Application of an ozonation–adsorption–ultrafiltration system for surface water treatment

Investigations are presented on the effect of the preliminary ozonation on ultrafiltration (UF) and powdered activated carbon (PAC) /UF process performance, especially on permeate flux decline and the effectiveness of model organics removal. Flat membranes from regenerated cellulose were used. A model solution was prepared as a mixture of humic acids and phenol. PAC dosage was equal to 100 mg/l⁻¹. The ozone dosages were in the range of 1–3 mg O₃ l⁻¹ (0.2–0.6 mg O₃/mg TOC). It was found that the most advantageous configuration was preliminary ozonation with an ozone dosage of 0.4 mgO₃/mg TOC–UF. The permeate flux reached a value equal to the pure water flux value. Moreover, a very high effectiveness of model organics removal was obtained: TOC was reduced by about 96% and UV₂₅₄ absorbance was removed completely. When PAC was added to the feed containing humic acids without ozonation, a drop in a permeate flux was observed compared to UF. Similarly, the addition of PAC to feed treated with ozone resulted in a significant drop in the permeate flux in comparison with pure water flux, regardless of ozone dosage applied.     

Selection of Endophytic Strains for Enhanced Bacteria-Assisted Phytoremediation of Organic Pollutants Posing a Public Health Hazard

Anthropogenic activities generate a high quantity of organic pollutants, which have an impact on human health and cause adverse environmental effects. Monitoring of many hazardous contaminations is subject to legal regulations, but some substances such as therapeutic agents, personal care products, hormones, and derivatives of common organic compounds are currently not included in these regulations. Classical methods of removal of organic pollutants involve economically challenging processes. In this regard, remediation with biological agents can be an alternative. For in situ decontamination, the plant-based approach called phytoremediation can be used. However, the main disadvantages of this method are the limited accumulation capacity of plants, sensitivity to the action of high concentrations of hazardous pollutants, and no possibility of using pollutants for growth. To overcome these drawbacks and additionally increase the efficiency of the process, an integrated technology of bacteria-assisted phytoremediation is being used recently. For the system to work, it is necessary to properly select partners, especially endophytes for specific plants, based on the knowledge of their metabolic abilities and plant colonization capacity. The best approach that allows broad recognition of all relationships occurring in a complex community of endophytic bacteria and its variability under the influence of various factors can be obtained using culture-independent techniques. However, for practical application, culture-based techniques have priority.     

Reflector luminaire with high power light-emitting diodes for general lighting

The lighting parameters of LEDs are constantly improving. They should not however be applied directly in general lighting luminaires. Luminous intensity distribution solid of high power LEDs is inappropriate for the uniform lighting of a target surface and produces too high of a luminance for this luminaire for large elevation angles. We analyzed the luminous intensity curves allowing us to achieve the best possible lighting uniformity and limited distribution of the luminous flux. Specially manufactured reflectors with limited height were applied in the designed luminaire model. The application of 30 white and additionally six red diodes in the same luminaire provided the resulting optical radiation with the color temperature of 3702 K and a color rendering index of 81.     

Understanding 'clean-up' of III-V native oxides during atomic layer deposition using bulk first principles models

The use of III-V materials as the channel in future transistor devices is dependent on removing the deleterious native oxides from their surface before deposition of a gate dielectric. Trimethylaluminium has been found to achieve in situ 'clean-up' of the oxides of GaAs and InGaAs before atomic layer deposition (ALD) of alumina. Here we propose six reaction mechanisms for 'clean-up,' featuring exchange of ligands between surface atoms, reduction of arsenic oxide by methyl groups and desorption of various products. We use first principles Density Functional Theory (DFT) to determine which mechanistic path is thermodynamically favoured based on models of the bulk oxides and gas-phase products. We therefore predict that 'clean-up' of arsenic oxides mostly produces As4 gas. Most C is predicted to form C2H6 but with some C2H4, CH4 and H2O. An alternative pathway is non-redox ligand exchange, which allows non-reducible oxides to be cleaned-up.     

Advancing membrane electrodes and optical ion sensors

While potentiometric sensors experienced a golden age in the 1970s that drove innovation and implementation in the clinical laboratory as sensors of choice, it has been only fairly recently that a theoretical understanding coupled with modern materials approaches transformed the area of membrane electrodes from a playful, yet empirical field to one firmly rooted in scientific understanding. This paper summarizes key progress in the field during the past two decades, emphasizing that the key impulses at the time originated from the emerging field of optical ion sensors. This simplified and transformed the underlying theory of their potentiometric membrane electrode counterparts, where subsequently substantial progress was made, including the realization of ultra-trace detection limits. The better understanding of zero-current ion fluxes and transport processes in turn allowed the development of approaches utilizing dynamic electrochemistry principles, thereby drastically expanding the field of membrane electrodes and making available a range of new methodologies that would have been difficult to predict only a few years ago. These significant developments are now starting to come back and influence the field of optical sensors, where the control and triggering of dynamic processes, away from simpler equilibrium principles, are becoming a highly promising field of research.     

