Milling tests with the Fritsch Planetary Ball Mill

Introduction

- Nanotechnology widely deals with nanoscale particle between 1-100 nm¹.
- Alternative definition of nano fertilizer (larger particle size): fertilizer which particle size is smaller than 500 mm and altered properties².
- Nanoparticles can be synthesized or produced by physical, chemical, biological and aerosol techniques. Physical synthesis methods include sedimentation processes, rotor speed mills, high energy ball mills and mixer mills.
- In general, phosphorus (P) nanoparticles are prepared by purifying rock phosphate and grinding them with a high energy ball mill or mixer mill smaller than 500 nm and altered properties².
- This report describes the experimental trial and results of mineral fertilizer grinding using FRITSCH premium line Planetary Mills (High Energy Ball Mills) to obtain nanosize particles.

Grinding tests of the fertilizer samples using Planetary Mills were conducted at the FRITSCH office and laboratory of the German Center in Singapore. Mr. Diels Ding as an expert in grinding processes, as well as Business Manager for Asia Pacific – Fritsch GmbH directly conducted the trials. He also provided informative insights and a meaningful discussion ensued about grinding and milling processes and nanomaterial. The samples were tested in dry and wet conditions for the milling process, with the following description:

* Table 2: Result of the grinding process of samples, photos and particle size distribution in the report for download.

1. Is it possible or not to grind the fertilizer samples and reach nano size particles less than (<) 100 nm? Yes, it’s possible, but this is challenging due the following:

• Several steps of milling processes are needed with various size of grinding balls (20 mm to 0.1 mm), it could take longer (several hours)
• Various particle size distributions, cannot be uniform in desired nano size; all or larger particle sizes may still exist in a significant percentage.
• Product recovery: after milling, the next challenge is the separation of the milled sample from the small grinding balls - (for large grinding balls it is easy, but for very small grinding balls* it could be difficult). *High consumption of very small grinding balls
• For nano size milling, this should be wet milling, therefore a proper solvent must be used, water cannot be utilized for every type of fertilizer and other solvents such as Iso-Propanol etc. could mean additional costs.