Glutaraldehyde Cross-linked Chitosan Research Articles

Novel High-Performance Functionalized and Grafted Bio-Based Chitosan Adsorbents for the Efficient and Selective Removal of Toxic Heavy Metals from Contaminated Water.

Novel functionalized and/or grafted crosslinked chitosan adsorbents were synthesized and used to remove several toxic heavy metal ions such as nickel, lead, chromium, and cadmium ions from contaminated water. The chitosan biopolymer was functionalized by maleic anhydride (CS_MA) acting also as a crosslinking agent. Glutaraldehyde-crosslinked chitosan (CS_GA) grafted with poly(methyl methacrylate) (CS_MMA) was also synthesized. The synthesized adsorbents were characterized using a variety of analytical techniques such as SEM, TGA, and FTIR, which confirmed their chemical structures and morphology. The adsorption capacity of the adsorbents was analyzed under various conditions of contact time, adsorbent dose, initial concertation, temperature, and pH and evaluated against those of pure chitosan (CS) and the crosslinked chitosan(CS_GA). The ultimate removal conditions were 0.5 g/100 mL adsorbent dose, an initial metal ion concentration of 50 ppm, a temperature of 45 °C, and pH 9. CS_MMA had the highest removal percentages for all metal ions, ranging from 92% to 94%. The adsorption was demonstrated to fit a pseudo-first-order model that followed a Langmuir adsorption isotherm. The results highlight the capacity of the synthesized polymers to efficiently remove major toxic contaminants at low cost from contaminated water, present especially in low-income areas, without harming the environment.

Experimental and density functional theory investigation of surface-modified biopolymer for improved adsorption of mixtures of per- and polyfluoroalkyl substances in water

Glutaraldehyde (GTH) cross-linked chitosan (CTN) biopolymer-based and polyethyleneimine (PEI) functionalized (GTHCTNPEI) aerogels were proven promising for removing mixtures of long- and short chain per- and polyfluoroalkyl substances (PFAS) in water. In this study, to further improve the performance of the aerogel for short-chain PFAS and undecafluoro-2-methyl-3-oxahexanoic acid (GenX) removal, GTHCTNPEI aerogel chunks with an average size of 13.4 mm were turned into flakes with an average size of 9.1 mm. The GTHCTNPEI flakes achieved >99 % removal of all target PFAS, including long- and short-chain PFAS and >97 % for GenX after 10 h. In addition, the flakes can be regenerated and reused for at least four cycles. When added to tap water spiked with PFAS at initial concentrations of 30, 70, or 100 ng/L, the flakes removed almost 100 % of all tested PFAS. Mechanistic investigations using density functional theory (DFT) revealed strong stabilizing hydrophobic and electrostatic interactions between the aerogels and PFAS, with GTHCTNPEI to PFAS binding energies ranging between -24.0 – -30.1 kcal/mol for PFOA; -41.3 – -48.5 kcal/mol for PFOS; and -40.5 – -47.3 kcal/mol for PFBS. These results demonstrate the great potential of the flakes for removing PFAS from drinking water, surface water, and groundwater.

Fully integrated wearable microneedle biosensing platform for wide-range and real-time continuous glucose monitoring

Wearable microneedle sensors for continuous glucose monitoring (CGM) have great potential for clinical impact by allowing access to large data sets to provide individualized treatment plans. To date, their development has been challenged by the accurate wide linear range tracking of interstitial fluid (ISF) glucose (Glu) levels. Here, we present a CGM platform consisting of a three-electrode microneedle electrochemical biosensor and a fully integrated radio-chemical analysis system. The long-term performance of the robust CGM on diabetic rats was achieved by electrodepositing Prussian blue (PB), and crosslinking glucose oxidase (GOx) and chitosan to form a 3D network using glutaraldehyde (GA). After redox by GOx, PB rapidly decomposes hydrogen peroxide and mediates charge transfer, while the 3D network and graphite powder provide enrichment and release sites for Glu and catalytic products, enabling a sensing range of 0.25–35 mM. Microneedle CGM has high sensitivity, good stability, and anti-interference ability. In diabetic rats, CGM can accurately monitor Glu levels in the ISF in real-time, which are highly consistent with levels measured by commercial Glu meters. These results indicate the feasibility and application prospects of the PB-based CGM for the clinical management of diabetes. Statement of SignificanceThis study addresses the challenge of continuous glucose monitoring system design where the narrow linear range of sensing due to the miniaturization of sensors fails to meet the monitoring needs of clinical diabetic patients. This was achieved by utilizing a three-dimensional network of glutaraldehyde cross-linked glucose oxidase and chitosan. The unique topology of the 3D network provides a large number of sites for glucose enrichment and anchors the enzyme to the sensing medium and the conductive substrate through covalent bonding, successfully blocking the escape of the enzyme and the sensing medium and shortening the electron transfer and transmission path.

