Ewa Karwowska

Bioleaching of metals from printed circuit boards supported with surfactant-producing bacteria.

This study has evaluated the possibility of bioleaching zinc, copper, lead, nickel, cadmium and chromium from printed circuit boards by applying a culture of sulphur-oxidising bacteria and a mixed culture of biosurfactant-producing bacteria and sulphur-oxidising bacteria. It was revealed that zinc was removed effectively both in a traditional solution acidified by a way of microbial oxidation of sulphur and when using a microbial culture containing sulphur-oxidising and biosurfactant-producing bacteria. The average process efficiency was 48% for Zn dissolution. Cadmium removal was similar in both media, with a highest metal release of 93%. For nickel and copper, a better effect was obtained in the acidic medium, with a process effectiveness of 48.5% and 53%, respectively. Chromium was the only metal that was removed more effectively in the bioleaching medium containing both sulphur-oxidising and biosurfactant-producing bacteria. Lead was removed from the printed circuit boards with very low effectiveness (below 0.5%). Aerating the culture medium with compressed air increased the release of all metals in the medium with sulphur and biosurfactant, and of Ni, Cu, Zn and Cr in the acidic medium. Increasing the temperature of the medium (to 37°C) had a more significant impact in the acidic environment than in the neutral environment.

The influence of metal speciation in combustion waste on the efficiency of Cu, Pb, Zn, Cd, Ni and Cr bioleaching in a mixed culture of sulfur-oxidizing and biosurfactant-producing bacteria

Metal leachability from ash and combustion slag is related to the physico-chemical properties, including their speciation in the waste. Metals speciation is an important factor that influences the efficiency of metal bioleaching from combustion wastes in a mixed culture of acidophilic and biosurfactant-producing bacteria. It was observed that individual metals tended to occur in different fractions, which reflects their susceptibility to bioleaching. Cr and Ni were readily removed from wastes when present with a high fraction bound to carbonates. Cd and Pb where not effectively bioleached when present in high amounts in a fraction bound to organic matter. The best bioleaching results were obtained for power plant slag, which had a high metal content in the exchangeable, bound to carbonates and bound to Fe and Mg oxides fractions- the metal recovery percentage for Zn, Cu and Ni from this waste exceeded 90%.

Comparative Assessment of Antimicrobial Efficiency of Ionic Silver, Silver Monoxide, and Metallic Silver Incorporated onto an Aluminum Oxide Nanopowder Carrier

The present paper provides comparative assessment of antimicrobial efficiency of ionic silver (Ag

Influence of Al2O3/Pr Nanoparticles on Soil, Air and Water Microorganisms

One of the greatest challenges for science nowadays is the protection of the natural environment. Synthetic nanoparticles are released into the environment with industrial and household wastes, and their release can be expected to increase constantly with increasing use of nanoparticles in industry and their increasing share in various consumer products. The penetration of nanoparticles into the water, soil, or air ecosystems may disturb seriously the functioning of the natural environment. In the present study we examined how the active aluminum nano-oxide in the gamma form used as a neutral carrier for the praseodymium (Pr) nanoparticles affected their behavior. Praseodymium is very useful in many branches of science and in everyday life, although in its free form, it is commonly considered to be cyto-toxic, eco-toxic, and phyto-toxic. Our experiments were aimed to find whether the aluminum nano-oxide can act as a nano-stabilizer for the metal nanoparticles, and also to examine whether their bounding on the carrier decreases or eliminates their toxicity to the soil or water microorganisms present in the natural environment. Our experiments have shown that the aluminum nano-oxide is suitable to function as a nano-stabilizer for the Pr nanoparticles. The Al2O3/Pr nanoparticles produced by the dry (conducted in an organic solvent) thermal decomposition of an organic precursor, are not ecotoxic, or less ecotoxic to bacteria isolated from environmental samples, in particular to gram-positive caryopsis of the Micrococcus and Staphylococcus genera isolated from air samples.

Synthesis and Bioactivity of RGO/TiO 2 -Noble Metal Nanocomposite Flakes

This study aims to describe the influence of adding graphene oxide to TiO2-noble metal (Me=Ag, Au or Pd) composite nanoparticles on their bioactivity (formation of RGO/TiO2-Me nanocomposite system). The obtained nanocomposite flakes and reference TiO2-Me nanoparticles were characterized using SEM, HRTEM and XPS spectroscopy, N2 sorption analysis and helium pycnometer. The analysis of the antibacterial properties of synthesized nanocomposites revealed a growth inhibiting effect of TiO2-Ag particles on gram positive bacteria such as: Staphylococcus aureus, Sarcina lutea and Bacillus subtilis. In the case of nanocomposite flakes containing RGO the visible changes in bacteriostatic properties were observed, including unexpected reversal of the antimicrobial activity of silver-containing nanoparticles into the stimulation of growth of applied bacterial strains. The stimulation of growth was not observed for TiO2-Au and Pd nanoparticles deposited on the surface of RGO.

