Chitosan Gel Beads Research Articles

Surfactant modification of chitosan hydrogel beads for Ni@NiO core-shell nanoparticles formation and its catalysis to 4-nitrophenol reduction

Chitosan (CS) in its hydrogel bead form is widely used to remove metal ions from aqueous medium. In the present work CS gel beads were modified with sodium dodecyl sulfate (SDS), an anionic surfactant, in a novel way, with formation of bilayer (admicelle) on to it. The concentration of SDS used for CS bead modification was 6000mg/L. These surfactant-modified chitosan beads were designated as POSTCS beads. In the next step, Ni(II) was loaded on the SDS bilayer present in the POSTCS beads through a process called ‘adsolubilization'. The loading of nickel was ∼4 times higher in POSTCS beads compared to that in normal CS beads. The property of surfactant to form admicelle helped in enhanced Ni(II) adsorption, and its stabilization. Further Ni@NiO core-shell type particles were formed on POSTCS beads by borohydride reduction. The particles were characterized by XRD, FTIR, SEM/EDX and TEM analysis. The as-prepared particles exhibited excellent catalytic activity for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of borohydride. The reduction was carried out with various catalyst doses, and it was found to follow first order rate. The turn over number (TON) and turn over frequency (TOF) of the catalyst at a dose of 2.0g/L and 1×10−4M 4-NP concentration were found to be 3.0115×1019 molecules/g and 5.019×1016 molecules/g/s, respectively.

Equilibrium modeling of mono and binary sorption of Cu(II) and Zn(II) onto chitosan gel beads

Abstract The objective of the work are in-depth experimental studies of Cu(II) and Zn(II) ion removal on chitosan gel beads from both one- and two-component water solutions at the temperature of 303 K. The optimal process conditions such as: pH value, dose of sorbent and contact time were determined. Based on the optimal process conditions, equilibrium and kinetic studies were carried out. The maximum sorption capacities equaled: 191.25 mg/g and 142.88 mg/g for Cu(II) and Zn(II) ions respectively, when the sorbent dose was 10 g/L and the pH of a solution was 5.0 for both heavy metal ions. One-component sorption equilibrium data were successfully presented for six of the most useful three-parameter equilibrium models: Langmuir-Freundlich, Redlich-Peterson, Sips, Koble-Corrigan, Hill and Toth. Extended forms of Langmuir-Freundlich, Koble-Corrigan and Sips models were also well fitted to the two-component equilibrium data obtained for different ratios of concentrations of Cu(II) and Zn(II) ions (1:1, 1:2, 2:1). Experimental sorption data were described by two kinetic models of the pseudo-first and pseudo-second order. Furthermore, an attempt to explain the mechanisms of the divalent metal ion sorption process on chitosan gel beads was undertaken.

Ion-imprinted chitosan gel beads for selective adsorption of Ag+ from aqueous solutions

In this study, the Ag+-imprinted chitosan gel beads were synthesized to selectively adsorb Ag+ from bimetallic aqueous solutions containing the same molar concentration of Ag+ and Cu2+. The Ag+-imprinting not only helps to achieve extremely high selectivity of Ag+, but also enhances the uptake capacity of the target Ag+ by protecting some amine groups, the primary binding sites of metal ions from cross-linking. The maximum uptake of Ag+ by the ion-imprinted chitosan beads was found to be 89.20mgg−1 at 25.0°C with an initial Ag+ concentration of 352.95mgL−1 and the biosorbent dosage of 1.0gL−1. The adsorption equilibrium and kinetics of Ag+ by the ion-imprinted chitosan beads can be better described by Langmuir isotherm and the intraparticle diffusion model. FTIR and XPS analyses suggested that amine functional groups involve the binding of Ag+ via complexation at higher solution pH (3.0≤pH≤5.0) and ion exchange at lower solution pH (1.0≤pH<3.0).

