BTEX decomposition by ozone in gaseous phase

Environment management is turning its efforts to control the air pollution. Nowadays, gas phase contaminants coming from different sources are becoming into the main cause of serious human illness. Particularly, benzene, toluene, ethylbenzene and xylene (BTEX) are getting more and more attention from the scientific community due the high level of volatilization showed by these compounds and their toxicity. Decomposition of these compounds using different treatments is requiring lots of new strategies based on novel options. In the present work the use of ozone was proposed as possible alternative treatment in the gaseous phase of VOC's liberated from water by stripping. This study deals with the decomposition by ozone in gaseous phase of model mixtures of BTEX stripped from water. The experiments were realized in a tubular reactor with fixed length (1.5 m length and diameter of 2.5 cm). The experiments were conducted in two stages: in the first one, organics was ventilated by oxygen flow to liberate BTEX to the gaseous phase; second stage deals with the liberated BTEX decomposition by ozone in the tubular reactor. Ozonation efficiency was determined measuring the VOC's concentration at the output of the tubular reactor. This concentration was compared to the concentration obtained at the input of the reactor. The obtained results confirm the possibility to use of ozone for the VOC's decomposition in gaseous phase. Also, the dynamic relationship between degradation and liberation was studied and characterized.

Engineering approaches to the microcirculation studies

This review focused on a few methodologies which the author, with a background of chemical engineering, has developed in the physiological studies of microcirculation. (1) Fluorescent tracers to visualize mass transfer and hemodynamics: By means of a high sensitive SIT camera equipped in an intravital microscope system, dynamic processes of the permeation of a fluorescent dye from the microvessels through the extravascular space to lymphatics was made to be visualized. Dynamic behaviors of the formed elements were also quantitatively analyzed by the selective fluorescent labeling technique. (2) The dye/light method to induce platelet thrombus in vivo: Intravascular platelet aggregation and subsequent thrombus formation leading to the complete occlusion of the vessels were produced in the microvasculature by the irradiation of filtered light in combination with the intravascular administration of sodium fluorescein. This method enables quantitative evaluation of thrombus formation process in terms of thrombus formation times. Effects of hemodynamic parameters on thrombogenesis in vivo were quantitatively analyzed. (3) Establishment of peritoneal disseminated tumor model: Colon tumor cells (RCN-9) were inoculated into the peritoneal cavity of male Fischer rats, and the intravital microscopic observation of angiogenic vascular growth accompanying tumor growth was made possible. Dynamic behavior of leukocytes in the microcirculation of solid tumor tissue was visualized using a fluorescent labeling technique combined with the use of a real-time confocal laser-scanning microscope.

Know-how and know-why in biochemical engineering

This contribution analyzes the position of biochemical engineering in general and bioprocess engineering particularly in the force fields between fundamental science and applications, and between academia and industry. By using culture technology as an example, it can be shown that bioprocess engineering has moved slowly but steadily from an empirical art concerned with mainly know-how to a science elucidating the know-why of culture behavior. Highly powerful monitoring tools enable biochemical engineers to understand and explain quantitatively the activity of cellular culture on a metabolic basis. Among these monitoring tools are not just semi-online analyses of culture broth by HPLC, GC and FIA, but, increasingly, also noninvasive methods such as midrange IR, Raman and capacitance spectroscopy, as well as online calorimetry. The detailed and quantitative insight into the metabolome and the fluxome that bioprocess engineers are establishing offers an unprecedented opportunity for building bridges between molecular biology and engineering biosciences. Thus, one of the major tasks of biochemical engineering sciences is not developing new know-how for industrial applications, but elucidating the know-why in biochemical engineering by conducting research on the underlying scientific fundamentals.