Comparative Assessment of Biocidal Activity of Different RGO/Ceramic Oxide-Ag Nanocomposites

The aim of this study was to compare the bioactivity of RGO/ceramic oxide-Ag nanocomposites. Different ceramic oxides (MexOy) i.e.: Al2O3, TiO2, SiO2 and ZnO2 were in situ co-deposited with Ag nanoparticles on the surface of RGO resulting in the formation of a nanocomposite structure of stacked flakes. The results of our investigations indicate that it is possible to obtain the targeted biocidal properties of the RGO/Ag system by choosing the appropriate ceramic oxide as a modificator of Ag nanoparticles. The strongest antimicrobial properties against E. coli, S. aureus and Bacillus sp. strains were achieved for RGO/SiO2-Ag nanocomposite whereas for Sarcina sp. bacteria the most effective biocide was RGO/TiO2-Ag nanocomposite.

The influence of petroleum products on the methane fermentation process.

In this study the influence of the petroleum products: diesel fuel and spent engine oil on the sewage sludge digestion process and biogas production efficiency was investigated. Microbiological, chemical and enzymatic analyses were applied in the survey. It was revealed that the influence of the petroleum derivatives on the effectiveness of the methane fermentation of sewage sludge depends on the type of the petroleum product. Diesel fuel did not limit the biogas production and the methane concentration in the biogas, while spent engine oil significantly reduced the process efficacy. The changes in physical-chemical parameters, excluding COD, did not reflect the effect of the tested substances. The negative influence of petroleum products on individual bacterial groups was observed after 7 days of the process, while after 14 days probably some adaptive mechanisms appeared. The dehydrogenase activity assessment was the most relevant parameter to evaluate the effect of petroleum products contamination. Diesel fuel was probably used as a source of carbon and energy in the process, while the toxic influence was observed in case of spent engine oil.

Influence of the Staphylococcus Aureus Bacteria Cells on the Zeta Potential of Graphene Oxide Modified with Alumina Nanoparticles in Electrolyte and Drinking Water Environment

The aim of this study was to describe the different aspects of the modification of surface charge of graphene oxide by deposition of Al2O3 nanoparticles on its surface. The novel reduced graphene oxide/Al2O3 nanocomposites were evaluated as an adsorbent for Staphylococcus aureus bacteria cells in electrolyte and drinking water environment. The zeta potential of GO flakes, Al2O3 nanoparticles and RGO/Al2O3 nanocomposite was investigated alone and in the presence of bacteria cells with a special emphasis on the analysis of the zeta potential curves. Our obtained results indicate that the chemical composition of water environment have a significant influence on the electrostatic interactions between sorbent and bacteria. In most cases, the adsorption of bacteria onto adsorbent surface changed its surface charge to similar to adsorbed cells. However, by taking into consideration the sensitiveness and variability of living system such as bacteria cell, we observed that the phenomenon of adsorption (i.e. the physical interactions with sorbent surface) also changed the surface charge of bacteria cells themselves.

MICROBIOLOGICAL AIR CONTAMINATION IN PREMISES OF THE PRIMARY HEALTH-CARE

Abstract The aim of this research was to evaluate the microbiological indoor air contamination level in chosen facilities of the primary health-care for adults and children. The total numbers of mesophilic bacteria, staphylococci, coli-group bacteria and moulds in both surgery rooms and patients’ waiting rooms were determined. Air samples were collected with a MAS 100 impactor and the concentration of microorganisms was estimated by a culture method. The microbiological air contamination level was diverse: the number of mesophilic bacteria ranged from 320 to 560 CFU/m3, number of staphylococci - 10-305 CFU/m3, coli group bacteria - 0-15 CFU/m3 and moulds - 15-35 CFU/m3. The bacteriological contamination level of the air in examined community health centers was higher than described in the literature for hospitals and exceeded the acceptable values proposed for the surgery objects. Streszczenie Przedmiotem pracy była analiza liczebności mikroorganizmów w wytypowanych pomieszczeniach służby zdrowia w placówce podstawowej opieki zdrowotnej. Zakres badań obejmował określenie stężenia bakterii mezofi lnych, gronkowców, bakterii grupy coli oraz grzybów pleśniowych w powietrzu poczekalni dla chorych, gabinetu lekarskiego oraz punktu szczepień. Próbki pobierano za pomocą aparatu MAS 100 fi rmy Merck a liczebność mikroorganizmów szacowano metodą hodowlaną. Stwierdzono, iż poziom zanieczyszczenia mikrobiologicznego powietrza badanych pomieszczeń był zróżnicowany. Liczebność bakterii mezofi lnych kształtowała się na poziomie 320-560 JTK/m3, gronkowców - 10-305 JTK/m3, bakterii grupy coli - 0-15 JTK/m3 a grzybów pleśniowych - 15-35 JTK/m3. Poziom zanieczyszczenia bakteriologicznego w badanej placówce opieki zdrowotnej był wyższy niż ten dopuszczalny dla pomieszczeń szpitalnych w tym sal operacyjnych.