Use of Spent Zeolite Sorbents for the Preparation of Lightweight Aggregates Differing in Microstructure

Wojciech Franus,Lidia Bandura,Grzegorz Jozefaciuk,Małgorzata Franus

doi:10.3390/min7020025

Wojciech Franus, Lidia Bandura + Show 2 more

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https://doi.org/10.3390/min7020025

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Abstract

Lightweight aggregates (LWAs) made by sintering beidellitic clay deposits at high temperatures, with and without the addition of spent zeolitic sorbents (clinoptilolitic tuff and Na-P1 made from fly ash) containing diesel oil, were investigated. Mineral composition of the aggregates determined by X-ray diffraction was highly uniformized in respect of the initial composition of the substrates. The microstructure of the LWAs, which were studied with a combination of mercury porosimetry, microtomography, nitrogen adsorption/desorption isotherms and scanning electron microscopy, was markedly modified by the spent zeolites, which diminished bulk densities, increased porosities and pore radii. The addition of zeolites decreased water absorption and the compressive strength of the LWAs. The spent Na-P1 had a greater effect on the LWAs’ structure than the clinoptilolite.

Highlights

Lightweight aggregates (LWAs) are building materials, produced from different minerals by rapid sintering/heating at high temperatures up to 1300 ◦ C [1]
Quanta 250 FEG microscope equipped with the energy dispersion scattering EDS-EDAX system for chemical composition analysis(FEI, Hilsboro, OR, USA)
The addition of spent zeolite sorbents increased the amount of the amorphous glassy phase in the LWAs, their mineral composition stayed intact, as evidenced by the X-raydiffraction diffraction (XRD) results

Summary

Introduction

Lightweight aggregates (LWAs) are building materials, produced from different minerals (including ordinary soil clay, perlite, vermiculite, and natural and synthetic zeolites) by rapid sintering/heating at high temperatures up to 1300 ◦ C [1]. Much effort has been recently invested to reuse different kinds of waste materials, in order to avoid their disposal in landfills and paying additional environmental taxes, as well as to reduce production costs [17,18] Many waste materials, such as combustion ashes [19], waste glass [15], sewage or industrial sludge [20,21,22,23], incinerator bottom ash [24], mining residues, heavy metal sludge, washing aggregate sludge [4], polishing residue, lignite coal fly ash [25,26], spent adsorbents [27,28]

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