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Hums E.,Consulting Environmental Catalysis | Musyoka N.M.,University of the Western Cape | Baser H.,Friedrich - Alexander - University, Erlangen - Nuremberg | Inayat A.,Friedrich - Alexander - University, Erlangen - Nuremberg | Schwieger W.,Friedrich - Alexander - University, Erlangen - Nuremberg
Research on Chemical Intermediates | Year: 2015

The kinetics of synthesis of zeolites Na-A and Na-X from fused South African class F coal fly ash were studied by using an ultrasound device as a real-time, in-situ diagnostic tool. Ex-situ techniques, for example XRD, ICP, and SEM, were used to complement the results of the kinetic study. Reaction rate, reaction order, and activation energy of crystallization processes in clear solution extracted from fused fly ash were calculated on the basis of ultrasound signal data recorded at different crystallization temperatures. Zeolite Na-X and zeolite Na-A crystals were both obtained without ageing. The zeolite Na-X sample showed contaminations of zeolite P and sodalite depending on the synthesis temperature. For zeolite Na-A the impact of ageing on the process of formation was also studied. © 2014 Springer Science+Business Media Dordrecht. Source


Musyoka N.M.,University of the Western Cape | Petrik L.F.,University of the Western Cape | Hums E.,Consulting Environmental Catalysis | Baser H.,Friedrich - Alexander - University, Erlangen - Nuremberg | Schwieger W.,Friedrich - Alexander - University, Erlangen - Nuremberg
Ultrasonics | Year: 2014

In this paper the applicability of an in situ ultrasonic diagnostic technique in understanding the formation process of zeolite X with a novel morphology was demonstrated. The complexity of the starting fly ash feedstock demands independent studies of the formation process for each type of zeolite since it is not known whether the crystallization mechanism will always follow the expected reaction pathway. The hierarchical zeolite X was noted to follow a solution phase-mediated crystallization mechanism which differs from earlier studies of the zeolite A formation process from unaged, clear solution extracted from fused fly ash. The use of the in situ ultrasonic monitoring system provided sufficient data points which enabled closer estimation of the time of transition from the nucleation to the crystal growth step. In order to evaluate the effect of temperature on the resulting in situ attenuation signal, synthesis at three higher temperatures (80, 90 and 94 °C) was investigated. It was shown, by the shift of the US-attenuation signal, that faster crystallization occurred when higher temperatures were applied. The novel hierarchical zeolite X was comprised of intergrown disc-like platelets. It was further observed that there was preferential growth of the disc-shaped platelets of zeolite X crystals in one dimension as the synthesis temperature was increased, allowing tailoring of the hierarchical morphology. © 2013 Elsevier B.V. All rights reserved. Source


Musyoka N.M.,University of the Western Cape | Petrik L.F.,University of the Western Cape | Fatoba O.O.,University of the Western Cape | Hums E.,Consulting Environmental Catalysis
Minerals Engineering | Year: 2013

In this study mine waters obtained from coal mining operations in South Africa were used as a substitute for pure water during the synthesis of zeolites from South African coal fly ash. Procedures that had been optimized to produce single phase zeolite Na-P1 and X using pure water were employed independently. The use of circumneutral mine water resulted in similar quality zeolite Na-P1 and X whereas the use of acidic mine drainage led to the formation of a single phase hydroxysodalite zeolite. Since these two wastes (fly ash and mine waters) are found in close proximity to each other, this study demonstrates that they can be used to ameliorate each other and at the same time produce saleable zeolitic products that can be used to offset their costs of disposal and treatment. © 2013 Elsevier Ltd. All rights reserved. Source


Hums E.,Consulting Environmental Catalysis | Baser H.,Friedrich - Alexander - University, Erlangen - Nuremberg | Schwieger W.,Friedrich - Alexander - University, Erlangen - Nuremberg
Research on Chemical Intermediates | Year: 2016

An in situ ultrasonic diagnostic technique was applied to monitoring the hydrothermal synthesis of zeolite A and X of clear solution extracted from alkaline fused class F coal fly ash. In this context, kinetic evaluations based on in situ ultrasonic diagnostic data displayed an important approach to study the synthesis process. The impact on nucleation and crystal growth was demonstrated by variation of a few relevant parameters such as reaction temperature, amount of water, Na2O and ageing time, including templated colloidal synthesis mixtures as model solution. To complement the kinetic analysis, ex situ techniques such as ICP, X-ray diffraction, scanning electron microscopy and dynamic light scattering were used to investigate liquid phase and reaction products extracted from the reaction mixture during the synthesis. © 2016 Springer Science+Business Media Dordrecht Source


Musyoka N.M.,University of the Western Cape | Petrik L.,University of the Western Cape | Hums E.,Consulting Environmental Catalysis
Advanced Materials Research | Year: 2012

Synthesis conditions for generating high quality zeolite type Na-P1, A, and X from a South African coal fly ash were identified in this study. XRF, XRD, FTIR and SEM analytical techniques were used to characterize the starting fly ash feedstock and the resulting synthesis product. Synthesis of these high quality zeolites types is expected to provide a competitive alternative for recycling the ever increasing quantity of fly ash produced in the South African coalfired power plants. This approach will not only be environment friendly but could also be attractive from an economic point of view since the cost of disposal of fly ash could be offset by the income generated from the sale of the synthesized zeolitic materials. © (2012) Trans Tech Publications, Switzerland. Source

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