J. Heimann

Bio: J. Heimann is an academic researcher from University of Silesia in Katowice. The author has contributed to research in topics: Magnetic susceptibility & Magnetization. The author has an hindex of 12, co-authored 54 publications receiving 933 citations. Previous affiliations of J. Heimann include Silesian University.

Adsorption of divalent metal ions from aqueous solutions using graphene oxide

Abstract: The adsorptive properties of graphene oxide (GO) towards divalent metal ions (copper, zinc, cadmium and lead) were investigated GO prepared through the oxidation of graphite using potassium dichromate was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FT-IR) The results of batch experiments and measurements by flame atomic absorption spectrometry (F-AAS) indicate that maximum adsorption can be achieved in broad pH ranges: 3–7 for Cu(II), 5–8 for Zn(II), 4–8 for Cd(II), 3–7 for Pb(II) The maximum adsorption capacities of Cu(II), Zn(II), Cd(II) and Pb(II) on GO at pH = 5 are 294, 345, 530, 1119 mg g−1, respectively The competitive adsorption experiments showed the affinity in the order of Pb(II) > Cu(II) ≫ Cd(II) > Zn(II) Adsorption isotherms and kinetic studies suggest that sorption of metal ions on GO nanosheets is monolayer coverage and adsorption is controlled by chemical adsorption involving the strong surface complexation of metal ions with the oxygen-containing groups on the surface of GO Chemisorption was confirmed by XPS (binding energy and shape of O1s and C1s peaks) of GO with adsorbed metal ions The adsorption experiments show that the dispersibility of GO in water changes remarkably after complexation of metal ions After adsorption, the tendency to agglomerate and precipitate is observed Excellent dispersibility of GO and strong tendency of GO–Me(II) to precipitate open the path to removal of heavy metals from water solution Potential application of GO in analytical chemistry as a solid sorbent for preconcentration of trace elements and in heavy metal ion pollution cleanup results from its maximum adsorption capacities that are much higher than those of any of the currently reported sorbents

X-ray examination, electrical and magnetic properties of R3Co single crystals (R ≡ Y, Gd, Dy and Ho)

Abstract: Single crystals of Y3Co, Gd3Co, Dy3Co and Ho3Co were obtained by the Czochralski method from a levitated melt. A description of the crystal growth technology is given. The crystal quality was examined by X-ray methods. Electrical resistivity and magnetic susceptibility have been measured. Y3Co exhibits Curie-Weiss behaviour with μeff = 1 μB (formula unit)−1. It is the first evidence for the existence of a magnetic moment on cobalt atoms in such a low concentration region. Gd3Co, Dy3Co and Ho3Co show an effective moment that is enhanced by 1 μb relative to the theoretical value for R3Co, assuming that only the R3+ ions contribute a magnetic moment equal to the free ion value. A negative curvature of the temperature-dependent electrical resistivity ϱ(T) is observed in the lower temperature range. For higher temperatures dρ dT is small, especially for Gd3Co ( 5.5 × 10 −8 Ω m K −1 ).

Environmental applications of graphene-based nanomaterials.

Abstract: Graphene-based materials are gaining heightened attention as novel materials for environmental applications The unique physicochemical properties of graphene, notably its exceptionally high surface area, electron mobility, thermal conductivity, and mechanical strength, can lead to novel or improved technologies to address the pressing global environmental challenges This critical review assesses the recent developments in the use of graphene-based materials as sorbent or photocatalytic materials for environmental decontamination, as building blocks for next generation water treatment and desalination membranes, and as electrode materials for contaminant monitoring or removal The most promising areas of research are highlighted, with a discussion of the main challenges that we need to overcome in order to fully realize the exceptional properties of graphene in environmental applications

Highly efficient enrichment of radionuclides on graphene oxide-supported polyaniline

Abstract: Graphene oxide-supported polyaniline (PANI@GO) composites were synthesized by chemical oxidation and were characterized by SEM, Raman and FT-IR spectroscopy, TGA, potentiometric titrations, and XPS. The characterization indicated that PANI can be grafted onto the surface of GO nanosheets successfully. The sorption of U(VI), Eu(III), Sr(II), and Cs(I) from aqueous solutions as a function of pH and initial concentration on the PANI@GO composites was investigated. The maximum sorption capacities of U(VI), Eu(III), Sr(II), and Cs(I) on the PANI@GO composites at pH 3.0 and T = 298 K calculated from the Langmuir model were 1.03, 1.65, 1.68, and 1.39 mmol·g–1, respectively. According to the XPS analysis of the PANI@GO composites before and after Eu(III) desorption, nitrogen- and oxygen-containing functional groups on the surface of PANI@GO composites were responsible for radionuclide sorption, and that radionuclides can hardly be extracted from the nitrogen-containing functional groups. Therefore, the chemical a...