Preparation of Xonotlite Nano-Fibres Using the Silica Source from Coal Fly Ash and Ca(OH)₂

E-ISSN： 1662-9795|2014|633|7-10

ISSN： 1013-9826

Source： Key Engineering Materials, Vol.2014, Iss.633, 2015-02, pp. : 7-10

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Abstract

Extracting aluminum oxide from high-alumina coal fly ash are significant to make up for the inadequacy of bauxite resource in China. How to comprehensively utilize silica components in coal fly ash is a key technical question in industrialization for extracting of alumina from coal fly ash. Desilication of coal fly ash (CFA) and preparation of xonotlite were studied using the silica-rich solution from the CFA as silica source and calcium oxide as calcium source respectively. The CFA is from a power plant at Shizuishan city in Ningxia, China. Xonotlite was successfully prepared by a series processes including predesilication, hydro-thermal synthesis. The experimental results indicated that SiO₂ in the coal fly ash changed into NaSiO₃ after the coal fly ash was treated by desilication using NaOH solution. Hydrated calcium silicate was obtained from the reaction of the solutions produced by desilication and Ca (OH)₂ at the condition of Ca/Si (mol)=1, T=160°Cand t=1h. Xonotlite was synthesized by the hydrated calcium silicate using the hydrothermal temperature of 260°C for 2 hours. Keywords: Coal Fly Ash, Pre-desilication, alkali Hydrothermally-treated, Xonotlite nanofibres