Glutaraldehyde Cross-linked Chitosan Beads Research Articles

Novel synthesis and physical properties of CoFe[formula omitted]O[formula omitted]@CoFe[formula omitted] core@shell nanostructures

In this work, CoFe2O4@CoFe2 (core@shell) nanoparticles were synthesized by an easy method without using special reagents or gases. Firstly, we have prepared glutaraldehyde crosslinked chitosan beads containing CoFe2O4 nanoparticles. Secondly, the beads were thermal treatment at high temperatures and in vacuum, at a pressure of 0.02 Torr and for 1 h. The CO gas released from chitosan during the thermal treatment helped to reduce the Fe3＋ and Co2+ to their zero valence state. Four samples were produced at temperatures of 400, 500, 600 and 700 °C, and their structure, particle size, morphology and magnetic properties were studied. The X-ray diffraction and Mössbauer spectroscopy showed the presence of CoFe2O4 and CoFe2 magnetic phases for samples prepared at 400 and 700 °C, respectively. For samples prepared at 500 and 600 °C we have obtained core@shell particles with crystallite sizes of 6.6–7.4 nm and 22.4–26.1 nm for CoFe2O4 and CoFe2 phases, respectively. The TEM images showed the presence of nanoparticles with a core@shell configuration, we found evidences that the shell CoFe2 is made of a single crystal. Magnetic measurements showed that the CoFe2O4 and CoFe2 phases, for sample treated at 600 °C, are exchange coupled leading to a (BH)max= 0.67 MGOe. We have tuned the thickness of the CoFe2 phase to be ∼9.0 nm, this value is smaller than the critical size of 10.2 nm obtained according to the Kneller-Hawig theory, therefore satisfying the physical condition for the magnetic coupling between CoFe2 and CoFe2O4 phases.

Carbon quantum dots and chitosan-based heterogeneous silver catalyst for reduction of nitroaromatic compounds.

Chitosan plays a crucial role in catalysis, environmental remediation, and sustainable chemistry as a renewable and cationic polysaccharide. Chitosan-based metal catalysts are used in a broad range of chemical transformations. In the study, carbon quantum dots (CQDs) were derived from Momordica charantia fruits by microwave irradiation following a green chemistry approach. Three catalysts were designed: Ag(0)-chitosan, Ag(0)-chitosan-M. charantia fruit powder, and Ag(0)-chitosan-CQDs. The catalyst supports were prepared by stabilizing CQDs or M. charantia powder within the polymeric matrix of chitosan beads. Metallic silver particles were anchored onto glutaraldehyde cross-linked chitosan beads from the aqueous solution of silver nitrate. The heterogeneous silver catalysts were used to reduce toxic nitroaromatics (4-nitrophenol, 2-nitroaniline, 1,2-diamino-4-nitrobenzene, 2,4-dinitrophenol). The regeneration of catalysts was also covered. The reused catalysts retained their catalytic activities after ten cycles. The study suggested that presence of CQDs or M. charantia powder could improve the efficiency of the chitosan-based metallic silver catalysts.

Modifying Thermostability and Reusability of Hyperthermophilic Mannanase by Immobilization on Glutaraldehyde Cross-Linked Chitosan Beads

In the current study, the purified β-mannanase (Man/Cel5B) from Thermotoga maritima was immobilized on glutaraldehyde cross-linked chitosan beads. The immobilization of Man/Cel5B on chitosan beads was confirmed by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. After immobilization, the protein loading efficiency and immobilization yield were found to be 73.3% and 71.8%, respectively. The optimum pH for both free and immobilized enzymes was found to be pH 5.5. However, the optimum temperature of immobilized Man/Cel5B increased by 10 °C, from 85 °C (free Man/Cel5B) to 95 °C (Immobilized). The half-life of free and immobilized enzymes was found to be 7 h and 9 h, respectively, at 85 °C owing to the higher thermostability of immobilized Man/Cel5B. The increase in thermostability was also demonstrated by an increase in the energy of deactivation (209 kJmol−1) for immobilized enzyme compared to its native form (92 kJmol−1), at 85 °C. Furthermore, the immobilized Man/Cel5B displayed good operational stability as it retained 54% of its original activity after 15 repeated catalytic reactions concerning its free form.

