PREPARATION AND ADSORPTION OF THIOUREA MODIFIED GLUTARALDEHYDE-CROSSLINKED CHITOSAN RESINS

The preparation and adsorption of thiourea modified glutaraldehyde-crosslinked chitosan resin （Thio-chitosan） using cyanuric chloride as activator was studied. The adsorptive capacity of thio-chitosan with 15% apparent degree of crosslinking （DC, mass ration of glutaraldehyde to chitosan） to Cu（Ⅱ） was 160mg/g （dry weight）. The adsorption of Cu（Ⅱ） was correlated with Freundlich and Langmuir isotherm equation. Cu（Ⅱ） adsorbed on thio-chitosan column （ 1cm×10cm） was eluted with 0.5mol/L H2SO4, 6mol/L HCI and 3% thiourea solution with the recovery of 88.3%, 86.1% and 95.3%, respectively. The thio-chitosan resin can be applied to the separation and recovery of metal ions.

ADSORPTION SELECTIVITY FOR Cu^(2+),Ni^(2+),Co^(2+)IONS USING CROSSLINKING CHITOSAN RESINS IMPRINTED BY METAL IONS

Metal ion-imprintedly crosslinked chitosan resin 1 and resin 2 were prepared by theuse of Cu2+ and Ni2+ as template ions and glutaraldehyde as crosslinking agent, respectively.Through investigation on the adsorption capacities and binding constants for Cu2+, Ni2+andCo2+ ions on chitosan resins, resin 1 and resin 2 exhibit the adsorption selectivity for themixture solution of 1:1 Cu2+ and Ni2+ ions. The adsorption selectivity of metal ion-imprintedresins for their template ions is much higher than that of uncrosslinked chitosan resin.

Adsorption of methyl orange from aqueous solution by composite magnetic microspheres of chitosan and quaternary ammonium chitosan derivative

Novel composite magnetic microspheres containing chitosan and quaternary ammonium chitosan derivative(CHMMs) were prepared by inverse suspension method,and used for the methyl orange(MO) removal from aqueous solutions.The CHMMs were characterized by a scanning electron microscope,a transmission electron microscope,and Fourier transform infrared spectroscopy,respectively.Compared with the chitosan beads,the incorporation of quaternary ammonium chitosan derivative significantly reduced the particle size.The MO adsorption by CHMMs was investigated by batch adsorption experiments.The adsorption kinetics was conformed to the pseudo second-order kinetics equation.The adsorption isotherm followed the Langmuir model better than the Freundlich model and the calculated maximum MO adsorption capacity was 266.6 mg·g^-1 at 293 K.Thermodynamic studies indicated that the MO adsorption was endothermic in nature with the enthalpy change(△H°) of 99.44 kJ·mol^-1.The CHMMs had a stable performance for MO adsorption in the pH range of 4-10,but high ionic strength deteriorated the MO removal due to the shielding of the ion exchange interaction.A 1 mol·L^-1 NaCl solution could be used to regenerate the exhausted CHMMs.The proposed CHMMs can be used as an effective adsorbent for dye removal or recovery from the dye wastewater.

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...

Adsorption of Cu（ll）, Ni（ll） and Pb（ll） Ions in Aqueous Solutions by a Biopolymer Chitosan at Different Molecular Weights

In this study, the feasibility of using chitosan, a multifunctional environmentally friendly biopolymer, at different molecular weights to simultaneously adsorb various metal ions from aqueous solutions was evaluated. The experiments were carried out to estimate adsorptivity and selectivity of three molecular weights chitosan, 3.60 × 105 （Chl）, 5.97 × 105 （Ch2） and 9.47 × 105 （Ch3） g/mol, towards Cu（II）, Ni（II）, and Pb（II） ions in aqueous solutions. Experimental results indicated that chitosan of high molecular weight （Ch3） was the best at adsorption capacity than the others. On chitosan solutions followed by Ni（II） and then Cu（II）. the other hand, Pb（lI） had the highest adsorption ability in the three

