Raw Chitosan Beads Research Articles

Chitosan Hydrogel Beads Supported with Ceria for Boron Removal.

In this study, a chitosan hydrogel supported with ceria (labelled Ce-CTS) was prepared by an encapsulation technique and used for the efficient removal of excess B(III) from aqueous solutions. The functionalisation of chitosan with Ce(IV) and the improvement in the adsorptive behaviour of the hydrogel were determined by SEM-EDS, FTIR, XRD, and inductively coupled plasma optical emission spectrometer (ICP-OES) analyses and discussed. The results demonstrate that Ce-CTS removes boric acid from aqueous solutions more efficiently than either cerium dioxide hydrate or raw chitosan beads, the precursors of the Ce-CTS biosorbent. The maximum adsorption capacity of 13.5 ± 0.9 mg/g was achieved at pH 7 after 24 h. The equilibrium data of boron adsorption on Ce-CTS fitted the Freundlich isotherm model, while the kinetic data followed the Elovich pseudo-second-order model, which indicated that the process was non-homogeneous. The dominant mechanism of removal was the reaction between boric acid molecules and hydroxyl groups bound to the ceria chelated by chitosan active centres. Due to its high efficiency in removing boron, good regeneration capacity and convenient form, Ce-CTS may be considered a promising biosorbent in water purification.

Removal of nickel(II) ions by histidine modified chitosan beads

In order to increase the nickel adsorption capacity of raw chitosan beads (CB), they were chemically modified with histidine (HIS–ECH–CB) by using crosslinking agent, epichlorohydrine (ECH). The nature and morphology of the sorbent were characterized using FTIR, TGA and SEM analysis. For optimization of adsorption conditions, sorption experiments were performed by varying contact time, pH, temperature and initial nickel concentration. Based on the adsorption experiment, the HIS–ECH–CB showed the significant adsorption capacity of 55.6mg/g under the optimal adsorption condition. Nickel adsorption isotherms data were fitted to Freundlich isotherm. Thermodynamic parameters namely ΔG°, ΔH° and ΔS° of the Ni(II) adsorption process were calculated. The negative values of Gibbs free energy of adsorption (ΔG°) indicated the spontaneity of the adsorption of Ni(II) ions on the histidine modified chitosan. Desorption of Ni(II) ions from HIS–ECH–CB could be done rapidly by using 0.1M HCl, HNO3 and EDTA solutions and the beads could be used again to adsorb Ni(II) ions.

Preparation of amino terminated polyamidoamine functionalized chitosan beads and its Cr(VI) uptake studies

Chitosan beads, functionalized by amino terminated hyperbranched dendritic polyamidoamine (up to 3rd generation) were prepared by Michael addition of methyl acrylate to amino groups on the chitosan surface and amidation of terminal ester groups by ethylene diamine. All the three generation chitosan beads were used for chromium removal along with raw chitosan beads. However, the 3rd generation polyamidoamine chitosan beads (3ACB) have been protonated using HCl (3ACBP)/loaded with zirconium using ZrOCl2·8H2O (3ACBZr) to enhance the sorption capacity towards Cr(VI). The zirconium loaded chitosan beads showed higher Cr(VI) sorption than the other modified chitosan beads. The zirconium loaded chitosan beads were characterized using SEM, EDAX, FT-IR, XRD, DSC and TGA. The system variables studied include agitation time, initial concentration of sorbate, pH, co-ions in the medium and temperature on the sorption of chromium. The chromium uptake onto 3ACBZr obeys the Freundlich isotherm. Thermodynamic studies revealed that the nature of chromium sorption is spontaneous and endothermic. The mechanism of chromium sorption onto the sorbent was established.