Development of a chitosan-multi-walled carbon nanotubes composite for application in solid-phase adsorption toxin tracking of microcystins

Contamination of water and food with cyanotoxins poses human health risks, and hence the need for sensitive early warning tools to monitor these in water. A composite of glutaraldehyde-crosslinked chitosan and multi-walled carbon nanotubes (ChMWCNTs) was synthesised and tested for potential use as a solid-phase adsorption toxin tracking (SPATT) adsorbent for monitoring microcystins (MCs) in fresh water. The composite was characterised by Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller theory and scanning electron microscopy. Batch adsorption experiments to assess the effect of contact time, adsorbent dosage and initial microcystin-LR (MC-LR) concentration were conducted. The composite was found to be efficient in adsorbing MC-LR, showing 97% removal and a maximum adsorption capacity of 4.639 μg/g under optimised conditions of 5 μg/L of MC-LR, adsorbent dose of 0.03 g/5 mL and 30 min contact time. The adsorption kinetics were better explained by a pseudo-second-order model, inferring chemisorption adsorption. The isotherm data better fitted the Langmuir isotherm model, thus inferring monolayer surface adsorption. For desorption, 100% methanol was the most effective, with an efficiency of 84.71%. The composite effectively adsorbed and desorbed three congeners of MCs (–LR, –RR and –YR) when tested in raw dam water, regardless of its lower maximum adsorption capacity compared to those of other adsorbents used for similar purposes. Significance: Monitoring of microcystins is problematic in large reservoirs and rivers. Chitosan can be crosslinked and modified to enhance its adsorption properties. Composites of chitosan and carbon nanotubes efficiently adsorb and desorb microcystins. This study is possibly the first to apply a chitosan-based sorbent in solid-phase toxin tracking (SPATT) to be used as an early warning tool in passive monitoring of microcystins in water resources. Open data set: https://doi.org/10.6084/m9.figshare.20992291.v1

The Composite Material of (PEDOT-Polystyrene Sulfonate)/Chitosan-AuNPS-Glutaraldehyde/as the Base to a Sensor with Laccase for the Determination of Polyphenols.

The described research aimed to develop the properties of the conductive composite /poly(3,4-ethylenedioxy-thiophene-poly(4-lithium styrenesulfonic acid)/chitosan-AuNPs-glutaraldehyde/ (/PEDOT-PSSLi/chit-AuNPs-GA/) and to develop an electrochemical enzyme sensor based on this composite material and glassy carbon electrodes (GCEs). The composite was created via electrochemical production of an /EDOT-PSSLi/ layer on a glassy carbon electrode (GCE). This layer was covered with a glutaraldehyde cross-linked chitosan and doped with AuNPs. The influence of AuNPs on the increase in the electrical conductivity of the chitosan layers and on facilitating the oxidation of polyphenols in these layers was demonstrated. The enzymatic sensor was obtained via immobilization of the laccase on the surface of the composite, with glutaraldehyde as the linker. The investigation of the surface morphology of the GCE/PEDOT-PSSLi/chit-AuNPs-GA/Laccase sensor was carried out using SEM and AFM microscopy. Using EDS and Raman spectroscopy, AuNPs were detected in the chitosan layer and in the laccase on the surface of the sensor. Polyphenols were determined using differential pulse voltammetry. The biosensor exhibited catalytic activity toward the oxidation of polyphenols. It has been shown that laccase is regenerated through direct electron transfer between the sensor and the enzyme. The results of the DPV tests showed that the developed sensor can be used for the determination of polyphenols. The peak current was linearly proportional to the concentrations of catechol in the range of 2-90 μM, with a limit of detection (LOD) of 1.7 μM; to those of caffeic acid in the range of 2-90 μM, LOD = 1.9 μM; and to those of gallic acid in the range 2-18 μM, LOD = 1.7 μM. Finally, the research conducted in order to determine gallic acid in a natural sample, for which white wine was used, was described.