Preparation and characterization of chitosan gel beads crosslinked by organic titanium

Chitosan (CTS) gel was successfully prepared by organic titanium (OT) ionic crosslinking agent. The viscoelastic properties of CTS gel was investigated through rheological measurement. The sol-gel transition point (t cr ) of gel prepared with CTS (22.5 g•L−1) and OT (1.5 %) was determined at 339 s, with the increases of either CTS or OT concentration, the gelation became faster and the sol-gel transition time became shorter. The optimal chitosan gel beads were prepared with 35 g•L−1 chitosan and 7 % organic titanium (OT) at room temperature for 1 h reaction. The SEM data indicated that the gel beads had special shape with rough and poriferous surface. The effective grain size range was 1.0–1.2 mm. It was confirmed by TG data that the gel beads performed better in thermal stability than original chitosan. Swelling experiments showed that the swelling ability of gel beads strongly depended on the pH value of buffer solution. On the whole, the modified CTS/OT gel beads showed high adsorption capacity, good mechanical properties, strong acidic and alkali resistances, it could serve as potential drug deliver and the absorbent for heavy metal ions.

Adsorption of Methylene Orange on Embedding Carbon Nanotubes Sodium Alginate /Chitosan Gel Beads

This study focused on the carboxylation method on multiwalled carbon nanotube (MWCNT) structure and property. The applicability of a novel adsorbent, the SA/MWCNT-CTS composite were obtained by controlling the reaction conditions. The SA/MWCNT-CTS composite was applied to the absorption of methyl orange (MO) from simulated dye wastewater .Adsorption dynamics and thermodynamics of SA/MWCNT-CTS microspheres were examined by UV-visible spectroscopy, and the associated adsorption mechanism was preliminarily investigated. Changes in the absorbance, throw ratio, conductivity, and the pH value of MO solution of MO solution during adsorption by SA/MWCNT-CTS microspheres were also studied. Results showed that the prepared SA/MWCNT-CTS microspheres retained excellent inherent chemical stability and had strong MO adsorption capacity. CS contains many hydroxyl groups, which are involved in the adsorption of organic dye. The adsorption process had a negative value of free energy change (∆G0); therefore, the process was a spontaneous reaction. At lower MO equilibrium concentrations, the SA/MWCNT-CTS microspheres had a greater capacity for adsorption.

Synergistically improved adsorption of anionic surfactant and crystal violet on chitosan hydrogel beads

While a plethora of gel beads have shown to exhibit excellent adsorbent properties, biogel beads are more attractive because of their diverse nature and biocompatibility. To this regard, chitosan hydrogel beads, where ‘synergistic effect’ plays a significant role in the efficiency of adsorption, have shown great promise. The normal adsorption rate of sodium dodecylsulfate (SDS) on chitosan hydrogel beads is greatly enhanced in presence of crystal violet (CV) dye. In such situations, simultaneously enhanced adsorption rate for both the adsorbates (viz., SDS and CV) are observed. This synergistic adsorption on a hydrogel, chitosan is being reported herein, to the best of our knowledge, for the first time. Underlying ionic interaction between the cationic part of the dye and the anionic head group of the surfactant molecule already embedded in the chitosan gel bead makes this synergism possible. The adsorption of SDS on chitosan hydrogel beads is studied in detail. The ionic interaction is manifested in the pseudo-second order kinetics of SDS removal by chitosan beads. In this article, we report our findings of quantitative analyses on SDS adsorption via the study of Langmuir adsorption isotherm (Qmax=76.9mgg−1). Desorption studies are performed on chitosan gel beads after simultaneous adsorption of CV and SDS. Interestingly, the gel beads desorb the CV up to ∼47% on long standing, leaving aside SDS in the beads. This authenticates selectivity in the desorption process. In an effort to develop eco-friendly processes implementing ‘zero waste’ management strategies, we find that the dye can be recovered quantitatively from the beads with acetone.