Adsorption of Cr(III) from an Aqueous Solution by Chitosan Beads Modified with Sodium Dodecyl Sulfate (SDS)

This study is to prepare chitosan beads modified with sodium dodecyl sulfate (SDS) to effectively remove Cr(III) from an aqueous solution. The characterizations of SDS-chitosan by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), Fourier transform-infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) proved the successful synthesis of the adsorbent. The adsorption of Cr(III) on the SDS material was investigated by varying experimental conditions such as pH, contact time and adsorbent dosage. The maximum adsorption capacity of SDS-chitosan for Cr(III) was estimated to be 3.42 mg?g-1. The results of adsorption kinetics and isothermal models show that the adsorption process conforms to the pseudo-second-order and Langmuir isotherm models, indicating that the adsorption is single-layer chemical adsorption. Thermodynamic analyses indicate that the adsorption of Cr(III) is an endothermic reaction. These results show that the new adsorbent has obvious application prospect to eliminate Cr(III).

An ion-imprinted polymer supported by attapulgite with a chitosan incorporated sol-gel process for selective separation of Ce(Ⅲ)

The surface ion-imprinting concept and chitosan incorporated sol-gel process were applied to the synthesis of a new attapulgitesupported polymer for selective separation of Ce（III） from aqueous solution. The imprinting mechanism of prepared ion-imprinted polymer were discussed with the Characteristics of FT-IR and SEM. Results from the experiments of adsorption capacity and selectivity suggested that ion-imprinted polymer offered a fast kinetics for the adsorption of Ce（III） under the optimum conditions. Its maximum adsorption capacity was 38.02 mg/g, and the selective recognition towards Ce（III） was much higher than that of the non-imprinted polymer and attapulgite. The prepared functional polymer was shown to be promising for selective separation and enrichment of trace Ce（III） in environmental samples. ？2009 Yong Sheng Yan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Equilibrium and kinetics of adsorption of Ca(Ⅱ) ions onto KCTS and HKCTS

The adsorption of Ca（ II ） ions from aqueous solution by ehitosan a-ketoglutaric acid （KCTS） and hydroxamated chitosan a-ketoglutaric acid （HKCTS） was studied in a batch adsorption system. The Langmuir and Freundlich adsorption models were applied to describing the equilibrium isotherms, and isotherm constants were determined. The kinetics of the adsorption with respect to the initial Ca（II） ions concentration, temperature and pH was investigated. The pseudo-first-order and second-order kinetic models were used to describe the kinetic data and the rate constants were evaluated. The results show that the experimental data fit well to the Langmuir isotherms with a high correlation coefficient （R2）. The pseudo-second-order rate expression provides the best fitting kinetic model. The pseudo second-order kinetic model is indicated with the activation energy of 26.22 kJ/mol and 6.16 kJ/mol for KCTS and HKCTS, respectively. It is suggested that the overall rate of adsorption of Ca（ II ） ions is likely to be controlled by the chemical process.

Crosslinked chitosan nanofiber mats fabricated by one-step electrospinning and ion-imprinting methods for metal ions adsorption

The Pb(Ⅱ)ion-imprinting electrospun crosslinked chitosan nanofiber mats were fabricated by one-step electrospinning and ion-imprinting methods and their application as adsorbents for metal ions was also investigated.The resulting chitosan nanofiber mats were characterized by scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS)and thermal gravimetric analysis(TGA).The Pb(Ⅱ)ion-imprinting electrospun crosslinked chitosan nanofiber mats were used as adsorbents for the removal of Pb(Ⅱ)ions from aqueous or acid solutions.The effects of p H values,contact time,content of crosslinker(glutaraldehyde)on Pb(Ⅱ)ions adsorption were studied.The results indicated that the Pb(Ⅱ)ion-imprinting electrospun crosslinked chitosan nanofiber mats had the highest adsorption capacity of 110.0 mg/g at p H 7.The kinetic study demonstrated that the adsorption of Pb(Ⅱ)ions followed the pseudo-second-order model.The equilibrium isotherm data showed that the Langmuir model was the most suitable for predicting the adsorption isotherm of the studied system.The Pb(Ⅱ)ion-imprinting electrospun crosslinked chitosan nanofiber mats had good adsorption selectivity,which illustrates the equilibrium adsorption capacity in the order of Pb(Ⅱ)>Cu(Ⅱ)>Zn(Ⅱ)>Cd(Ⅱ)>Ni(Ⅱ).The Pb(Ⅱ)ion-imprinting electrospun crosslinked chitosan nanofiber mats were stable and had good reuse ability.

