Discoloration of zeolite A powder is a common problem when natural raw materials such as kaolin clay are used because of the formation of colored iron compounds. In this study, we report on a novel method to produce zeolite A with excellent optical properties, from clays. The brightness is as high as 94.5 and the yellowness is as low as 3.0. The product is comprised of intergrown zeolite A crystals with cubic habit and a length ranging between 0.5 and 2 μm. Good optical properties are obtained when the raw material contains magnesium, as some natural raw materials do, or alternatively, when a magnesium compound is added to the raw material. Magnesium probably forces iron inside colorless extraneous magnesium aluminosilicate compounds. This simple process appears very promising for the preparation of zeolite A with good optical properties from inexpensive natural raw materials.
Bibliographical noteFunding Information:
The financial support by the Swedish Institute in the SIDA Program is acknowledged. Financial support from Bio4energy is also acknowledged. The authors also wish to thank The Knut and Alice Wallenberg Foundation for financial support with the Magellan SEM instrument.
© 2014 Elsevier B.V. All rights reserved.
- Amorphous material
- Chemical synthesis
- Optical properties
- Oxide materials
- Scanning electron microscopy