One of the main challenges in recycling gypsum from refurbishment plasterboard waste for
the production of new plasterboards comes from the difficulty to achieve consistent purity values higher
than 92 wt% via current treatment technologies. These treatments generally rely solely on magnetic and
manual physical separation combined with grinding. Although gypsum purity values ranging from 75 wt%
to 90 wt% can be achieved, this depends mainly on the quality of the refurbishment plasterboard waste
received, as current treatments have limited efficiency and customisation possibilities. As a result, the
highest practical rate of recycled gypsum in new plasterboards is currently around 20 wt%. Therefore,
physical and chemical treatments have the potential to increase the content of recycled gypsum in new
plasterboards. As part of the ICEBERG project from the European Union's Horizon 2020 Research and
Innovation Framework Programme under grant agreement No. 869336, hydrocyclone separation and
acid purification have been evaluated in this work to achieve purity values above 96 wt% in gypsum from
refurbishment plasterboard waste. The plasterboards were crushed and sieved to obtain gypsum
particles less than 250 µm in size. For hydrocyclone separation testing, a centrifugal pump was used to
produce a gypsum slurry in a mixing tank and to feed the slurry to a commercial mini-hydrocyclone of 2
inches in diameter. Acid leaching was performed at atmospheric pressure on the initial waste gypsum
and on a sample collected at the hydrocyclone, using different temperatures, residence times and
sulphuric acid solutions. The purity of gypsum obtained from individual and sequential hydrocyclone
separation and acid leaching tests was determined through X-ray fluorescence. Furthermore, the
calcination behaviour dihydrate phase content of the sample with the highest purity was determined
through thermal gravimetric analysis. Hydrocyclone separation was not effective for gypsum purification
but acid leaching at 90 °C for 1 hour using a 5 wt% H2SO4 solution produced recycled gypsum with more
than 96 wt% chemical purity and dihydrate content.
Funding
European Union's Horizon 2020 research and innovation programme under grant agreement No 869336
History
School
Architecture, Building and Civil Engineering
Published in
Proceedings Sardinia 2021. 18th International Waste Management and Landfill Symposium
Source
18th International Symposium on Waste Management and Sustainable Landfilling