Sanitär- und Kommunaltechnik; Umwelttechnik
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Paper des Monats
- ja (18)
1,3,5-Tris-(2,3-dibromopropyl)-1,3,5-triazine-2,4,6-trione (TDBP-TAZTO) is an emerging brominated flame retardant which is widely used in several plastic materials (electric and electronic equipment, musical instruments, automotive components).
However, until today, no photochemical studies as well as the identification of possible phototransformation products (PTPs) were described in literature. Therefore, in this study, UV-(C) and simulated sunlight irradiation experiments were performed to investigate the photolytic degradation of TDBP-TAZTO and to identify relevant PTPs for the first time. The UV-(C) Irradiation experiments show that the photolysis reaction follows a first-order kinetic model. Based on this, the photolysis rate constant k as well as the half-life time t1/2 were calculated to be k = (41 ± 5 ×10−3) min−1 and t1/2=(17±2) min. In comparison, a minor degradation of TDBP-TAZTO and no formed phototransformation products were obtained under simulated sunlight. In order to clarify the photochemical behavior, different chemicals were added to investigate the influence on indirect photolysis: (i) H2O2 for generation of hydroxyl radicals and (ii) two quenchers (2-propanol, sodium azide) for scavenging oxygen species which were formed during the irradiation experiments. Herein, nine previously unknown PTPs of TDBP-TAZTO were detected under UV-(C) irradiation and identified by HPLC-(HR)MS. As a result, debromination, hydroxylation, and dehydrobromination reactions could be presumed as the main degradation pathways by high-resolution mass spectrometry. The direct as well as the OH radical-induced indirect photolysis were observed.
One-part-geopolymers, produced by addition of water to a mixture of solid silica and sodium alumi-nate, are a less exhaustively studied approach to form geopolymeric binders. Depending on the silica source, the reaction products show significant amounts of zeolite Na-A besides amorphous compounds. Previously, 29Si MAS NMR has been used to analyze the chemical structure of such one-part geopolymers, having crystalline structures and amorphous phases (Q2, Q3, Q4).
In this work, pure zeolites and three different one-part-geopolymers cured for 1 day were investigated by 29Si-27Al TRAPDOR NMR. It was used to identify aluminum phases in overlapping silicon sites. Zeolites Na-X (Si/Al=1.4) and Na-Y (Si/Al=2.7) served as model systems to measure the TRAPDOR effect of the structural units Q4(mAl). Both materials show several Q4(mAl) signals, which are all separated by their chemical shifts. The more aluminum surrounds the silicon tetrahedron the higher are the normalized TRAPDOR difference signals (S0/∆S). The intensity ratios between Q4(mAl) to Q4({m-1}Al) of these signals is fixed but vary slightly between both zeolites. These results are transferred to the complex geopolymer structure.
The initial focus of this research was on the development of a general workflow for the documentation and monitoring of historical stained glass windows using structured light scanning. Therefore windows from different churches, time periods and with different corrosion and damage phenomena were scanned before and after conservation measures. To evaluate the execution of the restoration measures the data was compared using 3D inspection software to examine the differences in geometry between the two scans. Various problems had to be solved, for example, how to deal with heavily reflective surfaces and the extreme contrast between light and dark surfaces, as seen in the borders between ‘Schwarzlot’ painting and plain glass. The application of materials for matting the surfaces, such as Cyclododecane spray, was impossible due to the high accuracy of the surface measurement required for 3D inspection. Regarding the contrast differences of the surfaces, the creation of exposure fusions and the use of polarization filters to reduce reflections were tested. In addition to the general problems encountered when recording translucent surfaces, the historical glasses caused additional problems in calculating surface comparisons. For example, the windows have to be moved and turned around several times, both during the conservation process and while scanning, causing deformations of the geometry due to the flexible lead rods allowing a certain degree of movement.
On the basis of a lot of investigation on the spectral sensitivity of photo degradation of plastics and on the underestimated influence of temperature and relative humidity on degradation processes a new type of weathering device was presented at the end of the seventies:
It was a combination of a radiation source with fluorescent UV lamps and a precise climatic cabinet.
The radiation emission from a combination of four different types of fluorescent UV lamps was superimposed on the specimen surfaces in the climatic cabinet to match the UV part of solar radiation as closely as possible. Air temperature was controlled to within ± 1 °C, and relative humidity to within ± 5 %RH.
As the lamps’ emission is focussed on the UV range almost no radiation heating of the sample occurs. Therefore, the temperature of the sample, which is the quantity of consideration for the degradation, is nearly identical with the chamber’s air temperature, which is the quantity to be controlled. Also, therefore, high humidity can be obtained on the sample surface. The limitation of the emission to the UV range is sufficient for the study of the polymer matrix.
This type of weathering device offers an exactness of microclimatic control of the sample’s surface, which should be a standard for weathering devices. Even now it is the only weathering device which generates pure relative humidity (without aerosol).
