A solid-state chemical method for synthesizing MgO nanoparticles with superior adsorption properties

As a traditional and effective adsorbent, MgO is a low-cost, eco-friendly, nontoxic, and economical material for wastewater treatment. However, multistep processing and the use of organic agents result in high costs and lead to environmental pollution, strongly inhibiting the practical application of MgO. Herein, a simple solid-state chemical route has been used to prepare small-sized MgO nanoparticles with a large specific surface area of 213 m2 g-1 without using liquid solvents, template agents, or surfactants. This facile method is a green strategy that is suitable for large-scale production, avoiding complex preparation processes and serious environmental pollution. The obtained small-sized MgO nanoparticles showed a superior adsorption capacity of 2375 mg g-1 towards Congo red, originating from the large specific surface area and surface features (hydrogen bonds and electrostatic interactions). The adsorption behavior obeyed a pseudo-second-order rate equation and the Langmuir isotherm adsorption model. This study provides a route for the synthesis of oxides with large specific surface areas and obtained an adsorbent with superior adsorption capacity.

Atomic-scale investigation of MgO growth on fused quartz using angle-dependent NEXAFS measurements

The phenomena related to thin film growth have always been interesting to the scientific community. Experiments related to these phenomena not only provide an understanding but also suggest a path for the controlled growth of these films. For the present work, MgO thin film growth on fused quartz was investigated using angle-dependent near-edge X-ray absorption fine structure (NEXAFS) measurements. To understand the growth of MgO, sputtering was allowed for 5, 10, 25, 36, 49, 81, 144, 256, and 400 min in a vacuum better than 5.0 × 10-7 torr. NEXAFS measurements revealed the evolution of MgO at the surface of fused quartz for sputtering durations of 144, 256, and 400 min. Below these sputtering durations, no MgO was observed. NEXAFS measurements further envisaged a systematic improvement of Mg2+ ion coordination in the MgO lattice with the sputtering duration. The onset of non-interacting molecular oxygen on the surface of the sputtered species on fused quartz was also observed for sputtering duration up to 81 min. Angle-dependent measurements exhibited the onset of an anisotropic nature of the formed chemical bonds with sputtering, which dominated for higher sputtering duration. X-ray diffraction (XRD) studies carried out for sputtering durations of 144, 256, and 400 min exhibited the presence of the rocksalt phase of MgO. Annealing at 700 °C led to the dominant local electronic structure and improved the crystallinity of MgO. Rutherford backscattering spectrometry (RBS) and cross-sectional scanning electron microscopy (SEM) revealed a layer of almost 80 nm was obtained for a sputtering duration of 400 min. Thus, these angle-dependent NEXAFS measurements along with XRD, RBS, and SEM analyses were able to give a complete account for the growth of the thin films. Moreover, information specific to the coordination of the ions, which is important in case of ultrathin films, could be obtained successfully using this technique.

Three-dimensional hollow porous raspberry-like hierarchical Co/Ni@carbon microspheres for magnetic solid-phase extraction of pyrethroids

A three-dimensional magnetic hollow porous raspberry-like hierarchical Co/Ni@carbon microspheres (3D Co/Ni@carbon) were synthesized by using a bimetal-organic framework (Co/Ni-MOF) as a precursor and subsequent calcination under nitrogen. The 3D Co/Ni@carbon is a novel solid phase extractant that displays outstanding extraction capability and separation efficiency for the pyrethroid pesticides ethofenprox and bifenthrin. This is ascribed to the beneficial effects of facile analyte transport (due to the presence of free pores), the abundant number of adsorption sites (which warrant efficient extraction), and the excellent structural stability of the material. The 3D Co/Ni@carbon was applied to dispersive magnetic solid-phase extraction (d-MSPE), and the two pyrethroids were quantified by HPLC (UV detection wavelength: 220 nm). The method has a high preconcentration factor (937-1012) and give recoveries that range between 85.6-106.9%, with RSDs (for n = 5) of <6% in case of real samples. Graphical abstract The hierarchical porous Co/Ni@carbon microsphere as adsorbent was fabricated, and it showed high extraction efficiency for two pyrethroids.

Template-free synthesis of nanoparticle-built MgO and Zn-doped MgO hollow microspheres with superior performance for Congo red adsorption from water

A template-free route was developed to synthesize MgO and Zn-doped MgO hollow microspheres with ultrahigh adsorption performances and excellent reusability.