Laboratory evaluation of acid leaching conditions to purify gypsum from refurbishment plasterboard waste

This work presents results related to a novel recycling process for gypsum from refurbishment plasterboard waste developed within the European Union’s Horizon 2020 research project ICEBERG. 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 chemical purity levels > 92 wt% via current physical treatment technologies. The main objective of this work is to evaluate different acid leaching conditions to maximise the acid leaching process efficiency. The impact of gypsum particle size, gypsum/solution ratio, heating rate, stirring rate and gypsum slurry volume on the chemical purity of recycled gypsum was determined. Gypsum particles sizes < 250 µm, slow heating rate of 4 °C/min and stirring rates of 150 rpm produced recycled gypsum with the highest purity. This work has identified for the first time the optimum laboratory-scale acid leaching conditions to produce high purity recycled gypsum from refurbishment plasterboard waste.