The favorable and unfavorable effects of oxide and intermetallic phases in conductive materials using laser micro technologies

In laser technological processes, which are connected with phase transitions, special changes in material structure occur. These changes of structure include among others phase composition as well as morphology. The changed structure determines the electrical, mechanical and functional properties of the material. The problems become of greater importance in laser microtechnologies when areas with changed structure have dimensions measurable in micrometers, and volume of an order of 10⁻³ mm³. The favorable and unfavorable effects of the structural changes of materials and functional properties of elements produced by means of laser microtechnology have been analyzed in the paper.     

AstPT Catalyses both Reverse N1‐ and Regular C2 Prenylation of a Methylated Bisindolyl Benzoquinone

Prenylated bisindolyl benzoquinones exhibit interesting biological activities, such as antidiabetic or anti‐HIV activities. A number of these compounds, including asterriquinones, have been isolated from Aspergillus terreus. In this study, we identified two putative genes by genome mining, ATEG_09980 and ATEG_00702, which share high sequence similarity with the known bisindolyl benzoquinone prenyltransferase TdiB from Aspergillus nidulans. The coding sequences were cloned and overexpressed in E. coli. The overproduced recombinant proteins were purified to near homogeneity and used for enzyme assays with asterriquinone D in the presence of dimethylallyl diphosphate. HPLC analysis showed that product formation was only detected in enzyme assays with EAU29429 encoded by ATEG_09980, not in those with EAU39348 encoded by ATEG_00702. Product isolation and structure elucidation by NMR and MS analyses led to identification of N1‐reversely and C2‐regularly monoprenylated derivatives, as well as N1′,N1′′reversely, N1′‐reversely, C2′′‐regularly diprenylated derivatives. This proved that EAU29429 functions as an asterriquinone prenyltransferase (AstPT) and indicated the involvement of EAU29429 rather than EAU39348 in the biosynthesis of methylated asterriquinones. Furthermore, incubation of monoprenylated enzyme products with AstPT resulted in the formation of the diprenylated derivatives.     

Studies on the effect of humic acids and phenol on adsorption-ultrafiltration process performance

Application of pressure-driven membrane processes, such as ultrafiltration (UF) and microfiltration (MF) for surface water treatment have become very popular during last decades. Membrane fouling by humic substances (HS) is one of the major limiting factors in these processes. In order to alleviate the unfavorable effects of the presence of HS in the feed on the process performance UF and MF are often combined with adsorption on powdered activated carbon (PAC). The main goal of the present study was to evaluate the effect of humic acid (HA) on membrane fouling during UF. Moreover, the effect of PAC addition to the feed on UF process, especially on flux decline was determined. The applicability of the adsorption-ultrafiltration (PAC/UF) system to purification of water containing low (phenol) and high molecular (HA) was also investigated. Three different polymer UF membranes, prepared from polysulfone (PSF), cellulose acetate (CA) or polyacrylonitrile (PAN) were applied. It was found that the membranes prepared from PSF and CA are very susceptible to fouling caused by HA. The permeate flux decreased for ca. 50% during UF of HA solution through the PSF membrane and for ca. 45%-through the CA membrane. In the case of the PAN membrane, a negligible effect of HA on the flux was observed. On the basis of the FTIR spectra it was found that the drop in the permeate flux through these membranes may result from interactions between the negatively charged functional groups present on the membrane surface, such as carboxyl groups (CA) and sulfone groups (PSF) with HA, which results in coating of the membrane surface with HA. When PAC was added to the feed containing HA, the permeate flux through the CA and PAN membranes was maintained on a practically unchanged level. However, in case of the PSF membrane, a 50% drop in the permeate flux in comparison with the flux value, when process was conducted without PAC addition was observed. That was supposed to be due to attractive forces among hydrophobic PAC particles, HA molecules and PSF membrane surface. The performed studies showed that the application of PAC/UF system was very effective in the removal of organic substances having both, low and high molecular weights. The role of PAC suspended in a feed in the PAC/UF system is the adsorption of low molecular organic compounds, which cannot be removed by UF alone.     

Calorimetric and Electromotive Force Measurements of Al-Li-Zn Liquid Solutions

The solution calorimetry and electromotive force methods were used for the study of the mixing enthalpy and partial excess Gibbs energy of the Al-Li-Zn liquid solutions. Calorimetric investigations were conducted for solutions with the ratio of X _Li/X _Al and X _Li/X _Zn = 0.8/0.2 and at the temperatures of 942 and 978 K, respectively. The electromotive force studies were performed at two temperatures: 873 and 923 K by the titration technique and for dilute solutions. Based on the data of the mixing enthalpy change and the partial excess Gibbs energy of Li available in the literature, together with that obtained in these studies, the ternary interaction parameters were elaborated. The comparative analysis of the experimental mixing enthalpy change generally showed a good agreement with the values calculated based on different models. The observed deviations between the experimental and the calculated values were, for most of the experimental data, lower than 1 kJ/mol. The experimental partial excess Gibbs energy of Li showed a satisfactory agreement with that modeled on the basis of the ternary parameters elaborated in this work.