Xiangjun Li

Fabrication of novel magnetic chitosan grafted with graphene oxide to enhance adsorption properties for methyl blue

A novel magnetic composite bioadsorbent composed of magnetic chitosan and graphene oxide (MCGO) was prepared as the magnetic adsorbent. The morphology, chemical structure and magnetic property of the MCGO were characterized by Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD) and Scanning electronic microscope (SEM), respectively. Adsorption of methyl blue (MB) onto MCGO was investigated with respect to pH, adsorption time, initial MB concentration and temperature. Kinetics data and adsorption isotherm, obtained at the optimum pH 5.3, were better fitted by pseudo-second-order kinetic model and by Langmuir isotherm, respectively. The values of activation parameters such as free energy (ΔG, -0.74∼-1.46kJmol(-1)), enthalpy (ΔH, -10.28kJmol(-1)) and entropy (ΔS, -36.35Jmol(-1)K(-1)) were determined, respectively, indicating that the adsorption was spontaneous, favorable and exothermic process in nature. Moreover, the MCGO was stable and easily recovered, the adsorption capacity was about 90% of the initial saturation adsorption capacity after being used four times.

Highly selective adsorption of lead ions by water-dispersible magnetic chitosan/graphene oxide composites

Magnetic chitosan/graphene oxide (MCGO) materials were fabricated through a facile and fast process and their application as excellent adsorbents for metal ions was also demonstrated. The characteristics results of FTIR, SEM, TEM, VSM and XRD showed that MCGO was successfully prepared. The SEM and TEM revealed that magnetic chitosan had been assembled on the surface of graphene oxide layers with a high density. The XRD and VSM indicated the MCGO had enough magnetic response to meet the need of magnetic separation. The magnetic chitosan grafted with graphene oxide sheets showed an increased surface area. The MCGO was used as sorbents for the removal of Pb(II) ions from large volumes of aqueous solutions. The effects of pH, contact time, and concentration on Pb(II) ions sorption were investigated. The results indicated that Pb(II) ions sorption on MCGO was strongly dependent on pH. The abundant functional groups on the surfaces of MCGO played an important role on Pb(II) sorption. Equilibrium studies showed that the data of Pb(II) adsorption followed the Langmuir model. The maximum adsorption capacity for Pb(II) was estimated to be 76.94 mg/g. The MCGO was stable and easily recovered.

Adsorbent for chromium removal based on graphene oxide functionalized with magnetic cyclodextrin-chitosan

A simple chemical bonding method to synthesize magnetic cyclodextrin-chitosan/graphene oxide (CCGO) was reported. The adsorption behaviors of Cr(VI) in aqueous solution on CCGO were systematically investigated. As the results shown that, with the advantage of high surface area, abundant hydroxyl and amino groups of CCGO, and the magnetic property of Fe3O4, the Cr(VI) can be easily and rapidly extracted from the water by magnetic attraction under investigation. The adsorption equilibrium of CCGO for Cr(VI) corresponded with Langmuir isotherm, and the novel adsorbent exhibited better Cr(VI) removal efficiency in solutions with low pH. It was found that the Cr(VI) adsorption performance of CCGO strongly depends on their surface charge concentration and specific surface area. These results provide evidences for estimating and optimizing the removal of metal ions from the wastewater by using of CCGO composites in the future.

Preparation of novel magnetic chitosan/graphene oxide composite as effective adsorbents toward methylene blue.

A novel magnetic composite bioadsorbent composed of magnetic chitosan and graphene oxide (MCGO) was prepared as the magnetic adsorbent toward methylene blue. The magnetic composite bioadsorbent was characterized by SEM, FTIR and XRD measurements. The effect factors including pH, contact time and temperature on the adsorption properties of methylene blue onto MCGO were investigated. The resulting shows extraordinary adsorption capacity and fast adsorption rates for removal of methylene blue. The kinetics are well-described by pseudo-second-order kinetic. The experimental data of isotherm followed the Langmuir isotherm model and the Freundlich model, respectively. This work shows that the MCGO could be utilized as an efficient, magnetically separable adsorbent for the environmental cleanup.

