Limei Cui

Removal of mercury and methylene blue from aqueous solution by xanthate functionalized magnetic graphene oxide: Sorption kinetic and uptake mechanism.

Xanthate functionalized magnetic graphene oxide (Fe3O4-xGO) was successfully synthesized through linking xanthate groups to a kind of graphenes magnetic material (Fe3O4-GS). Fe3O4-xGO was found to be an ideal adsorbent for Hg(II) and methylene blue removal with a higher adsorption capacity. The synthesized adsorbent was characterized by SEM, TEM, FTIR, XRD, and BET respectively. Fe3O4-xGO can be simply recovered from water with magnetic separation at low magnetic field within only 1min. The adsorption capacity was found to be 118.55mg g(-1) for Hg(2+) (contact time for 180min, pH at 7 and temperature at 25°C) and 526.32mg g(-1) for methylene blue (contact time for 120min, pH at 5.5 and temperature at 25°C), respectively. Kinetic data showed good correlation with pseudo-second-order equation and the Langmuir model was found to fit for the isotherm data, which showed the contaminant sorption was accomplished mainly via chelation or ion exchange. The results of thermodynamic studies (ΔG<0, ΔH>0, ΔS>0) illustrate that the adsorption process was endothermic and spontaneous in nature. The experimental results suggest that Fe3O4-xGO has the potential applications in the environmental management.

Mechanism of Pb(II) and methylene blue adsorption onto magnetic carbonate hydroxyapatite/graphene oxide

Magnetic carbonate hydroxyapatite/graphene oxide (M-CHAP/GO) was successfully prepared by loading magnetic carbonate hydroxyapatite (M-CHAP) onto graphene oxide sheets and was found to be an ideal adsorbent for heavy metal (Pb(II)) and dye (methylene blue). The obtained adsorbent was characterized by SEM, FTIR, XRD, BET, TGA, XPS and zeta potential, respectively. M-CHAP/GO nano-particles possessed a favorable and stable morphology. Moreover, the good magnetic properties of M-CHAP/GO made it simple to recover from water with magnetic separation. The equilibrium adsorption capacity was 277.7 mg g−1 for Pb(II) and 546.4 mg g−1 for methylene blue under the optimal conditions. The pseudo-second-order equation and the Langmuir model showed good correlation with the experimental data and explained well the mechanism of adsorption. It was found that the adsorption process was accomplished mainly via chelation and ion exchange. Thermodynamic studies (ΔG 0, ΔS > 0) implied that the adsorption process was endothermic and spontaneous in nature. The other adsorption mechanisms are further researched in this article. All the experimental results show that M-CHAP/GO nano-particles have potential application in the future of environmental management.

The removal of lead ions from aqueous solution by using magnetic hydroxypropyl chitosan/oxidized multiwalled carbon nanotubes composites.

Magnetic hydroxypropyl chitosan/oxidized multiwalled carbon nanotubes (MHC/OMCNTs) composites were fabricated and applied as the adsorbent to study the adsorption characteristic of lead ions in aqueous solution. The results of Fourier transform infrared spectrum (FTIR), X-ray powder diffraction (XRD) and scanning electron microscope (SEM) showed that the MHC/OMCNTs composites were synthesized successfully. The effects of the solution pH and the contact time were investigated, indicating that the optimal pH and contact time were pH 5.0 and 120min, respectively. The removal of lead ions was rather quick and the kinetic adsorption can be well described by pseudo-second-order model. The experimental results showed that the Sips model is more suitable than Langmuir, Freundlich and Dubinin-Radushkevich models. Furthermore, the parameters of the adsorption thermodynamic calculated in this research such as free energy (ΔG, -2.304 to -5.078kJmol(-1)), enthalpy (ΔH, 39.03kJmol(-1)) and entropy (ΔS, 138.7Jmol(-1)K(-1)) indicated that the adsorption process was endothermic and spontaneous. Therefore, the results in this research suggest that the MHC/OMCNTs composites are ideal adsorbent for the removal of lead ions in aqueous solution.