Evaluation of Cr(VI) adsorption on glutaraldehyde crosslinked chitosan beads using cyclic voltammetry employing gold electrode

Hexavalent chromium is one of the toxic heavy metals found in wastewaters from industries like electroplating, leather tanning, and steel manufacturing. The Cr(VI) removal and quantitative detection are among the major concerns from an environmental toxicity point of view. In the present work, we report an effective electrochemical technique for Cr(VI) monitoring based on the utilization of gold electrode. The technique developed is user-friendly, non-destructive, and provides real-time monitoring of Cr(VI) from wastewaters in contrast to other spectroscopic and optical techniques. The technique developed was applied in monitoring Cr(VI) removal from synthetic Cr(VI) samples using chitosan cross-linked glutaraldehyde (C + G) beads. The parameter optimization for Cr(VI) removal using C + G beads was done. The experimental data of Cr(VI) adsorption on C + G beads obtained using cyclic voltammetry were further used for kinetic and thermodynamic studies. Kinetic and thermodynamic studies found that Cr(VI) adsorption follows pseudo-second-order kinetics and Modified Langmuir isotherm. The maximum adsorption capacity of C + G beads for Cr(VI) was found to be 28.65 mg g−1. These results obtained indicate that the cyclic voltammetric technique using gold electrode can be effectively applied for Cr(VI) analysis from wastewaters.

Immobilization of Pleurotus nebrodensis WC 850 laccase on glutaraldehyde cross-linked chitosan beads for enhanced biocatalytic degradation of textile dyes

Immobilized laccases with aggrandized catalytic activity and stability have demonstrated potential applicability in wastewater treatment. Herein, a purified laccase from Pleurotus nebrodensis WC 850 was effectively immobilized onto high-quality spherical chitosan beads using the cross-linking method. The maximum immobilization yield was achieved by chitosan beads developed using a 2.5 % chitosan solution after 6 h of incubation in 1.0 % glutaraldehyde solution. The detection of copper by EDX analysis confirmed the occurrence of the enzyme in the laccase coupled beads. Chitosan-immobilized laccase (CTS-Lac) performed over wide working pH and temperatures with an optimum pH of 7.0 and 50 °C. Kinetic parameters Km and Vmax for CTS-Lac were calculated to be 120 μM and 597 U/mL, respectively. CTS-Lac achieved high decolorization efficiencies for different reactive and disperse dyes (83–90 %). Preservation of 84.19 % and 54.21 % of its initial activity after 3 and 8 consecutive dye removal cycles indicates a stable dye degradation performance in the repeated batches. After treatment with the enzymes, BOD, COD, and TOC levels were reduced to 92.25–96.55 %, 91.90–94.94, and 77.01–93.29 %, respectively, in the dye solutions. Conclusively, immobilized laccase treatment might appear a good choice for bioremediation of dye-laden industrial wastewater due to substantial degradation and appreciable improvement in water quality parameters.

Enhanced Gold(III) adsorption using glutaraldehyde-crosslinked chitosan beads: Effect of crosslinking degree on adsorption selectivity, capacity, and mechanism

Recovery of gold from electronic waste (e-waste) has received significant attention due to its high economic value. This study reports glutaraldehyde-crosslinked chitosan (GCC) beads as highly efficient bioadsorbents for the separation of auric ions (Au(III)) from acidic e-waste leaching solutions. With increasing extent of glutaraldehyde-crosslinking, the GCC beads showed enhanced adsorption selectivity and capacity toward Au(III). The Au(III) adsorption capacity, however, was saturated with a further increase in the crosslinking time due to increasing self-oligomerization of glutaraldehyde. High adsorption selectivity was also observed for other precious metals such as Pd(II), Pt(IV), Ir(III), Os(IV), and Ag(I), but negligible adsorption was found for most other metals. The high Au(III) adsorption capacity and selectivity of GCC beads was attributed to multiple mechanisms such as electrostatic attraction, chelation, and reduction of Au(III), based on a range of spectroscopic evidence (FTIR, XRD, XPS, SEM, and TEM) and Au(III) adsorption behavior. The adsorbed Au(III) was reduced to Au(I) and then to Au(0), forming Au-nanoparticles as the main Au species with increasing adsorption time. The GCC beads showed a good reusability in repeated Au(III) adsorption–desorption cycle tests and were used to successfully separate high purity gold (96.7%) from an acidic e-waste leaching solution.