Chitosan—The Application of a Natural Polymer against Iron Hydroxide Deposition

As a consequence of mining, heavy metal ions can be exposed to the environment hence contaminate ground water and surface water amongst others. The natural polymer chitosan was proved to be an excellent adsorber material for the effective removal of iron and sulfate ions in batch as well as in column experiments. The adsorption behavior of iron ions, as well as sulfate ions was investigated by utilizing chitosan flakes as a natural adsorbent. The removal was studied using adsorbance measurements, SEM and SEM-EDX. The adsorption capacity of chitosan was determined at different times. The received adsorption capacities for iron ions were very promising with a maximum adsorption capacity of 85 mg/g and a rate of separation of 100%. The maximum adsorption capacity obtained for sulfate ions was 188.8 mg/g and a rate of 80%.

Modulation of Electrochemical Oscillations by Specific Adsorption of Cl- during the Electrooxidation of Methanol on Pt Electrode

Potential oscillation during the electrocatalytic oxidation of methanol can be modulated by the specific adsorption of Cl- on the platinum electrode, which suppresses the electrocatalytic oxidation of methanol, and makes the cross cycle in the cyclic voltammogram become smaller and finally disappear with the increase of Cl- concentration. The method is also applicable to the electrocatalytic oxidation of other small organic molecules.

Effective and selective adsorption of uranyl ions by porous polyethylenimine-functionalized carboxylated chitosan/oxidized activated charcoal composite

Composite materials have elicited much interest because of their superior performance in the removal of toxic and radioactive uranyl ions from aqueous solutions.With polyethyleneimine as a functional group,carboxylated chitosan as a matrix,and oxidizing activated carbon as a nanofiller,this study synthesized a novel environment-friendly polyethylenimine-functionalized carboxylated chitosan/oxidized activated charcoal(PCO)biocomposite with a unique three-dimensional porous structure.PCO was synthesized through an easy chemical cross-linking method.Detailed characterization certified the formation of the unique three-dimensional porous structure.The obtained PCO was used to remove uranyl ions from an aqueous solution,demonstrating the maximum adsorption capacity of 450 mg·g^(−1).The adsorption capacity of PCO decreased by less than 7.51%after five adsorption-desorption cycles.PCO exhibited good adsorption selectivity(K_(d)=3.45×10^(4) mL·g^(−1))for uranyl ions.The adsorption mechanism of PCO was also discussed.The material showed good potential for application in the treatment of wastewater containing uranyl ions.

SYNTHESIS AND PROPERTIES OF SULFHYDRYL CHITOSAN

A new adsorbent for heavy metal ions, sulfhydryl chitosan (S chitosan), was produced by treatment of chitosan with sulhydryl acetic acid in the presence of sulfuric acid as a catalyst. Its structure was confirmed by elemental analysis and FT IR spectra analysis. The adsorption properties of sulfhydryl chitosan for Cu(Ⅱ), Cd(Ⅱ), Pb(Ⅱ), Cr(Ⅲ) and Ni(Ⅱ) were investigated, and the effect of pH value on adsorption, adsorption kinetics, and selective adsorption was examined. It was shown that S chitosan has good adsorption for Pb(Ⅱ), Cu(Ⅱ) and Cd(Ⅱ) like chitosan, is also insoluble in acid solution; has good adsorption kinetic properties for heavy metal ions; and can be used in acid solution. The adsorption capacities of S chitosan can be affected by media acidity. The adsorbed Cu(Ⅱ) Cd(Ⅱ)and Pb(Ⅱ) could be eluted by diluted chlorhydric acid.

