Biomedical subjects

Astrid Rehorek

Publications and source records attributed to Astrid Rehorek.

7 recordsLinked to original sources

PubMed2005

Online LC-MS-MS process monitoring for optimization of biological treatment of wastewater containing azo dye concentrates.

A biological high-performance treatment process comprising two 40-L reactor compartments has been developed for purification and decoloration of concentrated textile wastewater containing up to 15 g L(-1) reactive dyestuff. The decoloration rate of 95% meets the requirements of German legislation for textile wastewater treatment. Successful process development and optimization was achieved by use of high-performance liquid chromatography, with diode-array and electrospray tandem mass spectrometric (LC-ESI-MS-MS) detection, coupled with inline microfiltration membrane-sampling devices, applied online to bioreactors as a process analytical tool for the first time. The optimum process performance was found by correlation of dye and decoloration product-specific concentrations with summary properties such as redox potential and dissolved oxygen content. Details of the degradation and decoloration mechanism for the azo dye reactive black 5 was revealed by using mass spectrometry for structure elucidation.

Azo Compounds↗

PubMed2005

Strategies for continuous on-line high performance liquid chromatography coupled with diode array detection and electrospray tandem mass spectrometry for process monitoring of sulphonated azo dyes and their intermediates in anaerobic-aerobic bioreactors.

On-line HPLC with diode array detection (DAD) coupled to electrospray tandem mass spectrometry (ESI-MS/MS) is presented as an integrated quality control and process integrated optimisation tool for the continuous monitoring of sulphonated azo dyes (SADs) and their intermediates in anaerobic and aerobic bioprocesses. Ion-pair RP-HPLC is found out to be more suitable for simultaneous monitoring of aromatic amines (AAs), sulphonated aromatic amines (SAAs) and sulphonated azo dyes in comparison to RP-HPLC with polar embedded phases. Monitoring of the anaerobic degradation of the diazo Reactive Black 5 displays the dependency of a two stage azo group reduction mechanism on the redox potential of the bioreactor. An autoxidation sensitive intermediate released from the anaerobic reduction is characterised by ESI-MS/MS for the first time. The functionality of the method is demonstrated by the control and evaluation of selective adaptation of bacteria to certain pollutants and the identification of unknown intermediates causing re-gaining colour released from azo dye treatment.

Aerobiosis↗

PubMed2005

Degradation of azo dyes by Trametes villosa laccase over long periods of oxidative conditions.

Trametes villosa laccase was used for direct azo dye degradation, and the reaction products that accumulated after 72 h of incubation were analyzed. Liquid chromatography-mass spectrometry (LC-MS) analysis showed the formation of phenolic compounds during the dye oxidation process as well as a large amount of polymerized products that retain azo group integrity. The amino-phenol reactions were also investigated by 13C-nuclear magnetic resonance and LC-MS analysis, and the polymerization character of laccase was shown. This study highlights the fact that laccases polymerize the reaction products obtained during long-term batch decolorization processes with azo dyes. These polymerized products provide unacceptable color levels in effluents, limiting the application of laccases as bioremediation agents.

Aminophenols↗

PubMed2005

Degradation of azo dyes by laccase and ultrasound treatment.

The goal of this work was to investigate the decomposition of azo dyes by oxidative methods, such as laccase and ultrasound treatments. Each of these methods has strong and feeble sides. The laccase treatment showed high decolorization rates but cannot degrade all investigated dyes (reactive dyes), and high anionic strength led to enzyme deactivation. Ultrasound treatment can decolorize all tested dyes after 3 h at a high energy input, and prolonged sonication leads to nontoxic ionic species, which was demonstrated by ion chromatography and toxicity assays. For the first time, it was shown that a combination of laccase and ultrasound treatments can have synergistic effects, which was shown by higher degradation rates. Bulk light absorption and ion-pairing high-performance liquid chromatography (IP-HPLC) were used for process monitoring, while with reversed-phase HPLC, a lower number of intermediates than expected by IP-HPLC was found. Liquid chromatography-mass spectrometry indicated that both acid orange dyes lead to a common end product due to laccase treatment. Acid Orange 52 is demethylated by laccase and ultrasound treatment. Further results confirmed that the main effect of ultrasound is based on *OH attack on the dye molecules.

Azo Compounds↗

PubMed2004

Application of power ultrasound for azo dye degradation.

Power ultrasound of 850 kHz at 60, 90 and 120 W was used for the degradation of industrial azo dyes Acid Orange 5 and 52, Direct Blue 71, Reactive Black 5 and Reactive Orange 16 and 107. The results show that power ultrasound is able to mineralize azo dyes to non-toxic end products, which was confirmed by respiratory inhibition test of Pseudomonas putida. All investigated dyes have been decolorized and degraded within 3-15 h at 90 W and within 1-4 h at 120 W, respectively. Mass spectrometric investigations show, that hydroxyl radicals attack azo dyes by simultaneous azo bond scission, oxidation of nitrogen atoms and hydroxylation of aromatic ring structures. A volumetric scale-up showed a correlation between the energy input and the absolute amount of degraded dye. Up to an energy input of about 90 W no enzymatic deactivation of laccase was observed which might be helpful for a simultaneous action of sonochemical and enzymatic treatments.

Azo Compounds↗

PubMed2003

Process monitoring of anaerobic azo dye degradation by high-performance liquid chromatography-diode array detection continuously coupled to membrane filtration sampling modules.

Process integrated microfiltration and ultrafiltration based membrane sampling modules were compared by means of HPLC with diode array detection based monitoring of an anaerobic azodye biodegradation process. The sampling matrix consisted of anaerobic sludge from a municipal wastewater treatment plant. The hydrolysed azo dye Reactive Black 5 (RB5-H) and three products (ionic and nonionic) released from reductive cleavage under anaerobic conditions were continuously monitored by simultaneously separation by ion-pair chromatography. Microfiltration membrane-based sampling showed no retention for any compound observed. Sampling by ultrafiltration significantly retained the observed ionic compounds between 58 and 83% whereas a nonionic compound was not retained. On-line monitoring of an oxygen-sensitive compound was possible whereas off-line detection failed. Robust long time monitoring could be performed for up to 1 week without cleaning the membrane.

Anaerobiosis↗

PubMed2002

Monitoring of azo dye degradation processes in a bioreactor by on-line high-performance liquid chromatography.

A technical solution and development of a method for on-line HPLC monitoring of bioreactor processes in a membrane reactor system are presented. Experiences in system design for the continuous coupling of a bioreactor system with capillary by-pass circuits using membrane flow cells and a dual HPLC system are reported. A continuously working integrated sample purification step by ultrafiltration with the membrane cell coupling is established. Using electrical switching valves and separated pumping and eluent systems, the dual HPLC system allows diode array detection as well as measurement of the refractive index. The application of the on-line HPLC monitoring system is demonstrated by measuring the anaerobic H-acid degradation kinetics. H-acid, 1-amino-8-hydroxynaphthalene-3,6-disulfonic acid, is one of the most important coupling components for a variety of direct, mordant, reactive dyes which remains in the process water and the textile dyeing effluents in high concentration.

Azo Compounds↗