Zeolitization of mineral wastes by molten-salt method:: NaOH-KNO3 system

Salt-thermal method exhibits several features such as high production yield, large-scale conversion, low elemental loss, and environmentally benign nature. This study has investigated the optimization of the NaOH-KNO3 system for the zeolitization of fly ash and elucidated the characteristics of the resulting zeolitic materials. The following are the optimal reaction conditions for zeolitization of fly ash in NaOH-KNO3 system: a temperature of 250 degrees C, 0.3- 0.5 weight ratio of NaOH/KNO3 and 0.7-1.4 weight ratio of KNO3/fly ash. The NaOH-KNO3 system is also confirmed for facile zeolitization of anthracite briquette, kaolinite, and pumice. The NaOH-KNO3 system is likely to result in KNO3 occlusion or/and trapping. Because KNO3 supplies two plant nutrients, the zeolitic materials synthesized by the NaOH-KNO3 system could be used in agriculture as soil conditioners and fertilizer additives. It is clearly shown in this study that KNO3 could be employed in place of NaNO3 in the salt-thermal method with a potential use of the product as soil conditioner and fertilizer.