Browsing by Author "Lee, Kueir-Rarn"

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Fabrication of hydrothermally reduced graphene oxide/chitosan composite membranes with a lamellar structure on methanol dehydration
(2017-06-01)
Hung, Wei-Song
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Chang, Sue-Mm
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Lecaros, Rumwald Leo G.
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Ji, Yan-Li
;
An, Quan-Fu
Reduced graphene oxide (rGO) has been prepared through hydrothermal reduction, an environmentally safe reduction of graphene oxide (GO). rGO is used to fabricate a highly compatible and orderly stacked lamellar structure of composite membranes with chitosan (CS). This method also facilitates a continuous large-scale fabrication of membranes. Conventionally, GO and CS are the preferred compounds for this type of fabrication because of their hydrophilic nature. Nevertheless, when they are mixed together, the occurrence of ionic complexation (-COO-H3+N-R) between the negatively charged carboxylate ions of GO and the positively charged protonated amines of CS create extreme membrane aggregation. Hydrothermal reduction is useful for preventing undesired ionic complexation from mixing rGO and CS because it can remove most carboxylate ions from GO. Consequently, the hydrophilic CS molecular chain is inserted in between the rGO laminates, improving the dispersion and enabling the rGO/CS to stack-up and self-assemble into a lamellar structure. Furthermore, excellent methanol dehydration can be observed through pervaporation, which is attributed to the selective water channels formed in the rGO laminates. (C) 2017 Elsevier Ltd. All rights reserved.
Factors affecting phenol transfer through polydimethylsiloxane composite membrane
(2008-12-31)
Lee, Mao-Sung
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Huang, Chihpin
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Lee, Kueir-Rarn
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Pan, Jill R.
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Chang, Wang-Kuan
Polydimethylsiloxane composite membrane was employed for the separation of phenol and sodium chloride in synthetic wastewater. The major operational parameters affecting phenol transfer through this composite membrane were screened by the orthogonal array and range analysis. The results showed that the significance of parameters on the permeate flux followed the order of phenol concentration, membrane skin layer thickness, recirculation rate, and sodium chloride concentration after 6 and 48 h operations. Optimal operation range was determined by the response surface methodology coupled with central composite design. The higher was the phenol concentration in the influent or the thicker was the membrane skin layer thickness, the higher was the permeate flux through membrane. Also, the higher was the recirculation rate, the higher was the permeate flux through membrane.