Removal of Cr(VI) by glutaraldehyde-crosslinked chitosan encapsulating microscale zero-valent iron: Synthesis, mechanism, and longevity

Microscale zero-valent iron (mZVI) has shown great potential for groundwater Cr(VI) remediation. However, low Cr(VI) removal capacity caused by passivation restricted the wide use of mZVI. We prepared mZVI/GCS by encapsulating mZVI in a porous glutaraldehyde-crosslinked chitosan matrix, and the formation of the passivation layer was alleviated by reducing the contact between zero-valent iron particles. The average pore diameter of mZVI/GCS was 8.775 nm, which confirmed the mesoporous characteristic of this material. Results of batch experiments demonstrated that mZVI/GCS exhibited high Cr(VI) removal efficiency in a wide range of pH (2-10) and temperature (5-35°C). Common groundwater coexisting ions slightly affected mZVI/GCS. The material showed great reusability, and the average Cr(VI) removal efficiency was 90.41% during eight cycles. In this study, we also conducted kinetics and isotherms analysis. Pseudo-second-order model was the most matched kinetics model. The Cr(VI) adsorption process was fitted by both Langmuir and Freundlich isotherms models, and the maximum Langmuir adsorption capacity of mZVI/GCS reached 243.63 mg/g, which is higher than the adsorption capacities of materials reported in most of the previous studies. Notably, the column capacity for Cr(VI) removal of a mZVI/GCS-packed column was 6.4 times higher than that of a mZVI-packed column in a 50-day experiment. Therefore, mZVI/GCS with a porous structure effectively relieved passivation problems of mZVI and showed practical application prospects as groundwater Cr(VI) remediation material with practical application prospects.

Efficient Adsorption and Catalytic Reduction of Phenol Red Dye by Glutaraldehyde Cross-Linked Chitosan and Its Ag-Loaded Catalysts: Materials Synthesis, Characterization and Application

In this study, glutaraldehyde cross-linked chitosan support, as well as the catalysts obtained after loading Ag metal (Ag/Chitosan), were synthesised and applied for adsorption and reduction of phenol red dye in an aqueous solution. The Ag/chitosan catalysts were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis techniques. The catalytic reduction and adsorption performance of phenol red dye with Ag/chitosan and cross-linked chitosan, respectively, was performed at ambient reaction conditions. The reduction of dye was carried out using sodium borohydride (NaBH4) as the reducing agent, while the progress of adsorption and reduction study was monitored with ultraviolet-visible (UV-vis) spectrophotometry technique. The reduction of the phenol red dye varied with the amount of catalyst, the concentration of NaBH4, Ag metal loading, reaction temperature, phenol red dye concentration and initial pH of the dye solution. The dye solution with a nearly-neutral pH (6.4) allowed efficient adsorption of the dye, while acidic (pH = 4) and alkaline (pH = 8, 11, 13.8) solutions showed incomplete or no adsorption of dye. The reusability of the Ag/chitosan catalyst was applied for the complete reduction of the dye, where no significant loss of catalytic activity was observed. Hence, the applicability of cross-linked chitosan and Ag/catalyst was thus proven for both adsorption and reduction of phenol red dye in an aqueous solution and can be applied for industrial wastewater treatment.

Adsorption property and mechanism of glutaraldehyde-crosslinked chitosan for removal of 2,4-dichlorophenoxyacetic acid from water

In this work, glutaraldehyde-crosslinked chitosan (GCC) was prepared and its ability to remove 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solutions was systematically studied.

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.

