Search

The removal of Ni (II), Mn (II) and Zn (II) from crude yellow cake onto chitosan cross-linked by Epichlorohydrin (CS-ECH) and polyvinyl alcohol (PVA) were investigated in nitrate solutions. The influence of contact time, pH, temperature and initial metal concentrations on the adsorption processes were investigated using batch modes. Langmuir and Fruindlish models were used for investigation of adsorption isotherm. The results showed that the equilibrium adsorption behavior of metal ions onto CS-ECH and PVA could be fitted to Langmuir model. The total maximum adsorption capacity of CS-ECH and PVA were calculated, and the results indicate the higher values of CS-ECH than PVA, due to the properties of chemical structure of CS-ECH. The adsorption kinetics parameters were also tested using pseudo-first-order, pseudo-second-order models, and interparticle diffusion models. The results indicate the adsorption processes of metal ions on both CS-ECH and PVA followed the pseudo-first-order and the pseudo-second-order models which meaning the mixed adsorption, except the adsorption of Mn (II) on PVA is only described by the pseudo-second-order equation. The results indicate the adsorption processes of metal ions followed the pseudo-second-order models for both CS-ECH and PVA. Otherwise, the values of thermodynamic parameters (ΔHoads, ΔSoads, and ΔGoads) of metal ions removal by CS-ECH and PVA exhibit the spontaneity, and exothermicity of adsorption processes.

A fast-swelling porous poly(acrylic acid co-acrylamide) crosslinked by N-Maleyl chitosan superabsorbent hydrogels were prepared by free radical graft copolymerization reaction for partially neutralized acrylic acid (AA), acrylamide (Am) using ammonium persulphate (APS) as an initiator, and N-Maleyl chitosan (N-MACH) as crosslinker. The structure of the synthesized hydrogels were investigated by FTIR spectroscopy and scanning electron microscope (SEM). Acetone and sodium bicarbonate were used as porosity generator (porogens) during the polymerization process. Surfactant (span 80) was used as a micelle template and foam stabilizer. The swelling studies showed improvement of hydrogel behavior with increasing of crosslinker concentration. Otherwise, the porous structure and swelling rate of the hydrogels improved by the incorporation of acetone and NaHCO3. While the incorporation of span 80 in the gelling process can enhance the porosity structure. Morphological studies showed that the porosity generators and surfactant created highly porous structures. The density of all the highly porous superabsorbents hydrogels (HPSH) synthesized was ranged from 0.6 to 1.04 g/cm3. These HPSHs exhibited a higher rate of swelling at time range from 28 to 269 minutes.

Three anionic chitosan surfactant with different hydrophobic tails labeled Chitosan-R8, Chitosan-R12 and Chitosan-R16 were prepared and their surface behavior in aqueous solution was determined by surface tension measurements at three different temperatures 20, 40 and 60 °C. The affinity of the synthesized anionic chitosan surfactant to form micelle enhanced with increasing the hydrophobic chain length as well as raising the solution temperature up to 60 °C. The anionic chitosan surfactant showed a great influence as capping agent for the in-situ preparation of silver nanoparticles (AgNPs) based on photochemical reduction method using sunlight as reducing agent. The chemical structure of chitosan surfactant showed a great effect on the size and stability of the prepared AgNPs. The Chitosan-R16 with longer hydrophobic tail, produce a uniform, small size & stable AgNPs compared to shorter tail Chitosan-R12 & Chitosan-R8. The prepared anionic chitosan showed good inhibiting effect against the steel corrosion in the 1.0 M HCl. The corrosion inhibition efficiency was determined using three different techniques, proving the ability of the new chitosan surfactant to inhibit the steel corrosion. The XPS results confirmed the formation of chitosan inhibitor on the steel surface.

