Production of kaolin for the paper-coating industry in the Brazilian Amazon region generates large amounts of waste, most of which is kaolinite. It is known that such materials can be used to synthesize zeolites. The use of kaolin waste for zeolite synthesis could, in principle, help social and economic development while providing valuable materials for industry. Additionally, there is a significant environmental appeal if such wastes could be used instead of new raw materials.
This study focused on the production of zeolite A. Samples of the raw material were first calcined (700°C/2h) to obtain metakaolinite for further reaction with NaOH solution. Different parameters were evaluated to optimize the synthesis conditions of zeolite A. The results showed that zeolite A with a large degree of structural order was generally obtained as the only zeolitic product. The following synthesis conditions were used: temperature 110°C, time 24 h and a Na/Al ratio of 1.36. Hydroxysodalite was also obtained under specific conditions.