Vitrification of blast furnace slag and fluorite tailings for giving diopside-fluorapatite glass-ceramics

doi:10.1016/j.matlet.2018.02.020

Materials Letters

Volume 218, 1 May 2018, Pages 309-312

https://doi.org/10.1016/j.matlet.2018.02.020 Get rights and content

Highlights

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Blast furnace slag and fluorite tailings were vitrified into fluorapatite based glass-ceramics.
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The addition of fluorite tailings will bring the enhancement of crystallization.
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Needle-like fluorapatite with interlocked structure enhances the physical properties.

Abstract

The feasibility of the preparation of diopside-fluorapatite based glass-ceramics from blast furnace slag and fluorite tailings was investigated. The results showed that the crystallization of parent glass was strongly dependent on its initial composition of raw materials. With low content of fluorite tailings, the only crystallization product was fluorapatite (Ca₅(PO₄)₃F). Further increase of fluorite tailings will bring the enhancement of crystallization, resulting in the formation of diopside phase (Ca(Mg,Al)(Si,Al)₂O₆). The diopside-fluorapatite based glass-ceramics with Vickers hardness of 7.36 GPa could be obtained from raw materials with a composition of 40 mass% blast furnace slag and 60 mass% fluorite tailings.

Introduction

Blast furnace slag (BFS) is a major by-product generated during pig iron production. The conversion of BFS into glass-ceramics has dual advantages of the minimization of waste and economical interest [1], [2], [3], [4]. Quartz sand, clay [2], kaolin [3] and pure silica [4] were chosen as proper supplements for BFS during the glass-ceramics preparation due to their relatively higher content of SiO₂. Fluorite tailings (FT) is an industrial waste generated from the flotation process of fluorite ore. The improper disposal would cause potential metallic and fluorine contamination to the water and soil [5]. The utilization of fluorite tailings and blast furnace slag as raw materials for glass-ceramic formation would be of great interest to the potential industrial application. In addition, considering high content of SiO₂ and CaF₂ in FT, the former component would be expected to be favored for diopside formation by adjusting CaO/SiO₂ ratio in the glass network [6], and the latter has been proven to be effective for the crystallization by reducing the viscosity of the crystallizing glass [7], [8], [9].

The fluorapatite based glass-ceramics are known as potential candidates for bioremediation and optoelectronics applications due to its excellent bioactive and mechanical properties [10], [11], [12], [13], [14]. In this research, we employed P₂O₅ into two different types of wastes, i.e. BFS, FT, to investigate the feasibility of the formation of diopside-fluorapatite based glass-ceramics in the (CaF₂-P₂O₅)-CaO-MgO-Al₂O₃-SiO₂ system. The influence of initial composition of raw materials on the crystallographic and microstructure evolution during the heat treatment will be studied in detail.

Section snippets

Experimental method

The blast furnace slag powder (Iron & Steel Company, Shandong Province, China) and the fluorite tailings (Jiangxi Province, China) were used as starting materials for parent glass formation. With respect to the selected basic composition of parent glasses (100%), additional 3 wt% P₂O₅ was incorporated. The corresponding chemical compositions of different batches are summarized in Table 1.

The raw materials were mixed by a planet ball milling with a speed of 120 rpm for 6 h. Then the mixtures

Crystallization behavior of parent glasses

The glass stability of five batches with particles sizes below 75 um were evaluated by DSC tests. As shown in Fig. 1, the endothermic peaks associated with glass transition temperatures (T_g) were observed between 647 and 674 °C. The sample F₅ has the lowest value maybe attributed to its highest fluorine content among five batches. The exothermic peak of crystallization (T_c) was detected in the temperature range of 930–981 °C. According to the literatures [6], [9], [15], the increase of fluorine

Conclusions

With the introduction of fluorite tailings into blast furnace slag, the increase of silica and CaF₂ in the parent glass brought better crystallization and diopside phase formation were induced. With respect to thermal behavior of glass, heat treatment of glass with the composition of 40 wt% of blast furnace slag and 60 wt% of fluorite tailings resulted in well sintered glass-ceramics with diopside and fluorapatite as the main crystalline phases. The obtained glass-ceramics showed its density of

Acknowledgements

The Project is supported by National Natural Science Foundation of China (No. 51574169, 51704202 and 51604178). The authors also thank for analysis support from Soochow University.

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Vitrification of blast furnace slag and fluorite tailings for giving diopside-fluorapatite glass-ceramics

Highlights

Abstract

Introduction

Section snippets

Experimental method

Crystallization behavior of parent glasses

Conclusions

Acknowledgements

J. Eur. Ceram. Soc.

J. Non-Cryst. Solids

Ceram. Int.

Mater. Des.

Ceram. Int.

Ceram. Int.

J. Eur. Ceram. Soc.

Acta Biomater.

J. Eur. Ceram. Soc.