Adsorption of allura red dye by cross-linked chitosan from shrimp waste

The present study was designed to evaluate the chitosan, which has been obtained by deacetylation of chitin, as a biosorbent. The chitin was isolated from fermented shrimp waste by an important local industrial food biopolymer. The aim of this work was the characterization of chitosan and preparation of cross-linked chitosan- tripolyphosphate (chitosan-TPP) beads for the removal of allura red food dye from aqueous solutions. Conditions of batch adsorption such as pH, time and adsorbent dose were examined. The effectiveness of cross-linked chitosan beads for dye removal was found to be higher for pH 2 (98%, percentage of dye removal) and tends to decrease at pHs of 3 to 11 (up to 49%). The values of percentage removal show that the adsorption capacity increases with time of contact and dosage of chitosan-TPP, but red dye adsorption is mainly influenced by pH level. The cross-linked chitosan-TPP beads can significantly adsorb allura red monoazo dye from aqueous solutions even at acidic pHs unlike raw chitosan beads that tend to dissolve in acidic solutions. Consequently, this modified chitosan has characteristics that allow minimization of environmental pollution and widening the valorization of shrimp waste.

Selective sorption of Fe(III) using modified forms of chitosan beads

AbstractModified chitosan beads (CB) were prepared and used for the removal of Fe(III) ions from aqueous solution. The advantages of modified CB than raw CB have been explored. The sorption capacity (SC) of the modified forms of CB namely, protonated CB, carboxylated CB, and grafted CB were found to be 3533, 3905, and 4203 mg kg−1, respectively, while the raw CB showed the SC of 2913 mg kg−1 only. Batch adsorption studies were conducted to optimize various equilibrating conditions like contact time, pH, and coions. The sorbents were characterized by FTIR, WDXRF, and SEM with EDAX analysis. The sorption process has been explained with Freundlich and Langmuir isotherms. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS° were calculated to understand the nature of sorption. Modified CB are more selective for Fe(III) than Cu(II), which inturn higher than Cr(VI). A suitable mechanism for iron sorption onto modified CB was established. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Sorption behaviour of copper on chemically modified chitosan beads from aqueous solution

In order to increase the copper sorption capacity (SC) of raw chitosan beads (CB), they were chemically modified into protonated chitosan beads (PCB), carboxylated chitosan beads (CCB) and grafted chitosan beads (GCB) which showed a significant SC of 52, 86 and 126 mg/g respectively while raw chitosan beads (CB) displayed only 40 mg/g. Among the sorbents studied, GCB experienced a higher SC than CB, PCB and CCB. Sorption experiments were performed by varying contact time, pH, presence of co-anions, different initial copper concentrations and temperature for optimization. The nature and morphology of the sorbents were discussed using FTIR and SEM analysis. The copper uptake onto PCB, CCB and GCB obeys the Freundlich isotherm. Thermodynamic studies revealed that the nature of copper sorption is spontaneous and endothermic.

Sorption of chromium(VI) using modified forms of chitosan beads

Modified forms of chitosan beads were prepared and used for chromium removal from the aqueous solution. The prepared chitosan beads viz., protonated chitosan beads (PCB), carboxylated chitosan beads (CCB) and grafted chitosan beads (GCB) possess enhanced chromium sorption capacities (SCs) of 3239, 3647 and 4057 mg/kg respectively than the raw chitosan beads (CB) which possess the SC of 1298 mg/kg with a minimum contact time of 10 min. The sorption experiments were carried out in batch mode to optimize various influencing parameters viz., contact time, pH, common ions and temperature. The sorbents were characterized by FTIR and SEM with EDAX analysis. The modified chitosan beads remove chromium by means of electrostatic adsorption coupled reduction and complexation. The adsorption data was fitted with Freundlich and Langmuir isotherms. The calculated values of thermodynamic parameters indicate the nature of chromium sorption. A field trial was carried out with water collected from a nearby industrial area.