Immobilization of fungal laccase on glutaraldehyde cross-linked chitosan beads and its bio-catalytic potential to degrade bisphenol A

Abstract Bisphenol A is an endocrine disrupting compound that is continuously released into the environment. In this study, a laccase from Trametes versicolor was covalently immobilized onto high quality chitosan beads as carrier support chemically cross-linked with glutaraldehyde. Chitosan beads (average 2.0 mm diameter) developed using 2.5% (w/v) chitosan and functionalized with 2.0% (v/v) glutaraldehyde for 3 h yielded maximum immobilization efficiency (∼84.7%). The surface topology of laccase-attached chitosan support was envisaged and compared with control beads by scanning electron microscope (SEM). The immobilized biocatalyst showed good operational stability, retaining 71.24% of its original activity after 10 repeated catalytic cycles with reference to its native form. Storage stability profile exhibited the superiority of the laccase-immobilized chitosan beads presenting over 90% of activity after preserving for 28 days at 4 °C, whereas free enzyme showed only 47.3% activity under the same conditions. In addition, the chitosan-based biocatalytic system achieved almost complete removal of bisphenol A from the aqueous solution after 150 min of the transformation process. Conclusively, these results proposed the use of the chitosan hydrogel beads immobilized laccase as a promising and environmentally friendly biocatalyst for the degradation of environmental pollutants, particularly the removal of phenolic compounds in wastewater.

Immobilization of Burkholderia cepacia lipase on crosslinked chitosan-based support for the synthesis of geranyl acetate

Abstract In this study, glutaraldehyde-crosslinked chitosan beads were prepared and characterized for the immobilization of Burkholderia cepacia lipase (BCL, 23,000 U/g). The crosslinking time and the concentration of glutaraldehyde were evaluated. The morphological modifications and the chemical interaction between the chitosan beads and the crosslinking agent were investigated by Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and ninhydrin assay. In general, both the concentration of glutaraldehyde (1.25 and 5.0% v/v) and crosslinking time (6 and 12 h) showed a minor influence on the intensity of the interaction between the crosslinking agent and chitosan. The immobilized BCL was employed in the transesterification of geraniol with vinyl acetate in an organic medium. The effects of the temperature (25–40 °C), reaction time (24–72 h), lipase mass used for the immobilization (20–100 mg) and type of organic solvent were evaluated along with the reusability of the biocatalyst. The lipase (BCL) remained stable and active under mild reaction conditions (35 °C for up to 72 h of reaction). The immobilized lipase showed greater stability in non-polar solvents (log P > 3.0), allowing its reuse, with a gradual loss in the catalytic activity for up to 120 days of storage. The results demonstrated that this immobilization process is efficient and of low cost.

