Study on the extracted process of mullite from coal fly ash by-product sodium silicate

Abstract

The mullite was directly extracted from coal fly ash through removing iron and silica without sintering process by-product sodium silicate. The effect of processing parameters on the leaching rate of iron and silica was investigated. The physical properties, phase composition and microstructure of the mullite extracted from the original fly ash were characterized by using X-ray fluorescence spectrometer, X-ray diffractometer, fourier transform infrared spectroscopy, scanning electronic microscope and energy dispersive spectroscope. The technical indicators of sodium silicate were also tested. The results show that the maximum iron extraction reaches 85.9 mass % when firstly with a magnetic separation process then leaching with 20 mass % of hydrochloric acid solution at 85°C for 3 h. The 40.4 mass % leaching rate of silica was presented after leaching with 25 mass % of sodium hydroxide at 95°C for 4.5 h. As a result, the beneficiated extracted sample exhibited a mullite content of 82 mass %, the corundum content of 18 mass %. This method provides a potential way on the utilization of coal fly ash to prepare mullite.