Chitosan is the second abundant biopolymer present on earth after cellulose. Chitosan is extracted from the shells of shrimp and other crustaceans. Several methods were reported for its extraction, but the most commercial is the deacetylation of chitin. Chitosan as a biopolymer has numerous applications and uses. But, its mechanical, chemical and biological characteristics can be enhanced by modification of its chemical structures. Several modification methods and derivatives were reviewed in the literatures, and several were collected in this review. The reviewed modified chitosan derivatives herein were five types of derivatives. The first is substituted chitosan derivatives including thiolated, phosphorylated, and N-phthaloylated derivatives. The second is crosslinked chitosan derivatives including chitosan-glutaraldehyde, chitosan-ethylene diamine tetraacetic acid, and chitosan-epichlorohydrin derivatives. The third is carboxylic acid derivatives of chitosan obtained from carboxyalkylation, acrylation, methacrylation, and benzoylation of chitosan. The fourth is ionic chitosan derivatives including highly cationic and sulfated derivatives. The last is bounded chitosan to specific molecules including cyclodextrin, thiosemicarbazone, dioxime, and crown ether precursors. The review also highlights the reported advantages and applications of the modified chitosan and the synthetic routes of the biopolymer modification.

Chitosan has acylated with l-arginine in the presence of H2SO4 as a catalyst to the aim of increasing the adsorption efficiency. Chitosan (CS) and chitosan-O-arginine (CS-Arg) were characterized and investigated by elemental analysis, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The results obtained from elemental analysis exhibited presence of sulfur content, indicate that sulfuric acid still a crosslinker between CS-Arg chains, also the degree of substitution (DS) of l arginine in CS backbone was 1.83, indicate the acylation process has took place in both C3-OH and C6-OH of CS. XRD results exhibited that CS-Arg is more crystalline than CS, due to the formation of intra and inter molecular hydrogen bonds between amino and hydroxyl groups. The removal of heavy metals (Mn2+, Pb2+and Al3+) and total organic carbon (TOC) from wastewater by CS and CS-Arg in batch mode has been studied at different adsorbent dosages, temperatures and contact times. The maximum removal efficiency for three metal ions using CS achieved 99.6%, 99.1% and 98.9%, respectively, while by using CS-Arg were 97.1%, 94.3% and 99%. However, the maximum adsorption capacity of TOC by CS achieved 50 mg/g and 40.35 mg/g by CS-Arg. The total maximum adsorption capacity of CS-Arg is lower than CS. Keywords: Arginine, Chitosan, Heavy metals, Total organic carbon

Chitosan was reacted by tannic acid to obtain three modified chitosan biopolymer. Their chemical structures were characterized by FTIR and elemental analysis. The prepared biopolymers were used to adsorb Al(III) and Pb(II) metal ions from industrial wastewater. The factors affecting the adsorption process were biosorbent amount, initial concentration of metal ion and pH of the medium. The adsorption efficiency increased considerably with the increase of the biosorbent amount and pH of the medium. The adsorption process of biosorbent on different metal ions was fitted by Freundlich adsorption model. The adsorption kinetics was followed Pseudo-second-order kinetic model. The adsorption process occurred according to diffusion mechanism which was confirmed by the interparticle diffusion model. The modified biopolymers were efficient biosorbents for removal of Pb(II) and Al(III) metal ions from the medium.

Biocompatible and biodegradable polymers have a significant impact in a wide range of biomedical applications such as wound healing. For this purpose, demanded materials must have, a specific physical, chemical, biological, biomechanical properties and able to be broken down and removed after they have served their function to provide effective therapy. In the recent progress of biomedical treatment of wounds, there is a continuous need to improve both the appearance and functionality of the regenerated healed tissue. Modern clinical findings in that approach make use of the versatility, efficacy and functionality of chitosan composites. This chapter presents an overview of biocompatible and biodegradable polymers focusing on chitosan-based composites, underlying concepts of their properties and the ways to tailor their potential in biomedical engineering/management of wound healing. However, providing novel strategies that achieve a low cost and shorter wound closure is an ongoing challenge to be addressed. Finally, new insights concluded from our recent study cases reports for novel chitosan grafted poly (N-methyl aniline) nanoparticles that show an advanced therapeutic dressing via interesting photo-therapy results within a promising photo-driven skin regeneration under visible-light irradiation. The photoactive surface of grafted chitosan could produce reactive oxidizing species by which infectious microorganisms could be killed. Therefore, the wounded tissues are repaired and regenerated.

