Mikael Motelica-Heino

Determination of palladium, platinum and rhodium concentrations in urban road sediments by laser ablation-ICP-MS

The introduction of catalytic converter technology to cars has alleviated gaseous exhaust emissions but in turn has resulted in emissions of the three platinum group metals (PGMs), Pd, Pt and Rh, contained in the automobile catalyst. The environmental effects of PGMs are still largely unknown and their accurate determination is particularly difficult because concentrations are at trace levels. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is a direct trace element measurement technique and can be used for the rapid characterization of metals in solid environmental matrices. Here, the capability of LA-ICP-MS for the direct quantitative determination of PGMs in road sediments was assessed. Two Nd:YAG laser systems operating at 266 and 1064 nm, respectively, were coupled to an ICP-MS. Uncontaminated road sediments were spiked with PGMs, both as solution and as solid certified reference material, and used to assess the analytical performance of the technique and to calibrate the instrument. Interferences due to the formation of molecular ions and double charged ions were investigated. The LA-ICP-MS was then used to determine the concentration of PGMs in a recent urban road sediment and the results were compared with high resolution-ICP-MS measurements after microwave sample digestion with Aqua Regia. The LA-ICP-MS allows the quantitative analysis of Pd, Pt, and Rh in road sediments at sub microgram per gram levels with a relative standard deviation of 10% and with estimated detection limits in the lower nanogram per gram range. Good agreement between LA-ICP-MS and HR-ICP-MS analysis could be obtained for Pt and Rh (<3% R.S.D. at ca. 100 ng g−1) whereas the determination of Pd remains subject to interferences.

Laser ablation of synthetic geological powders using ICP-AES detection: effects of the matrix, chemical form of the analyte and laser wavelength

A systematic study of the influence of the physical and chemical properties of analogues of geological samples and of laser wavelength on laser ablation was conducted. Different chemical forms of several test elements were investigated, first as pure elements, then mixed in various matrices. Synthetic model samples were prepared from different crystalline compounds of Mg, Al and Fe spiked in SiO 2 or CaCO 3 and manufactured in the form of pressed pellets that were analysed by laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES). This study was performed at two laser wavelengths (1064 and 266 nm) with a Nd:YAG laser and using ICP-AES as an elemental detector. These various steps made it possible to demonstrate that the LA-ICP-AES response factors of the analytes are strongly dependent on their chemical form and on the bulk composition of the matrix. These effects were also found to be laser wavelength dependent and the use of a UV laser did not lead to any improvements to minimise these effects. In contrast, there was no influence of the grain size or binding pressure of the pressed pellets. However, normalisation to a matrix element could compensate for differences in the response factors of the analytes. Implications for direct quantitative elemental analysis of geological materials by laser ablation related techniques are that calibration without matching in terms of the mineralogical and chemical composition of the matrix and of the chemical forms of the analytes can lead to systematic errors in the determination of the element concentration.

Study on Europium-Doped Hydroxyapatite Nanoparticles by Fourier Transform Infrared Spectroscopy and Their Antimicrobial Properties

Fourier transform infrared spectroscopy (FT-IR) analysis was conducted on europium-doped hydroxyapatite, (PO4)6(OH)2 nanocrystalline powders (Eu:HAp) with . Antimicrobial studies were also performed for the first time on Eu:HAp. The antimicrobial properties of Eu:HAp nanoparticles with on Gram-negative (E. coli ATCC 25922, Pseudomonas aeruginosa 1397) and Gram-positive (Staphylococcus aureus 0364, Enterococcus faecalis ATCC 29212) bacteria systems and a species of fungus (Candida albicans ATCC 10231) were reported. Our study demonstrates that the antimicrobial activity of Eu:HAp nanoparticles is dependent on the europium concentration.

