Co(II)-Ti(IV)-substituted magnetoplumbite-type (M-type) barium ferrite nanoparticles were synthesized via the sol-gel technique employing ethylene glycol as the gel precursor. Structural and magnetic properties were characterised via X-ray diffraction (XRD), high resolution transmission electron microscopy and superconducting quantum interference device magnetometry. The particle sizes of the M-type BaCoXTiXFe12-2XO19 (0.2 ≤ ≤ 1.0) were found to be 900 Å – 1500 Å. The XRD results confirmed that the Co(II)-Ti(IV) substituted ferrites in the range of 0.2 ≤ ≤ 1.0 substitution had the M-type ferrite as the dominant phase. The hysteresis loss per-cycle decreased with increasing Co(II)-Ti(IV) substitution in M-type ferrites which showed reduced values in coercivity and remnant magnetisation with moderate effect on the saturation magnetisation.
The magnetic adsorbents i.e. oil palm frond-magnetic particles (OPF-MP) and oil palm frond activated carbon-magnetic particles (OPFAC-MP) have been prepared by impregnation of iron oxide via co-precipitation method. The magnetic adsorbents and their parent materials were characterized using Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), Brunauer Emmett Teller (BET), Barrett, Joyner & Halenda (BJH) and t-plot method, x-ray diffraction (XRD) and also using vibrating sample magnetometry (VSM) to study their properties and surface chemistry. The activated carbon magnetic adsorbent confers high surface area of 700 m2/g with amorphous structure and magnetic properties of 2.76 emu/g. The OPF-MP and OPFAC-MP were then applied in adsorption study for ions removal of Pb(II), Zn(II) and Cu(II). OPFAC-MP has shown high removal efficiency of 100 % with adsorption capacity up to 15 mg/g of Pb(II), Zn(II) and Cu(II) ions compared to OPF-MP. In addition, the magnetic adsorbents were also compared with their parent materials to observe the effect of magnetic particles. Accordingly, the impregnation of magnetic particles enhances the metal ions adsorption comparing to their parent materials.
In this work, zinc chromite (ZnCr2O4) nanostructures have been synthesized through co-precipitation method. The effect of various parameters such as alkaline agent, pH value, and capping agent type was investigated on purity, particle size and morphology of samples. It was found that particle size and morphology of the products could be greatly influenced via these parameters. The synthesized products were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), fourier transform infrared (FT-IR) spectra, X-ray energy dispersive spectroscopy (EDS), photoluminescence (PL) spectroscopy, diffuse reflectance spectroscopy (DRS) and vibrating sample magnetometry (VSM). The superhydrophilicity of the calcined oxides was investigated by wetting experiments and a sessile drop technique which carried out at room temperature in air to determine the surface and interfacial interactions. Furthermore, the photocatalytic activity of ZnCr2O4 nanoparticles was confirmed by degradation of anionic dyes such as Eosin-Y and phenol red under UV light irradiation. The obtained ZnCr2O4 nanoparticles exhibit a paramagnetic behavior although bulk ZnCr2O4 is antiferromagnetic, this change in magnetic property can be ascribed to finite size effects.
The authors describe a method for solvent-free mechano-chemical synthesis of a bioinspired sorbent. A 2D ultra-thin carbon sheet similar to graphene oxide was prepared using a natural waste (onion sheet). The formation of 2D carbon sheets was confirmed by Raman spectroscopy, X-ray photoelectron spectroscopy and ATR-IR. The surface morphology was characterized by field emission scanning electron microscopy and high-resolution tunneling electron microscopy. The carbon sheets were decorated with crystalline MnFe2O4 nanoparticles by solid-state reaction at room temperature. The presence of magnetic particles in the final product was confirmed by vibrating sample magnetometry and electron microscopy. The synergistic effect of carbon sheets and MnFe2O4 led to an enhanced sorption of arsenic species compared to bare carbon sheets or to MnFe2O4 nanoparticles. A column was prepared for the simultaneous preconcentration and determination of trace levels of As(III) and As(V) from water samples. The preconcentration factors are between 900 and 833 for As(III) and As(V) species, respectively. The linearity of the calibration plot ranges from 0.4-10 ng mL-1. The detection limits (at 3σ) for both As(III) and As(V) are 30 pg mL-1. The Student's t values for the analysis of spiked samples are lower than the critical Student's t values at a 95% confidence level. The recoveries from spiked water samples range between 99 and 102.8%. Graphical abstract Schematic representation of the preparation of carbon sheets similar to graphene oxide from onion sheaths after pyrolysis at 800 °C. The prepared carbon sheet-MnFe2O4 composite shows excellent arsenic sorption and preconcentration down to the pg mL-1 concentration.