Synthesis of magnetic β-cyclodextrin-chitosan/graphene oxide as nanoadsorbent and its application in dye adsorption and removal.

Magnetic β-cyclodextrin-chitosan/graphene oxide materials (MCCG) were fabricated through a facile chemical route and their application as excellent adsorbents for dye removal were also demonstrated. The characteristics results of FTIR, SEM, TEM and XRD showed that MCCG was successfully prepared. The results showed that, benefiting from the surface property of graphene oxide, hydrophobicity of β-cyclodextrin, the abundant amino and hydroxyl functional groups of chitosan, and from the magnetic property of Fe(3)O(4), the adsorbent possesses quite a good and versatile adsorption capacity to the dye under investigation, and can be easily and rapidly extracted from water by magnetic attraction. Most importantly, the adsorbent can be easily and efficiently regenerated for reuse with hardly any compromise of the adsorption capacity. The adsorption kinetics, isotherms and thermodynamics were investigated to indicate that the kinetics and equilibrium adsorptions were well-described by pseudo-second-order kinetic and Langmuir isotherm model, respectively. The thermodynamic parameters suggested that the adsorption process was spontaneous and endothermic in nature. The inherent advantages of the nano-structured adsorbent, such as adsorption capacity, easy, handy operation, rapid extraction, and regeneration, may pave a new, efficient and sustainable way towards highly-efficient dye pollutant removal in water and wastewater treatment.

Removal of alizarin red from water environment using magnetic chitosan with Alizarin Red as imprinted molecules

A novel, chitosan coating on the surface of magnetite (Fe(3)O(4)) (MIMC) was successfully synthesized using alizarin red (AR) as a template for adsorption and removal of AR from aqueous solutions. Characterization of the obtained MIMC was achieved by FTIR spectra, SEM micrographs and XRD. Batch adsorption experiments were performed to investigate the adsorption conditions, selectivity and reusability. The results showed that the maximum adsorption capacity was 40.12 mg/g, observed at pH 3 and temperature 30°C. Equilibrium adsorption was achieved within 50 min. The kinetic data, obtained at the optimum pH 3, could be fitted with a pseudo-second-order equation. Adsorption process could be well described by Langmuir adsorption isotherms and the maximum adsorption capacity was calculated as 43.08 mg/g. The selectivity coefficient of AR and other dyes onto MIMC indicated an overall preference for AR, which was much higher than non-imprinted magnetic chitosan beads. Moreover, the sorbent represented high stability and good repeatability.

Flow injection chemiluminescence sensor based on core-shell magnetic molecularly imprinted nanoparticles for determination of sulfadiazine.

A novel flow injection chemiluminescence (FI-CL) sensor for determination of sulfadiazine (SDZ) using core-shell magnetic molecularly imprinted polymers (MMIPs) as recognition element is developed. Briefly, a hydrophilic MMIPs layer was produced at the surface of Fe(3)O(4)@SiO(2) magnetic nanoparticles (MNPs) via combination of molecular imprinting and reversible stimuli responsive hydrogel. And it provided the MMIPs with excellent adsorption capacity and rapid adsorption rate due to the imprinted sites mostly situated on the surface of MMIPs. Then the prepared SDZ-MMIPs were packed into flow cell to establish a novel FI-CL sensor. The sensor provided a wide linear range for SDZ of 4.0×10(-7) to 1.0×10(-4) mol L(-1) with a detection limit of 1.54×10(-7) mol L(-1). And the relative standard deviation (RSD) for the determination of 1.0×10(-6) mol L(-1) SDZ was 2.56% (n=11). The proposed method was applied to determine SDZ in urine samples and satisfactory results were obtained.