Carcinogenic organic pollutants pose a threat to human health and the environment; therefore, appropriate solutions are required for their removal. In this study, three hybrid systems composed of surfactants and silver nanoparticles (AgNPs) were prepared based on three cationic Gemini surfactants exhibiting different hydrophobic tail lengths. The AgNPs were synthesized by a photochemical reduction method using sunlight as a surplus source of a reducing agent. The reaction was conducted in the presence of previously synthesized cationic Gemini surfactants as capping agents. It was found that surfactants with longer hydrophobic tails induced the formation of AgNPs displaying a smaller particle size, more uniform structure, and higher stability in solution compared to those prepared using surfactants with shorter hydrophobic tails. The results were confirmed by ultraviolet-visible (UV–Vis) spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). The surface behavior of the amphiphilic surfactants and their hybrid systems with AgNPs was investigated at 25, 45, and 65 °C by performing surface tension measurements. It was determined that increasing the hydrophobic tail length and temperature resulted in increased micellization. Moreover, grafting the synthesized cationic Gemini surfactants with AgNPs enhanced the surface parameters. The synthesized surfactant–AgNPs hybrid systems showed good catalytic activity in converting carcinogenic p-nitrophenol (p-NP) into less toxic p-aminophenol (p-AP) in the presence of NaBH4 as the reducing agent. The effect of the chain length variation on the catalytic performance of AgNPs was studied for the first time. Overall, combination of the synthesized cationic Gemini surfactants with AgNPs led to a significant enhancement in the biological performance.

Chitosan is the most plentiful, renewable marine polymer; it is also one of the most potential eco-friendly candidates for surface coating purposes with excellent film forming ability, corrosion protection ability due to its barrier property and affinity towards metals. In this study, extraction and characterization of chitosan were investigated via several analyses such as elemental analysis, FTIR, 1HNMR and degree of deacetylation. The extracted chitosan was mixed as natural organic filler with epoxy coating in varying loading levels from 2% to 20% to form chitosan − epoxy coating composite. This work represents the corrosion resistance and the antimicrobial activity of a composite formed by chitosan and epoxy coating. The corrosion resistance was evaluated via salt spray test; Gram-negative bacteria, Gram-positive bacteria and fungi were used to study the antimicrobial activity of different concentrations of chitosan − epoxy coating composite. The dynamic mechanical analysis (DMA) of the coating composite was also studied, to characterize the viscoelastic properties of the extracted chitosan. Mechanical and chemical resistance was also investigated. The obtained results showed that, the chitosan − epoxy coating composite showed uniform and lower corrosion rates than that of blank epoxy coating. The antimicrobial effect of chitosan in different loading showed that, the antimicrobial effect strengthened as the loading of chitosan increased. The antimicrobial activity of chitosan for Gram- positive bacteria were higher than to Gram- negative bacteria and fungi. The DMA reported in this work showed that, chitosan may be useful to improve the viscoelstic characteristics of epoxy coating. The mechanical and chemical resistance was also improved and this improvement increases with increase chitosan loading up to, and including, a 15% chitosan.

In this work, chitosan was modified by the esterification with L-alanine in the presence of H2SO4 as a catalyst to increase the number of amino groups with the aim of increasing the adsorption efficiency. Chitosan (CS) and chitosan-O-alanine (CS-Aln) were characterized and investigated by elemental analysis, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The results obtained from elemental analysis and IR indicated the presence of sulfuric acid after neutralization as a crosslinker between CS-Aln chains. Also CS-Aln is more amorphous than CS due to the ionic bonds of crosslinker. The removal of three heavy metals (Mn2+, Pb2+ and Al3+) and total organic carbon (TOC) from wastewater by CS and CS-Aln in the batch mode has been studied at different adsorbent dosages, temperatures and contact times. The maximum metal ions removal efficiency using CS achieved 99.6%, 99.1% and 98.9%, respectively, while by using CS-Aln 95.3%, 99.3% and 98.9% were achieved. However, the maximum adsorption capacity of TOC by CS achieved 50 mg/g and 89 mg/g by CS-Aln. The total maximum adsorption capacity of CS-Aln is higher than CS.

