Andra Predescu

Characterization and Application Results of Two Magnetic Nanomaterials

The toxicity of heavy metals for the environment can be solved by using the adsorption properties of magnetic nanomaterials. These types of nanomaterials can remove pollutants, especially from wastewaters. This study was conducted to determine whether two magnetic nanomaterials can be used as adsorbents for heavy metals (Cr, Cd, Cu, Zn, and Ni) from aqueous solutions under acidic conditions. Qualitative and quantitative elemental information and structural and surface characteristics before and after use as adsorbents were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The obtained data showed a good correlation with the Langmuir adsorption model using the two magnetic nanomaterials in aqueous solutions. The crystalline structure of the FeO powder was identified with XRD. The TEM images of FeO nanoparticles indicated a good dispersion of particles of 85.5 nm. The SEM analysis for FeO-PAA (magnetite covered with sodium alginate) showed spherical particles of magnetite wrapped into the polymer with dimension of ∼200 nm. According to the adsorption Langmuir model, the removal efficiency for uncoated FeO decreased in order: Cr(VI) > Cu(II) > Zn(II) > Ni(II) > Cd(II). For the FeO-PAA nanocomposite (45% w/w Fe in a mass of polymer), the adsorption phenomena appears as follows: Cr(VI) > Cd(II) > Cu(II) ∼ Zn(II) > Ni(II). Langmuir parameters indicated a favorable monolayer adsorption at pH 2.5. The nanocomposite FeO-PAA can be used as an adsorbent with the same performance as uncoated FeO but with the advantage of stability under conditions where industrial wastewaters have an acidic pH.

Characterization of Magnetic Nanoiron Oxides for the Removal of Metal Ions from Aqueous Solution

ABSTRACT Two nanostructured hybrid materials are reported that include uncoated magnetic nanoiron oxides and magnetic nanoiron oxides treated with rose leaf extract. Atomic and molecular absorption spectrometry were used to evaluate the sensitivity of these materials for the isolation of Cr(VI), Zn(II), Pb(II), and Ca(II) from aqueous solution. The structure and physicochemical properties of the resulting nanohybrids were characterized by scanning electron microscopy coupled with energy-dispersive spectroscopy, atomic force microscopy, and X-ray diffraction. The results show that following 15 min of contact in acidic solution, the uncoated magnetic nanoiron oxides removed approximately 90% of Cr(VI), while the magnetic nanoiron oxides coated with rose leaf extract removed 92% of the analyte. These correspond to most industrial wastewater conditions. For the removal of Ca(II) and Zn(II), it was necessary to adjust the pH to neutral to maximize the efficiency. Pb(II) showed maximum removal efficiency when the solution is basic. The simple rose extract suspension was also used for metal removal with high capacity. The results demonstrate that the magnetic nanoiron oxides were uniformly distributed in the rose leaf extract. The extract served as a capping agent due to the presence of polyphenolics.

Synthesis and characterization of dextran-coated iron oxide nanoparticles

Synthesis and characterization of iron oxide nanoparticles coated with a large molar weight dextran for environmental applications are reported. The first experiments involved the synthesis of iron oxide nanoparticles which were coated with dextran at different concentrations. The synthesis was performed by a co-precipitation technique, while the coating of iron oxide nanoparticles was carried out in solution. The obtained nanoparticles were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction spectrometry, Fourier transform infrared spectroscopy and superconducting quantum interference device magnetometry. The results demonstrated a successful coating of iron oxide nanoparticles with large molar weight dextran, of which agglomeration tendency depended on the amount of dextran in the coating solution. SEM and TEM observations have shown that the iron oxide nanoparticles are of about 7 nm in size.

Recycled Polypropylene Improved with Thermoplastic Elastomers

The use of recycled polypropylene (RPP) as raw material for various industries has been known. However, the mechanical and thermal properties of recycled products are lower than those of raw material. The objective of this study was to obtain and investigate the modified recycled polypropylene (RPP) with commercial elastomers for possible applications. The compounded RPP-based thermoplastic elastomers were investigated in order to determine their thermal properties (melt flow index (MFI), differential scanning calorimetry (DSC), VICAT softening temperature (VST), and heat deflection temperature (HDT)), structural characteristics (optical microscopy, atomic force microscopy (AFM), and X-ray diffraction (XRD)), and mechanical properties (tensile properties, density, and IZOD impact). The RPP compounded with 10% elastomer recorded higher tensile properties than the unmodified RPP. Also, IZOD impact strength increased from  kJ/m2 (registered for RPP) to  kJ/m2 for the PPR/SIS30 compound, while the degree of crystallinity decreased for all compounds. The obtained results recommend the RPP/elastomers compounds both for environmental remediation from postconsumer PP wastes and to realize new goods with high performance for various applications.

Failure Analysis of a Metallic Component Used in Hospital Cooling Equipment

The paper presents the investigations made on samples taken from the related rotor blade of an hospital cooling equipment.The failure analysis was made in order to find if the failure appear because the metallic material used or was functional problem.The objectives of our analysis and techniques used are described below:determining the chemical composition by optical emission spectrometry;determining the hardness of the material;metallographic analysis by optical microscopy;micro compositional and microstructural analysis by scanning electron microscopy (SEM) and by microanalysis, energy dispersive X-ray (EDAX). Research has highlighted the quality of piece elaboration and casting, which led to a long life of its use.

Nano-Iron Oxides Used for Environmental Applications

The paper emphasizes the importance of use the nano-iron oxides as treatment materials for wastewaters decontamination, having in mind the size of these compounds and specific surface area suitable for retaining toxic metals such as chromium or cadmium presented as major pollutants for industrial wastewaters. Also, the magnetic properties of the nano-iron oxides offer the possibility of a fast removal of these from the system, after wastewaters treatment. The obtaining of some core-shell composites with nano-iron oxides as core represent an advantage because of the dissolving tendency of the nano-iron oxides under acidic conditions, the situation being common to the industrial wastewaters.