Preparation of Chitosan Beads for Trypsin Immobilization

ABSTRACTThe present study deals with the potential application of chitosan macrobeads for immobilization of trypsin. Macrobeads were prepared by precipitation and their mechanical properties were improved by covalent cross-linking using glutaraldehyde. Scanning electron microscopy studies showed that the beads size varied between 2.5 mm and 3.5 mm depending on the chitosan content and molar excess of glutaraldehyde. Trypsin (EC. 3.4.21.4) was chosen as model enzyme for immobilization on the chitosan gel beads pre-activated with glutaraldehyde. Catalytic properties and kinetic parameters of free and immobilized trypsin were determined and the impact of various technological parameters on enzyme activity was investigated. The obtained results showed that the optimal pH and temperature for the hydrolytic reaction catalyzed by immobilized trypsin for low molecular weight substrates were pH 8.0 and 50°C, respectively. The effect of substrate concentration was also studied and the values of the constants thus determined were: Km=1,54 mM/L and Vmax - 3.3 μM/min.

Adsorption of lanthanum by magnetic alginate‐chitosan gel beads

AbstractBACKGROUND: The risk of environmental pollution is aggravated by the increasing application of considerable amounts of rare earth elements in advanced materials. This paper reports the preparation of novel magnetic alginate–chitosan gel beads and their application for adsorption of lanthanum ions from aqueous solution.RESULTS: Stable magnetic alginate–chitosan gel beads with average diameter 0.85 ± 0.05 mm were prepared by loading iron oxide nanoparticles onto a combined alginate and chitosan absorbent. The performance of the prepared beads for the adsorption of lanthanum ions from aqueous solution was tested. It was found that various parameters, such as aqueous pH, contact time, metal ion concentration, ion strength and temperature, have an effect on the adsorption. Adsorption equilibrium was reached in 10 h and the maximum uptake capacity was 97.1 mg g−1. From the analysis of pH, FTIR and XPS data, it is proposed that lanthanum adsorption proceeds through mechanisms of cation exchange, electrostatic interaction and surface complexation, with the oxygen atoms the main binding sites. In addition, lanthanum ions could be selectively separated from coexisting base metal ions such as Pb (II), Cd (II), Co (II), Ni (II) and Cu (II) in the aqueous solution.CONCLUSION: The prepared magnetic alginate–chitosan gel beads exhibit high uptake capacity and selectivity for lanthanum sorption, and thus can be used for adsorptive recovery of lanthanum from aqueous solutions. Copyright © 2010 Society of Chemical Industry

Real-time monitor on the release of salicylic acid from chitosan gel beads by means of dielectric spectroscopy

The release processes of salicylic acid (SA) from the chitosan gel beads (CGB) with different crosslinking densities were monitored in real time by means of dielectric spectroscopy. Distinct dielectric relaxations attributed to interfacial polarization were observed, which exhibited obvious dependences on the crosslinking density and the release time. In line with Hanai’s equation, the properties of CGB and release media were quantitatively determined from the dielectric profiles. Based on these properties and dielectric behaviors, the release profiles were analyzed. It was found that only the dispersion of CGB with the lowest crosslinking density exhibited release behavior, while other dispersions showed an obvious adsorption process following a burst of drug diffusion. The total loading and release amount of SA were determined and compared, and the influence of crosslinking degree on the drug loading and release was discussed. In addition, the release behavior was confirmed to be diffusionally controlled, and the diffusion coefficient of SA was determined.