Removal of Hg(II) from aqueous solution by resin loaded magnetic β-cyclodextrin bead and graphene oxide sheet: Synthesis, adsorption mechanism and separation properties

Resin loaded magnetic β-cyclodextrin bead and graphene oxide sheet (MCD-GO-R) was synthesized successfully and found to be an excellent adsorbent for Hg(II) removal. The as-prepared adsorbent was characterized by SEM, FTIR, BET, magnetization curve and zeta potential analysis respectively. Good magnetic performance made MCD-GO-R simply recover from aqueous solution at low magnetic field within 30s. And also, the rich functional groups and outstanding dispersity play an important role in the adsorption process. The maximum adsorption capacity was 88.43 mg g(-1) at 323 K and pH 7.1. The as-prepared adsorbent could perform well in a wide pH range from 4.0 to 10.0. Static adsorption experimental data showed good correlation with pseudo-second-order model and Freundlich isotherm models. It was found that the contaminant adsorption was accomplished mainly via chelation or ion exchange and come to equilibrium in only 30 min. All experimental results, especially the excellent reproducibility and resistance to ion interference, suggest that MCD-GO-R has promising applications in water treatment.

Fabrication of magnetic water-soluble hyperbranched polyol functionalized graphene oxide for high-efficiency water remediation

Magnetic water-soluble hyperbranched polyol functionalized graphene oxide nanocomposite (MWHPO-GO) was successfully prepared and applied to water remediation in this paper. MWHPO-GO was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), magnetization curve, zeta potential, scanning electron microscope (SEM) and transmission electron microscope (TEM) analyses. MWHPO-GO exhibited excellent adsorption performance for the removal of synthetic dyes (methylene blue (MB) and methyl violet (MV)) and heavy metal (Pb(II)). Moreover, MWHPO-GO could be simply recovered from water with magnetic separation. The pseudo-second order equation and the Langmuir model exhibited good correlation with the adsorption kinetic and isotherm data, respectively, for these three pollutants. The thermodynamic results (ΔG < 0, ΔH < 0, ΔS < 0) implied that the adsorption process of MB, MV and Pb(II) was feasible, exothermic and spontaneous in nature. A possible adsorption mechanism has been proposed where π-π stacking interactions, H-bonding interaction and electrostatic attraction dominated the adsorption of MB/MV and chelation and electrostatic attraction dominated the adsorption of Pb(II). In addition, the excellent reproducibility endowed MWHPO-GO with the potential for application in water remediation.

A novel magnetic polysaccharide–graphene oxide composite for removal of cationic dyes from aqueous solution

In this paper, carboxymethyl functionalized chitosan was used for the synthesis of a magnetic polysaccharide–graphene oxide composite (SCGO). Compared with the magnetic chitosan–graphene oxide composite reported before, adsorption capacity in this research had improved significantly. The calculated maximum adsorption capacity values for methylene blue (MB) and malachite green (MG) were 358.4 mg g−1 and 289.1 mg g−1, respectively. The morphology, chemical properties and physical structure of SCGO were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). The influence factors which included pH, adsorbent dose, ionic strength and contact time on the adsorption properties of MB and MG onto SCGO were investigated. The adsorption kinetics of MB and MG on SCGO were well-described by pseudo-second order kinetic models. The experimental data of the isotherm followed the Temkin isotherm model and the Langmuir model, respectively. Thermodynamic analysis was also performed to calculate the changes in free energy (ΔG), enthalpy (ΔH), and entropy (ΔS). The results obtained from this research suggested that SCGO was a potential adsorbent for effective removal of methylene blue and malachite green.

Magnetic hydroxypropyl chitosan functionalized graphene oxide as adsorbent for the removal of lead ions from aqueous solution

AbstractMagnetic hydroxypropyl chitosan/graphene oxide (MHCGO) composites have been synthesized and employed as adsorbent for removal of lead ions from aqueous solution. X-ray powder diffraction, Fourier transform infrared spectrum, and scanning electron microscope showed that the MHCGO composites were fabricated successfully. The effects of adsorbent dosage, pH, and contact time on the adsorption of lead ions have been discussed, and the optimal adsorption conditions have been acquired. The results indicated that the adsorption of lead ions on MHCGO was dependent on pH with the optimum pH nearly 5.5. The adsorption process was fairly quick and the time to reach adsorption equilibrium is 100 min. The adsorption kinetics could be described by the pseudo-second-order model very well. Adsorption data fitted well with Freundlich model. The effect of temperature on lead ions adsorption was studied and was shown to be spontaneous.