Potential Elimination of Chromium (VI) by Chemically Biochar Derived from Pennisetum Setaceum

This study consisted of a novel potential adsorbent material that could efficiently remove chromium (VI) from aqueous solutions. The optimum operating conditions were investigated including pH, agitation period. In this research, biochar derived from fountain grass (Pennisetum setaceum) coated with glutaraldehyde-crosslinked chitosan and treated with succinic acid to add functional groups was used to create an eco-friendly sorbent (CPES). It demonstrated that 3.0 is the ideal pH for the Cr (VI) adsorption process. The equilibrium stirring time is 120 minutes. The Langmuir and Freundlich models have been used to examine experimental data. According to the results, and the Freundlich model performed a better fit of the result than the Langmuir one. Cr (VI) has a maximum adsorption capacity of 30.96 mg/g. The Gibbs free energy change (êG), enthalpy change (êH), and entropy change (êS) thermodynamic parameters were determined. The fact that êG was negative demonstrated that Cr (VI) adsorption onto the CPES adsorbent occurred spontaneously.

Effect of glutaraldehyde-chitosan crosslinked graphene oxide on high temperature properties of SBS modified asphalt

Composite material using glutaraldehyde (GA) cross-linked chitosan (CTS) and graphene oxide (GO-CTS-GA) was designed applying electrostatic interaction strategy under strong alkali environment. GO-CTS-GA was in turn applied to prepare styrene butadiene styrene (SBS) GO-CTS-GA/SBS composite modified asphalt (MA)_binder. The effect of GO-CTS-GA on the physical properties of SBS modified asphalt binder was investigated and its mechanism of action was analyzed. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy tests confirmed the retainment of GO flakes microscopic dimensions while compensating for the chemical structural defects and mechanical property damage of GO. The results of dynamic shear rheometer and multi-stress creep recovery tests indicated that the GO-CTS-GA/SBS-MA binder exhibited better viscosity performance and elasticity performance, rutting resistance and high temperature thermal stability. At 64 °C, the loss modulus of 0.10 % GO-CTS-GA/SBS-MA was 29.5 % and 25.2 % higher than that of SBS-MA and GO/SBS-MA, respectively. SEM and TEM analyses of the four components of asphalt binder before and after modification revealed that the change of asphaltene microscopic morphology seriously affects the stability of asphalt colloidal system. Fourier transform infra-red analysis of the MA binder revealed that the change of saturation fraction and colloidal polarity by GO-CTS-GA is responsible for the dispersion and cross-linking of SBS chain segments in the asphalt binder phase. This study provides important reference information for nanomaterials to change the macroscopic mechanical properties by modulating the microstructure, physical and chemical properties of asphalt binder at the micro and nano-scale.

PH-responsive drug release and antibacterial activity of chitosan-coated core/shell borate glass-hydroxyapatite microspheres

Multifunctional drug delivery system that can treat bone infection and concurrently accelerate bone tissue regeneration is highly desirable. In this study, we developed a pH-responsive local drug carrier in which a core/shell microsphere consisting of a borate glass core and a mesoporous hydroxyapatite HA shell (BG-HA) was coated with glutaraldehyde-crosslinked chitosan (CS). At neutral pH, a negligible concentration of vancomycin was released from the BG-HA@CS microspheres. However, in an acidic environment, the pores on the HA shell were uncapped due to the swelling of CS, thus accelerating the drug release. The advantage of the BG-HA@CS was evidenced by comparing with HA@CS that was prepared by fully converting borate glass followed by CS coating. The dissolution of the unconverted borate glass core upon immersing in PBS led to an increase in the local pH. This change of pH regulated the swelling/de-swelling behaviours of CS, thereby realizing more sustained drug release. Furthermore, it revealed that the vancomycin-loaded BG-HA@CS provided highly effective antibacterial activity against S. aureus and E. coli, while the vancomycin-loaded HA@CS did not show inhibitory effect on E. coli. The results indicated that the BG-HA@CS would be a promising multifunctional delivery system that can achieve self-regulated drug release, control the acidic environment of bone infection sites and promote bone tissue regeneration.

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.

