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Acid leaching technology for post-consumer gypsum purification
Miguel Castro-Diaz1, Mohamed Osmani1, Sergio Cavalaro1
1Loughborough University, Loughborough, England, LE11 3TU, UK.
Open Research Europe
|February 19, 2024
Summary
This study developed an acid leaching purification method to recycle post-consumer gypsum waste into high-purity calcium sulfate dihydrate. The purified gypsum can be reused in plasterboard manufacturing, with a magnesium-rich byproduct suitable for soil fertilizer.
Area of Science:
- Materials Science
- Chemical Engineering
- Environmental Science
Background:
- Post-consumer gypsum waste from demolition contains contaminants and salts, hindering its reuse in plasterboard manufacturing.
- Mechanical recycling methods are insufficient to remove these impurities effectively.
- Valorization of this waste stream is crucial for sustainable construction practices.
Purpose of the Study:
- To develop and optimize an acid leaching purification technology for post-consumer gypsum.
- To improve mechanical pre-treatment for enhanced gypsum valorization.
- To assess the quality and potential applications of the purified gypsum and byproducts.
Main Methods:
- Laboratory-scale acid leaching purification using sulfuric acid at elevated temperatures.
- Calcination of purified gypsum to produce stucco.
- Characterization using X-ray fluorescence, X-ray diffraction, thermal gravimetric analysis, scanning electron microscopy, and particle size analysis.
Main Results:
- Optimal purification achieved with 5 wt% sulfuric acid at 90 °C for 1 hour.
- Purified gypsum yielded stucco with comparable setting times to commercial products, albeit with higher water demand.
- A magnesium-rich gypsum byproduct was successfully precipitated from the wastewater.
Conclusions:
- Achieved >96 wt% chemical purity and calcium sulfate dihydrate content in purified post-consumer gypsum.
- Recommendations for industrial scale-up include acid neutralization before filtration, using fine gypsum particles (<2 mm), and specific stirring speeds (50 rpm).
- The magnesium-rich byproduct shows potential as a soil fertilizer, adding economic value to the process.
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