Adsorption of graphene oxide/chitosan porous materials for metal ions

Porous graphene oxide/chitosan （PGOC） materials were prepared by a unidirectional freeze-drying method. Their porous structure, mechanical property and adsorption for metal ions were investigated. The results show that the incorporation of graphene oxide （GO） significantly increased the compressive strength of the PGOC materials. The saturated adsorption capacity of Pb^2＋ increased about 31%, up to 99 mg/g when 5 wt% GO was incorporated These biodegradable, nontoxic, efficient PGOC materials will be a potential adsorbent for metal ions in aqueous solution.

Adsorption of Au(Ⅲ) ions on xanthated crosslinked chitosan resin in hydrochloric acid medium

Xanthated crosslinked chitosan(XCCS) resin prepared under microwave irradiation were used for adsorbing Au(Ⅲ) ions in hydrochloric acid medium.The influence of pH and temperature on the adsorption capacity of XCCS was investigated.The original XCCS and the loaded XCCS were characterized by scanning electron microscope(SEM) and X-ray diffraction(XRD),respectively.The results indicate that the XCCS has ability to adsorb Au(Ⅲ) ions and the maximum adsorption capacity of Au(Ⅲ) ions on XCCS is observed at pH 1 and 20℃.The data of batch adsorption tests are fitted to kinetic models and isotherm models,respectively.The kinetics of adsorption process is found to follow pseudo-second-order kinetic rate model,and equilibrium data agree very well with the Langmuir model.Thermodynamic calculation of the Au(Ⅲ) ions adsorption process indicates that the adsorption process is spontaneous and endothermic.

Adsorption and reduction of platinum(Ⅳ) chloride complex ions on activated carbon

The adsorption kinetics of platinum（IV） chloride complex ions on the activated carbon Norit GF40 was investigated. Experiments were carried out at different initial concentrations of Pt（IV） chloride complex ions, temperature, rate of mixing and pH. It was found that the value of activation energy of the studied process is equal to 19.7 kJ/mol. From the ICP MS analysis it was confirmed that platinum ions （Pt（IV） and Pt（II）） are removed from the solution due to the adsorption and are further reduced to the metallic state. Such mechanism was confirmed by XPS analysis which showed that on the carbon surface three forms of platinum species, i.e. Pt（0）, Pt（II） and Pt（IV）, exist. The presence of platinum in the solution at different oxidation states was also confirmed spectrophotometrically by identification of their characteristic absorption bands. The metallic form of Pt present on the surface of activated carbon was observed in the form of small spherical islands with the diameter not exceeding 500 nm. Those islands consist of smaller, flake-shape particles with a thickness of about 35 nm.

Adsorptive removal of iron and manganese ions from aqueous solutions with microporous chitosan/polyethylene glycol blend membrane

Microporous chitosan （CS） membranes were directly prepared by extraction of poly（ethylene glycol） （PEG） from CS/PEG blend membrane and were examined for iron and manganese ions removal from aqueous solutions. The different variables affecting the adsorption capacity of the membranes such as contact time, pH of the sorption medium, and initial metal ion concentration in the feed solution were investigated on a batch adsorption basis. The affinity of CS/PEG blend membrane to adsorb Fe（II） ions is higher than that of Mn（II） ions, with adsorption equilibrium achieved after 60 min for Fe（II） and Mn（II） ions. By increasing CS]PEG ratio in the blend membrane the adsorption capacity of metal ions increased. Among all parameters, pH has the most significant effect on the adsorption capacity, particularly in the range of 2.9-5.9. The increase in CS/PEG ratio was found to enhance the adsorption capacity of the membranes. The effects of initial concentration of metal ions on the extent of metal ions removal were investigated in detail. The experimental data were better fitted to Freundlich equation than Langmuir. In addition, it was found that the iron and manganese ions adsorbed on the membranes can be effectively desorbed in 0.1 mol/L HCl solution （up to 98% desorption efficiency） and the blend membranes can be reused almost without loss of the adsorption capacity for iron and manganese ions.