Structure, Orientation and Stability of Lysozyme Confined in layered Materials

The confinement of lysozyme in 3 layered materials based on montmorillonite and lamellar double hydroxides exhibiting different surface charges was studied. The protein structure and orientation in these materials were determined by X-ray diffraction, time resolved fluorescence and fluorescence anisotropy. For montmorillonite exchanged with sodium and modified with a non-ionic surfactant (tri-ethylene glycol mono n-decyl ether), the lysozyme was found to be located in the interlayer space with the “end-on” and “side-on” orientations, respectively. Conversely, no lysozyme intercalation was observed with a lamellar double hydroxide modified with an anionic surfactant (sodium octylsulfate), since the protein was adsorbed on the surface of the particles. Fourier transformed infrared spectroscopy analysis shows that lysozyme confinement in the interlayer space preserves its structure after dehydration, whereas some structural changes were observed for lysozyme adsorbed on the particle surface.

Nonionic organoclay: A ‘Swiss Army knife’ for the adsorption of organic micro-pollutants?

A Na exchanged montmorillonite (Mt) was used as a starting layered material for the preparation of two organoclays synthesized with benzyl decyltrimethyl ammonium (BDTA) cationic surfactant and the tri-ethylene glycol mono n-decyl ether(C10E3), a nonconventional nonionic surfactant. The adsorption of the surfactants was performed at an amount of 0.7 times the cation exchange capacity (CEC) for BDTA and below the critical micelle concentration (cmc) where C10E3 is in a monomer state, leading to the intercalation of a lateral monolayer surfactant arrangement within the interlayer space and about 5-7% organic carbon content in organoclays. The environmental properties of both nonionic (C10E3Mt) and cationic (BDTAMt) organoclays were compared to those of the starting Mt clay with the sorption of three micro-pollutants: benzene, dimethyl-phthalate and paraquat. The adsorption isotherms and the derivative data determined through the fitting procedure by using Langmuir, Freundlich and Dubinin-Radushkevitch equation models explicitly highlighted the importance of the chemical nature of the micropollutants, which play on the adsorbents efficiency. The adsorption data combined with FTIR and XRD supplementary results suggest that C10E3Mt nonionic organoclay, although being less efficient for the retention of the different micropollutants, turned out to be the most polyvalent adsorbent since such hybrid material could adsorb the entire studied organic compounds.

Magnetic Properties and Biological Activity Evaluation of Iron Oxide Nanoparticles

The aim of this study was to provide information about the biological properties of iron oxide nanoparticles (IO-NPs) obtained in an aqueous suspension. The IO-NPs were characterized by transmission electron microscopy (TEM). Analysis of hysteresis loops data at room temperature for magnetic IO-NPs sample indicated that the IO-NPs were superparamagnetic at room temperature. The calculated saturation magnetization for magnetic iron oxide was = 18.1 emu/g. The antimicrobial activity of the obtained PMC-NPs was tested against Gram-negative (Pseudomonas aeruginosa 1397, Escherichia coli ATCC 25922), Gram-positive (Enterococcus faecalis ATCC 29212, Bacillus subtilis IC 12488) bacterial as well as fungal (Candida krusei 963) strains. The obtained results suggested that the antimicrobial activity of IO-NPs is dependent on the metallic ions concentrations and on the microbial growth state, either planktonic or adherent. The obtained IO-NPs exhibited no cytotoxic effect on HeLa cells at the active antimicrobial concentrations.

Transfer and degradation of polyacrylamide-based flocculants in hydrosystems: a review

The aim of this review was to summarize information and scientific data from the literature dedicated to the fate of polyacrylamide (PAM)-based flocculants in hydrosystems. Flocculants, usually composed of PAMs, are widely used in several industrial fields, particularly in minerals extraction, to enhance solid/liquid separation in water containing suspended matter. These polymers can contain residual monomer of acrylamide (AMD), which is known to be a toxic compound. This review focuses on the mechanisms of transfer and degradation, which can affect both PAM and residual AMD, with a special attention given to the potential release of AMD during PAM degradation. Due to the ability of PAM to adsorb onto mineral particles, its transport in surface water, groundwater, and soils is rather limited and restricted to specific conditions. PAM can also be a subject of biodegradation, photodegradation, and mechanical degradation, but most of the studies report slow degradation rates without AMD release. On the contrary, the adsorption of AMD onto particles is very low, which could favor its transfer in surface waters and groundwater. However, AMD transfer is likely to be limited by quick microbial degradation.

