Abstract
The fixation of heavy metals (Ba, Cu, Pb) in an alkali-activated matrix was investigated. The matrix consisted of fly ash and blast furnace slag (BFS). The mixture of NaOH and Na-silicate was used as alkaline activator. Three analytical techniques were used to describe the fixation of heavy metals—X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), and X-ray powder diffraction (XRD). All heavy metals formed insoluble salts after alkaline activation. Ba was fixed as BaSO4, and only this product was crystalline. EDS mapping showed that Ba was cumulated in some regions and formed clusters. Pb was present in the form of Pb(OH)2 and was dispersed throughout the matrix on the edges of BFS grains. Cu was fixed as Cu(OH)2 and also was cumulated in some regions and formed clusters. Cu was present in two different chemical states; apart from Cu(OH)2, a Cu–O bond was also identified.
Highlights
Heavy metals are a significant part of various industrial and chemical waste materials, which can be a serious environmental threat
The history of activated material (AAM) began in 1940s, when Kühl [3] and later Purdon [4] used an alkali activator for the activation of blast furnace slag
The aim of this study was to describe, how heavy metals (Ba, Pb, Cu) are fixed within the matrix based on the alkali-activated mixture of fly ash and blast furnace slag (BFS), what their chemical state is, and how they are distributed in the matrix
Summary
Heavy metals are a significant part of various industrial and chemical waste materials, which can be a serious environmental threat. Waste materials with heavy metal content are processed by the set of procedures called stabilization/solidification. During these procedures, many different materials such as concrete and glass are used. The history of AAMs began in 1940s, when Kühl [3] and later Purdon [4] used an alkali activator for the activation of blast furnace slag. AAMs include broad types of materials—blast furnace slag, metakaolin, fly ash, etc. AAMs can vary in chemical or phase composition, and an alkali activator (high pH) is always used during the preparation of them
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