Enhanced Adsorption of Zn(II) onto Graphene Oxides Investigated Using Batch and Modeling Techniques

Potential molecular and graphene oxide chelators to dissolve amyloid-β plaques in Alzheimer's disease: a density functional theory study

The onset of Alzheimer's disease (AD) is caused by amyloid-β (Aβ) aggregation. Elevated levels of metals, specifically copper, zinc, iron, and aluminum, accumulate in senile Aβ; plaque deposits, disrupting normal brain homeostasis and cognitive functions. In this investigation, we studied the potential of several molecular and graphene oxide chelators to be used for future AD research and chelation therapy. To understand the interactions between selected metals (Cu, Zn, Fe, and Al), the Aβ peptide, and various potential metal chelating compounds, we implemented the density functional theory (DFT) method to calculate the binding energies of each metal-molecule complex. The binding energy of each metal-chelator complex was compared with that of the metal-Aβ compound to determine the chelation potential of the selected chelator. The potential chelating agents studied were 8-hydroxyquinoline-2-carboxaldehyde isonicotinoyl hydrazone (INNHQ), 8-hydroxyquinoline-2-carboxaldehyde 2-furoyl hydrazone (HQFUH), quercetin, and graphene oxide (GO). Our calculated binding energies revealed that the HQFUH molecule holds direct ability to chelate copper, zinc, iron, and aluminum. In addition, the GO complex with a 12.5% oxygen concentration demonstrates aluminum chelation ability. Our results demonstrate that HQFUH and GO can be used in future AD drug development research and therapy to target toxic metal-Aβ interactions and reduce Aβ aggregation.

Retraction: Tuning the chemistry of graphene oxides by a sonochemical approach: application of adsorption properties

[This retracts the article DOI: 10.1039/C5RA02021B.].

Lignocellulose@ Activated Clay Nanocomposite with Hierarchical Nanostructure Enhancing the Removal of Aqueous Zn(II)

A lignocellulose@ activated clay (Ln@AC) nanocomposite with a hierarchical nanostructure was successfully synthesized by the chemical intercalation reaction and applied in the removal of Zn(II) from an aqueous solution. Ln@AC was characterized by N2 adsorption/desorption isotherms and X-Ray Diffraction (XRD), scanning Electron Microscope (SEM), transmission Electron Microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FTIR) analysis, and the results indicate that an intercalated-exfoliated hierarchical nanostructure was formed. The effects of different adsorption parameters on the Zn(II) removal rate (weight ratio of Ln to AC, Ln@AC dosage, initial Zn(II) concentration, pH value, adsorption temperature, and time) were investigated in detail. The equilibrium adsorption capacity reached 315.9 mg/g under optimal conditions (i.e., the weight ratio of Ln to AC of 3:1, Ln@AC dosage of 1 g/L, initial Zn(II) concentration of 600 mg/L, pH value of 6.8, adsorption temperature of 65 °C, and adsorption time of 50 min). The adsorption process was described by the pseudo-second-order kinetic model, Langmuir isotherm model, and the Elovich model. Moreover, Zn(II) could be easily eluted by HCl, and the effects of HCl concentration, desorption temperature, and ultrasonic desorption time on desorbed amount were tested. Desorption studies revealed that with an HCl concentration of 0.25 mol/L, desorption temperature of 70 °C, and ultrasonic desorption time of 20 min, the maximum desorption capacity and efficiency were achieved at 202.5 mg/g and 64.10%, respectively. Regeneration experimental results indicated that the Ln@AC exhibited a certain recyclable regeneration performance. Due to such outstanding features, the novel Ln@AC nanocomposite proved to have great adsorption potential for Zn(II) removal from wastewater, and exhibited an extremely significant amount of adsorbed Zn(II) when compared to conventional adsorbents.

Studying Ni(II) Adsorption of Magnetite/Graphene Oxide/Chitosan Nanocomposite

In this paper, Fe3O4/graphene oxide/chitosan (FGC) nanocomposite was synthesized using coprecipitation method for application to removal of nickel ion (Ni(II)) from aqueous solution by adsorption process. To determine residue Ni(II) ions concentration in aqueous solution after adsorption process, we have used UV-Vis spectrophotometric method, which is an effective and exact method for Ni(II) monitoring at low level by using dimethylglyoxime (DMG) as a complex reagent with Ni(II), which has a specific adsorption peak at the wavelength of 550 nm on UV-Vis spectra. A number of factors that influence Ni(II) ions adsorption capacity of FGC nanocomposite such as contact time, adsorption temperature, and adsorbent dosage were investigated. Results showed that the adsorption equilibrium is established after 70 minutes with the adsorbent dosage of 0.01 g.mL−1 at 30°C (the room temperature). The thermodynamic and kinetic parameters of this adsorption including free enthalpy change (∆G0), enthalpy change (∆H0), entropy change (∆S0), and reaction order with respect to Ni(II) ions were also determined. The Ni(II) ions adsorption equilibrium data are fitted well to the Langmuir isotherm and the maximum monolayer capacity (qmax) is 12.24 mg.g−1. Moreover, the FGC adsorbent can be recovered by an external magnet; in addition, it can be regenerated. The reusability of FGC was tested and results showed that 83.08% of removal efficiency was obtained after 3 cycles. The synthesized FGC nanocomposite with many advantages is a promising material for removal of heavy metal ions from aqueous solution to clean up the environment.

Adsorption of Sb (III) on Oxidized Exfoliated Graphite Nanoplatelets

In this work, Sb (III) adsorption on oxidized exfoliated graphite nanoplatelets (ox-xGnP) was evaluated for the first time, to the best of our knowledge. The ox-xGnP were characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), Brunauer⁻Emmet⁻Teller (BET) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM) equipped with energy-dispersive X-ray spectroscopy (EDX), and Zeta potential analysis. The adsorption parameters, such as pH and contact time, were optimized, and the best adsorption capacity obtained was 8.91 mg g^-1 at pH = 7.0, 1.0 mg ox-xGnP/100 mL solution, T = 293 K, 1.0 mg L^-1, Sb (III), 25 min contact time. The best correlation of the kinetic data was described by a pseudo-first-order kinetic model, with R² = 0.999. The adsorption isotherms of Sb (III) onto ox-xGnP were best described by the Langmuir isotherm model. The thermodynamic parameters showed that the adsorption process was exothermic and spontaneous.