Optimization of pore structure of a clayey diatomite

Abstract

Low-grade, clayey diatomite occurs around the world as a large source of diatom material. The clayey diatomite used in this study consists predominantly of cyclotella diatoms. Their skeletons are coated with impurities of mostly clays, making it difficult to detach and separate. In our experiments, we used hydraulic dispersion and ultrasonic cavitation methods under certain solid:liquid ratios and pH conditions to detach and separate the clays from the diatomite to prepare high-grade diatom concentrate. The concentrate subsequently went through calcination (optimized at 580 °C) and ultrasonic cavitation to enhance its contents of silica from 83 to 90% (wt.) and of amorphous silica from 62.73 to 73.74% (wt.), volume average particle diameter from 7.93 to 6.0 μm, D₉₇ from 17.32 to 6.93 μm, and specific surface area from 92.51 to 111.53 m²/g, while effectively reducing contents of Al₂O₃ and Fe₂O₃, optimizing diatom pore structures, and obtaining favorable distribution of particle and pore sizes. The experiments provide an effective separation and refinement protocol for manufacturing high-grade diatom concentrate from low-grade clayey diatomite by optimizing its pore structure and other properties. The high-grade diatom concentrate can be used in chemical engineering, environmental, and construction materials such as filters, adsorbents, and catalytic carriers.

Keywords:

• Clayey diatomite
• diatom concentrate
• pore structure
• refinement
• optimization

Acknowledgments

We thank two anonymous reviewers for their constructive comments and suggestions that help improve the original manuscript.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China under Grants No. 51564008 and No. 41662005; and Guangxi Natural Science Foundation under Grant No. 0542012.