In situ crystallization of CHA / FAU zeolites on volcanic stone in the absence of organic agents

Abstract

Japan has over 100 active volcanoes, which accounts for approximately 10% in the world. This paper discloses a novel way of utilizing volcanic stone. Microporous zeolites were crystallized on the macroporous volcanic stone by in situ crystallization method which is one-step soft hydrothermal treatment in NaOH solution with no additives. The volcanic stone has two roles in this method. One role is sources of SiO 2 , Al 2 O 3 , and alkali cations for crystallizing zeolites, and another role is a macroporous support of the zeolites. Each type of zeolite, CHA (0.38 nm pore) and FAU (0.74 nm pore), was mainly crystallized on the whole surface of the volcanic stone, which was controlled by adjusting concentration of NaOH solution. All the composite samples showed higher specific surface area than the raw volcanic stone. The highest value achieved in FAU zeolite sample was 439 m 2 /g which is as high as a commercial powdery zeolite. The adsorption abilities of the composite samples for ammonium ion measured by batch experiments were higher than the commercial powdery zeolite. • Zeolite-stone composites were prepared by in situ crystallization of volcanic stone. • Zeolites were precipitated without collapsing macroporous structure of the stone. • CHA-type zeolite was successfully crystallized in the absence of organic agents. • The highest surface area was 439 m 2 /g, as high as a commercial zeolite powder. • The samples showed higher adsorption abilities for NH 4 + than the commercial zeolite.