume of a saturated solution, and (3) the type of solvent used, in polymorphic control. Growing millimeter-sized crystals directly on the chip of template has also provided a convenient technology enabling platform for examining the crystal-template interface by solid-state characterization techniques such as ESCA.

Large two-photon absorbance of chitosan–ZnS quantum dots nanocomposite film

ZnS semiconductor nanoparticles with average size of 3.4 nm were prepared in situ in chitosan film. TEM, UV–vis spectra and PL spectra show the ZnS nanoparticles in chitosan template were monodispersed and well passivated. The two-photon absorption coefficient ( β) of the chitosan–ZnS quantum dots (QDs) nanocomposite film was obtained to be 2.29×10 2 cm/Gw from a standard Z-scan setup with femtosecond laser pusles at 790 nm wavelength. Results show the novel biomacromolecule/QDs nanocomposite film has large third-order optical nonlinear absorption, the mechanism responsible for which was discussed.

Bioabsorption qualities of chitosan-absorbable vascular templates

PURPOSE: The scope of endovascular surgical techniques has expanded to include the treatment of diseases considered at one time to be amenable only to surgical treatment. The development of the biodegradable template follows as an extension of current permanent stent technology. The goal of our project is to develop and test chitosan as an absorbable template for the vascular system. Methods Ultrapure chitosan, heparin sodium salt and lysozyme, and contrast agents MD-76R and Oxilan-350 were used to give radioopaque quality. Prototype chitosan vascular templates were obtained by a dip coating method in which alternate layers of chitosan were coagulated with nonsolvents or heparin. The amount of loaded and released heparin was determined using Azure II colorimetric assay. In vitro enzymatic degradation of templates was evaluated using lysozyme solutions in phosphate buffered saline. Mechanical properties were analyzed using the Dynamic Mechanical Analyzer, DMA-7 (Perkin Elmer, Foster City, Calif.). The microstructure of freeze-dried templates was investigated by field emission scanning electron microscopy (FE SEM) using an LEO 982 electron microscope (Zeiss, Thornwood, NY). In vivo deployment of the templates was undertaken in 10 full-sized pigs ( Sus scrofa). After open expose and control of the iliac artery, a closed balloon catheter technique was used to advance and place the balloon catheter and template. The balloon was then expanded, deploying a Palmaz stent with a chitosan template anchored distally. Patency and deployment of the stent-template complex was confirmed by an arteriogram. The animals were sacrificed at 1, 2, 3, 4, and 5 weeks poststent placement, and arterial sections were taken for microscopic analysis. The amount of chitosan remaining was estimated to determine an in vivo rate of absorption. Results On hematoxilyn and eosin staining of the section arterial samples, a marked inflammatory response was noted and progressed with duration of in vivo contact. A giant cell foreign body reaction coupled with intense intimal hyperplasia and organized thrombus was also noted and progressed with duration of time in vivo. Also noted was the degradation of the template material with only small remnants of material noted within the giant cell by week 4. Clinically, none of the pigs developed limb ischemia or evidence of thromboembolic events. Conclusions In this in vivo study, the chitosan template proved to be biodegradable but elicited an intense thrombotic and foreign body reaction despite heparin bonding. Further investigation is ongoing as to decreasing the thrombogenic and antigenic qualities of the template materials by either alteration of the base material or addition of bioactive side chains.

Polyelectrolyte complex between chitosan and poly(2-acryloylamido-2-methylpropanesulfonic acid)

A new polyelectrolyte complex between chitosan and poly(2-acryloylamido-2-methylpropanesulfonic acid) (PAMPS) was prepared by mixing aqueous solutions of its components or by free radical polymerization on chitosan template. The complex formation was sensitive to the ionic strength of the medium. The complex was stable in acidic and neutral medium and dissociated at pH > 8. Its composition did not depend on pH values of the medium and the way of preparation. The mixing dilute aqueous solutions of chitosan and PAMPS resulted in the formation of nanoparticles with mean particle diameter 250 nm and monomodal distribution.

99/00949 Electrochemical lithium-doping of oil coke thermo-treated in air : Danil'chuk, T. N. et al. Russ. J. Electrochem., 1998, 34, (7), 690–697

The ultra-low density AlCl3-chitosan composite aerogel was prepared via a novel solution-freeze-drying technology. Then, the AlCl3-chitosan aerogel was carbonized or calcined to remove the chitosan template, yielding ultra-low density Al2O3-based aerogels with good formation ability. The density of Al2O3-based aerogels were about 9 mg/cm3 via this method. Moreover, the Al2O3-based aerogel obtained from the calcination of AlCl3-chitosan aerogel copied the open networks of thin flakes layered structure of chitosan template. The as-prepared Al2O3 aerogel had a low thermal conductivity of about 0.039 W/m K after high temperature treatment at 1000 °C, demonstrating its good thermal insulation property. The results of TG/DSC showed that the Al2O3-(0.2 wt% Pt) catalysts could decrease decomposition temperature of ammonium perchlorate (AP) by 51.1 °C and the exothermic heat was increased from 133.2 J/g to 1552.7 J/g. The maximum adsorption amounts for U(VI) of Al2O3 aerogel reached 769.9 mg/g, which was about 2 times higher than that of Al2O3 with other forms. Accordingly, the Al2O3 aerogel with thin flakes layered structure and ultra-low density possessed great potential application in thermal insulation, adsorption and catalyst supports. Meanwhile, the solution-freeze-drying technology is simple and easy to control, providing a new strategy for the preparation of ultra-low density metal oxide aerogels.