Enhanced Macroporous Cationic Chitosan Hydrogel by Freezing and Thawing Method with Superadsorption Capacity for Anionic Dyes

In this study, we have developed a simple technique to prepare cationic chitosan hydrogel with interconnected porous structure using freeze–thaw process and the obtained hydrogel was named FCS hydrogel. Scanning electron microscopy (SEM) imaging discovered that the synthesized hydrogel demonstrated interconnected porous structure in the scope of 5–20 μm. We also showed that the FCS hydrogel exhibits pH responsiveness behavior, and demonstrated reversible swelling and de-swelling behaviors maintaining their mechanical stability. We demonstrate that the FCS hydrogel swelling capacity decreased at alkaline pH and rose with a decline in pH value. Besides, the FCS hydrogel presented specific surface area of 78.25 ± 8.75 m2 g−1, due to the cryogenic treatment of glutaraldehyde cross-linked chitosan hydrogel could increase the surface area and permeability of composite hydrogel and then strongly increasing the adsorption capacity. Subsequently, the FCS monolithic hydrogel tested dyes removal, which provides a high removal efficiency towards anionic dyes including congo red (CR) and sodium fluorescein (SFL) dyes. Significantly, we show that the FCS hydrogel could be regenerated and reused as an adsorbent for wastewater treatment without significant loss of pollutants removal efficiency over a number of adsorption and washing cycles. This study offers a promising environmental friendly and sustainable interconnected porous hydrogel for anionic dye removal from wastewater.

Eco-friendly ferrocene-functionalized chitosan aerogel for efficient dye degradation and phosphate adsorption from wastewater

Developing highly efficient, biodegradable and eco-friendly adsorbents to remove pollutants from wastewater has been a significant and long-term global challenge. Herein, a novel aerogel (Fc-CS) has been developed through the functionalization of glutaraldehyde-crosslinked chitosan with ferrocene groups. Methylene blue (MB) and eutrophication ions (PO43−) have been chosen as model pollutants to evaluate the adsorption efficiency of Fc-CS aerogel. The results demonstrated that Fc-CS aerogel possessed high specific surface area and good thermal stability. Freundlich model fitting revealed that both PO43− and MB were adsorbed in a multilayered fashion on the Fc-CS aerogel through complex adsorption mechanisms, and pseudo-second-order kinetic model fitting confirmed the involvement of chemical adsorption. Benefiting from the appending of ferrocene groups, Fc-CS aerogel not only showed excellent PO43− adsorption performance, but also provided a Fenton-like active center to catalyze dyes degradation. According to the Langmuir isothermal model, the maximum adsorption capacity for PO43− was approximately 1141 mg·g−1, exceeding those of most previously reported bio-based adsorbents. The addition of H2O2 significantly enhanced the MB removal efficiency of Fc-CS aerogel from 8.20% to 92.79% by triggering a Fenton-like reaction. After five cycles, no significant attenuation in removal efficiency was observed for either MB or PO43−, with or without H2O2. This eco-friendly and recyclable biomaterial could be an attractive candidate for removing MB and PO43− from aquatic systems. The present work provided a feasible pathway to design and develop highly efficient bio-aerogel for wastewater treatment and environmental remediation.

Superamphiphilic Chitosan Cryogels for Continuous Flow Separation of Oil-In-Water Emulsions.

Chitosan is a typical hydrophilic biomass building block widely used in material science and engineering. However, its intrinsic amphiphilicity has been seldom noted so far. Herein, a series of glutaraldehyde-crosslinked chitosan cryogels with superamphiphilicity are fabricated at moderately frozen conditions through a freezing–thawing process. The micron-sized porous cryogel samples display a 0° contact angle toward both water and oil, 0° water contact angle under oil, and over 120° oil contact angle underwater. By comparing the wetting behavior of the tablet compressed by pure chitosan powders, the superamphiphilicity of the chitosan sample is proven to be independent on crosslinkers. This special wettability endows the chitosan cryogels with high separation efficiency for various surfactant-stabilized oil-in-water emulsions under continuous flow mode driven by gravity as well as a peristaltic pump.

Using chitosan-based heterogeneous catalyst for degradation of Acid Blue 25 in the effective electro-Fenton process with rotating cathodes

