Synthesis of Zeolite A from Bituminous Fly Ash by Microwave-Assisted Hydrothermal Method

BFA is a solid residue from a coal power plant containing high silica and alumina, which are the essential constituents for the formation of zeolite. The ash was pretreated under a hydrothermal process at temperatures of 50°C and 70°C for 12 and 24 hours using 3 M NaOH solution to dissolute Si4+ and Al3+ species from the ash. The results showed that soluble silica was present in the filtrate at 78 wt.% with the Si/Al molar ratio of 64.17 when the ash was pretreated at the temperature of 70°C for 24 hours. After pretreatment, the NaOH-NaAlO2 solution was added to the filtrate to adjust the Si/Al molar ratio between 0.8 and 2.3 and heated in a microwave at the temperature between 75°C and 105°C for 1 hour. The XRD technique revealed that Zeolite A was formed at the Si/Al molar ratio of 0.8 and under microwave heating between 95°C and 105°C for 1 hour. The QXRD confirmed that 100% of Zeolite A was obtained from microwave heating either at the temperature of 95°C and 105°C. A sharp cutting angle of each cubic crystal was observed from the SEM micrograph.