Effect of organic amendments on the mobility of trace elements in phytoremediated techno-soils: role of the humic substances

The efficiency of aided phytostabilization using organic amendments such as ramial chipped wood (RCW) and composted sewage sludge (CSS) was studied on contaminated techno-soils, on nine experimental plots. The objective was to characterize the role of fulvic (FA) and humic acids (HA) on the mobilization of trace elements, specifically As, Cu, Mo, Pb and Zn. Results showed that the addition of CSS increased the total organic carbon and nitrogen content more than with RCW and as a result, the C/N ratio in the CSS soil was higher than in the RCW and non-amended (NE) soil, reflecting the high decomposition of soil organic matter in the CSS soil compared with the other soils. The RCW and CSS amendments increased the hydrogen index (HI) values and the oxygen index (OI) values compared with the NE soil, especially for the soil treated with CSS which contained more aliphatic than aromatic compounds. The addition of CSS to the techno-soil significantly increased the percentage of Corg associated with the HA fractions compared with the RCW and NE soils. The soil amended with CSS showed the highest E4/E6 ratio and the lowest E2/E3 ratio of FA. Zn and As were more abundant in the FA fraction than in the HA fraction, whereas Pb, Cu and Mo were more associated to HA than to FA in the treated and untreated soils, which may explain the difference in their mobility and availability.

Evaluation of samarium doped hydroxyapatite, ceramics for medical application: antimicrobial activity

Samarium doped hydroxyapatite (Sm:HAp), Ca10-xSmx(PO4)6(OH)2 (HAp), bionanoparticles with different xSm have been successfully synthesized by coprecipitation method. Detailed characterization of samarium doped hydroxyapatite nanoparticles (Sm:HAp-NPs) was carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR). The biocompatibility of samarium doped hydroxyapatite was assessed by cell viability. The antibacterial activity of the Sm:HAp-NPs was tested against Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli) and Gram-positive bacteria (Enterococcus faecalis and Staphylococcus aureus). A linear increase of antimicrobial activity of P. aeruginosa has been observed when concentrations of Sm:HAp-NPs in the samples with xSm = 0.02 were higher than 0.125 mg/mL. For Sm:HAp-NPs with xSm = 0.05 a significant increase of antibacterial activity on E. coli was observed in the range 0.5-1 mg/mL. For low concentrations of Sm:HAp-NPs (xSm = 0.05) from 0.031 to 0.125 mg/mL a high antibacterial activity on Enterococcus faecalis has been noticed. A growth of the inhibitory effect on S. aureus was observed for all concentrations of Sm:HAp-NPs with xSm = 0.02.

Macro and microchemistry of trace metals in vitrified domestic wastes by laser ablation ICP-MS and scanning electron microprobe X-ray energy dispersive spectroscopy

Management of domestic wastes often relies on incineration, a process that eliminates large amount of wastes but also produces toxic residues that concentrate heavy metals. Those hazardous secondary wastes require specific treatment. Vitrification is seen as a powerful way to stabilise them. However, concern exists about the long term behaviour of these glass wastes and the potential release of toxic species into the environment. The answers will come with further investigation into the physico-chemical evolution of the vitrified wastes and the mobility of hazardous elements within the matrix with appropriate analytical methods. Laser ablation coupled with inductively coupled mass spectrometry (LA-ICP-MS) is a challenging technique for the chemical analysis of trace elements in solid materials. This paper presents an evaluation of the potential of LA- ICP-MS for macro and microanalysis of trace metals in domestic vitrified wastes with regards to other physical analytical techniques of solids such as scanning electronprobe X-ray energy dispersive spectroscopy (SEM-EDXS). Two typical samples, vitreous and crystallised, are used to compare the analytical performances of the two techniques. SEM-EDXS was used for mineralogical characterisation and chemical analysis of the mineralogical phases. Relative micro-analysis and bulk quantitative analysis of 30 major, minor and trace elements was performed by LA-ICP-MS: precision was between 10 and 20% for most elements and quantitative analysis proved possible with an accuracy of 20% and relative detection limits of 0.1 mg kg(-1).