Synthesis of Zr(IV) entrapped chitosan polymeric matrix for selective fluoride sorption

The Zr(IV) loaded carboxylated chitosan beads (Zr-CCB) was synthesised and fluoride removal studies were carried out in batch equilibration method. The results shows an enhanced defluoridation capacity (DC) of Zr-CCB (4850 mg F −/kg) than the carboxylated chitosan beads (CCB) and raw chitosan beads (CB) which possesses the DCs of 1385 and 52 mg F −/kg, respectively. The mechanism of fluoride removal by Zr-CCB is governed by both adsorption and complexation. The presence of functional groups, elements and the surface morphology of the sorbent were confirmed by FTIR and SEM with EDAX analysis. The experimental data have been analysed using Freundlich, Langmuir and Dubinin–Radushkevich (D–R) isotherms. The best fit isotherm model was identified using various methods of non-linear analysis. Thermodynamic parameters such as Δ G°, Δ H° and Δ S° were calculated to predict the nature of fluoride sorption. A field trial was carried out with fluoride water collected from a nearby fluoride-endemic village.

Enhanced and selective fluoride sorption on Ce(III) encapsulated chitosan polymeric matrix

AbstractChitosan beads (CB) possesses low defluoridation capacity (DC) have been suitably modified by carboxylation followed by chelation with Ce(III) to enhance its DC. The carboxylated chitosan beads (CCB), which has a desirable DC of 1385 mgF−/kg, has been further chemically modified by incorporating Ce3+ ion into CCB (Ce‐CCB) and its DC was found to be 4798 mgF−/kg, whereas raw chitosan beads (CB) possesses 52 mgF−/kg only. The maximum DC of Ce‐CCB was observed at pH 7 and showed selectivity toward fluoride in presence of other coanions. The sorbent was characterized using FTIR and SEM with EDAX analysis. The sorption data was fitted with Freundlich and Langmuir isotherms and kinetic models. The calculated thermodynamic parameters, viz., ΔG°, ΔH° and ΔS° indicate the nature of fluoride sorption. A field trial was carried out with fluoride water collected from a nearby fluoride‐endemic village to test the suitability of Ce‐CCB at field conditions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Development of multifunctional chitosan beads for fluoride removal

Chitosan beads (CB) which have negligible defluoridation capacity (DC) have been chemically modified by introducing multifunctional groups, viz., NH 3 + and COOH groups by means of protonation and carboxylation in order to utilize both amine and hydroxyl groups for fluoride removal. The protonated cum carboxylated chitosan beads (PCCB) showed a maximum DC of 1800 mg F −/kg whereas raw chitosan beads displayed only 52 mg F −/kg. Sorption process was found to be independent of pH and slightly influenced in the presence of other common anions. The fluoride sorption on modified forms was reasonably explained by Freundlich and Langmuir isotherms. The sorbents were characterised by FTIR and SEM with EDAX analysis. The sorption process follows pseudo-second-order and intraparticle diffusion kinetic models. The suitability of PCCB has been tested with field sample collected from a nearby fluoride endemic area.

Sorption behaviour of fluoride on carboxylated cross-linked chitosan beads

Carboxylated cross-linked chitosan beads (CCB) showed a significant defluoridation capacity (DC) of 1385 mgF −/kg than the raw chitosan beads (CB) which displayed only 52 mgF −/kg. Sorption experiments were performed by varying contact time, pH, presence of co-anions and temperature. The nature and morphology of the sorbent were discussed using FTIR and SEM with EDAX analysis. The stability of the beads in solution was explained in terms of swelling ratio of the beads. The fluoride uptake onto CCB obeys both Freundlich and Langmuir isotherms. Thermodynamic studies revealed that the nature of fluoride sorption is spontaneous and endothermic. Sorption kinetics is mainly controlled by pseudo-second-order and intraparticle diffusion models. 0.1 M HCl was identified as the best eluent. The suitability of CCB at field conditions has been tested with field sample collected from a nearby fluoride-endemic area.

