Three novel dendritic chitosan derivatives for inhibiting acid corrosion of petroleum pipelines

In the process of exploration and development of oil and gas fields, the acidic environment of oil reservoir, production and transport processes cause corrosion of pipelines and equipment, resulting in huge economic losses and production safety risks. Corrosion inhibitors were widely used in oil industry because of simple operation process and economical. In this study, three environmentally friendly corrosion inhibitors were synthesized based on the natural polysaccharide chitosan. Corrosion inhibition of three dendritic chitosan derivatives (We name them BH, CH and DH) on mild steel in 1 mol/L HCl solution with natural ventilation system was evaluated by weight loss experiment, electrochemical analysis and surface morphology characterization. The experimental results showed that when the three dendritic chitosan derivatives added in the corrosive medium were 500 mg L^(−1), the corrosion inhibition efficiencies were all more than 80%. Based on quantum chemical calculation, inhibition mechanisms of three dendritic chitosan derivatives were investigated according to molecular structures. The results showed that the benzene ring, Schiff base and N atom contained in the molecule were the active centers of electron exchange, which were more likely to form a film on the carbon steel surface, thereby slowing or inhibiting corrosion. The results also predicted the corrosion inhibition effect BH > DH > CH, which was consistent with the experimental conclusion.

Pb(Ⅱ) biosorption using chitosan and chitosan derivatives beads: Equilibrium, ion exchange and mechanism studies

The study examined the adsorption of Pb（II） ions from aqueous solution onto chitosan, chitosan-GLA and chitosan-alginate beads. Several important parameters influencing the adsorption of Pb（II） ions such as initial pH, adsorbent dosage and different initial concentration of Pb（II） ions were evaluated. The mechanism involved during the adsorption process was explored based on ion exchange study and using spectroscopic techniques. The adsorption capacities obtained based on non–linear Langmuir isotherm for chitosan, chitosan-GLA and chitosan-alginate beads in single metal system were 34.98, 14.24 and 60.27 mg/g, respectively. However, the adsorption capacity of Pb（II） ions were reduced in the binary metal system due to the competitive adsorption between Pb（II） and Cu（II） ions. Based on the ion exchange study, the release of Ca2＋, Mg2＋, K＋ and Na＋ ions played an important role in the adsorption of Pb（II） ions by all three adsorbents but only at lower concentrations of Pb（II） ions. Infrared spectra showed that the binding between Pb（II） ions and the adsorbents involved mostly the nitrogen and oxygen atoms. All three adsorbents showed satisfactory adsorption capacities and can be considered as an efficient adsorbent for the removal of Pb（II） ions from aqueous solutions.

Synthesis of a new chitosan derivative and assay of Escherichia coli adsorption

A new chitosan derivative is prepared using chitosan.Ethyl chlorocarbonate was first introduced to the hydroxyl group of phthaloylchitosan through a nucleophilic reaction.Hydrazine was then added to recover the amino groups of chitosan and promote cross-linking.The structure of this new chitosan derivative was characterized by Fourier transform infrared（FT-IR）and proton nuclear magnetic resonance（1H NMR）spectroscopy,and its physical properties were determined by X-ray diffraction（XRD）,differential scanning calorimetry（DSC）,and thermogravimetric analysis（TGA）.The thermal and chemical stabilities of the new derivative were improved compared with those of native chitosan.Assay of Escherichia coli adhesion on a film based on this chitosan derivative showed good adsorption and biofilm formation.

The Adsorption Effect of Quaternized Chitosan Derivatives on Bile Acid

Three quatemized chitosan derivatives were synthesized and their adsorption performance of bile acid from aqueous solution was studied. The adsorption capacities and rates of bile acid onto quatemized chitosan derivatives were evaluated. The kinetic experimental data properly correlated with the second-order kinetic model, which indicated that the chemical sorption is the rate-limiting step. The results showed that the quatemized chitosan derivatives are favorable adsorbents for bile acid.

