This work focuses on the development of a procedure to study the mechanism of leaching of lead from sub-micrometer lead glass particles using 0.3 mol L-1 HNO3 as a leachant. Glass particles with an effective size distribution range from 0.05 to 1.4 μm were generated by laser ablation (213 nm Nd:YAG laser) and collected on an inline 0.2 μm syringe filter. Subsequently, the glass particles on the filter were subjected to on-line leaching and continuous monitoring of lead (Pb-208) in the leachate by quadrupole ICP-MS. The lead leaching profile, aided by the particle size distribution information from cascade impaction, was numerically fitted to a mathematical model based on the glass intraparticle diffusion, liquid film distribution and thermodynamic glass-leachant distribution equilibrium. The findings of the modeling show that the rate-limiting step of leaching is the migration of lead from the core to the surface of the glass particle by an ion-exchange mechanism, governed by the apparent intraparticle lead diffusivity in glass which was calculated to be 3.1x10-18 m2 s-1. Lead leaching is illustrated in the form of graphs and animations of intraparticle lead release (in time and intraparticle position) from particles with sizes of 0.1 and 0.3 μm.
COBISS.SI-ID: 5311514
A LA-ICP-MS method based on a 213 nm Nd : YAG laser and a quadrupole ICP-MS has been developed for mapping of mercury in root cross-sections of maize (Zea mays L.) to investigate the mechanism of mercury uptake from soil and its transformation and compartmentalization. Conventional rastering was found to be unusable due to sorption of mercury onto the internal parts of the LA device, giving rise to memory effects resulting in serious loss of resolution and inaccurate quantification. Spot analysis on a virtual grid on the surface of the root sections using washout times of 10 s in between spots greatly alleviated problems related to these memory effects. By ablating straight through the root sections the calibration process was simplified as matrix-matching and internal standardization could be circumvented. Mercury-spiked freeze-drying embedding medium, sectioned similarly to the root sections, was used for the preparation of the standards. Standards and root sections were subjected to spot analysis using the following operational parameters: beam diameter, 15 μm; laser fluence, 2.5 J cm-2; repetition rate, 20 Hz; dwell time, 1 s; acquisition time, 0.1 s. The mercury peaks for standards and roots sections could be consistently integrated for quantification and construction of the 2D mercury maps for the root sections. This approach was successfully used to investigate the mercury distribution in root sections of maize grown in soil spiked to a level of 50 mg kg-1 (DW) HgCl2. It was found that mercury ions practically do not cross root plasma membranes of the endodermal barrier, but are entirely retained in the root apoplastic space. This implies that maize plants grown on Hg contaminated areas only to a lesser extent translocate Hg to the upper edible parts.
COBISS.SI-ID: 2821455
New insights into the functioning, i.e. electrochemical behaviour and analytical performance, of the in-situ prepared antimony film electrodes (SbFEs) under square-wave anodic stripping (SW-ASV) and cyclic (CV) voltammetry conditions are presented by studying several key operational parameters using Pb(II), Cd(II) and Zn(II) as model analyte ions. Five different carbon- and metal-based substrate transducer electrodes revealed a clear advantage of the former ones while the concentration of the precursor Sb(III) ion exhibited a distinct influence on the ASV functioning of the SbFE. Among six acids examined as potential supporting electrolytes, the HNO3 was demonstrated to yield nearly identical results in conducting ASV experiments with SbFE as so far almost exclusively used HCl. This is extremely important as HNO3 is commonly employed acidifying agent in trace metal analysis, especially in elemental mass spectrometry measurements. We confirmed the formation of poorly soluble oxidized Sb species at the substrate electrode surface at the end of each stripping step, i.e. at the potentials beyond the anodic dissolution of the antimony film. Hence, the significance of the cleaning and initializing the surface of a substrate electrode after accomplishing a stripping step was thoroughly studied in order to find conditions for a complete removal of the adhered Sb-oxides and thus to assure a memory-free functioning of the in situ prepared SbFE. Finally, the practical analytical application of the proposed ASV method was successfully tested and evaluated by measuring the three metal analytes in ground (tap) and surface (river) water samples acidified with HNO3. Our results approved the appropriateness of the SbFE and the proposed method for measuring low microgram per liter levels of some toxic metals, particularly taking into account the possibility of on-field testing and the use of low cost instrumentation.
COBISS.SI-ID: 36731141
Nanostructured iron(III) oxide deposits are grown by chemical vapor deposition (CVD) at 400−500°C on Si(100) substrates from Fe(hfa)2TMEDA (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; TMEDA = N,N,N',N'-tetramethylethylenediamine), yielding the selective formation of α-Fe2O3 or the scarcely studied ε-Fe2O3 polymorphs under suitably optimized preparative conditions. By using Ti(OPri)4 (OPri = iso-propoxy) and water as atomic layer deposition (ALD) precursors, we subsequently functionalized the obtained materials at moderate temperatures ((300 °C) by an ultrathin titanomagnetite (Fe3−xTixO4) overlayer. An extensive multitechnique characterization, aimed at elucidating the system structure, morphology, composition and optical properties, evidenced that the photoactivated hydrophilic and photocatalytic behaviour of the synthesized materials is dependent both on iron oxide phase composition and ALD surface modification. The proposed CVD/ALD hybrid synthetic approach candidates itself as a powerful tool for a variety of applications where semiconductor-based nanoarchitectures can benefit from the coupling with an ad hoc surface layer.
COBISS.SI-ID: 2875387
A novel and recyclable synthetic method using an ionic liquid as a green solvent was developed for synthesis of ecocomposite materials from cellulose (CEL) and chitosan (CS). Adding CEL into CS substantially increases tensile strength of the composite while entirely retaining the adsorbing properties of CS. The composite is much better adsorbent for microcystin than other materials used for removal of cyanotoxins from water. It can adsorb four times more microcystin compared to the best known adsorbent. The composite can be reused because adsorbed microcystin can be desorbed quantitatively.
COBISS.SI-ID: 2702075