Sample Preparation of Electrical and Electronic Scrap

The objectives of the new EU Directives WEEE (Waste Electrical and Electronic Equipment) and RoHS (Restriction of Hazardous Substances) are the ecologically beneficial disposal of electrical and electronical devices (WEEE) resp. the restriction of the use of certain hazardous substances in these devices. Every manufacturer, seller, recycler and disposer of such products is affected by the new regulations.

They are now obliged to demonstrate through analytical determinations that the directives are being observed.

In this context, neutral-to-analysis sample preparation can pose a problem, as electrical and electronic waste is usually a heterogeneous mixture of metal, ceramics, plastics and composites. These materials have different breaking properties, therefore, it is necessary to carry out preliminary size reduction. For this, the RETSCH Heavy Duty Cutting Mill SM 2000 has proved to be particularly suitable as it can handle hard and ductile as well as soft-elastic materials. Up to 5 litres of sample material can be ground to a fineness < 6 mm. With the help of a sample divider, a representative sub-sample is taken from the pre-crushed material which can then be pulverized to analytical fineness.

The fine grinding of the sample down to 200 µm is carried out in the RETSCH Ultra-Centrifugal Mill ZM 200 which not only allows for short grinding times but is also gentle on the material. It is recommendable to use liquid nitrogen or dry ice as a grinding aid. This not only improves the breaking properties and avoids frictional heat but also ensures that volatile fractions are not adversely affected. Other RETSCH mills, such as the Vibratory Disc Mill RS 100 or the Planetary Ball Mill PM 100, are also suitable for fine grinding, depending on the breaking behaviour of the sample material.

When the sample is ground to a fineness of approximately 200 µm, it is ready for analysis as either the bulk sample or as a tablet (after processing in a tablet press such as the Retsch PP 25).