Preparation of magnetic ionic liquid/chitosan/graphene oxide composite and application for water treatment

Magnetic chitosan and graphene oxide-ionic liquid (MCGO-IL) composites as biodegradable biosorbents were synthesized by impregnating MCGO with ionic liquid. The characteristic results of FTIR, SEM, and XRD showed that MCGO-IL were successfully prepared with large surface area and good magnetic responsiveness. They were used for the removal of Cr(VI) from simulated wastewater with a fast solid-liquid separation in the presence of external magnetic field. The influence of various analytical parameters on the adsorption of Cr(VI) such as pH, contact time, and initial ion concentration were studied in detail. The adsorption followed a pseudo-second-order kinetics. The equilibrium adsorption was well-described by the Langmuir isotherm mode and the maximum adsorption capacity was 145.35 mg/g. The stronger intermolecular hydrogen bond between MCGO-IL and Cr(VI) and the hydroxyl and amine groups were believed to be the metal ion binding sites. Moreover, the MCGO-IL could be repeatedly used by simple treatment without obvious structure and performance degradation. The obtained results indicated that the impregnation of the room temperature IL significantly enhances the removal efficiency of Cr(VI). The MCGO-IL may be suitable materials in heavy metal ion pollution cleanup if they are synthesized in large scale and at low price in near future.

Electrochemical sensor based on magnetic graphene oxide@gold nanoparticles-molecular imprinted polymers for determination of dibutyl phthalate

A novel composite of magnetic graphene oxide @ gold nanoparticles-molecular imprinted polymers (MGO@AuNPs-MIPs) was synthesized and applied as a molecular recognition element to construct dibutyl phthalate (DBP) electrochemical sensor. The composite of MGO@AuNPs was first synthesized using coprecipitation and self-assembly technique. Then the template molecules (DBP) were absorbed at the MGO@AuNPs surface due to their excellent affinity, and subsequently, selective copolymerization of methacrylic acid and ethylene glycol dimethacrylate was further achieved at the MGO@AuNPs surface. Potential scanning was presented to extract DBP molecules from the imprinted polymers film rapidly and completely. As a consequence, an electrochemical sensor for highly sensitive and selective detection of DBP was successfully constructed as demonstration based on the synthesized MGO@AuNPs-MIPs composite. Under optimal experimental conditions, selective detection of DBP in a linear concentration range of 2.5 × 10(-9)-5.0 × 10(-6)mol/L was obtained. The new DBP electrochemical sensor also exhibited excellent repeatability, which expressed as relative standard deviation (RSD) was about 2.50% for 30 repeated analyses of 2.0 × 10(-6)mol/L DBP.

Adsorbent for hydroquinone removal based on graphene oxide functionalized with magnetic cyclodextrin–chitosan

Magnetic cyclodextrin-chitosan/graphene oxide (CCGO) with high surface area was synthesized via a simple chemical bonding method. The characteristics results of FTIR, SEM, TEM and XRD showed that CCGO was prepared. The large saturation magnetization (22.35 emu/g) of the synthesized nanoparticles allows fast separation of the CCGO from liquid suspension. These composites could efficiently remove hydroquinone from simulated wastewater with a facile subsequent solid-liquid separation because of their large area, abundant hydroxyl and amino groups with handy operation, and hydrophobicity. The hydroquinone removal process was found to obey the Freundlich adsorption model and its kinetics followed pseudo-second-order rate equation. The hydroquinone removal mechanism of CCGO might be attributed to the electrostatic adsorption of hydroquinone in the form of negatively charged hydroquinone by positively charged chitosan, accompanying hydroquinone absorbed by cavities of the cyclodextrin, and forming hydrogen bonds between hydroquinone and the hydroxyl groups on the surface of CCGO. The used CCGO could be recovered with ethanol. This study provides a promising nanostructured adsorbent with easy separation property for heavy metal ions removal.