Fabrication and properties of superabsorbent complex gel beads composed of hydrolyzed polyacrylamide and chitosan

AbstractA novel method for preparing complex beads composed of hydrolyzed polyacrylamide (HPAM) and chitosan, based on the electrostatic attraction between COO− of HPAM and Al3+ and between COO− and NH3+ of chitosan, was established. In the two‐stage crosslinking process, first Al3+ was used as a crosslinking agent for the crosslinking of HPAM molecules, which were used as the skeleton structure of the gel beads. In the second stage, chitosan diffused into the skeleton structure. The gel beads were characterized with scanning electron microscopy, inductively coupled plasma mass spectrometry, Fourier transform infrared spectroscopy, and thermogravimetric analysis. There was a chitosan component in the gel beads, and these gel beads had porous and rough surfaces. The swelling properties of the HPAM–chitosan gel beads were measured in water, in acidic, neutral, and alkaline buffers, and in different saline solutions. The swelling ratio was as high as 3675 g/g in water and 170 g/g in a 0.15 mol/L NaCl solution. The beads showed pH sensitivity in buffers of different pH values and salt sensitivity in different saline solutions. The order of the equilibrium absorbency of the gel beads in different saline solutions was Na+ &gt; K+ &gt; Mg2+ &gt; Ca2+ &gt; Al3+. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Sulfasalazine release from alginate-N,O-carboxymethyl chitosan gel beads coated by chitosan

In the present study, spherical beads were prepared from a water-soluble chitosan (N,O-carboxymethyl chitosan, NOCC) and alginate with ionic gelation method. Then, swollen calcium–alginate–NOCC beads were coated with chitosan. To prepare drug loaded beads, sulfasalazine (SA) was added to the initial aqueous polymer solution. The effect of coating, as well as drying procedure, on the swelling behavior of unloaded beads and SA release of drug loaded ones were evaluated in simulated gastrointestinal tract fluid. The rate of swelling and drug release were decreased for air-dried and coated beads in comparison with freeze-dried and uncoated ones, respectively. No burst release of drug was observed from whole tested beads. Chitosan coated beads released approximately 40% of encapsulated drug in simulated gastric and small intestine tract fluid. Based on these results, the chitosan coated alginate–NOCC hydrogel may be used as potential polymeric carrier for colon-specific delivery of sulfasalazine.

Chitosan gel beads immobilized Cu (II) for selective adsorption of amino acids

Chitosan (CS) gel beads were prepared by using phase inversion and precipitation technique. The gel beads could bind copper (II), by which Cu (II) ion-immobilized chitosan gel beads (CS-Cu 2+ gel beads) were prepared, and the amount of the immobilized Cu (II) was about 35 mg/g when the CS gel beads were incubated in 150 ppm cupric sulfate solution. The CS-Cu 2+ gel beads could selectively adsorb histidine (His) from the mixed solution containing His and tryptophan (Trp); and the selective coefficient which was defined as the adsorbed amount ratio of His to Trp was about 8.0 at the pH value of 7.4. The effect of the pH value on the amino acid adsorption was also studied. In order to investigate the relationship of the amino acid adsorption and protein adsorption, the adsorbed amounts for IgG and albumin were determined; and the results indicated that the CS-Cu 2+ gel beads could adsorb a larger amount of IgG than albumin due to the larger amount of the exposed residual His. The study provided a sorbent and a method to selectively remove His and IgG.

Dielectric analysis of chitosan gel beads suspensions: Influence of low crosslinking agent concentration on the dielectric behavior

Dielectric measurements were carried out for the suspensions of chitosan gel beads (CGB) crosslinked with glutaraldehyde (GA), ranging in crosslinking time from 1 to 180 min at six fixed low GA concentrations over a frequency range from 40 to 110 MHz. The distinct dielectric relaxations observed in the frequency range of 10 4–10 5 Hz were explained by the effects of the interfacial polarization. By fitting the experimental data with Cole-Cole equation the dielectric parameters of the suspensions were obtained, and the phase parameters were calculated using Hanai's method. The influence of crosslinking on the dielectric spectra of CGB was investigated by viewing the crosslinking time dependencies of conductivity increment (Δ κ), relaxation frequency ( f 0 ), permittivity of CGB ( ε i ), conductivity of CGB ( κ i ) and conductivity of continuous media ( κ a ) at six fixed GA concentrations. Some information were gained, such as, thinner electric double layer, particle with rougher surface and more compact gel backbone with increasing crosslinking time. The basic information obtained can provide valuable references for the preparation of CGB and the application to more extensive fields such as controlled-release technology of medicament.

