Mesoporous 4A zeolum and preparation method thereof

Abstract

The invention relates to a mesoporous 4A zeolum and a preparation method thereof, belonging to the preparation fields of inorganic materials and ion exchangers, in particular to a mesoporous 4A zeolum containing 3-8nm mesopores in zeolum crystal particles and a preparation method thereof, wherein the mesopores can boost the cation exchange speed of the zeolum. The preparation method comprises thefollowing steps: firstly, carrying out surface silanization on nano silica with organic silane coupling agent; taking the nano silica subjected to the surface silanization as a silicon source; addingsodium aluminate, sodium hydroxide and deionized water; and carrying out crystallization synthesis on the mixture under the hydrothermal condition. The porosity of the mesopores in the zeolum crystalcan be regulated through changing the burdening ratio of the organic silane coupling agent to the silica. The mesopores can effectively shorten the diffusion paths of diffused molecules or ions in the micropores of the zeolum and reduce the diffusion resistance, thereby accelerating the exchange speed of cations especially larger hydrated cations and sodions in the zeolum. The preparation method is simple and is easy to control.

Description

technical field [0001] The mesoporous 4A zeolite and the preparation method thereof of the invention belong to the field of preparation of inorganic materials and ion exchangers. Specifically, it relates to a mesoporous 4A zeolite which contains both micropores and mesopores in the zeolite grains, and thus has a higher cation exchange rate than single microporous zeolite and a preparation method thereof. Background technique [0002] Since the 1990s, countries around the world have banned the application of phosphorus-containing additives in synthetic detergents. This is because although sodium tripolyphosphate is used as a detergent additive, it can interact with Ca in water. 2+ , Mg 2+ Ions form water-soluble chelates to cover these ions to achieve the purpose of softening water, but the discharge of a large amount of phosphorus-containing wastewater will cause the deterioration of the quality of rivers, lakes and seas. Among them, zeolite, as an environmentally friendly...

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Problems solved by technology

But, there is certain defect when 4A zeolite is used as detergent builder, and this is because the pore diameter of the micropore in 4A zeolite crystal is less, although can reduce the calcium ion content in water by ion exchange preferably, but to the magnesium ion in water exchange is subject to certain restrictions

This is due to the high charge density of magnesium ions, which easily generate large hydrated ions in water, which hinders their diffusion in the pores of 4A zeolite, resulting in low magnesium ion exchange efficiency.

The same reason also limits the application of 4A zeolite in other industries, such as hard water softening, wastewater treatment containing magnesium ions, etc.

[0004] The low-silicon X-type zeolite with the same silicon-aluminum ratio has a larger micropore diameter than 4A zeolite, which makes it easier to diffuse the hydrated magnesium ions with a larger radius in the micropores, but the preparation of low-silicon X-type zeolite The cost is much higher than 4A zeolite

Reducing the size of zeolite crystal grains can increase the ion exchange rate of zeolite. However, some methods of synthesizing small crystal zeolites require very dilute synthetic gels, which reduces the batch yield during the synthesis process and increases the preparation cost; At the same time, too small particles make solid-liquid separation more difficult and the storage volume becomes larger

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