Miroslava Václavíková

Nanostructures in environmental pollution detection, monitoring, and remediation

abstract We present preliminary results of our joint investigations to monitor and mitigate environmental pollution, a leading contributor to chronic and deadly health disorders and diseases affecting millions of people each year. Using nanotechnology-based gas sensors; pollution is monitored at several ground stations. The sensor unit is portable, provides instantaneous ground pollution concentrations accurately, and can be readily deployed to disseminate real-time pollution data to a web server providing a topological overview of monitored locations. We are also employing remote sensing technologies with high-spatial and spectral resolution to model urban pollution using satellite images and image processing. One of the objectives of this investigation is to develop a unique capability to acquire, display and assimilate these valuable sources of data to accurately assess urban pollution by real-time monitoring using commercial sensors fabricated using nanofabrication technologies and satellite imagery. This integrated tool will be beneficial towards prediction processes to support public awareness and establish policy priorities for air quality in polluted areas. The complex nature of environmental pollution data mining requires computing technologies that integrate multiple sources and repositories of data over multiple networking systems and platforms that must be accurate, secure, and reliable. An evaluation of information security risks and strategies within an environmental information system is presented. In addition to air pollution, we explore the efficacy of nanostructured materials in the detection and remediation of water pollution. We present our results of sorption on advanced nanomaterials-based sorbents that have been found effective in the removal of cadmium and arsenic from water streams.

Removal of cadmium, zinc, copper and lead by red mud, an iron oxides containing hydrometallurgical waste

Abstract Red mud, a residue of the alumina production industry which is actually a solid waste, has been studied as a potential sorbent for the removal of toxic bivalent cations (i.e. Cd, Zn, Cu and Pb) from aqueous solutions in the presence of 0.01 M NaNO3. The experimental data were modeled with Langmuir and Freundlich isotherms and fitted quite well. The relatively high uptake indicated that red mud can adsorb considerable amounts of cadmium and zinc from near-neutral aqueous solutions (maximum uptake capacity for cadmium: 68 mg-g1 at pH 6 and ca. 133 mg-g1 for zinc at pH 7). A significant uptake was also observed for copper and lead at pH 6 and 7 respectively which was attributed to precipitation of the respective insoluble hydroxides. TCLP leaching tests before and after the metal removal have shown that read mud is an environmentally compatible material that could be used for the wastewater treatment. Regeneration possibilities have also been observed.

Degradation of Reactive Black 5 by electrochemical oxidation

Degradation of commercial grade Reactive Black 5 (RB5) azo dye by chemical and electrochemical treatment was examined using a dimensionally stable anode and stainless steel cathodes as electrode materials, with NaCl as supporting electrolyte. The electrochemical treatment was compared to the chemical treatment with hypochlorite generated by electrolysis. The compounds present in the commercial grade RB5 azo dye and the products of its electrochemical degradation were separated using ion-pairing high performance liquid chromatography on reversed phase. The separated species were detected by diode array detector and electrospray ionization mass spectrometry. A suitable ion-pairing reversed phase HPLC-MS method with electrospray ionization for the separation and identification of the components was developed. The accurate mass of the parent and fragment ions were used in the determination of the empirical formulas of the components using the first-order mass spectra. Structural formulas of degradation products were proposed using these information and principles of organic chemistry and electrochemistry.

Tailoring bifunctional hybrid organic–inorganic nanoadsorbents by the choice of functional layer composition probed by adsorption of Cu2+ ions

Spherical silica particles with bifunctional (≡Si(CH2)3NH2/≡SiCH3, ≡Si(CH2)3NH2/≡Si(CH2)2(CF2)5CF3) surface layers were produced by a one-step approach using a modified Stöber method in three-component alkoxysilane systems, resulting in greatly increased contents of functional components. The content of functional groups and thermal stability of the surface layers were analyzed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, and 13C and 29Si solid-state NMR spectroscopy revealing their composition and organization. The fine chemical structure of the surface in the produced hybrid adsorbent particles and the ligand distribution were further investigated by electron paramagnetic resonance (EPR) and electron spectroscopy of diffuse reflectance (ESDR) spectroscopy using Cu2+ ion coordination as a probe. The composition and structure of the emerging surface complexes were determined and used to provide an insight into the molecular structure of the surfaces. It was demonstrated that the introduction of short hydrophobic (methyl) groups improves the kinetic characteristics of the samples during the sorption of copper(II) ions and promotes fixation of aminopropyl groups on the surface of silica microspheres. The introduction of long hydrophobic (perfluoroctyl) groups changes the nature of the surface, where they are arranged in alternately hydrophobic/hydrophilic patches. This makes the aminopropyl groups huddled and less active in the sorption of metal cations. The size and aggregation/morphology of obtained particles was optimized controlling the synthesis conditions, such as concentrations of reactants, basicity of the medium, and the process temperature.

Removal of Cd2+ And Pb2+ from Aqueous Solutions Using Bio-Char Residues

Abstract In this paper, wheat straw and rapeseed residues before and after microwave pyrolysis during biooil production were studied as potential sorbents of heavy metals. The sorbents were characterized by elemental analysis and FTIR spectroscopy. Sorption properties of the materials were investigated using batch adsorption-equilibrium experiments and the effect of initial Cd and Pb concentration was studied. The experimental data fit Langmuir adsorption isotherm. The maximum sorption affinity of studied materials was observed in the case of rapeseed and its sorption capacity was 31.6 and 83.5 mg/g for Cd and Pb, respectively.