Chitosan was extracted and characterized using several analyses. The produced chitosan was reacted by glycine and chloroacetic acid. Chemical structures of biosorbents were confirmed. Adsorption efficiencies of the two biosorbents in neutral and alkaline medium at 25 °C were determined using atomic absorption spectroscopic analysis. Adsorption capacity of modified biosorbents toward Cu(II) and Co(II) ions was determined and compared to virgin chitosan. The biosorbents showed lower adsorption efficiency toward copper and cobalt ions compared to virgin biosorbent. Furthermore, adsorption capacity of glycine–chitosan was higher than chloroacetic acid–chitosan biosorbents, which attributed to chelating of amino groups than chloro-substituted polymer. Thermodynamic studies showed the spontaneous behavior of the adsorption process of metal ions under the studied conditions. Entropy changes indicate that the adsorption of the metal ions are endothermic process, and lower values of ΔS° indicate the affinity toward metal ions by the biosorbents at different degrees depending on their chemical structures.

Chitosan (CTS) was first prepared by proper treatment of shrimp shells and the cross-linked chitosan (CCTS) was then synthesized by its reaction with epichlorohydrin ( ECH ) under alkaline conditions. Adsorption of uranium from aqueous nitrate solution onto CCTS was investigated batch wise. The adsorption isotherm and the adsorption kinetic as well as thermodynamic studies of this adsorption are carried out. The influence factors on uranium (VI) adsorption were optimized and were found to include an initial pH of 3 and a contact time of 120 min. The Langmuir adsorption model was then applied for the mathematical description of the obtained adsorption equilibrium and where its data greatly agree with that model and where the maximum adsorption capacity was estimated to be 903 mg/g. Adsorption kinetics data were also tested using pseudo-first-order and pseudo-second-order models and where the studied adsorption followed the latter. In addition, determination of the thermodynamic parameters (Δ G °, Δ H ° and Δ S °) using van’t Hoff equation has indicated that the prepared CCTS can conveniently be used for uranium adsorption from its aqueous solution.

Surface properties of the dodecyl isothiouro- nium cationic surfactant in a mixed solvent of water and polyethylene glycol of different molecular weights varied from ethylene glycol to polyethylene glycol-600 were determined using surface tension and conductivity mea- surements. The results showed an increase in the surface properties including critical micelle concentration, effec- tiveness and efficiency, compared to the surfactant in pure water as the solvent. The interaction between the cationic surfactant and the glycols was described and the molecular weight of the different glycols was rationalized.

Three series of nonionic surfactants derived from polytriethanolamine containing 8, 10, and 12 units of triethanolamine were synthesized. Structural assignment of the different compounds was made on the basis of FTIR and 1H-NMR spectroscopic data. The surface parameters of these surfactants included critical micelle concentration (CMC), surface tension at the CMC (γCMC), surfactant concentration required to reduce the surface tension of the solvent by 20 mN m−1 (pC20), maximum surface excess (Γmax), and the interfacial area occupied by the surfactant molecules (Amin) using surface tension measurements. The micellization and adsorption free energies were calculated at 25 °C.

The chitosan was prepared and mixed with some metal salts (FeCl3, Co(OAc)2 and NiCl2) by different concentrations to form chitosan-metal complexes. The metal ions which strongly complexed to the amino groups of chitosan like Fe showed a smooth surface product, amorphous phase, thermally more stable and high electrical conductivity than other complexes, while the Co ions which the weakly complexed with chitosan showed a rough surface product, crystalline phase, thermally less stable and low electrical conductivity. The chitosan-metal complexes have a higher electrical conductivity than chitosan pure at room temperature.

The chitosan was prepared and mixed with some metal salts (FeCl3, Co(CH3COO)2 and NiCl2) with different concentrations to form chitosan-metal complexes. The characterizations of these complexes were carried out by FTIR and their morphological studies were carried out by scanning electron microscope (SEM) and wide angle X-ray diffraction apparatus. The thermo gravimetric analysis (TGA) and differential scanning calorimetric (DSC) also were carried out. The metal ions which strongly complexed to the amino groups of chitosan like Fe+++ showed a smooth surface product, amorphous phase and thermally more stable than other complexes. The chitosan-metal complexes have a higher electrical conductivity than chitosan compounds at room temperature.