Preparation of porous chitosan gel beads for copper(II) ion adsorption

In this paper, chitosan porous beads were prepared by using a phase inversion technique, and then used for the adsorption and removal of copper(II) ions. The porosity, diameter and other characteristics were characterized. With the increase of chitosan and NaOH concentration used to prepare the beads, the amount of adsorbed Cu 2+ per gram of the beads decreased. A maximum adsorption amount was observed at a pH value of 6.0 for the cross-linked porous chitosan beads. The amount of the adsorbed Cu 2+ increased with the Cu 2+ concentration used in the adsorption experiments. By the relationship of the ratio of the equilibrium Cu 2+ concentration in the solution ( C e) to the adsorbed equilibrium amount ( P e) ( C e/ P e) and C e, we concluded that the adsorption of Cu 2+ to the porous chitosan beads was Langmuir adsorption. The Cu 2+-loaded porous chitosan beads were stable in water, which is useful for further study on selectively adsorption of IgG. The results suggested that the porous chitosan beads were useful adsorbents for copper ions removal in water treatment, and the Cu 2+-loaded beads may be good sorbents for IgG removal in blood purification.

Determination of kinetic parameters from isothermal calorimetry for interaction processes of pyrimethamine with chitosan derivatives

The interaction of the antifolate drug pyrimethamine with chitosan derivatives, namely, chit-GLT (glutaraldehyde cross-linked chitosan gel beads) and chit-Cu (chit-GLT beads treated with copper solution) has been investigated from isothermal calorimetry at 298 and 308 K, being studied in terms of the Avrami and pseudo-first- and second-order kinetic models. The Avrami model provided a high fitting with the experimental data. The results have pointed out the slower kinetic for pyrimethamine sorption on chit-GLT compared to chit-Cu, in agreement with the reaction time obtained from calorimetry.

Characterization and immobilization of liposome-bound cellulase for hydrolysis of insoluble cellulose

The liposome-bound cellulase was prepared by covalently coupling cellulase with the enzyme-free liposomes bearing aldehyde groups so that cellulase was located solely on the outer membrane of liposomes. The modified cellulase possessed the higher activity efficiency and lipid-based specific activity than the cellulase-containing liposomes reported previously. The enzyme-free liposomes bearing aldehyde groups were covalently immobilized with the chitosan gel beads and the free cellulase was coupled with the treated gel beads to prepare the immobilized liposome-bound cellulase. The activity efficiency of the immobilized liposome-bound cellulase was much higher than that of the conventionally immobilized cellulase. The results on reusability of the immobilized liposome-bound cellulase in the hydrolysis of either soluble or insoluble cellulose showed that the immobilized liposome-bound cellulase had the higher remaining cellulase activity and reusability than the conventionally immobilized cellulase for the hydrolysis of either type of cellulose. The liposomal membrane was suggested to be efficient in maintaining the cellulase activity during the hydrolysis.

Removal of airborne hexavalent chromium mist using chitosan gel beads as a new control approach

Airborne hexavalent chromium is a known human respiratory carcinogen and allergen. Many workers are exposed to hexavalent chromium in various processes which chromium electroplating plants are the most common. In this study, the feasibility of a new control approach to remove this pollutant using chitosan beads as a biosorbent was investigated. Hexavalent chromium sorption was studied relative to pH, pollution concentration, sorbent concentration, temperature, and air velocity using one factor at a time approach and Taguchi experimental design. Polluted air with different chromium mist concentrations (10-5000 µg/m 3 ) was contacted to chitosan beads (3.3-20 g/L), floating in distilled water with adjusted pH (3-7), using an impinger at different temperatures (20 and 35 °C), and various velocities (1.12 and 2.24 m/s). The ANOVA test result showed that, there were statistical significant differences between factor levels except optimized pH levels. The higher ions removal efficiencies were achieved at lower levels of air velocities, pollution concentrations, and higher levels of solution pH values, temperatures, and sorbent concentrations.

