Abstracts


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Doped-TiO2: A Review
Adriana Zaleska

Titanium dioxide represents an effective photocatalyst for water and air purification and for self-cleaning surfaces. Additionally, it can be used as antibacterial agent because of strong oxidation activity and superhydrophilicity. TiO2 shows relatively high reactivity and chemical stability under ultraviolet light (λ < 387nm), whose energy exceeds the band gap of 3.3 eV in the anatase crystalline phase. The development of photocatalysts exhibiting high reactivity under visible light (λ > 400 nm) should allow the main part of the solar spectrum, even under poor illumination of interior lighting, to be used. Visible light-activated TiO2 could be prepared by metal-ion implantation, reducing of TiO2, nonmetal doping or sensitizing of TiO2 with dyes. This paper reviews preparation methods of doped-TiO2 with metallic and nonmetallic species, including various types of dopants and doping methods currently available. The mechanism of heterogeneous photocatalysis in the presence of TiO2 is also discussed.

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Mass-Recirculating Systems in CO₂Capture Technologies: A Review
Wojciech M. Budzianowski

Mass recirculation is an approach that can substantially enhance CO₂ capture and fuel conversion processes in energy generating systems. The current review investigates significant patented developments utilizing mass-recirculating systems in air-fuel, oxy-fuel and membrane-assisted CO₂ capture technologies over the last 10 years (2000-2009). Main specific objectives and roles of mass recirculation in variety of power generating systems with CO₂avoidance are expounded with focus on the enhancement of existing CO₂separations and fuel conversions. All searches are also directed at seeking for novelty aspects in different CO₂ capture systems but having a common feature, i.e. utilizing an effective approach - mass recirculation. The paper is organized as follows. In section 3, available CO₂ separation processes are briefly described, e.g. chemical absorption, cryogenic and membrane separation etc. In sections 4-5, the most important patents are briefly characterized in each of 5 selected categories. The effects of mass recirculation and combustion products enrichment on CO₂ separation processes and reactions in fuel combustion and oxyforming are covered. The main benefits of mass recirculation are comprehensively presented in tabular form with respect to specific categories of disclosures. Finally, in section 6, a brief comment on the future directions of CO₂ capture technologies with mass recirculation is provided.

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Microbubble Generation
William B. Zimmerman, Vaclav Tesar, Simon Butler and Himiyage C.H. Bandulasena

In general, there are three ways of generating microbubbles. The most common class uses compression of the air stream to dissolve air into liquid, which is subsequently released through a specially designed nozzle system, to nucleate small bubbles as potentially nanobubbles, based on the cavitation principle. These bubbles subsequently grow into much larger bubbles through the rapid dissolution of the supersaturated liquid. The second class uses power ultrasound to induce cavitation locally at points of extreme rarefaction in the standing ultrasonic waves. The third class uses an air stream delivered under low offset pressure, and airs to break off the bubbles due to an additional feature, whether it be mechanical vibration, or flow focussing, or fluidic oscillation. Conventional air diffusers rely on the structure of porous material for the nozzles to generate small bubbles, but fluidic oscillation in general promises to break off the forming bubble while it is still a hemispherical cap - the smallest shape for which bubble formation from a pore is likely to occur given the strong adverse affect of surface tension at higher curvatures. The first two classes of microbubble generation are usually associated with high power densities and power consumption by either the compression or ultrasonic treatment. The third class should have the lowest power consumption, provided it achieves the application targets of bubble size distribution, air phase holdup, and bubble dispersion. In this paper, recent patents in microbubble generation are categorized into the first and the third classes above. The subject area is reviewed for its importance in several fields of application, particularly generalized flotation processes and bioreactor treatments.

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Enzyme Immobilization in Biotechnology
Cynthia Spahn and Shelley D. Minteer

Enzymes are proteins that catalyze chemical reactions. Unlike more traditional organic and inorganic catalysts, enzymes are large and fragile molecules, so over the years, scientists and engineers have found it more difficult to immobilize enzyme catalysts on easily separateable supports for use and re-use in a variety of technologies. Over the last decade, enzyme immobilization has become more important in industry, medicine, and biotechnology. This review will detail recent patents for techniques for enzyme immobilization, along with patents for chemical and biotechnological processes that can employ immobilized enzymes, which allow for the re-use of the enzymatic catalysts. These techniques include methods varying from physical adsorption and covalent attachment to entrapment in polymers and sol-gels. These techniques have shown value in the development of biosensors, bioprocessing for the chemical industry and the pharmaceutical industry, and bioremediation.

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Precipitation Processes with Supercritical Fluids: Patents Review
Maria J. Cocero and Angel Martin

Supercritical fluid techniques for materials precipitation have been proposed as an alternative to conventional precipitation processes as they can improve the performance of these processes in terms of reduction of particle size and control of morphology and particle size distribution, without degradation or contamination of the product. These techniques have received much attention during the last years, and their feasibility and performance have been proved for many substances. Several precipitation technologies, in which the supercritical fluid plays different roles (solvent, anti solvent, co solvent, solute, atomization agent … ) have been developed. This article presents a review of the patents related to supercritical precipitation technologies, with emphasis on the description of the different precipitation methods and mechanisms exploited by these technologies, and on the technical solutions given for the practical problems of the technologies.