# Improving Recovery of Diatoms Bio-Silica Using Chemical Treatment with VAUS TM

## TL;DR

This study introduces a new chemical method using VAUS™ to efficiently and biocompatibly remove organic matter from diatoms, improving bio-silica recovery.

## Contribution

A novel chemical treatment using VAUS™ is proposed for efficient and biocompatible removal of organic matter from diatoms.

## Key findings

- TOC removal efficiency was highest at 35kHz frequency using VAUS™.
- XRD analysis showed NaOCl effectively removed organic matter compared to high-temperature baking.
- EDS analysis revealed significant differences in C and Si elements with varying frequencies.

## Abstract

High-temperature baking is a typical method to remove organic matter from diatoms, but it’s not suitable for bio-silica because of the high crystallinity. This study provides a method using the VAUS™ to remove organic matter from diatoms more quickly and biocompatibly. Organic matter was removed by using VAUS™, while NaOCl was utilized to remove the organic matter from the silicate frustule. The optimal frequency for organic matter removal was investigated to domestically produced M. nummuloides. The removal efficiency of TOC/TN was calculated and analyzed. The C and Si elements were analyzed in EDS, while visual confirmation of organic matter removal was analyzed by using XRD. TOC RE% at a frequency of 35kHz exhibited the highest value, indicating a statistically significant difference. XRD analysis demonstrated that the organic matter was almost removed using NaOCl compared to the high-temperature baked M. nummuloides. In the EDS analysis, there were significant differences in the C and Si elements with respect to frequency. This is very similar to the values from the positive control group, high-temperature baked M. nummuloides. This new procedure of applying periodic negative pressure to NaOCl pre-treatment is considered to be an effective method of chemically removing organic matter from diatoms.