Synthesis of zeolites Na-P1 from South African coal fly ash: effect of impeller design and agitation
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Date
2013
Journal Title
Journal ISSN
Volume Title
Publisher
MDPI
Abstract
South African fly ash has been shown to be a useful feedstock for the synthesis
of some zeolites. The present study focuses on the effect of impeller design and agitation
rates on the synthesis of zeolite Na-P1 which are critical to the commercialization of this
product. The effects of three impeller designs (4-flat blade, Anchor and Archimedes screw
impellers) and three agitation speeds (150, 200 and 300 rpm) were investigated using a
modified previously reported synthesis conditions; 48 hours of ageing at 47 °C and static
hydrothermal treatment at 140 °C for 48 hours. The experimental results demonstrated that
the phase purity of zeolite Na-P1 was strongly affected by the agitation rate and the type of
impeller used during the ageing step of the synthesis process. Although zeolite Na-P1 was
synthesized with a space time yield (STY) of 15 ± 0.4 kg d−1m−3and a product yield of
0.98±0.05 g zeolites/g fly ash for each impeller at different agitation speeds, zeolite
formation was assessed to be fairly unsuccessful in some cases due the occurrence of
undissolved mullite and/or the formation of impurities such as hydroxysodalite with the
zeolitic product. This study also showed that a high crystalline zeolite Na-P1 can be
synthesized from South African coal fly ash using a 4-flat blade impeller at an agitation
rate of 200 rpm during the ageing step at 47 °C for 48 hours followed by static
hydrothermal treatment at 140 °C for 48 hours.
Description
Keywords
Fly ash, Zeolites, Impeller design, Agitation, Zeolites Na-P1
Citation
Mainganye, D. et al. (2013). Synthesis of zeolites Na-P1 from South African coal fly ash: effect of impeller design and agitation. Materials, 6: 2074 - 2089