Synthesis,characterization,and antioxidant activity of carboxymethyl chitosan derivatives containing sulfonium salt

To improve the solubility and bioactivity of chitosan,a new class of carboxymethyl chitosan derivatives possessing sulfonium salts was successfully designed and synthesized,including Methyl sulfi de carboxymethyl chitosan(MCMCS),Ethyl sulfi de carboxymethyl chitosan(ECMCS),Propyl sulfi de carboxymethyl chitosan(PCMCS),and Butyl sulfi de carboxymethyl chitosan(BCMCS).To determine the structure of the new class of the derivatives,methods of the Fourier transform infrared spectroscopy(FT-IR),^(1)H nuclear magnetic resonance spectrometer(^(1)H NMR),and^(13)C nuclear magnetic resonance spectrometer(^(13)C NMR)were used.Moreover,the antioxidant activity of the derivatives for three types of free radicals,i.e.,hydroxyl radical,superoxide radical,and 1,1-diphenyl-2-picrylhydrazyl(DPPH)radical was evaluated in vitro.In addition,the L929 cells were adopted to test the cytotoxicity of chitosan and its derivatives by CCK-8 assay.The class of the carboxymethyl chitosan derivatives showed a strong scavenging ability against the three free radicals at 1.6 mg/mL,with scavenging rate of over 70%and some up to 100%.At this high rate,the overall cell viability in the toxicity test reached more than 80%,indicating that the synthetic derivative had a little cytotoxicity.The results show that the introduction of carboxymethyl group to chitosan increased the water-solubility of chitosan,and the combination of sulfonate ions with diff erent chain lengths further enhanced the antioxidant activity of chitosan.Therefore,the sulfonium-containing carboxymethyl chitosan derivatives had excellent bioactivity with good application prospects in food,biomedicine,and medical fi elds.

PREPARATION AND CHARACTERIZATION OF NOVEL CHITOSAN DERIVATIVES:ADSORPTION EQUILIBRIUM OF IRON(Ⅲ) ION

The adsorption of Fe(Ⅲ)ions from aqueous solution by chitosan alpha-ketoglutaric acid(KCTS)and hydroxamated chitosan alpha-ketoglutaric acid(HKCTS)was studied in a batch adsorption system.Experiments were carried out as function of pH,temperature,agitation rate and concentration of Fe(Ⅲ)ions.The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and isotherm constants were determined.The Langmuir model agrees very well with experimental data.The pseudo-first-order a...

Novel nanoparticles composed of chitosan and β-cyclodextrin derivatives as potential insoluble drug carrier

This research was aim to develop novel cyclodextrin/chitosan （CD/CS） nanocarriers for insoluble drug delivery through the mild ionic gelation method previously developed by our lab. A series of different β- cyclodextrin （β-CD） derivatives were incorporated into CS nanoparticles including hydroxypropyl-β- cyclodextrin （HP-β-CD）, sulphobutylether-β-cyclodextrin （SB-β-CD）, and 2,6-di-O-methy-βcyclodex- trin （DM-β-CD）. Various process parameters for nanoparticle preparation and their effects on physicochemical properties of CD/CS nanoparticles were investigated, such as the type of CD derivatives, CD and CS concentrations, the mass ratio of CS to TPP （CS/TRP）, and pH values. In the optimal condition, CDICS nanoparticles were obtained in the size range of 215-276 nm and with the zeta potential from 30.22 mV to 35.79 mY. Moreover, the stability study showed that the incorporation of CD rendered the CD/CS nanocarriers more stable than CS nanoparticles in PBS buffer at pH 6.8. For their easy preparation and adjustable parameters in nanoparticle formation as well as the diversified hydrophobic core of CD derivatives, the novel CD/CS nanoparticles developed herein might represent an interesting and versatile drug delivery platform for a variety of poorly water-soluble drugs with different physicochemical properties.