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Acid leaching technology for post-consumer gypsum purification

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posted on 2024-02-09, 15:22 authored by Miguel Castro-DiazMiguel Castro-Diaz, Mohamed OsmaniMohamed Osmani, Sergio Pialarissi-CavalaroSergio Pialarissi-Cavalaro, Paul Needham, Bill Parker, Tatiana Lovato

Background: Contaminants and water-soluble salts present in mechanically recycled gypsum from refurbishment and demolition (post-consumer) plasterboard waste limit its use as a secondary raw material in plasterboard manufacturing.  This research addresses this limitation, developing a novel acid leaching purification technology combined with an improved mechanical pre-treatment for post-consumer gypsum valorization.  

Methods: Laboratory-scale acid leaching purification was performed with a borosilicate beaker, hot plate, and overhead stirrer.  Stuccos were produced after calcination of gypsum at 150 °C for 3 hours.  Samples were characterized through X-ray fluorescence, X-ray diffraction, thermal gravimetric analysis, scanning electron microscopy and particle size analysis.  

Results: Acid leaching at 90 °C for 1 h using a 5 wt% sulfuric acid solution was revealed to be the optimum purification conditions.  Stuccos produced from purified gypsum under optimum conditions had similar initial setting times to that of a commercial stucco but with higher water demand, which could be reduced by optimizing the calcination conditions.  A magnesium-rich gypsum was precipitated from the wastewater.

Conclusions: Purified post-consumer gypsum with > 96 wt% chemical purity and calcium sulfate dihydrate content was produced.  The research recommends acid neutralization prior filtration, use of gypsum particles < 2 mm in size, and stirring speed of 50 rpm to reduce the economic and environmental impacts of the acid leaching purification process at industrial scale.  The magnesium-rich gypsum could potentially be marketed as soil fertilizer.

Funding

Innovative Circular Economy Based solutions demonstrating the Efficient recovery of valuable material Resources from the Generation of representative End-of-Life building materials

European Commission

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History

School

  • Architecture, Building and Civil Engineering

Published in

Open Research Europe

Volume

3

Publisher

F1000 Research Ltd

Version

  • VoR (Version of Record)

Rights holder

© Castro-Diaz M et al.

Publisher statement

This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Publication date

2023-09-15

Copyright date

2023

eISSN

2732-5121

Language

  • en

Depositor

Prof Mohamed Osmani. Deposit date: 12 October 2023

Article number

148

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