Herein, the capability of glutaraldehyde cross-linked magnetic chitosan nanoparticles (Fe3O4/CS/GA NPs) was investigated as a heterogeneous electro-Fenton catalyst for the degradation of Acid Blue 25. A cylindrical reactor with rotating cathodes was used for performing the electro-Fenton process. Fe3O4/CS/GA NPs were characterized by Fourier-Transform Infrared Spectroscopy (FT-IR), X-ray Powder Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-Ray (EDX), and Vibrating Sample Magnetometer (VSM). According to the results, the dye removal efficiency reached 94.83% after 90 min under the optimal conditions of Fe3O4/CS/GA NPs with the iron content of 15 mmol Fe/g chitosan and concentration of 0.3 g/L, natural pH of dye (6.8), initial dye concentration of 150 mg/L, the current intensity of 0.7 A, and rotational speed of 100 rpm. Also, Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) removal reached 74.19% and 61.53% after 120 min, respectively. Average oxidation state (AOS) and carbon oxidation state (COS) values were increased after treatment, indicating that wastewater's biodegradability was improved. Moreover, the heterogeneous electro-Fenton process using optimal Fe3O4/CS/GA NPs resulted in about 16% improvement in the removal efficiency compared to the homogeneous process. The catalyst showed good reusability up to 5 cycles. The amounts of leached iron into the solution were much less than allowable amounts of the Iranian wastewater discharge standard, thus no need for secondary treatment. Furthermore, scavengers studies under the optimum conditions showed the dye degradation occurred mainly by surface-bonded hydroxyl radicals. In short, this study proved, Fe3O4/CS/GA NPs are a promising heterogeneous electro-Fenton catalyst due to their low cost, excellent stability and reusability, negligible iron leaching, environmental compatibility, and superior catalytic activity in a wide range of pH.

Performance Evaluation of Glutaraldehyde Cross-Linked Chitosan Functionalized with Go Incorporated Sbs Modified Asphalt by Via Electrostatic Interaction Under Alkali Treatment

Performance Evaluation of Glutaraldehyde Cross-Linked Chitosan Functionalized with Go Incorporated Sbs Modified Asphalt by Via Electrostatic Interaction Under Alkali Treatment

Glutaraldehyde-cross-linked chitosan–alginate composite for organic dyes removal from aqueous solutions

We present an approach for synthesis of a micro-porous composite of two well-known biopolymers, namely chitosan and alginate, using glutaraldehyde as the cross-linking agent. Alginate and chitosan were pre-treated before being mixed, and the two biopolymers' proportions were also monitored. Chitosan was modified using aniline with the help of formaldehyde crosslinker and then the twizer was further crosslinked with alginate using glutaraldehyde. The synthesized composite, glutaraldehyde cross-linked chitosan–alginate composite [(Cs-F-An)-G-Al] was characterized using spectral techniques and employed as a potential adsorbent for three dyes namely Brilliant green, Methyl orange and Patent Blue V. The pHPZC of the material was 7.5 and the maximum monolayer adsorption capacity (Qmax) was found to be 235.82, 198.09 and 117.34 mg g−1 for BG (at pH 8.0), MO (at pH 6.0) and PBV (at pH 3.0) respectively. It was found that the adsorption process follows a Freundlich adsorption isotherm and pseudo second order kinetics. A thermodynamic study revealed that the process of adsorption was enthalpy-driven and spontaneous in nature. Interestingly, the values of the adsorption capacity obtained in column adsorption method are in close agreement with those obtained in batch adsorption experiments, which shows the potential of the synthesized composite for uptake of dyes.

Novel amidinothiourea-modified chitosan microparticles for selective removal of Hg(II) in solution

Glutaraldehyde-crosslinked chitosan microparticles (CGP) prepared via the inversed-phase emulsification were successively modified by epichlorohydrin (ECH) and amidinothiourea (AT) as novel adsorbent (CGPET) for selective removal of Hg(II) in solution. FTIR, EA, XPS, SEM-EDX, TG, DTG, and XRD results indicated that CGPET had ample −NH2 and CS, relative rough surface, mean diameter of ~40 μm, great thermal stability, and crystalline degree of 2.4%, beneficial to the uptake of Hg(II). The optimum parameters (pH 5, dosage 1 g/L, contact time 4 h, and initial concentration 150 mg/L) were acquired via batches of adsorption experiments. Adsorption behavior was well described by the Liu isothermal and pseudo-second-order kinetics models, and the maximum adsorption capacity was 322.51 mg/g, surpassing many reported adsorbents. Regeneration and coexisting-ion tests demonstrated that CGPET had outstanding reusability (Rr > 86.89% at the fifth cycle) and selectivity (Rs > 93%). Besides, its potential adsorption sites and mechanisms were proposed.