In this study, commercial kaolin from Kaolin (M) Bhd.
was used as the raw material for the synthesis of NaA zeolites. Kaolin was subjected to metakaolinization in order to produce a metakaolin. Later, the metakaolin was zeolitized, to produce NaA zeolites. Prior to use, the kaolin was treated with 2.5 % sodium hexametaphosphate. One kilogram of kaolin was treated with 5 L of distilled water containing 2.5 % of sodium hexametaphosphate. An IKA mechanical stirrer was used to homogenously stir the mixture at 4,000 rpm for 2 h.
After 1 h of settling time, the supernatant was taken out and dried in an oven for 72 h. The treated kaolin was converted to metakaolin by calcined at 900 °C for 2 h in a muffle furnace. In order to obtain the desired zeolite, an alkaline hydrothermal reaction was carried out on the treated zeolite. Sodium hydroxide 2.75 M was added to the metakaolin in the ratio of 13.3 mL NaOH/g metakaolin. The mixture was thoroughly mechanically stirred (200 rpm) at 70 °C for 2 h.
The mixture was left at 60 °C in the oven for 12 h for completion of the crystallization process. After that, the zeolite was separated by vacuum filtration and was dried at 105 °C for 24 h in the oven.