393 research outputs found

    Solvent resistant microporous/nanoporous polymeric hollow fiber and flat film membranes and their applications

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    The separation and purification of organic-solvent-based process streams may be carried out by membrane processes such as nanofiltration/ultrafiltration/microfiltration and membrane solvent extraction. Lack of solvent stability and chemical stability of most commercially available membranes is limiting the utilization of the above mentioned membrane technologies. This dissertation was primarily focused on developing solvent resistant hollow fiber and flat film membranes for separation and purification of organic-solvent-based process streams. Available porous polymeric supports (Polypropylene (PP), Polyethersulfone (PES) and Nylon) suitable for the required solvent-stable applications were chosen first and then the supports were modified to satisfy the requirements for the applications. Membrane modification techniques employed were interfacial polymerization (IP) and poly(ethyleneimine) (PEI) self crosslinking. Thin film composite (TFC) nanofiltration and ultrafiltration membranes were fabricated on PBS, Nylon and hydrophilized PP support membranes. Before carrying out IP, PP was hydrophilized by pre-wetting with acetone and treating with hot chromic acid solution. The introduced procedure of “modified IP” involved wetting next with the aqueous monomer solution followed by the organic monomer solution. Nanofiltration membranes were characterized using solutes, safranin 0 (MW 351) and brilliant blue R (MW 826) dyes in methanol; ultrafiltration membranes were characterized with a 70% alcoholic solution of zein (MW 35,000). These membranes were also studied for long term solvent stability in ethanol and toluene. The membrane based on PP was first hydrophilized by the techniques of “modified [P” and PHI self crosslinking. For possible applications in microfiltration of aqueous systems, these hydrophilized membranes were characterized by the water permeation rate. Crosslinking of PHI was implemented on the lumen side of the Nylon hollow fibers to reduce the pore size; then, their performance in membrane solvent back extraction was studied. Extraction of phenol from MIBK into an aqueous caustic solution was studied as a model system for reactive back extraction; extraction of acetic acid from MIBK into water was studied as a model system for nonreactive back extraction. Hollow fibers of PBS were coated on the lumen side by IP. The IP layer was again coated with silicone to make the IP coating impervious to water. The coated PES fibers were then tested for heat transfer performance. All modified membranes were also characterized using scanning electron microscopy. Thin film composite nanofiltration and ultrafiltration membranes were successfully fabricated on PP and PBS hollow fiber supports; high rejections of solutes and high solvent fluxes were achieved in UF and NT membranes. However, only the PP-based TFC membranes retained their characteristics after solvent exposure for the studied period of time. Permanent hydrophilization of PP was achieved by the “modified IP procedure. Reduced pores on the lumen side of Nylon hollow fibers provided stable aqueous-organic interface for solute transport in membrane solvent back extraction; the coating improved the extraction performance of the membranes. Better heat transfer performance was achieved in the coated PBS hollow fibers when compared with the nonporous PP hollow fibers

    Krasovskii's Passivity

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    In this paper we introduce a new notion of passivity which we call Krasovskii's passivity and provide a sufficient condition for a system to be Krasovskii's passive. Based on this condition, we investigate classes of port-Hamiltonian and gradient systems which are Krasovskii's passive. Moreover, we provide a new interconnection based control technique based on Krasovskii's passivity. Our proposed control technique can be used even in the case when it is not clear how to construct the standard passivity based controller, which is demonstrated by examples of a Boost converter and a parallel RLC circuit

    A review of the importance of recycling lithium-ion batteries for lithium, in view of impending electric vehicle industry

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    Automobile electrification is one the technological developments, that will commence an earth friendly transport system, by mitigating emissions and hopefully lead to a less fossil fuel dependent society. With commercial success attained by models like Nissan’s leaf and Chevy’s Volt, the consumer market looks promising to assimilate vehicle electrification. At present these technologies include HEVs (hybrid electric vehicles), PHEVs (plug-in hybrid electric vehicles), EVs (complete electric vehicles). A closer look at these technologies will lead us to one of the crucial components of electric vehicles, the “batteries”. This component decides one of the key performance factors which is the energy storage and usage, which means it is the basis for public acceptability. The lithium-ion battery chemistries are chosen to fulfill this requirement. Although lithium constitutes of a small fraction of the complete battery weight, still its contin-ued availability in future is debated among many resource analysts
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