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- Volume 3, 2012
Annual Review of Chemical and Biomolecular Engineering - Volume 3, 2012
Volume 3, 2012
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Transport Phenomena in Chaotic Laminar Flows
Vol. 3 (2012), pp. 473–496More LessIn many important chemical processes, the laminar flow regime is inescapable and defines the performance of reactors, separators, and analytical instruments. In the emerging field of microchemical process or lab-on-a-chip, this constraint is particularly rigid. Here, we review developments in the use of chaotic laminar flows to improve common transport processes in this regime. We focus on four: mixing, interfacial transfer, axial dispersion, and spatial sampling. Our coverage demonstrates the potential for chaos to improve these processes if implemented appropriately. Throughout, we emphasize the usefulness of familiar theoretical models of transport for processes occurring in chaotic flows. Finally, we point out open challenges and opportunities in the field.
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Sustainable Engineered Processes to Mitigate the Global Arsenic Crisis in Drinking Water: Challenges and Progress
Vol. 3 (2012), pp. 497–517More LessMillions of people around the world are currently living under the threat of developing serious health problems owing to ingestion of dangerous concentrations of arsenic through their drinking water. In many places, treatment of arsenic-contaminated water is an urgent necessity owing to a lack of safe alternative sources. Sustainable production of arsenic-safe water from an arsenic-contaminated raw water source is currently a challenge. Despite the successful development in the laboratory of technologies for arsenic remediation, few have been successful in the field. A sustainable arsenic-remediation technology should be robust, composed of local resources, and user-friendly as well as must attach special consideration to the social, economic, cultural, traditional, and environmental aspects of the target community. One such technology is in operation on the Indian subcontinent. Wide-scale replication of this technology with adequate improvisation can solve the arsenic crisis prevalent in the developing world.
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Complex Fluid-Fluid Interfaces: Rheology and Structure
Vol. 3 (2012), pp. 519–543More LessComplex fluid-fluid interfaces are common to living systems, foods, personal products, and the environment. They occur wherever surface-active molecules and particles collect at fluid interfaces and render them nonlinear in their response to flow and deformation. When this occurs, the interfaces acquire a complex microstructure that must be interrogated. Interfacial rheological material properties must be measured to appreciate their role in such varied processes as lung function, cell division, and foam and emulsion stability. This review presents the methods that have been devised to determine the microstructure of complex fluid-fluid interfaces. Complex interfacial microstructure leads to rheological complexity. This behavior is often responsible for stabilizing interfacial systems such as foams and emulsions, and it can also have a profound influence on wetting/dewetting dynamics. Interfacial rheological characterization relies on the development of tools with the sensitivity to respond to small surface stresses in a way that isolates them from bulk stresses. This development is relatively recent, and reviews of methods for both shear and dilatational measurements are offered here.
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Atomically Dispersed Supported Metal Catalysts
Vol. 3 (2012), pp. 545–574More LessOur aim in this review is to assess key recent findings that point to atomically dispersed noble metals as catalytic sites on solid supports, which may be viewed as ligands bonded to the metal. Both zeolites and open metal oxide supports are considered; the former offer the advantages of uniform, crystalline structures to facilitate fundamental understanding, and the latter offer numerous advantages in applications. The notion of strong interactions between metals and supports has resurfaced in the recent literature to explain how subnanometer clusters and even atoms of noble metals such as platinum and gold survive under often harsh reaction conditions on some supports, such as ceria and perovskites. Individual cations of platinum, palladium, rhodium, or other metals anchored to supports through M–O bonds can be formed on these supports in configurations that are stable and catalytically active for several reactions illustrated here, notably, oxidation and reduction. The development of effective synthesis methods and the identification of suitable stabilizers and promoters are expected to lead to the increasing application of atomically dispersed noble metal catalysts for practical processes characterized by efficient resource utilization and cost savings.
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