The paper is focused on investigation of different treatment procedures for the removal of toxic fractions from a landfill leachate, which could not be treated biologically due to its toxicity and persistency. The applied methods were air stripping, adsorption to activated carbon and zeolite clinoptiolite and Fenton oxidation. It has been determined, that no method alone is efficient enough for complete treatment of landfill leachate and that biotests are necessary supplements for complete evaluation of treatment efficiency.
COBISS.SI-ID: 33885701
A continuously operated Ψ-shaped microreactor was used for lipase-catalyzed synthesis of isoamyl acetate in the 1-butyl-3-methylpyridinium dicyanamide/n-heptane two-phase system. At preliminarily selected conditions the amount of produced isoamyl acetate was almost three-fold better as compared to the intensely mixed batch process. This was mainly a consequence of efficient reaction–diffusion dynamics in the microchannel system, where the developed flow pattern comprising of intense emulsification provided a large interfacial area for the reaction and simultaneous product extraction.
COBISS.SI-ID: 30820357
A liquid–liquid phase transfer catalyzed (PTC) esterification reaction of 4-t-butylphenol in aqueous phase (1 M sodium hydroxide solution) and 4-methoxybenzoyl chloride in organic phase (dichloromethane) in a microchannel under parallel laminar flow conditions was studied in this work. Tetrabutylammonium bromide was used as the PTC. Stable liquid–liquid hydrodynamic flow and a defined specific interfacial area in a microreactor offer considerable benefits over conventional batch reactors and are crucial to study interactions between kinetics and mass transfer effects. Mentioned features were used to develop a 3D mathematical model considering convection in the flow direction, diffusion in all spatial directions, and reactions in organic and aqueous phases. Results have shown a much higher mass transfer rate of the PTC between both phases as the one predicted by the 3D mathematical model. It may be assumed that the instability of parallel flow, along with the mass transfer of catalyst between both phases, causes rippling and erratic pulsation at the interface which then leads to interfacial convection and increased mass transfer rates. With a proposed correlation for mass transfer enhancement due to interfacial convection, all the experimental data were successfully predicted by the model.
COBISS.SI-ID: 36262917
A process for providing intermediate compounds as building blocks for effectively producing statins is described. The presented process is based on acetoxyacetaldehyde and acetaldehyde as substrates, which are presented in an aldol reaction catalyzed by a crude deoxyribose-5-phosphate aldolase (DERA) expressing culture lysate. Different addition regimes of both reactants into a reaction mixture were applied. For the highest concentration of product ((2S,4R)-4,6-dihydroxytetrahydro-2H-pyran-2-yl)methyl acetate, in the presented crude DERA expressing culture lysate-catalyzed reaction used further in the production of statins, the best addition time of reactants is described. Improved process conditions and reactants’ feeding regime were achieved by converting a batch reaction to a fed-batch process, reaching the highest concentration of product ((2S,4R)-4,6-dihydroxytetrahydro-2H-pyran-2-yl)methyl acetate near 77 g/L. The complete process was designed in a practical and economical manner and could be used further on an industrial scale.
COBISS.SI-ID: 36649733
Batch anionic ring-opening polymerization of octamethylcyclotetrasiloxane in emulsion using nonionic and cationic emulsifiers was studied. The concentration of emulsifiers was set above their critical micelle concentration. Effects of emulsifier concentration, nonionic/cationic emulsifier ratio and cationic emulsifier/initiator (KOH) ratio on the kinetics, average particle size and distribution and on the average molecular weight and distribution were investigated and discussed. At the beginning of the polymerization, empty micelles, active micelles (polymer particles) and monomer droplets co-exist in emulsion. The transport of monomer from monomer droplets towards empty micelles was confirmed by monomer droplets and empty micelles disappearance and by formation of smaller particles. The transport of monomer from monomer droplets towards polymer particles was not confirmed, since the average polymer particle size did not increase during polymerization. It was proposed, that at lower conversions, monomer diffuse from polymer particle interior to particle surface, while at higher conversions, the monomer diffuse from larger to smaller polymer particles. Emulsifier concentration, nonionic/cationic emulsifier ratio and cationic emulsifier/KOH ratio have an evident effect on the kinetics and on the average molecular weight, thus demonstrating that cationic emulsifier participates to the initiation reaction.
COBISS.SI-ID: 34739717