Continuous cane sugar inversion process using immobilized invertase

AbstractBACKGROUNDSugarcane juice is mostly used by industry for manufacturing sucrose and invert sugars. However, during enzymatic processing of raw sugarcane juice for an extended period of time, maintaining enzyme stability is a major bottleneck in food and agricultural industries. The present work reports use of invertase immobilized on glutaraldehyde crosslinked chitosan beads, for continuous inversion of sugarcane juice for an extended period of time.RESULTSComplete inversion of clarified sugarcane juice was obtained in a continuous process for 4 days at an optimized flow rate of 0.3 cm3 min−1 and at a room temperature of 303 K. Only 4% decrease was seen in inversion efficiency up to the 7th day. Adsorptive behaviour of invert sugars on chitosan in the column led to a delay in product equilibrium. The immobilized invertase exhibited the maximum rate of reaction at a sucrose concentration of 0.5 mol dm−3 showing good stability in the pH range 3.0 to 6.0 and temperature range 30 °C to 60 °C.CONCLUSIONSThe covalent immobilization of invertase on chitosan beads enhanced enzyme stability and as a result, the enzyme became more resistant to denaturation during storage and reuse compared with the free enzyme. Thus, better conversion was obtained in the continuous inversion of sugarcane juice for extended periods of time. © 2016 Society of Chemical Industry

Effective removal of sulfur dyes from water by biosorption and subsequent immobilized laccase degradation on crosslinked chitosan beads

In this study, sulfur dyes were effectively removed from water samples through biosorption and subsequent immobilized laccase degradation on glutaraldehyde-crosslinked chitosan beads (GA-CBs). The Langmuir equation described the biosorption isotherms of the single dyes, sulfur blue 15 (SB15) and sulfur brown GD (SBGD), well. The decreased biosorption of one dye was found in binary mixtures by increasing the concentration of the second dye, and the extended Freundlich equation could reasonably describe such isotherms. Laccase immobilized on GA-CBs showed a high catalytic ability and provided reusability even at low laccase concentrations. In the treatment of single dyes at an initial concentration of 200mgL−1, for example, over 81.6% and 70.8% of SB15 and SBGD, respectively, were removed at a pH of 6.5 after the successive biosorption and enzymatic degradation with a biosorbent dose of 3.6gL−1, an initial laccase activity of 2.24UL−1, and 2.66×10−4mg(gsupport)−1 of immobilized laccase. In the treatment of binary mixtures under the same conditions, the efficiency of each dye decreased. The overall removals of SB15 and SBGD from binary mixtures containing 100mgL−1 of SB15 and 100mgL−1 of SBGD became 78.2% and 52.6%, respectively.

Nitrate decontamination through functionalized chitosan in brackish water

N, N, N-Triethyl ammonium functionalized cross-linked chitosan beads (TEACCB) was prepared by alkylation of glutaraldehyde cross-linked chitosan beads to remove nitrate from brackish water. Physico-chemical characteristics of TEACCB were analyzed using FTIR, SEM, EDAX, TGA, DTA, BET surface area, swelling ratio and pHzpc. The maximum nitrate removal capacity of TEACCB was 2.26meq/g and is higher than other reported chitosan based adsorbents. Nitrate removal ratio in the presence and absence of common anions like chloride and sulphate demonstrated the selectively of TEACCB towards nitrate. The kinetic data of nitrate removal fitted well with the pseudo-second-order kinetic model. The thermodynamic parameters indicated that nitrate removal could be spontaneous and exothermic in nature. TEACCB was reused with 100% efficiency after regenerating with 0.05N HCl. Column study was carried out to remove nitrate from brackish water. These results are very significant to develop TEACCB based nitrate removal technology with great efficiency.

Synergistic biosorption between phenol and nickel(II) from Binary mixtures on chemically and biologically modified chitosan beads

The biosorption of phenol and Ni(II) from binary mixtures on glutaraldehyde-crosslinked chitosan beads modified with histidine and Saccharomyces cerevisiae (SC-HIS-CCBs) was studied at 30°C. Batch biosorption was performed at the optimal pH of 4.0. Under the concentration ranges studied (25–250mgL−1 of Ni(II) and 25–250mgL−1 of phenol), the amounts of the biosorption of both phenol and Ni(II) increased in the presence of the second component in contrast to the corresponding single phenol and Ni(II) systems. That is, synergistic biosorption between phenol and Ni(II) on the SC-HIS-CCBs was observed, particularly for phenol. Isotherm modeling showed that simultaneous biosorption of phenol and Ni(II) from binary solutions could be acceptably described by the modified Langmuir model, which could reflect the nature of chemical adsorption.