Wrapping and inclusion of organic molecules with ultrathin, amorphous metal oxide films

In this review, we overview metal oxide nanostructures in which organic molecules play important roles as templates, as structural units, and, in some cases, as hosts. Their structural precision and diversity are discussed from the viewpoint of the topology of a metal-oxygen network. Supramolecular capsules of metal oxides are prepared by the self-assembly of polyoxometalates. Zeolites and mesoporous materials are synthesized by using organic molecules with their assemblies acting as templates. The topological networking of silsesquioxanes makes it possible to produce novel nanocomposites and microporous materials. In the final section, we demonstrate our recent studies into molecular imprinting, the encapsulation of a fluorescent dye, and the wrapping of individual polymer chains. Ultrathin, amorphous metal oxide films can retain the shape of organic molecules and can be used to create molecular composites by precisely wrapping individual molecules. These films are also effective in insulating molecular functions from external environments. The advantages of amorphous metal oxides are discussed in relation to the properties of the corresponding crystalline metal oxides and their potential prospects in nanotechnology.

Catalytically active polymers obtained by molecular imprinting and their application in chemical reaction engineering

Molecular imprinting is a way of creating polymers bearing artificial receptors. It allows the fabrication of highly selective plastics by polymerizing monomers in the presence of a template. This technique primarily had been developed for the generation of biomimetic materials to be used in chromatographic separation, in extraction approaches and in sensors and assays. Beyond these applications, in the past few years molecular imprinting has become a tool for producing new kinds of catalysts. For catalytic applications, the template must be chosen, so that it is structurally comparable with the transition state (a transition state analogue, TSA) of a reaction, or with the product or substrate. The advantage of using these polymeric catalysts is obvious: the backbone withstands more aggressive conditions than a bio material could ever survive. Results are presented showing the applicability of a molecularly imprinted catalyst in different kinds of chemical reactors. It is demonstrated that the catalysts can be utilized not only in batch but also in continuously driven reactors and that their performance can be improved by means of chemical reaction engineering.

A continuous membrane bioreactor for ester synthesis in organic media: II. Modeling Of MBR continuous operation

A model was developed to describe the conversion degree in a membrane bioreactor (MBR) for the synthesis of short-chain esters as a function of the flow rate. The transesterification reaction was catalyzed by a recombinant cutinase of Fusarium solani pisi microencapsulated in reversed micelles of AOT/isooctane. The differences of product concentration in permeate and retentate together with the deactivation profiles led to an enzyme distribution evaluation that describes the experimental values attained. The model considers the bioreactor design as well as its hydrodynamics and the enzyme kinetics. The approach included the analysis of the MBR operation as a CSTR, a PFR, and a series of continuous reactors. The comparative efficiency of these reactor types is discussed. The enzyme distribution was estimated for all the cases. The best description was obtained considering a series of two CSTRs. The modeling results led to a re-evaluation of cutinase operational stability. Deactivation rates correlated very well with the hydrodynamic aspects of biocatalyst location.

A continuous membrane bioreactor for ester synthesis in organic media: I. Operational characterization and stability

The feasibility of continuous ester synthesis in a membrane bioreactor (MBR) by a recombinant cutinase from Fusarium solani pisi was investigated, using the optimal conditions previously attained by medium engineering. The objective was to analyze the MBR behavior as a differential or an integral reactor. The main component of the reactor was an anisotropic ceramic membrane with 15,000 NMWCO. The operating variables included the influence of substrates ratio and flow rate on the conversion degree and on the productivity. The highest conversion degree was obtained using 1M of hexanol and 0.1M of butyl acetate as acyl donor. The use of these substrate concentrations led to a conversion degree of 79.3% and a specific productivity of 41 g hexyl acetate/(d x g cutinase), when the permeate flow rate was 0.025 mL/min. The increase of flow rate to 0.4 mL/min decreased the conversion to 35.6%, although the productivity was enhanced to 294 g product/day x g enzyme. The MBR characterization involved the calculations of mass balance, recirculation rate, conversion per pass, number of cycles, and hydraulic residence time. The operational stability was also evaluated in a longterm experiment over 900 hours and the enzyme half-life was estimated to be approximately 2 years.

The preparation and properties of pyruvate kinase attached to porous sheets, and the operation of a two-enzyme continuous-feed reactor

1. The covalent attachment of pyruvate kinase to filter-paper disks and some kinetic properties of the resultant enzymically active porous sheets are described. 2. A two-enzyme reactor was constructed by using water-insoluble sheets of lactate dehydrogenease in conjunction with the above-mentioned sheets possessing pyruvate kinase activity.