Effect of the pH value of seed coating solution on microstructure of silicalite-1 zeolite separation layer grown on α-alumina support

Hu, Sigui, Kim, Min-Zy, Lee, Du-Hyoung, Sharma, Pankaj ORCID: https://orcid.org/0000-0003-2319-260X, Han, Moon-Hee and Cho, Churl-Hee 2015. Effect of the pH value of seed coating solution on microstructure of silicalite-1 zeolite separation layer grown on α-alumina support. Membrane Journal 25 (5) , pp. 422-430. 10.14579/MEMBRANE_JOURNAL.2015.25.5.422

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Abstract

The present study announces that the pH value of seed coating solution makes a significant effect on the microstructure of silicalite-1 zeolite layer formed on α-alumina support. Seed with an average diameter of 75 nm was dispersed in ethanol to prepare three kinds of seed coating solutions with different pH values, and dip-coated on the support. The pH value was controlled to be 2.2, 7.0, and 9.3, respectively. In the secondary growth process, pH 7 seed solution resulted an uniform, 3 to 4 μm thick, completely covered, and 100 nm grained silicalite-1 zeolite separation layer. The uniformity and completeness were explained by a uniform, closely packed, multi-layered, and completely covered seed coating in the pH 7 condition. In the condition, α-alumina support and seed are oppositely charged: support is positively charged (8.4 mV) and seed, negatively (-1.7 mV). The opposite charging induced a strong electrostatic attraction between seed and support, which made the good seed coating state. On the other hand, pH 2.2 and pH 9.3 seed solutions resulted non-uniform, partially covered, and around 1μm grained zeolite separation layer, since seed and support are the same sign charged in the conditions. The same sign charging induced a strong electrostatic repulsion between seed and support which caused a low coverage of seed. It could be concluded that the pH value of seed coating solution is a key parameter to determine the microstructure of silicalite-1 zeolite separation layer.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry Cardiff Catalysis Institute (CCI)
ISSN:	1226-0088
Date of Acceptance:	23 October 2015
Last Modified:	15 Nov 2022 13:30
URI:	https://orca.cardiff.ac.uk/id/eprint/153547

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