Removal of toxic metal ions using chitosan coated carbon nanotube composites for supercapacitors

Environmental pollution and energy crisis are two major global challenges to human beings.Recovering energy from wastewater is considered to be one of the effective approaches to address these two issues synchronously.As the main pollutants in wastewater,toxic heavy metal ions are the potential candidates for energy storage devices with pseudocapacitive behaviors.In this study,toxic metal ions of Cr(VI)and Cu(II)are removed efficiently by chitosan coated oxygen-containing functional carbon nanotubes,and the corresponding equilibrium adsorption capacity is 142.1 and 123.7 mg g^(-1).Followed by carbonization of metal ions-adsorbed adsorbents,Cu-and Cr N-loaded carbon composites can be obtained.Electrochemical measurements show that the supercapacitor electrodes based on Cu-and Cr N-loaded carbon composites have specific capacitance of 144.9 and 114.9 F g^(-1)at2 m V s^(-1),with superior electrochemical properties to pure chitosan coated carbon nanotubes after carbonization.This work demonstrates a new strategy for the resource-utilization of other heavy metal ions for energy devices,and also provides a new way to turn environmental pollutants into clean energy.

Preparation and application of novel chitosan-cellulose composite materials to adsorb Pb(Ⅱ)and Cr(Ⅵ)ions from water

This paper reported the preparation and application of novel chitosan-cellulose composite absorbents for the adsorption of Pb(II)and Cr(VI)ions in water.First,oxycellulose or dialdehyde cellulose(DAC)was prepared by sodium periodate oxidation of microcrystalline cellulose(MCC).Second,based on the mechanism of the Mannich reaction,a chitosan/cellulose-based adsorbent(TSFCD)was produced through a cross-linking reaction of thiosemicarbazide(TS)with DAC and chitosan(CS),which was designed specifically for the adsorption of Cr^(6+)ions from water.Similarly,another chitosan/cellulose-based adsorbent(DBFCM)was also prepared with 2,5-dithiobiurea(DB)as the cross-linking agent for the adsorption of Pb^(2+)ions in water.The adsorption performance of TSFCD and DBFCM for Cr^(6+)and Pb^(2+)ions,respectively,was investigated under various process conditions.Variables included adsorption temperature,time,initial metal ion concentration,pH,and adsorbent dosage.The adsorption kinetics of TSFCD and DBFCM were studied,and isothermal models were developed.Results showed that the adsorption amount increased with the increase of the reaction time,and reached a maximum at about 300 min for the TSFCD/Cr^(6+)system,and at about 240 min for DBFCM/Pb^(2+)system.The adsorption performance of TSFCD for Cr^(6+)and DBFCM for Pb^(2+)improved at higher temperature,and leveled off at 40℃ and 50℃,respectively.In addition,the removal rate of Cr^(6+)increased from 49.96%to 70.22%when the TSFCD dosage increased from 0.5 g/L to 3.5 g/L.Similarly,the removal rate of Pb^(2+)increased from 22.23%to 99.45%with the increase of DBFCM dosage from 0.5g/L to 5.0g/L.The adsorption processes of Pb^(2+)and Cr^(6+)were in line with the pseudo-second-order kinetic and the Langmuir isothermal model.

壳聚糖复合水凝胶的制备方法及在水处理中的应用

壳聚糖由于来源广、吸附性能强和可自然降解等优点成为备受关注的天然吸附剂。壳聚糖复合水凝胶(CCH)材料是以壳聚糖为主要原料,通过化学、物理等方法改性后得到的新型复合材料。介绍了化学交联、物理交联以及互穿网络等合成壳聚糖复合水凝胶的主要方法。综述了近年来使用CCH对工业废水中常见染料、重金属离子和其他常见污染物的吸附机理和处理效果,讨论了当前利用CCH在处理工业废水中各种污染物时存在的问题及解决方法。最后对CCH在合成方法、选择性吸附、回收利用和智能改性等方面进行了展望,为深入研究提高CCH材料性能及拓宽其在工业废水处理中的应用范围提供了思路。