Application of the Catalyst MnTACN onto Cotton Fabric as a Novel Approach in the H2O2/UV Decolourisation Process

Lidija Tušek,Lidija Fras Zemljič,Bojana Vončina,Julija Volmajer Valh 한국섬유공학회 2022 Fibers and polymers Vol.23 No.9

In this article a novel approach for a catalytic advanced oxidation process using H2O2/UV/MnTACN isinvestigated, for the decolouration of Reactive Blue 4 (RB4) containing wastewater at room temperature. The catalyst 1,4,7-trimethyl-1,4,7-triazacyclononane (MnTACN) was not added to the batch reactor where the advanced oxidation process(AOP) was carried out conventionally, but was first applied to the cotton fabric to form a suitable catalyst carrier with a highspecific surface area. With the given experimental parameters (0.777 g/l H2O2; a mercury (Hg) lamp at 500 W; 40 mg/lsolution of Reactive Blue 4; room temperature), complete decolourisation with the MnTACN catalyst was achieved in only20 minutes. When the MnTACN catalyst adsorbed on the cotton fabrics is introduced into the process as a functional textilematerial, the decolouration of RB4 is much faster, and 100 % decolouration is achieved in 10 minutes. Although pretreatmentof the fabric with acid and/or UV/ozone before application of MnTACN influences the amount of adsorbedMnTACN, the decolouration process is almost unaffected over time. Pre-treatment of fabric with chitosan before theapplication of MnTACN affects the final decolourisation rate and efficiency negatively, and does not act synergistically withthe MnTACN. The same functional fabric with adsorbed MnTACN can be used in at least 5 consecutive AOPs, which makesthe process more environmentally friendly and cost effective, but also opens the possibility to a continuous wastewatertreatment process.

Enhancement of Phenolic Compounds Oxidation Using Laccase from Trametes versicolor in a Microreactor

Ana Jurinjak Tušek,Marina Tišma,Valentina Bregovic,Ana Pticar,Želimir Kurtanjek,Bruno Zelic 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.4

Laccases catalyse the oxidation of a wide range of substrates by a radical-catalyzed reaction mechanism,with a corresponding reduction of oxygen to water in a four-electron transfer process. Due to that, laccases are considered environmentally friendly enzymes, and lately there has been great interest in their use for the transformation and degradation of phenolic compounds. In this work, enzymatic oxidation of catechol and L-DOPA using commercial laccase from Trametes versicolor was performed, in continuously operated microreactors. The main focus of this investigation was to develop a new process for phenolic compounds oxidation, by application of microreactors. For a residence time of 72 s and an inlet oxygen concentration of 0.271 mmol/dm3, catechol conversion of 41.3% was achieved, while approximately the same conversion of L-DOPA (45.0%) was achieved for an inlet oxygen concentration of 0.544 mmol/dm3. The efficiency of microreactor usage for phenolic compounds oxidation was confirmed by calculating the oxidation rates;in the case of catechol oxidation, oxidation rates were in the range from 76.101 to 703.935 g/dm3/d (18 - 167 fold higher, compared to the case in a macroreactor). To better describe the proposed process, kinetic parameters of catechol oxidation were estimated, using data collected from experiments performed in a microreactor. The maximum reaction rate estimated in microreactor experiments was two times higher than one estimated using the initial reaction rate method from experiments performed in a cuvette. A mathematical model of the process was developed, and validated, using data from independent experiments.

Mass transfer coefficient of slug flow for organic solvent-aqueous system in a microreactor

Ana Jurinjak Tušek,Iva Anić,Želimir Kurtanjek,Bruno Zelić 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.6

Application of microreactor systems could be the next break-through in the intensification of chemical and biochemical processes. The common flow regime for organic solvent-aqueous phase two-phase systems is a segmented flow. Internal circulations in segments cause high mass transfer and conversion. We analyzed slug flow in seven systems of organic solvents and aqueous phase. To analyze how slug lengths in tested systems depend on linear velocity and physical and chemical properties of used organic solvents, regression models were proposed. It was shown that models based on linearization of approximation by potentials give low correlation for slug length prediction; however, application of an essential nonlinear model of multiple layer perceptron (MLP) neural network gives high correlation with R2=0.9. General sensitivity analysis was applied for the MLP neural network model, which showed that 80% of variance in slug length for the both phases is accounted for the viscosity and density of the organic phases; 10% is accounted by surface tension of the organic phase, while molecular masses and flow rates each account for 5%. For defined geometry of microreactor, mass transfer has been determined by carrying out the neutralization experiment with NaOH where acetic acid diffuses from organic phase (hexane) into aqueous phase. Estimated mass transfer coefficients were in the range kLa=4,652-1,9807 h−1.

Biotransformation in a Microreactor: New Method for Production of Hexanal

Anita Šalic,Ana Tušek,Želimir Kurtanjek,Bruno Zeli 한국생물공학회 2011 Biotechnology and Bioprocess Engineering Vol.16 No.3

In this study, enzymatic oxidation of hexanol to hexanal (green note fragrance) using NAD^+ dependent commercial alcohol dehydrogenase from S. cerevisiae was conducted in continuously operated tubular microreactors with internal volumes of 6 and 13 μL and in a tubular microreactor with a volume of 2 μL that was equipped with internal micromixers. Flow profiles in microchannel were observed in experiments in which the aqueous phase was stained brilliant blue and the hexane was kept colourless. The effects of enzyme and coenzyme inlet concentrations and flow ratios of the immiscible phases on the conversion of hexanol and the volumetric productivity of hexanal were analyzed. Significant improvement in the conversion of hexanol when compared to the classical macroscale process was obtained for c^(i,hexanol) = 5.5 mmol/L,c^(i,NAD+) = 0.55 mmol/L, and γ^(i,ADH) = 0.092 g/L. In the 6 μL microreactor 11.78% conversion of hexanol was attained after 72 sec, while in the macroscale process 5.3%conversion of hexanol was reached after 180 sec.

Local Sensitivity Analysis and Metabolic Control Analysis of the Biological Part of the BTEX Bioremediation Model

Tamara Jurina,Ana Jurinjak Tušek,Mirjana Curlin 한국생물공학회 2015 Biotechnology and Bioprocess Engineering Vol.20 No.6

Environmental distribution and bioremediation of hydrocarbon pollutants is described in the literature with complex mathematical models. Better understanding and easier model application require detailed model analysis. In this work, local sensitivity analysis of the kinetic parameters and metabolic control analysis of the biological part of the integrated BTEX bioremediation model were performed. Local sensitivity analysis revealed that the dissolved oxygen concentration (SO) and particulate iron (III) oxide concentration (SFe) were the most sensitive to both positive and negative parameter value perturbations. In the case of model reactions, aerobic growth (r1) and aerobic growth on acetate (r13) were observed to be the most sensitive. The elasticity, flux control, and concentration control coefficients were estimated by applying the metabolic control analysis methodology. Metabolic control analysis revealed a positive effect of ammonium on all analysed model reactions. The results also indicated the importance of perturbation of the enzyme level catalysing iron reduction on acetate on model fluxes, as well as the importance of enzyme level catalysing aerobic growth on model metabolite concentration. These results can be used in planning optimal operating strategy for BTEX bioremediation.