Consulting Environmental Catalysis

Erlangen, Germany

Consulting Environmental Catalysis

Erlangen, Germany

Time filter

Source Type

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.


Musyoka N.M.,University of the Western Cape | Petrik L.F.,University of the Western Cape | Gitari W.M.,University of Venda | Balfour G.,University of the Western Cape | Hums E.,Consulting Environmental Catalysis
Journal of Environmental Science and Health - Part A Toxic/Hazardous Substances and Environmental Engineering | Year: 2012

This study was aimed at optimizing the synthesis conditions for pure phase zeolite Na-P1 from three coal fly ashes obtained from power stations in the Mpumalanga province of South Africa. Synthesis variables evaluated were: hydrothermal treatment time (12-48 hours), temperature (100-160°C) and varying molar quantities of water during the hydrothermal treatment step (H 2O:SiO 2 molar ratio ranged between 0-0.49). The optimum synthesis conditions for preparing pure phase zeolite Na-P1 were achieved when the molar regime was 1 SiO 2: 0.36 Al 2O 3: 0.59 NaOH: 0.49 H 2O and ageing was done at 47C for 48 hours. The optimum hydrothermal treatment time and temperature was 48 hours and 140°C, respectively. Fly ashes sourced from two coal-fired power plants (A, B) were found to produce nearly same high purity zeolite Na-P1 under identical conditions whereas the third fly ash (C) lead to a low quality zeolite Na-P1 under these conditions. The cation exchange capacity for the high pure phase was found to be 4.11 meq/g. These results highlight the fact that adjustment of reactant composition and presynthesis or synthesis parameters, improved quality of zeolite Na-P1 can be achieved and hence an improved potential for application of zeolites prepared from coal fly ash. Copyright © 2012 Taylor and Francis Group, LLC.


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.


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.


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
Catalysis Today | Year: 2012

In this study, high phase purity of zeolite A was prepared from coal fly ash precursors. The molar regime of both the clear solution extract and unseparated fly ash slurry was adjusted to achieve the right composition for zeolite A crystallization. The formation process for zeolite A from coal fly ash precursors was monitored in detail using an in situ ultrasonic system and was complemented by use of ex situ techniques such as XRD, FTIR, SEM and FTIR. The findings from both the in situ ultrasonic monitoring process and ex situ techniques clearly contributed significantly in unmasking the formation process of zeolite A from coal fly ash compared to previous studies reported in the literature. The study also enriches the existing body of literature by deeply investigating the gel-solution-crystal interactions starting from this complex feedstock. Comparable ultrasonic signals were generated when both clear and unseparated fly ash based precursor solutions were used during the zeolite synthesis process. © 2012 Elsevier B.V. All rights reserved.


Musyoka N.M.,University of the Western Cape | Petrik L.F.,University of the Western Cape | Balfour G.,University of the Western Cape | Ndungu P.,University of the Western Cape | And 2 more authors.
Research on Chemical Intermediates | Year: 2012

With the intention of decreasing the experimental test runs during the optimization of synthesis of zeolites from fly ash, a 2 4 full-factorial experimental design was applied in this study. The preparation parameters that had showed significant influence on the synthesis of pure phase zeolite Na-P1 using one-step-ata- time experimental approach were included, but extended also to those parameters of importance identified in the literature. At the same time, it was important that the levels of variation of parameters not be restricted to the conditions where a pure phase of zeolite Na-P1 was formed. The four synthesis variables investigated were; NaOH concentration (NaOH:SiO 2 molar ratio ranged between 0.35 and 0.71), ageing temperature (35-55°C), hydrothermal treatment time (36-60 h) and temperature (130-150°C). The results obtained were assessed by the improvement in the cation exchange capacity (CEC) of the obtained zeolite, which showed that the phase purity is strictly controlled by the synthesis conditions. In the end, this approach provided sufficient understanding of the relationship between product properties and the four synthesis parameters, which took into account the individual effects as well as linear and nonlinear interacting phenomena. From the analysis, it was found that the main effects were ageing temperature and hydrothermal treatment time and temperature, which showed some interactions among each other. © Springer Science+Business Media B.V. 2011.


Musyoka N.M.,University of the Western Cape | Petrik L.F.,University of the Western Cape | Balfour G.,University of the Western Cape | Gitari W.M.,University of Venda | Hums E.,Consulting Environmental Catalysis
Journal of Environmental Science and Health - Part A Toxic/Hazardous Substances and Environmental Engineering | Year: 2011

The effect of using industrial waste brine solution instead of ultra pure water was investigated during the synthesis of zeolites using three South African coal fly ashes as Si feedstock. The high halide brine was obtained from the retentate effluent of a reverse osmosis mine water treatment plant. Synthesis conditions applied were; ageing of fly ash was at 47°C for 48 hours, and while the hydrothermal treatment temperature was set at 140°C for 48 hours. The use of brine as a solvent resulted in the formation of hydroxy sodalite zeolite although unconverted mullite and hematite from the fly ash feedstock was also found in the synthesis product.© Taylor & Francis Group, LLC.


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


Xie X.,Huazhong University of Science and Technology | Lu J.,Huazhong University of Science and Technology | Lu J.,South China University of Technology | Hums E.,Consulting Environmental Catalysis | And 2 more authors.
Energy and Fuels | Year: 2015

The mechanism underlying the deactivation of a commercial V2O5-WO3/TiO2 catalyst for NH3 selective catalytic reduction (SCR) of NOx through exposure to the flue gas of a coal-fired power plant was investigated by a transient kinetic analysis that focused on the distinction between the deactivation behaviors of adsorption sites and redox sites. The results showed that alkali dopants preferentially poison the active sites associated with vanadium (V5+-OH and/or V5+=O) rather than the sites associated with titania and tungsten. Obvious changes in the activation energies for NH3 desorption, oxidation, and SCR surface reaction over the used catalyst were observed. Kinetic variations showed that three other factors that are involved in the elementary surface steps are responsible for the catalyst deactivation rather than simply the decline of the NH3 adsorption capacity. Finally, the effects of these factors on the catalyst activity were analyzed at different temperatures. © 2015 American Chemical Society.


Xie X.,Thermal Power Research Institute | Hums E.,Consulting Environmental Catalysis | Lu J.,South China University of Technology
Research on Chemical Intermediates | Year: 2016

The impact of the surface heterogeneity of two commercial V2O5–WO3/TiO2 catalysts on the NH3–SCR–DeNOx process was investigated by kinetic modelling of the surface elementary steps. It was demonstrated that transient kinetic is sufficiently qualified to investigate the heterogeneity of catalytic active sites. In this context, possible deviations of the Langmuir adsorption isotherm formula were analyzed which still show a satisfactory deviation at temperatures below 623 K whereas the deviation increases rapidly at T > 623 K. © 2016 Springer Science+Business Media Dordrecht

Loading Consulting Environmental Catalysis collaborators
Loading Consulting Environmental Catalysis collaborators