Evaluation of novel reactive MgO activated slag binder for the immobilisation of lead and zinc

Jin, Fei ORCID: https://orcid.org/0000-0003-0899-7063 and Al-Tabbaa, Abir 2014. Evaluation of novel reactive MgO activated slag binder for the immobilisation of lead and zinc. Chemosphere 117 , pp. 285-294. 10.1016/j.chemosphere.2014.07.027

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Abstract

Although Portland cement is the most widely used binder in the stabilisation/solidification (S/S) processes, slag-based binders have gained significant attention recently due to their economic and environmental merits. In the present study, a novel binder, reactive MgO activated slag, is compared with hydrated lime activated slag in the immobilisation of lead and zinc. A series of lead or zinc-doped pastes and mortars were prepared with metal to binder ratio from 0.25% to 1%. The hydration products and microstructure were studied by X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The major hydration products were calcium silicate hydrate and hydrotalcite-like phases. The unconfined compressive strength was measured up to 160 d. Findings show that lead had a slight influence on the strength of MgO-slag paste while zinc reduced the strength significantly as its concentration increased. Leachate results using the TCLP tests revealed that the immobilisation degree was dependent on the pH and reactive MgO activated slag showed an increased pH buffering capacity, and thus improved the immobilisation efficiency compared to lime activated slag. It was proposed that zinc was mainly immobilised within the structure of the hydrotalcite-like phases or in the form of calcium zincate, while lead was primarily precipitated as the hydroxide. It is concluded, therefore, that reactive MgO activated slag can serve as clinker-free alternative binder in the S/S process.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Engineering
Publisher:	Elsevier
ISSN:	0045-6535
Date of Acceptance:	3 July 2014
Last Modified:	07 Nov 2022 10:46
URI:	https://orca.cardiff.ac.uk/id/eprint/133505

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