Immobilization of a thermostable, fungal recombinant chitinase on biocompatible chitosan beads and the properties of the immobilized enzyme.

A recombinant, thermostable fungal chitinase from the thermophilic fungus, Thermomyces lanuginosus, was immobilized on glutaraldehyde cross-linked chitosan beads, and the properties of the immobilized chitinase were studied. The enzyme was found to be almost completely immobilized in 6 H under shaking condition at 30 °C. The immobilized enzyme exhibited much wider pH optimum and was more stable at alkaline pH values as compared with the soluble enzyme. Both the forms of the enzyme were optimally active at 60 °C and stable at 50 °C for 3 H, and after 3 H, the activity of the soluble enzyme declined sharply, whereas the immobilized chitinase was stable up to 6 H without any significant loss in the activity. KM and Vmax values of the immobilized enzyme were 1.18 mM and 445.7 μmol/Min/mg of protein, respectively. The immobilized enzyme was stable at least for 1 month at 4 °C without any significant loss in the activity.

Modification of crosslinked chitosan beads with histidine and Saccharomyces cerevisiae for enhanced Ni(II) biosorption

Glutaraldehyde-crosslinked chitosan beads modified with histidine and Saccharomyces cerevisiae (SC–HIS–CCBs) were applied as new biosorbents for enhanced adsorption of Ni(II) from aqueous solutions. The SC–HIS–CCBs were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analysis. The effects of various parameters, such as pH, contact time, and amount of biosorbent, on Ni(II) biosorption were investigated. The optimal pH was found to be 6.0. Isotherm data fit the Freundlich equation well, although they could be described by the Langmuir equation. The pseudo-second-order kinetic model could better follow the biosorption process in contrast to the pseudo-first-order kinetic model. The thermodynamic parameters of Ni(II) biosorption, including Gibbs free energy change (ΔG), enthalpy change (ΔH), and entropy change (ΔS), were calculated. The negative ΔG value indicated the spontaneous nature of Ni(II) biosorption on the SC–HIS–CCBs.

Glutaraldehyde-crosslinked chitosan beads for sorptive separation of Au(III) and Pd(II): Opening a way to design reduction-coupled selectivity-tunable sorbents for separation of precious metals

Glutaraldehyde (GA)-crosslinked chitosan beads (GA-CS) are prepared with coagulating solution containing sodium tripolyphosphate and GA, and used for the adsorption of metals from binary-metal solution Au(III) and Pd(II). GA-CS exhibited selective sorption of Au(III) in the Au(III)–Pd(II) mixture. X-ray diffraction analyses showed that Au(III) was reduced to Au(0) following sorption, while Pd(II) was present as unreduced divalent form. Increased GA led to more selectivity toward Au(III), indicating that Au(III) selectivity is attributed to reduction-couple sorption of Au(III) with a reducing agent GA. Furthermore, a 2-step desorption process enabled selective recovery of Pd and Au using 5M HCl and 0.5M thiourea–1M HCl, respectively, leading to pure Pd(II) and Au(III)-enriched solutions. This finding may open a new way to design reduction-coupled selectivity-tunable metal sorbents by combination of redox potentials of metal ions and reducing agents.

Determination of total phenolic content in Prunella L. by horseradish peroxidase immobilized onto chitosan beads

Horseradish Peroxidase (HRP) was immobilized by covalent binding onto glutaraldehyde cross-linked chitosan beads and these beads were used for determination of total phenolic content in Prunella L. species. Central composite design (CCD) was employed to optimize the conditions for the maximum HRP activity and to understand the significance and interaction of the factors affecting the activity of immobilized HRP. The results indicated that enzyme concentration and immobilization time were significant factors for the immobilization of HRP. The optimum conditions were determined as enzyme concentration 0.25 mg mL−1, pH 8.0 and immobilization time 20h. The recovered activity was obtained as 81% after immobilization under optimal conditions. Total phenol content was determined in four Prunella L. species (Prunella vulgaris L., Prunella laciniata (L.) L., Prunella orientalis Bornm., Prunella grandiflora L.) extracted using methanol, water and methanol/water (4 : 1, v/v). The enzymatic method is based on the spectrophometric measurement of the final quinone-imine colored product, absorbing at 510 nm, by HRP oxidation in presence of hydrogen peroxide. The results were compared with those obtained by applying the Folin method. The highest total phenol content was obtained with the methanol/water (4 : 1, v/v) extract of Prunella vulgaris L. by immobilized HRP method (63.75 mg gallic acid equivalent (GAE) per g dried plant). Operational stability was determined with immobilized HRP and it indicated that a small enzyme deactivation (15%) occurred after 10 consecutive uses.

