[Application of IR spectra to the study of comprehensive utilization of fly ash]

Infrared (IR) spectra were used to study the fly ash both before and after having been treated by using sodium carbonate at 860 degrees C for 1.5 h. The IR results show that fly ash is composed of mullite and silica, which change into nepheline after being heated with sodium carbonate. According to these IR curves, different sodium carbonate amount makes the products different. For example, as fly ash:sodium carbonate > 1.2:1, the product is mainly nepheline with some mullite left. However, when increasing the use of sodium carbonate to the range of fly ash:sodium carbonate < 1.2:1, the mullite phase disappears, while some sodium carbonate remains; and the structure of nepheline has little change. So the authors choose fly ash:sodium carbonate = 1.2:1 as the best choice of the sodium carbonate amount factor. X-ray diffraction (XRD) analysis results of the same sample came to the same conclusion.