Efficient recycling of tin from waste products of PCB manufacturing

© Franz Wamhof

Tin is an important metal for producing soldering material for the electronics industry, for tin plate and for chemicals for the galvanizing industry and industrial catalysts. So called tin strippers are used in the production process to remove or “strip” superfluous tin layers from the printed circuit boards. These tin strippers are based on concentrated nitric acid as well as other additives. Up to 1,000 metric tonnes of tin stripper are used each year in Germany. Up to now, the spent tin strippers are usually disposed of as unutilized waste.

The “EZiRec” project wants to recycle the metal contained in these tin strippers. The focus here is on a hydrometallurgical process. The technological challenge is how to cleanly separate the tin and copper from the contaminated leaching solution containing nitrate. The process developed manages this step efficiently without compromising technological feasibility. The processed tin is sold to secondary smelters in Poland, Belgium or Spain that use a pyrometallurgical process to produce tin and copper of high purity from the hydrometallurgically pre-yielded materials.

Based on the results from the laboratory and field tests, the plant technology is being designed and constructed on the site of TIB Chemicals. The pilot is closely accompanied by laboratory work and analytics. The project’s objective is to develop a stable process able to deliver a continuously high quality product to secondary smelters even with variable sludge supplies. It should be able to recycle waste with high tin concentrations from a wide range of different industries, waste that is currently not or only poorly being processed in pyrometallurgical recycling processes. This means the technology will also be available to other users.