Removal of fluoride from aqueous solution using protonated chitosan beads

In the present study, chitosan in its more usable bead form has been chemically modified by simple protonation and employed as a most promising defluoridating medium. Protonated chitosan beads (PCB) showed a maximum defluoridation capacity (DC) of 1664 mg F −/kg whereas raw chitosan beads (CB) possess only 52 mg F −/kg. Sorption process was found to be independent of pH and altered in the presence of other co-existing anions. The sorbents were characterized using FTIR and SEM with EDAX analysis. The fluoride sorption on PCB follows both Freundlich and Langmuir isotherms. Thermodynamic parameters, viz., Δ G°, Δ H° Δ S° and E a indicate that the nature of fluoride sorption is spontaneous and endothermic. The sorption process follows pseudo-second-order and intraparticle diffusion kinetic models. 0.1 M HCl was identified as the best eluent. The suitability of PCB has been tested with field samples collected from a nearby fluoride-endemic area.

Enhanced fluoride sorption using La(III) incorporated carboxylated chitosan beads

The carboxylated chitosan beads (CCB), which have a defluoridation capacity (DC) of 1385 mg F −/kg, have been further chemically modified by incorporating La 3+ ion (La-CCB) and its DC was found to be 4711 mg F −/kg whereas the raw chitosan beads (CB) possess only 52 mg F −/kg. The fluoride removal by La-CCB is governed by both adsorption and complexation mechanism. The functional groups present in beads were identified by FTIR analysis. The surface condition and existence of fluoride on the beads was confirmed by SEM with EDAX analysis. The experimental data have been analyzed using Freundlich and Langmuir isotherm models. Thermodynamic parameters such as Δ G o , Δ H o and Δ S o were calculated to predict the nature of sorption. The kinetic studies were investigated with reaction-based and diffusion-based models. A field trial was carried out with fluoride water collected from a nearby fluoride-endemic village.

Characterization of metal ion interactions with chitosan by X-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy (XPS) is employed to study chemical interactions between three metal ions — Cu(II), Mo(VI), and Cr(VI) — and chitosan, a natural biopolymer extracted from crab shells. Three forms of chitosan are used — flakes, beads, and modified beads obtained by glutaraldehyde cross-linking. XPS provides identification of the sorption sites involved in the accumulation of metals, as well as the forms of species sorbed on the biopolymer. It is found that sorption occurs on amine functional groups for all the three metals. With copper, the sorption step is not followed by reduction of the metal. More complex phenomena are involved in molybdate removal. A partial reduction (about 20–25% of the total molybdenum content) occurs with chitosan beads and flakes. The distribution of reduced Mo(V) on the surface of the sorbent differs from that in the bulk of the sorbent for raw chitosan beads, while the glutaraldehyde cross-linking allows uniform distribution of reduced Mo(V) throughout the sorbent. The difference between these two forms of chitosan can be related to a complementary photoreduction step occurring on the surface of the biopolymer. For chromium, a similar trend with molybdenum is followed but to a greater extent; with cross-linked sorbents all chromate previously sorbed is reduced to Cr(III), while with raw chitosan beads Cr(VI) reduction does not exceed 60%.

Study of molybdate ion sorption on chitosan gel beads by different spectrometric analyses

Molybdate ion uptake both by raw chitosan and by glutaraldehyde cross-linked chitosan beads was investigated. This study focused on the identification of sorption mechanisms by means of several analytical procedures such as infra-red and reflectance spectrophotometries and CP-MAS 13C NMR analyses. Although the amine functions of glucosamine residues remain the major sites of interaction with the metal species, other functional groups can also be involved. It is certainly the case with carbonyl functions provided by the glutaraldehyde structure in cross-linked sorbents. Due to the large size of the polynuclear hydrolysed molybdate species, the sorption may involve several monomer units, resulting in additional linkages between the polymer chains. This behaviour can be confirmed by the chemical shifts of the carbon atoms observed by CP-MAS 13C NMR on raw chitosan beads, showing that the carbon atoms supporting the amino sites are not the only atoms affected by molybdate ion sorption. Moreover, cross-linking promotes a partial reduction of molybdenum species in the presence of some unreacted aldehyde groups.