Optimal Preparation of Immobilized Liposome-Bound Cellulase for Hydrolysis of Insoluble Cellulose in an External Loop Airlift Bioreactor

Immobilized liposome-bound cellulase (ILC) was optimally prepared for the ILC-catalyzed hydrolysis of insoluble cellulose in an external loop airlift bioreactor. The liposomes with mean diameters of 200, 100, and 50 nm were used to prepare three kinds of ILCs, i.e., ILC(200), ILC(100) and ILC(50), respectively. The activity and stability of ILC(100) were examined with soluble cellulose (CMC) in addition to the insoluble substrate of cellulose powder (CC31) in a shaking flask as well as the airlift bioreactors. The experiments were carried out with 45 degrees C and pH 4.8 being found to be optimal for the activity. The activity of ILC(100) was stable in either airlift or shaking flask bioreactor during the five times repeated hydrolyses of CC31 corresponding to a total reaction time of 240 h. This confirmed that the cellulase molecules were covalently bonded to the liposomes covalently bound to the chitosan gel beads. Nevertheless, the activity of ILC(100) with CMC steadily decreased throughout the repeated reactions, suggesting an adverse effect of CMC on the ILC(100) activity. Among the three ILCs, ILC(50) was found to be the most stable and productive biocatalyst during the repeated hydrolyses of insoluble CC31 in the airlift bioreactor. More than 70% of the initial activity of ILC(50) was retained even after the six times repeated reactions for 288 h. Conversely, the ILC(200) was found to be the most unstable catalyst. Such a difference in stability among these ILCs was suggested to be caused by the difference in physical stability of their liposome membranes to the liquid shear stress due to the rising bubbles and circulating liquid as well as that in the amount of the cellulase molecules unstably incorporated in the membranes. ILC(50) was thus shown to have the most potential for an efficient hydrolysis of insoluble cellulose in a practical airlift bioreactor.

Preparation and Adsorption Ability of Polysulfone Microcapsules Containing Modified Chitosan Gel

Chemically modified chitosan beads containing polyethyleneimine (PEI) were prepared to improve the metal ion adsorption capacity of the chitosan beads and their mechanical stability and to limit their biodegradability. The modified beads were encapsulated with the polymer material polysulfone by a novel surface coating method named the emulsion phase inversion method. The adsorption properties of the modified beads and the microstructures of the polysulfone coating layer were then analyzed. The experimental results showed that the PEI was successfully linked onto the chitosan beads. The density of the —NH 2 groups in the modified beads was significantly increased, while the water content was reduced. The coating layer thickness was about 200 μm. The modified chitosan gel beads had excellent Cu(II) adsorption capacity, with a maximum Cu(II) adsorption capacity 1.34 times higher than that of the unmodified beads. The results show that even with the polysulfone coating the adsorption kinetics of the modified beads is still better than those of the unmodified beads. The modifications improve the mass transfer performance of the chitosan beads as well as the bead stability.

Sustained insulin release with biodegradation of chitosan gel beads prepared by copper ions

Chitosan (CS) gel beads were prepared with chelated copper (II) ions as a vehicle for the delivery of peptide and protein drugs. Insulin, which is a model of peptide and protein drugs, was scarcely released from the CS gel beads in vitro, presumably due to the nature of interactions occurring between insulin, CS and the copper (II) ions. The efficacy of insulin released from the CS gel beads was confirmed by implantation into diabetic mice. A consistent reduction in blood glucose level was observed in vivo due to insulin release as the CS gel beads were degraded. Control over insulin release was achieved by altering the properties of the CS. Thus, CS gel beads are promising as a biocompatible and biodegradable vehicle by which peptide and protein drugs can be delivered.