8. Netzwerktreffen PerFluSan
(2020)
A bead suspension array for measuring emerging pollutants and anthropogenic markers in wastewater
(2016)
Background: The assessment of water quality demands for high-throughput and multi-target compatible analytical methods. On the one hand, the influence of sewage on natural surface waters must be routinely monitored - according to the European Water Framework Directive. On the other hand, estimation of removal efficiencies of pollutants, such as drug residues, is in the focus of industrial and public wastewater treatment. Immunoassays, such as ELISA, are often applied in this area owing to their cost-efficiency and high-throughput capability. However, it is only possible to measure a single analyte in one measurement. In contrast, array technology is capable for measuring multiple substances in parallel. Here we present a four-plex bead-based flow cytometric assay for measuring three drugs (carbamazepine, an anti-epileptic drug, diclofenac, an antiphlogistic and caffeine, a psychoactive substance) and the bile acid isolithocholic acid, which is proposed to be used as a fecal marker. The drugs can be detected from 1 to 4 µg/L and the bile acid can be detected up to 72 µg/L in wastewater, requiring a highly sensitive detection method.
Methods: We use core-shell particles as the spherical platform, consisting of a polystyrene core and a silica shell. Such beads can easily be encoded with an organic fluorophore in the core and functionalized with amino groups on the silica shell surface for creating binding sites for antibodies: Therefore, the marker substances are bound to the amino groups via NHS chemistry. The hybrid particles were synthesized in house. Polystyrene was chosen as core material because of its low density and high refractive index, both important requirements for the use in suspension arrays. Easy surface modifications using silane chemistry are accessible on the silica shell. For the determination of the pollutants, the beads are incubated with a mixture of the analyte-specific antibodies. The antibodies undergo a competitive reaction to bind the immobilized molecules on the surface of the beads or the free analyte in the solution, respectively. Bound antibodies can then be visualized via fluorophore-labelled secondary antibodies. For read-out a flow cytometer is used to virtually separate the different dye encoded beads and to measure the resulting Signal intensity of the immunoassay. A four-parametric function was used as calibration curve.
Results: In order to obtain highly selective binding of the antibodies, we investigated different types of silica shell surface modifications to overcome unspecific binding, finding that a PEG-modified surface is suitable to support our immunoassay format. Multiplexed small molecule detection can therefore be realized in a simple mix and read procedure without washing steps.
Conclusion: We presented a multiplexing suspension array for the detection of four marker substances in wastewater samples, based on an indirect immunoassay format with polystyrene core-silica shell microbeads. The resulting multiplexing assay is appropriate to detect the marker substances in the low µg/L range. Therefore, wastewater samples can be measured without further preconcentration.
A bead suspension array for measuring emerging pollutants and anthropogenic markers in wastewater.
(2016)
The assessment of water quality demands for high-throughput and multi-target compatible analytical methods. On the one hand, the influence of sewage on natural surface waters must be routinely monitored - according to the European Water Framework Directive. On the other hand, estimation of removal efficiencies of pollutants, such as drug residues, is in the focus of industrial and public wastewater treatment. Immunoassays, such as ELISA, are often applied in this area owing to their cost-efficiency and high-throughput capability. However, it is only possible to measure a single analyte in one measurement.
In contrast, array technology is capable for measuring multiple substances in parallel. Here we present a four-plex bead-based flow cytometric assay for measuring three drugs (carbamazepine, an anti-epileptic drug, diclofenac, an antiphlogistic and caffeine, a psychoactive substance) and the bile acid isolithocholic acid, which is proposed to be used as a fecal marker.
In this suspension array core-shell particles, consisting of a polystyrene core and a silica shell are used. They can be easily encoded with a fluorophore which is introduced to the core and functionalized with amino groups on the surface for creating binding sites for antibodies: Therefore, the marker substances are bound to the amino groups via NHS chemistry.
For the determination of the pollutants, the beads are incubated with a mixture of the analyte-specific antibodies. The antibodies undergo a competitive reaction to bind the immobilised molecules on the surface of the beads or the free analyte in the solution, respectively. Bound antibodies can then be visualized via fluorophore-labelled secondary antibodies. For read-out a flow cytometer is used to virtually separate the different encoded beads and to measure the resulting signal intensity of the immunoassay. In order to obtain highly selective binding of the antibodies, we investigated different types of surface modifications to overcome unspecific binding, finding that a PEG-based surface is suitable to support our immunoassay format. The resulting multiplexing assay is appropriate to detect the marker substances in the low µg/L range.
The screening of coatings shows that the modification by adding individual pigment was not sufficient to protect carbon steel even during a short-term exposure, indicated by the discoloration after only seven days of exposure.
Electrochemical tests indicated that the coating cathodically protects carbon steel or slows down the corrosion reaction.
A long-term exposure test confirmed that the PANI/SiO2 modified coating successfully protects the carbon steel in the Sibayak artificial geothermal water at 150 °C for 6 months.
This study assesses the structural vulnerability of part of a later medieval earthen building at
Ambel (near Zaragoza, Spain), once a preceptory or monastic house belonging to the Military
Orders. An inspection of its morphology and materials coupled with the results of an extensive
campaign of static monitoring reveals marked structural inhomogeneities, the product of more
than a thousand years of construction, failure, and repair from the 10th century to the present
day. Building materials are inappropriately juxtaposed, there are discontinuities between construction
phases and fundamental concerns remain over the long-term stability of the structure.
The current condition of the structure is mainly influenced by structural discontinuities introduced
at the time of construction, the unintended consequences of repair and modification and the
material decay that has affected the base of the rammed earth walls. The overall findings of the
static monitoring show that there is no related damage, variations in crack widths are related to
the building seasonal cycle. While static analysis is an essential prerequisite before a suitable
maintenance program can be fully defined, this study argues that no evaluation of the structural
behavior of any historic building can afford to ignore its archaeological “biography” of modification
and repair.