Outlook for graphene-based desalination membranes

We discuss here next-generation membranes based on graphene for water desalination, based on the results of molecular simulations, application of nanofabrication technologies, and experiments. The potential of graphene to serve as a key material for advanced membranes comes from two major possible advantages of this atomically thin two-dimensional material: permeability and selectivity. Graphene-based membranes are also hypothetically attractive based on concentration polarization and fouling, and graphene’s chemical and physical stability. Further research is needed to fully achieve these theoretical benefits, however. In addition, improvement in the design and manufacturing processes, so to produce performance and cost-effective graphene-based desalination devices, is still an open question. Finally, membranes are only one part of desalination systems, and current processes are not optimized to take full advantage of the higher selectivity and permeability of graphene. New desalination processes are, therefore, needed to unlock the full benefits of graphene.

Protection of Thiol Groups on the Surface of Magnetic Adsorbents and Their Application for Wastewater Treatment

The magnetite nanoparticles were functionalized with silica shells bearing mercaptopropyl (monofunctional) and mercaptopropyl-and-alkyl groups (bifunctional) by single-step sol-gel technique. The influence of synthetic conditions leading to increased amounts of active functional groups on the surface and improved capacity in the uptake of Ag(I), Cd(II), Hg(II), and Pb(II) cations was revealed. The physicochemical properties of obtained magnetic nanocomposites were investigated by FTIR, Raman, XRD, TEM, SEM, low-temperature nitrogen ad-/desorption measurements, TGA, and chemical microanalysis highlighting the efficiency of functionalization and mechanisms of the preparation procedures. The removal of the main group of heavy metal cations was studied in dependence from the pH, contact time and equilibrium concentration to analyze the complexes composition for the large scale production of improved adsorbents. It was demonstrated that introduction of the alkyl groups into the surface layer prevents the formation of the disulfide bonds between adjacent thiol groups. The obtained adsorbents were employed to treat real wastewater from Ruskov, Slovakia with concentration of Fe 319 ng/cm3, Cu 23.7 ng/cm3, Zn 36 ng/cm3, Mn 503 ng/cm3, Al 21 ng/cm3, As 34 ng/cm3, Pb 5.8 ng/cm3, Ni 35 ng/cm3, Co 4.2 ng/cm3, Cr 9.4 ng/cm3, Sb 6 ng/cm3, Cd 5 ng/cm3. These materials proved to be highly effective in the removal of 50% of all metal ions, espeсially Zn, Cd, and Pb ions from it and turned recyclable, opening for their sustainable use in water purification.

Fe-Oxides in Water Remediation Technologies

Water is essential for life, a strategic resource for every country and population. Its availability and sanitary safety is highly connected with the health and economic status of a population. The burden of disease due to polluted water is a major public health problem throughout the world. Many pollutants in water streams have been identified as toxic and harmful to the environment and human health, and among them arsenic, mercury and cadmium are considered those with the highest priority. Iron is the fourth most abundant element in the Earth’s crust, and reactions involving iron play a major role in the environmental cycling of a range of important contaminants. Our earlier research has shown that Fe oxides/oxyhydroxides are particularly effective adsorbents of a range of contaminants (toxic metals), due to their high (reactive) specific surface area. It has been proven that Fe is particularly effective in As removal as a chemical bond is created on Fe surface and As is stabilised and can be safely deposited. Removal of contaminants from waste streams through precipitation with (hydrous) ferric oxides is an established methodology in a number of industrial processes (high density sludge systems for arsenic control in effluents from the mining industry, and in the treatment of textile dye effluent).

Application of Fe-Nanoscale Materials Useful in the Removal of Arsenic from Waters

Two iron minerals (akaganeite and magnetite) were synthesized according to standard procedures and nanosized particles were obtained. The minerals were tested for their ability to remove As from water streams at pH value 3.5, with and without electrolyte (0.1 M conc.). Their capacities were calculated to 50 and 30 mg As/g of solid for akaganeite and magnetite, respectively. The sorption isotherms were modeled with Freundlich and Langmuir equations and good agreement was observed. Zeta potential studies have shown that both minerals sorbed As specifically, probably due to chemical forces between As oxyanions and surface Fe.

Proceedings of the 11th International Conference on Magnetic Fluids (ICMF 11) (Košice, Slovakia, 23-27 July 2007).

The 11th International Conference on Magnetic Fluids (ICMF 11) was held in Košice, Slovakia between 23-27 July 2007. Attendance at the conference was high and its motivation was in line with the ten previous ICMF conferences organized in Udine, Orlando, Bangor, Sendai-Tokyo, Riga, Paris, Bhavnagar, Timisoara, Bremen and Guarujá. The conference in Slovakia reflected the scientific communitys enthusiasm and worldwide support, with 256 participants, from 30 countries attending.The main objective of ICMF 11 was to promote progress and knowledge in the field of magnetic fluids regarding their chemistry, physical and magnetic properties, heat and mass transfer, surface phenomena, as well as their technological and biomedical applications. As research on magnetic fluids is essentially interdisciplinary, experts from related areas were invited to present their contributions with a view to increasing knowledge in the field and highlighting new trends. Submitted communications were refereed by members of the Scientific Organizing Committee and abstracts were assembled in a book of abstracts. Participants presented 180 posters in two poster sessions and 56 oral presentations. All presentations contributed to a greater understanding of the area, and helped to bridge the gap between physics, chemistry, technology, biology and medical sciences. Contributions to this conference are presented in 115 scientific papers, with some published in Journal of Physics: Condensed Matter and the rest in Magnetohydrodynamics. The organization of the conference was made possible by generous support from the Institute of Experimental Physics and Institute of Geotechnics of the Slovak Academy of Sciences, the University of Pavol Jozef Šafárik and the Slovak Physical Society. Financial support from Ferrotec, Cryosoft Ltd, Mikrochem, Liquids Research Ltd, Askony and US Steel Košice, is also gratefully acknowledged.