Biosorption of Manganese(II) Ions from Aqueous Solution by Glutaraldehyde Cross-Linked Chitosan Beads: Equilibrium and Kinetic Studies

The biosorption of manganese(II) ions from aqueous solution by glutaraldehyde cross-linked chitosan (GCC) was studied under equilibrium conditions. The biosorbent was characterised by FT-IR spectroscopy and scanning electron microscopy (SEM) methods. The effects of the variable experimental parameters such as pH, metal ion concentration, adsorbent amount, contact time and temperature on the adsorption process were investigated. The equilibrium adsorption data were interpreted via the Freundlich, Langmuir and Sips isotherm models. Based on the error function values, the kinetic data were fitted to a better extent by the pseudo-second-order kinetic model and the chemisorption model, relative to the pseudo-first-order, fractional order and Weber-Morris models. The monolayer adsorption capacity of GCC as obtained from the Langmuir isotherm at 25 °C was found to be 278 mg/g. Thermodynamic studies indicated that the adsorption process was spontaneous (Δ0 < 0) and exothermic (ΔH0 < 0).

Effect of pH on Competitive Adsorption of Cu(II), Ni(II), and Zn(II) from Water onto Chitosan Beads

The amounts of adsorption of Cu 2+ ,N i 2+ , and Zn 2+ from single, binary, and tertiary nitrate solutions onto glutaraldehyde cross-linked chitosan beads were measured. The beads had an average particle size and pore volume of 2 mm and 0.06 cm 3 /g, respectively, and had a BET surface area of 60 m 2 /g. All experiments were performed at 298 K as a function of initial pH (2.0-5.0), total metal concentration (0.77-17.0 mol/m 3 ), and molar concentration ratio (0.25-4) in the aqueous phase. It was shown that the amount of metal adsorption generally increased with increasing solution pH. Competitive adsorption was significant in binary and tertiary systems when Cu 2+ was present. The selectivity factor reached maximum in an equilibrium pH range of 5.1-5.3 and 4.5-4.9 for the Cu-Ni and Cu-Zn binary systems, respectively. This adsorbent provided a possibility for selective separation of Cu 2+ from such multi-component solutions.

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.

Metal-Anion Sorption by Chitosan Beads: Equilibrium and Kinetic Studies

Chitosan is a well-known biopolymer, whose high nitrogen content confers remarkable ability for the sorption of metal ions from dilute effluents. However, its sorption performance in both equilibrium and kinetic terms is controlled by diffusion processes. Gel bead formation allows an expansion of the polymer network, which improves access to the internal sorption sites and enhances diffusion mechanisms. Molybdate and vanadate recovery using glutaraldehyde cross-linked chitosan beads reaches uptake capacities as high as 7−8 mmol g-1, depending on the pH. The optimum pH (3−3.5) corresponded to the predominance range of hydrolyzed polynuclear metal forms and optimum electrostatic attraction. While for beads, particle size does not influence equilibrium, for flakes, increasing sorbent radius significantly decreases uptake capacities to 1.5 mmol g-1. Sorption kinetics are mainly controlled by intraparticle diffusion for beads, while for flakes the controlling mechanisms are both external and intraparticle diffusions. The gel conditioning increases the intraparticle diffusivity by 3 orders of magnitude: intraparticle diffusivities range between 10-13 and 10-10 m2 min-1, depending on the sorbent size and the conditioning.