Chitosan (Ch) grafted with poly(ethylene glycol) (Ch-g-mPEG) were synthesized using mPEG with molecular weights 2000 g/mol. The synthesized Ch-g-mPEG was characterized using gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), and X-ray diffraction (XRD) techniques. Ch-g-mPEG silver nanoparticles has been synthesized and characterized by high-resolution transmission electron microscopy (HRTEM) and energy dispersive analysis of X-rays (EDAX). The synthesized Ch-g-mPEG and its nanostructure were examined as corrosion inhibitors for carbon steel in 1M HCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results revealed that the inhibition efficiency obtained by Ch-g-mPEG self-assembled on silver nanoparticles is greater than that obtained by Ch-g-mPEG only. Potentiodynamic polarization results reveal that the synthesized compound could be classified as mixed-type corrosion inhibitors with predominant control of the cathodic reaction. The results of EIS indicate that the both charge transfer resistance and inhibition efficiency tend to increase by increasing the inhibitor concentration.

Biosorption of Cu(II), Co(II) and Fe(III) ions from aqueous solutions by rice husk, palm leaf and water hyacinth was investigated as a function of initial pH, initial heavy metal ions concentration and treatment time. The adsorption process was examined by two adsorption isotherms: Langmuir and Freundlich isotherms. The experimental data of biosorption process were analyzed using pseudo-first order, pseudo-second order kinetic models. The equilibrium biosorption isotherms showed that the three studied biosorbents possess high affinity and sorption capacity for Cu(II), Co(II) and Fe(III) ions. Rice husk showed more efficiency than palm leaf and water hyacinth. Adsorption of Cu(II) and Co(II) was more efficient in alkaline medium (pH 9) than neutral medium due to the high solubility of metal ion complexes. The metal removal efficiency of each biosorbent was correlated to its chemical structure. DTA studies showed formation of metal complex between the biosorbents and the metal ions. The obtained results showed that the tested biosorbents are efficient and alternate low-cost biosorbent for removal of heavy metal ions from aqueous media.

Chitosan immobilized bentonite (CIB) namely chitosan-coated bentonite (5% chitosan content) was synthesized in 2% acetic acid solution, followed by crosslinking, using epichlorohydrien (ECH). The so-obtained crosslinked chitosan immobilized on bentonite (CIB-ECH) and CIB composites were grafted with polyaniline (PANI) through oxidative-radical copolymerization using ammonium peroxydisulfate in acidic medium to produce PANI-grafted crosslinked chitosan immobilized on bentonite (PANI-g-CIB-ECH) and PANI-grafted-chitosan immobilized on bentonite (PANI-g-CIB) composites, respectively. The resultant composites were characterized by using X-ray diffraction (XRD), thermo gravimetric analysis/differential scanning calorimetry, scanning electron microscopy, Fourier transform infrared (FTIR), and electrical conductivity. XRD and FTIR analyses indicate that chitosan was not intercalated into the silicate layer. Also the electrical conductivity elucidates that the grafted composites fall in the range required for the application as electrostatic dissipation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41078.

Chitosan is one of the important biopolymers and it is extracted from exoskeletons of crustaceans in sea food waste. It is a suitable eco-friendly carbon steel corrosion inhibitor in acid media; the deacetylation degree of prepared chitosan is more than 85.16 %, and the molecular weight average is 109 kDa. Chitosan was modified to 2-N,N-diethylbenzene ammonium chloride N-oxoethyl chitosan (compound I), and 12-ammonium chloride N-oxododecan chitosan (compound II) as soluble water derivatives. The corrosion inhibition efficiency for carbon steel of compound (I) in 1 M HCl at varying temperature is higher than for chitosan and compound (II). However, the antibacterial activity of chitosan for Enterococcus faecalis, Escherichia coli, Staphylococcus aureus, and Candida albicans is higher than for its derivatives, and the minimum inhibition concentration and minimum bacterial concentration of chitosan and its derivatives were carried out with the same strain.